Improve database and RPC API for moving and linking channels, improve test legibility

Refactor channel store to combine the channels_by_id and channel_paths into a 'ChannelIndex'

crates/channel/src/channel_store.rs

@@ -1,3 +1,5 @@
+mod channel_index;
+
 use crate::channel_buffer::ChannelBuffer;
 use anyhow::{anyhow, Result};
 use client::{Client, Subscription, User, UserId, UserStore};
@@ -8,13 +10,15 @@ use rpc::{proto, TypedEnvelope};
 use std::{mem, sync::Arc, time::Duration};
 use util::ResultExt;
 
+use self::channel_index::ChannelIndex;
+pub use self::channel_index::ChannelPath;
+
 pub const RECONNECT_TIMEOUT: Duration = Duration::from_secs(30);
 
 pub type ChannelId = u64;
 
 pub struct ChannelStore {
-    channels_by_id: HashMap<ChannelId, Arc<Channel>>,
-    channel_paths: Vec<Vec<ChannelId>>,
+    channel_index: ChannelIndex,
     channel_invitations: Vec<Arc<Channel>>,
     channel_participants: HashMap<ChannelId, Vec<Arc<User>>>,
     channels_with_admin_privileges: HashSet<ChannelId>,
@@ -87,9 +91,8 @@ impl ChannelStore {
         });
 
         Self {
-            channels_by_id: HashMap::default(),
             channel_invitations: Vec::default(),
-            channel_paths: Vec::default(),
+            channel_index: ChannelIndex::default(),
             channel_participants: Default::default(),
             channels_with_admin_privileges: Default::default(),
             outgoing_invites: Default::default(),
@@ -116,7 +119,7 @@ impl ChannelStore {
     }
 
     pub fn has_children(&self, channel_id: ChannelId) -> bool {
-        self.channel_paths.iter().any(|path| {
+        self.channel_index.iter().any(|path| {
             if let Some(ix) = path.iter().position(|id| *id == channel_id) {
                 path.len() > ix + 1
             } else {
@@ -126,22 +129,23 @@ impl ChannelStore {
     }
 
     pub fn channel_count(&self) -> usize {
-        self.channel_paths.len()
+        self.channel_index.len()
     }
 
     pub fn channels(&self) -> impl '_ + Iterator<Item = (usize, &Arc<Channel>)> {
-        self.channel_paths.iter().map(move |path| {
+        self.channel_index.iter().map(move |path| {
             let id = path.last().unwrap();
             let channel = self.channel_for_id(*id).unwrap();
             (path.len() - 1, channel)
         })
     }
 
-    pub fn channel_at_index(&self, ix: usize) -> Option<(usize, &Arc<Channel>)> {
-        let path = self.channel_paths.get(ix)?;
+    pub fn channel_at_index(&self, ix: usize) -> Option<(&Arc<Channel>, &ChannelPath)> {
+        let path = self.channel_index.get(ix)?;
         let id = path.last().unwrap();
         let channel = self.channel_for_id(*id).unwrap();
-        Some((path.len() - 1, channel))
+
+        Some((channel, path))
     }
 
     pub fn channel_invitations(&self) -> &[Arc<Channel>] {
@@ -149,7 +153,7 @@ impl ChannelStore {
     }
 
     pub fn channel_for_id(&self, channel_id: ChannelId) -> Option<&Arc<Channel>> {
-        self.channels_by_id.get(&channel_id)
+        self.channel_index.by_id().get(&channel_id)
     }
 
     pub fn has_open_channel_buffer(&self, channel_id: ChannelId, cx: &AppContext) -> bool {
@@ -230,7 +234,7 @@ impl ChannelStore {
     }
 
     pub fn is_user_admin(&self, channel_id: ChannelId) -> bool {
-        self.channel_paths.iter().any(|path| {
+        self.channel_index.iter().any(|path| {
             if let Some(ix) = path.iter().position(|id| *id == channel_id) {
                 path[..=ix]
                     .iter()
@@ -285,6 +289,59 @@ impl ChannelStore {
         })
     }
 
+    pub fn link_channel(
+        &mut self,
+        channel_id: ChannelId,
+        to: ChannelId,
+        cx: &mut ModelContext<Self>,
+    ) -> Task<Result<()>> {
+        let client = self.client.clone();
+        cx.spawn(|_, _| async move {
+            let _ = client
+                .request(proto::LinkChannel { channel_id, to })
+                .await?;
+
+            Ok(())
+        })
+    }
+
+    pub fn unlink_channel(
+        &mut self,
+        channel_id: ChannelId,
+        from: Option<ChannelId>,
+        cx: &mut ModelContext<Self>,
+    ) -> Task<Result<()>> {
+        let client = self.client.clone();
+        cx.spawn(|_, _| async move {
+            let _ = client
+                .request(proto::UnlinkChannel { channel_id, from })
+                .await?;
+
+            Ok(())
+        })
+    }
+
+    pub fn move_channel(
+        &mut self,
+        channel_id: ChannelId,
+        from: Option<ChannelId>,
+        to: ChannelId,
+        cx: &mut ModelContext<Self>,
+    ) -> Task<Result<()>> {
+        let client = self.client.clone();
+        cx.spawn(|_, _| async move {
+            let _ = client
+                .request(proto::MoveChannel {
+                    channel_id,
+                    from,
+                    to,
+                })
+                .await?;
+
+            Ok(())
+        })
+    }
+
     pub fn invite_member(
         &mut self,
         channel_id: ChannelId,
@@ -464,7 +521,7 @@ impl ChannelStore {
     pub fn remove_channel(&self, channel_id: ChannelId) -> impl Future<Output = Result<()>> {
         let client = self.client.clone();
         async move {
-            client.request(proto::RemoveChannel { channel_id }).await?;
+            client.request(proto::DeleteChannel { channel_id }).await?;
             Ok(())
         }
     }
@@ -591,11 +648,11 @@ impl ChannelStore {
     }
 
     fn handle_disconnect(&mut self, cx: &mut ModelContext<Self>) {
-        self.channels_by_id.clear();
+        self.channel_index.clear();
         self.channel_invitations.clear();
         self.channel_participants.clear();
         self.channels_with_admin_privileges.clear();
-        self.channel_paths.clear();
+        self.channel_index.clear();
         self.outgoing_invites.clear();
         cx.notify();
 
@@ -642,17 +699,16 @@ impl ChannelStore {
             }
         }
 
-        let channels_changed = !payload.channels.is_empty() || !payload.remove_channels.is_empty();
+        let channels_changed = !payload.channels.is_empty() || !payload.delete_channels.is_empty();
         if channels_changed {
-            if !payload.remove_channels.is_empty() {
-                self.channels_by_id
-                    .retain(|channel_id, _| !payload.remove_channels.contains(channel_id));
+            if !payload.delete_channels.is_empty() {
+                self.channel_index.delete_channels(&payload.delete_channels);
                 self.channel_participants
-                    .retain(|channel_id, _| !payload.remove_channels.contains(channel_id));
+                    .retain(|channel_id, _| !payload.delete_channels.contains(channel_id));
                 self.channels_with_admin_privileges
-                    .retain(|channel_id| !payload.remove_channels.contains(channel_id));
+                    .retain(|channel_id| !payload.delete_channels.contains(channel_id));
 
-                for channel_id in &payload.remove_channels {
+                for channel_id in &payload.delete_channels {
                     let channel_id = *channel_id;
                     if let Some(OpenedChannelBuffer::Open(buffer)) =
                         self.opened_buffers.remove(&channel_id)
@@ -664,44 +720,15 @@ impl ChannelStore {
                 }
             }
 
-            for channel_proto in payload.channels {
-                if let Some(existing_channel) = self.channels_by_id.get_mut(&channel_proto.id) {
-                    Arc::make_mut(existing_channel).name = channel_proto.name;
-                } else {
-                    let channel = Arc::new(Channel {
-                        id: channel_proto.id,
-                        name: channel_proto.name,
-                    });
-                    self.channels_by_id.insert(channel.id, channel.clone());
-
-                    if let Some(parent_id) = channel_proto.parent_id {
-                        let mut ix = 0;
-                        while ix < self.channel_paths.len() {
-                            let path = &self.channel_paths[ix];
-                            if path.ends_with(&[parent_id]) {
-                                let mut new_path = path.clone();
-                                new_path.push(channel.id);
-                                self.channel_paths.insert(ix + 1, new_path);
-                                ix += 1;
-                            }
-                            ix += 1;
-                        }
-                    } else {
-                        self.channel_paths.push(vec![channel.id]);
-                    }
-                }
+            let mut channel_index = self.channel_index.start_upsert();
+            for channel in payload.channels {
+                channel_index.upsert(channel)
             }
+        }
 
-            self.channel_paths.sort_by(|a, b| {
-                let a = Self::channel_path_sorting_key(a, &self.channels_by_id);
-                let b = Self::channel_path_sorting_key(b, &self.channels_by_id);
-                a.cmp(b)
-            });
-            self.channel_paths.dedup();
-            self.channel_paths.retain(|path| {
-                path.iter()
-                    .all(|channel_id| self.channels_by_id.contains_key(channel_id))
-            });
+        for edge in payload.delete_channel_edge {
+            self.channel_index
+                .delete_edge(edge.parent_id, edge.channel_id);
         }
 
         for permission in payload.channel_permissions {
@@ -759,12 +786,4 @@ impl ChannelStore {
             anyhow::Ok(())
         }))
     }
-
-    fn channel_path_sorting_key<'a>(
-        path: &'a [ChannelId],
-        channels_by_id: &'a HashMap<ChannelId, Arc<Channel>>,
-    ) -> impl 'a + Iterator<Item = Option<&'a str>> {
-        path.iter()
-            .map(|id| Some(channels_by_id.get(id)?.name.as_str()))
-    }
 }

crates/channel/src/channel_store/channel_index.rs

@@ -0,0 +1,161 @@
+use std::{sync::Arc, ops::Deref};
+
+use collections::HashMap;
+use rpc::proto;
+use serde_derive::{Serialize, Deserialize};
+
+use crate::{ChannelId, Channel};
+
+pub type ChannelsById = HashMap<ChannelId, Arc<Channel>>;
+
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Serialize, Deserialize)]
+pub struct ChannelPath(Arc<[ChannelId]>);
+
+impl Deref for ChannelPath {
+    type Target = [ChannelId];
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl ChannelPath {
+    pub fn parent_id(&self) -> Option<ChannelId> {
+        self.0.len().checked_sub(2).map(|i| {
+            self.0[i]
+        })
+    }
+}
+
+impl Default for ChannelPath {
+    fn default() -> Self {
+        ChannelPath(Arc::from([]))
+    }
+}
+
+#[derive(Default, Debug)]
+pub struct ChannelIndex {
+    paths: Vec<ChannelPath>,
+    channels_by_id: ChannelsById,
+}
+
+
+impl ChannelIndex {
+    pub fn by_id(&self) -> &ChannelsById {
+        &self.channels_by_id
+    }
+
+    pub fn clear(&mut self) {
+        self.paths.clear();
+        self.channels_by_id.clear();
+    }
+
+    pub fn len(&self) -> usize {
+        self.paths.len()
+    }
+
+    pub fn get(&self, idx: usize) -> Option<&ChannelPath> {
+        self.paths.get(idx)
+    }
+
+    pub fn iter(&self) -> impl Iterator<Item = &ChannelPath> {
+        self.paths.iter()
+    }
+
+    /// Remove the given edge from this index. This will not remove the channel
+    /// and may result in dangling channels.
+    pub fn delete_edge(&mut self, parent_id: ChannelId, channel_id: ChannelId) {
+        self.paths.retain(|path| {
+            !path
+                .windows(2)
+                .any(|window| window == [parent_id, channel_id])
+        });
+    }
+
+    /// Delete the given channels from this index.
+    pub fn delete_channels(&mut self, channels: &[ChannelId]) {
+        self.channels_by_id.retain(|channel_id, _| !channels.contains(channel_id));
+        self.paths.retain(|channel_path| !channel_path.iter().any(|channel_id| {channels.contains(channel_id)}))
+    }
+
+    /// Upsert one or more channels into this index.
+    pub fn start_upsert(& mut self) -> ChannelPathsUpsertGuard {
+        ChannelPathsUpsertGuard {
+            paths: &mut self.paths,
+            channels_by_id: &mut self.channels_by_id,
+        }
+    }
+}
+
+/// A guard for ensuring that the paths index maintains its sort and uniqueness
+/// invariants after a series of insertions
+pub struct ChannelPathsUpsertGuard<'a> {
+    paths:  &'a mut Vec<ChannelPath>,
+    channels_by_id: &'a mut ChannelsById,
+}
+
+impl<'a> ChannelPathsUpsertGuard<'a> {
+    pub fn upsert(&mut self, channel_proto: proto::Channel) {
+        if let Some(existing_channel) = self.channels_by_id.get_mut(&channel_proto.id) {
+            Arc::make_mut(existing_channel).name = channel_proto.name;
+
+            if let Some(parent_id) = channel_proto.parent_id {
+                self.insert_edge(parent_id, channel_proto.id)
+            }
+        } else {
+            let channel = Arc::new(Channel {
+                id: channel_proto.id,
+                name: channel_proto.name,
+            });
+            self.channels_by_id.insert(channel.id, channel.clone());
+
+            if let Some(parent_id) = channel_proto.parent_id {
+                self.insert_edge(parent_id, channel.id);
+            } else {
+                self.insert_root(channel.id);
+            }
+        }
+    }
+
+    fn insert_edge(&mut self, parent_id: ChannelId, channel_id: ChannelId) {
+        let mut ix = 0;
+        while ix < self.paths.len() {
+            let path = &self.paths[ix];
+            if path.ends_with(&[parent_id]) {
+                let mut new_path = path.to_vec();
+                new_path.push(channel_id);
+                self.paths.insert(ix + 1, ChannelPath(new_path.into()));
+                ix += 1;
+            }
+            ix += 1;
+        }
+    }
+
+    fn insert_root(&mut self, channel_id: ChannelId) {
+        self.paths.push(ChannelPath(Arc::from([channel_id])));
+    }
+}
+
+impl<'a> Drop for ChannelPathsUpsertGuard<'a> {
+    fn drop(&mut self) {
+        self.paths.sort_by(|a, b| {
+            let a = channel_path_sorting_key(a, &self.channels_by_id);
+            let b = channel_path_sorting_key(b, &self.channels_by_id);
+            a.cmp(b)
+        });
+        self.paths.dedup();
+        self.paths.retain(|path| {
+            path.iter()
+                .all(|channel_id| self.channels_by_id.contains_key(channel_id))
+        });
+    }
+}
+
+
+fn channel_path_sorting_key<'a>(
+    path: &'a [ChannelId],
+    channels_by_id: &'a ChannelsById,
+) -> impl 'a + Iterator<Item = Option<&'a str>> {
+    path.iter()
+        .map(|id| Some(channels_by_id.get(id)?.name.as_str()))
+}

crates/channel/src/channel_store_tests.rs

@@ -127,7 +127,7 @@ fn test_dangling_channel_paths(cx: &mut AppContext) {
     update_channels(
         &channel_store,
         proto::UpdateChannels {
-            remove_channels: vec![1, 2],
+            delete_channels: vec![1, 2],
             ..Default::default()
         },
         cx,

crates/collab/Cargo.toml

@@ -72,7 +72,6 @@ fs = { path = "../fs", features = ["test-support"] }
 git = { path = "../git", features = ["test-support"] }
 live_kit_client = { path = "../live_kit_client", features = ["test-support"] }
 lsp = { path = "../lsp", features = ["test-support"] }
-pretty_assertions.workspace = true
 project = { path = "../project", features = ["test-support"] }
 rpc = { path = "../rpc", features = ["test-support"] }
 settings = { path = "../settings", features = ["test-support"] }
@@ -81,6 +80,7 @@ workspace = { path = "../workspace", features = ["test-support"] }
 collab_ui = { path = "../collab_ui", features = ["test-support"] }
 
 async-trait.workspace = true
+pretty_assertions.workspace = true
 ctor.workspace = true
 env_logger.workspace = true
 indoc.workspace = true

crates/collab/src/db/queries/channels.rs

@@ -1,5 +1,7 @@
 use super::*;
 
+type ChannelDescendants = HashMap<ChannelId, HashSet<ChannelId>>;
+
 impl Database {
     #[cfg(test)]
     pub async fn all_channels(&self) -> Result<Vec<(ChannelId, String)>> {
@@ -100,7 +102,7 @@ impl Database {
         .await
     }
 
-    pub async fn remove_channel(
+    pub async fn delete_channel(
         &self,
         channel_id: ChannelId,
         user_id: UserId,
@@ -149,6 +151,19 @@ impl Database {
                 .exec(&*tx)
                 .await?;
 
+            // Delete any other paths that incldue this channel
+            let sql = r#"
+                    DELETE FROM channel_paths
+                    WHERE
+                        id_path LIKE '%' || $1 || '%'
+                "#;
+            let channel_paths_stmt = Statement::from_sql_and_values(
+                self.pool.get_database_backend(),
+                sql,
+                [channel_id.to_proto().into()],
+            );
+            tx.execute(channel_paths_stmt).await?;
+
             Ok((channels_to_remove.into_keys().collect(), members_to_notify))
         })
         .await
@@ -319,6 +334,43 @@ impl Database {
         .await
     }
 
+    async fn get_all_channels(
+        &self,
+        parents_by_child_id: ChannelDescendants,
+        tx: &DatabaseTransaction,
+    ) -> Result<Vec<Channel>> {
+        let mut channels = Vec::with_capacity(parents_by_child_id.len());
+        {
+            let mut rows = channel::Entity::find()
+                .filter(channel::Column::Id.is_in(parents_by_child_id.keys().copied()))
+                .stream(&*tx)
+                .await?;
+            while let Some(row) = rows.next().await {
+                let row = row?;
+
+                // As these rows are pulled from the map's keys, this unwrap is safe.
+                let parents = parents_by_child_id.get(&row.id).unwrap();
+                if parents.len() > 0 {
+                    for parent in parents {
+                        channels.push(Channel {
+                            id: row.id,
+                            name: row.name.clone(),
+                            parent_id: Some(*parent),
+                        });
+                    }
+                } else {
+                    channels.push(Channel {
+                        id: row.id,
+                        name: row.name,
+                        parent_id: None,
+                    });
+                }
+            }
+        }
+
+        Ok(channels)
+    }
+
     pub async fn get_channels_for_user(&self, user_id: UserId) -> Result<ChannelsForUser> {
         self.transaction(|tx| async move {
             let tx = tx;
@@ -341,21 +393,7 @@ impl Database {
                 .filter_map(|membership| membership.admin.then_some(membership.channel_id))
                 .collect();
 
-            let mut channels = Vec::with_capacity(parents_by_child_id.len());
-            {
-                let mut rows = channel::Entity::find()
-                    .filter(channel::Column::Id.is_in(parents_by_child_id.keys().copied()))
-                    .stream(&*tx)
-                    .await?;
-                while let Some(row) = rows.next().await {
-                    let row = row?;
-                    channels.push(Channel {
-                        id: row.id,
-                        name: row.name,
-                        parent_id: parents_by_child_id.get(&row.id).copied().flatten(),
-                    });
-                }
-            }
+            let channels = self.get_all_channels(parents_by_child_id, &tx).await?;
 
             #[derive(Copy, Clone, Debug, EnumIter, DeriveColumn)]
             enum QueryUserIdsAndChannelIds {
@@ -559,6 +597,7 @@ impl Database {
         Ok(())
     }
 
+    /// Returns the channel ancestors, deepest first
     pub async fn get_channel_ancestors(
         &self,
         channel_id: ChannelId,
@@ -566,6 +605,7 @@ impl Database {
     ) -> Result<Vec<ChannelId>> {
         let paths = channel_path::Entity::find()
             .filter(channel_path::Column::ChannelId.eq(channel_id))
+            .order_by(channel_path::Column::IdPath, sea_query::Order::Desc)
             .all(tx)
             .await?;
         let mut channel_ids = Vec::new();
@@ -582,11 +622,25 @@ impl Database {
         Ok(channel_ids)
     }
 
+    /// Returns the channel descendants,
+    /// Structured as a map from child ids to their parent ids
+    /// For example, the descendants of 'a' in this DAG:
+    ///
+    ///   /- b -\
+    /// a -- c -- d
+    ///
+    /// would be:
+    /// {
+    ///     a: [],
+    ///     b: [a],
+    ///     c: [a],
+    ///     d: [a, c],
+    /// }
     async fn get_channel_descendants(
         &self,
         channel_ids: impl IntoIterator<Item = ChannelId>,
         tx: &DatabaseTransaction,
-    ) -> Result<HashMap<ChannelId, Option<ChannelId>>> {
+    ) -> Result<ChannelDescendants> {
         let mut values = String::new();
         for id in channel_ids {
             if !values.is_empty() {
@@ -613,7 +667,7 @@ impl Database {
 
         let stmt = Statement::from_string(self.pool.get_database_backend(), sql);
 
-        let mut parents_by_child_id = HashMap::default();
+        let mut parents_by_child_id: ChannelDescendants = HashMap::default();
         let mut paths = channel_path::Entity::find()
             .from_raw_sql(stmt)
             .stream(tx)
@@ -632,7 +686,10 @@ impl Database {
                     parent_id = Some(id);
                 }
             }
-            parents_by_child_id.insert(path.channel_id, parent_id);
+            let entry = parents_by_child_id.entry(path.channel_id).or_default();
+            if let Some(parent_id) = parent_id {
+                entry.insert(parent_id);
+            }
         }
 
         Ok(parents_by_child_id)
@@ -703,6 +760,191 @@ impl Database {
         })
         .await
     }
+
+    // Insert an edge from the given channel to the given other channel.
+    pub async fn link_channel(
+        &self,
+        user: UserId,
+        channel: ChannelId,
+        to: ChannelId,
+    ) -> Result<Vec<Channel>> {
+        self.transaction(|tx| async move {
+            // Note that even with these maxed permissions, this linking operation
+            // is still insecure because you can't remove someone's permissions to a
+            // channel if they've linked the channel to one where they're an admin.
+            self.check_user_is_channel_admin(channel, user, &*tx)
+                .await?;
+
+            self.link_channel_internal(user, channel, to, &*tx).await
+        })
+        .await
+    }
+
+    pub async fn link_channel_internal(
+        &self,
+        user: UserId,
+        channel: ChannelId,
+        to: ChannelId,
+        tx: &DatabaseTransaction,
+    ) -> Result<Vec<Channel>> {
+        self.check_user_is_channel_admin(to, user, &*tx).await?;
+
+        let to_ancestors = self.get_channel_ancestors(to, &*tx).await?;
+        let mut from_descendants = self.get_channel_descendants([channel], &*tx).await?;
+        for ancestor in to_ancestors {
+            if from_descendants.contains_key(&ancestor) {
+                return Err(anyhow!("Cannot create a channel cycle").into());
+            }
+        }
+        let sql = r#"
+                INSERT INTO channel_paths
+                (id_path, channel_id)
+                SELECT
+                    id_path || $1 || '/', $2
+                FROM
+                    channel_paths
+                WHERE
+                    channel_id = $3
+                ON CONFLICT (id_path) DO NOTHING;
+            "#;
+        let channel_paths_stmt = Statement::from_sql_and_values(
+            self.pool.get_database_backend(),
+            sql,
+            [
+                channel.to_proto().into(),
+                channel.to_proto().into(),
+                to.to_proto().into(),
+            ],
+        );
+        tx.execute(channel_paths_stmt).await?;
+        for (from_id, to_ids) in from_descendants.iter().filter(|(id, _)| id != &&channel) {
+            for to_id in to_ids {
+                let channel_paths_stmt = Statement::from_sql_and_values(
+                    self.pool.get_database_backend(),
+                    sql,
+                    [
+                        from_id.to_proto().into(),
+                        from_id.to_proto().into(),
+                        to_id.to_proto().into(),
+                    ],
+                );
+                tx.execute(channel_paths_stmt).await?;
+            }
+        }
+
+        if let Some(channel) = from_descendants.get_mut(&channel) {
+            // Remove the other parents
+            channel.clear();
+            channel.insert(to);
+        }
+
+        let channels = self.get_all_channels(from_descendants, &*tx).await?;
+
+        Ok(channels)
+    }
+
+    /// Unlink a channel from a given parent. This will add in a root edge if
+    /// the channel has no other parents after this operation.
+    pub async fn unlink_channel(
+        &self,
+        user: UserId,
+        channel: ChannelId,
+        from: Option<ChannelId>,
+    ) -> Result<()> {
+        self.transaction(|tx| async move {
+            // Note that even with these maxed permissions, this linking operation
+            // is still insecure because you can't remove someone's permissions to a
+            // channel if they've linked the channel to one where they're an admin.
+            self.check_user_is_channel_admin(channel, user, &*tx)
+                .await?;
+
+            self.unlink_channel_internal(user, channel, from, &*tx)
+                .await?;
+
+            Ok(())
+        })
+        .await
+    }
+
+    pub async fn unlink_channel_internal(
+        &self,
+        user: UserId,
+        channel: ChannelId,
+        from: Option<ChannelId>,
+        tx: &DatabaseTransaction,
+    ) -> Result<()> {
+        if let Some(from) = from {
+            self.check_user_is_channel_admin(from, user, &*tx).await?;
+
+            let sql = r#"
+                DELETE FROM channel_paths
+                WHERE
+                    id_path LIKE '%' || $1 || '/' || $2 || '%'
+            "#;
+            let channel_paths_stmt = Statement::from_sql_and_values(
+                self.pool.get_database_backend(),
+                sql,
+                [from.to_proto().into(), channel.to_proto().into()],
+            );
+            tx.execute(channel_paths_stmt).await?;
+        } else {
+            let sql = r#"
+                DELETE FROM channel_paths
+                WHERE
+                    id_path = '/' || $1 || '/'
+            "#;
+            let channel_paths_stmt = Statement::from_sql_and_values(
+                self.pool.get_database_backend(),
+                sql,
+                [channel.to_proto().into()],
+            );
+            tx.execute(channel_paths_stmt).await?;
+        }
+
+        // Make sure that there is always at least one path to the channel
+        let sql = r#"
+            INSERT INTO channel_paths
+            (id_path, channel_id)
+            SELECT
+                '/' || $1 || '/', $2
+            WHERE NOT EXISTS
+                (SELECT *
+                 FROM channel_paths
+                 WHERE channel_id = $2)
+            "#;
+
+        let channel_paths_stmt = Statement::from_sql_and_values(
+            self.pool.get_database_backend(),
+            sql,
+            [channel.to_proto().into(), channel.to_proto().into()],
+        );
+        tx.execute(channel_paths_stmt).await?;
+
+        Ok(())
+    }
+
+    /// Move a channel from one parent to another, returns the
+    /// Channels that were moved for notifying clients
+    pub async fn move_channel(
+        &self,
+        user: UserId,
+        channel: ChannelId,
+        from: Option<ChannelId>,
+        to: ChannelId,
+    ) -> Result<Vec<Channel>> {
+        self.transaction(|tx| async move {
+            self.check_user_is_channel_admin(channel, user, &*tx)
+                .await?;
+
+            let moved_channels = self.link_channel_internal(user, channel, to, &*tx).await?;
+
+            self.unlink_channel_internal(user, channel, from, &*tx)
+                .await?;
+
+            Ok(moved_channels)
+        })
+        .await
+    }
 }
 
 #[derive(Copy, Clone, Debug, EnumIter, DeriveColumn)]

crates/collab/src/db/tests.rs

@@ -1,4 +1,5 @@
 mod buffer_tests;
+mod channel_tests;
 mod db_tests;
 mod feature_flag_tests;
 

crates/collab/src/db/tests/channel_tests.rs

@@ -0,0 +1,844 @@
+use rpc::{proto, ConnectionId};
+
+use crate::{
+    db::{Channel, ChannelId, Database, NewUserParams},
+    test_both_dbs,
+};
+use std::sync::Arc;
+
+test_both_dbs!(test_channels, test_channels_postgres, test_channels_sqlite);
+
+async fn test_channels(db: &Arc<Database>) {
+    let a_id = db
+        .create_user(
+            "user1@example.com",
+            false,
+            NewUserParams {
+                github_login: "user1".into(),
+                github_user_id: 5,
+                invite_count: 0,
+            },
+        )
+        .await
+        .unwrap()
+        .user_id;
+
+    let b_id = db
+        .create_user(
+            "user2@example.com",
+            false,
+            NewUserParams {
+                github_login: "user2".into(),
+                github_user_id: 6,
+                invite_count: 0,
+            },
+        )
+        .await
+        .unwrap()
+        .user_id;
+
+    let zed_id = db.create_root_channel("zed", "1", a_id).await.unwrap();
+
+    // Make sure that people cannot read channels they haven't been invited to
+    assert!(db.get_channel(zed_id, b_id).await.unwrap().is_none());
+
+    db.invite_channel_member(zed_id, b_id, a_id, false)
+        .await
+        .unwrap();
+
+    db.respond_to_channel_invite(zed_id, b_id, true)
+        .await
+        .unwrap();
+
+    let crdb_id = db
+        .create_channel("crdb", Some(zed_id), "2", a_id)
+        .await
+        .unwrap();
+    let livestreaming_id = db
+        .create_channel("livestreaming", Some(zed_id), "3", a_id)
+        .await
+        .unwrap();
+    let replace_id = db
+        .create_channel("replace", Some(zed_id), "4", a_id)
+        .await
+        .unwrap();
+
+    let mut members = db.get_channel_members(replace_id).await.unwrap();
+    members.sort();
+    assert_eq!(members, &[a_id, b_id]);
+
+    let rust_id = db.create_root_channel("rust", "5", a_id).await.unwrap();
+    let cargo_id = db
+        .create_channel("cargo", Some(rust_id), "6", a_id)
+        .await
+        .unwrap();
+
+    let cargo_ra_id = db
+        .create_channel("cargo-ra", Some(cargo_id), "7", a_id)
+        .await
+        .unwrap();
+
+    let result = db.get_channels_for_user(a_id).await.unwrap();
+    assert_eq!(
+        result.channels,
+        vec![
+            Channel {
+                id: zed_id,
+                name: "zed".to_string(),
+                parent_id: None,
+            },
+            Channel {
+                id: crdb_id,
+                name: "crdb".to_string(),
+                parent_id: Some(zed_id),
+            },
+            Channel {
+                id: livestreaming_id,
+                name: "livestreaming".to_string(),
+                parent_id: Some(zed_id),
+            },
+            Channel {
+                id: replace_id,
+                name: "replace".to_string(),
+                parent_id: Some(zed_id),
+            },
+            Channel {
+                id: rust_id,
+                name: "rust".to_string(),
+                parent_id: None,
+            },
+            Channel {
+                id: cargo_id,
+                name: "cargo".to_string(),
+                parent_id: Some(rust_id),
+            },
+            Channel {
+                id: cargo_ra_id,
+                name: "cargo-ra".to_string(),
+                parent_id: Some(cargo_id),
+            }
+        ]
+    );
+
+    let result = db.get_channels_for_user(b_id).await.unwrap();
+    assert_eq!(
+        result.channels,
+        vec![
+            Channel {
+                id: zed_id,
+                name: "zed".to_string(),
+                parent_id: None,
+            },
+            Channel {
+                id: crdb_id,
+                name: "crdb".to_string(),
+                parent_id: Some(zed_id),
+            },
+            Channel {
+                id: livestreaming_id,
+                name: "livestreaming".to_string(),
+                parent_id: Some(zed_id),
+            },
+            Channel {
+                id: replace_id,
+                name: "replace".to_string(),
+                parent_id: Some(zed_id),
+            },
+        ]
+    );
+
+    // Update member permissions
+    let set_subchannel_admin = db.set_channel_member_admin(crdb_id, a_id, b_id, true).await;
+    assert!(set_subchannel_admin.is_err());
+    let set_channel_admin = db.set_channel_member_admin(zed_id, a_id, b_id, true).await;
+    assert!(set_channel_admin.is_ok());
+
+    let result = db.get_channels_for_user(b_id).await.unwrap();
+    assert_eq!(
+        result.channels,
+        vec![
+            Channel {
+                id: zed_id,
+                name: "zed".to_string(),
+                parent_id: None,
+            },
+            Channel {
+                id: crdb_id,
+                name: "crdb".to_string(),
+                parent_id: Some(zed_id),
+            },
+            Channel {
+                id: livestreaming_id,
+                name: "livestreaming".to_string(),
+                parent_id: Some(zed_id),
+            },
+            Channel {
+                id: replace_id,
+                name: "replace".to_string(),
+                parent_id: Some(zed_id),
+            },
+        ]
+    );
+
+    // Remove a single channel
+    db.delete_channel(crdb_id, a_id).await.unwrap();
+    assert!(db.get_channel(crdb_id, a_id).await.unwrap().is_none());
+
+    // Remove a channel tree
+    let (mut channel_ids, user_ids) = db.delete_channel(rust_id, a_id).await.unwrap();
+    channel_ids.sort();
+    assert_eq!(channel_ids, &[rust_id, cargo_id, cargo_ra_id]);
+    assert_eq!(user_ids, &[a_id]);
+
+    assert!(db.get_channel(rust_id, a_id).await.unwrap().is_none());
+    assert!(db.get_channel(cargo_id, a_id).await.unwrap().is_none());
+    assert!(db.get_channel(cargo_ra_id, a_id).await.unwrap().is_none());
+}
+
+test_both_dbs!(
+    test_joining_channels,
+    test_joining_channels_postgres,
+    test_joining_channels_sqlite
+);
+
+async fn test_joining_channels(db: &Arc<Database>) {
+    let owner_id = db.create_server("test").await.unwrap().0 as u32;
+
+    let user_1 = db
+        .create_user(
+            "user1@example.com",
+            false,
+            NewUserParams {
+                github_login: "user1".into(),
+                github_user_id: 5,
+                invite_count: 0,
+            },
+        )
+        .await
+        .unwrap()
+        .user_id;
+    let user_2 = db
+        .create_user(
+            "user2@example.com",
+            false,
+            NewUserParams {
+                github_login: "user2".into(),
+                github_user_id: 6,
+                invite_count: 0,
+            },
+        )
+        .await
+        .unwrap()
+        .user_id;
+
+    let channel_1 = db
+        .create_root_channel("channel_1", "1", user_1)
+        .await
+        .unwrap();
+    let room_1 = db.room_id_for_channel(channel_1).await.unwrap();
+
+    // can join a room with membership to its channel
+    let joined_room = db
+        .join_room(room_1, user_1, ConnectionId { owner_id, id: 1 })
+        .await
+        .unwrap();
+    assert_eq!(joined_room.room.participants.len(), 1);
+
+    drop(joined_room);
+    // cannot join a room without membership to its channel
+    assert!(db
+        .join_room(room_1, user_2, ConnectionId { owner_id, id: 1 })
+        .await
+        .is_err());
+}
+
+test_both_dbs!(
+    test_channel_invites,
+    test_channel_invites_postgres,
+    test_channel_invites_sqlite
+);
+
+async fn test_channel_invites(db: &Arc<Database>) {
+    db.create_server("test").await.unwrap();
+
+    let user_1 = db
+        .create_user(
+            "user1@example.com",
+            false,
+            NewUserParams {
+                github_login: "user1".into(),
+                github_user_id: 5,
+                invite_count: 0,
+            },
+        )
+        .await
+        .unwrap()
+        .user_id;
+    let user_2 = db
+        .create_user(
+            "user2@example.com",
+            false,
+            NewUserParams {
+                github_login: "user2".into(),
+                github_user_id: 6,
+                invite_count: 0,
+            },
+        )
+        .await
+        .unwrap()
+        .user_id;
+
+    let user_3 = db
+        .create_user(
+            "user3@example.com",
+            false,
+            NewUserParams {
+                github_login: "user3".into(),
+                github_user_id: 7,
+                invite_count: 0,
+            },
+        )
+        .await
+        .unwrap()
+        .user_id;
+
+    let channel_1_1 = db
+        .create_root_channel("channel_1", "1", user_1)
+        .await
+        .unwrap();
+
+    let channel_1_2 = db
+        .create_root_channel("channel_2", "2", user_1)
+        .await
+        .unwrap();
+
+    db.invite_channel_member(channel_1_1, user_2, user_1, false)
+        .await
+        .unwrap();
+    db.invite_channel_member(channel_1_2, user_2, user_1, false)
+        .await
+        .unwrap();
+    db.invite_channel_member(channel_1_1, user_3, user_1, true)
+        .await
+        .unwrap();
+
+    let user_2_invites = db
+        .get_channel_invites_for_user(user_2) // -> [channel_1_1, channel_1_2]
+        .await
+        .unwrap()
+        .into_iter()
+        .map(|channel| channel.id)
+        .collect::<Vec<_>>();
+
+    assert_eq!(user_2_invites, &[channel_1_1, channel_1_2]);
+
+    let user_3_invites = db
+        .get_channel_invites_for_user(user_3) // -> [channel_1_1]
+        .await
+        .unwrap()
+        .into_iter()
+        .map(|channel| channel.id)
+        .collect::<Vec<_>>();
+
+    assert_eq!(user_3_invites, &[channel_1_1]);
+
+    let members = db
+        .get_channel_member_details(channel_1_1, user_1)
+        .await
+        .unwrap();
+    assert_eq!(
+        members,
+        &[
+            proto::ChannelMember {
+                user_id: user_1.to_proto(),
+                kind: proto::channel_member::Kind::Member.into(),
+                admin: true,
+            },
+            proto::ChannelMember {
+                user_id: user_2.to_proto(),
+                kind: proto::channel_member::Kind::Invitee.into(),
+                admin: false,
+            },
+            proto::ChannelMember {
+                user_id: user_3.to_proto(),
+                kind: proto::channel_member::Kind::Invitee.into(),
+                admin: true,
+            },
+        ]
+    );
+
+    db.respond_to_channel_invite(channel_1_1, user_2, true)
+        .await
+        .unwrap();
+
+    let channel_1_3 = db
+        .create_channel("channel_3", Some(channel_1_1), "1", user_1)
+        .await
+        .unwrap();
+
+    let members = db
+        .get_channel_member_details(channel_1_3, user_1)
+        .await
+        .unwrap();
+    assert_eq!(
+        members,
+        &[
+            proto::ChannelMember {
+                user_id: user_1.to_proto(),
+                kind: proto::channel_member::Kind::Member.into(),
+                admin: true,
+            },
+            proto::ChannelMember {
+                user_id: user_2.to_proto(),
+                kind: proto::channel_member::Kind::AncestorMember.into(),
+                admin: false,
+            },
+        ]
+    );
+}
+
+test_both_dbs!(
+    test_channel_renames,
+    test_channel_renames_postgres,
+    test_channel_renames_sqlite
+);
+
+async fn test_channel_renames(db: &Arc<Database>) {
+    db.create_server("test").await.unwrap();
+
+    let user_1 = db
+        .create_user(
+            "user1@example.com",
+            false,
+            NewUserParams {
+                github_login: "user1".into(),
+                github_user_id: 5,
+                invite_count: 0,
+            },
+        )
+        .await
+        .unwrap()
+        .user_id;
+
+    let user_2 = db
+        .create_user(
+            "user2@example.com",
+            false,
+            NewUserParams {
+                github_login: "user2".into(),
+                github_user_id: 6,
+                invite_count: 0,
+            },
+        )
+        .await
+        .unwrap()
+        .user_id;
+
+    let zed_id = db.create_root_channel("zed", "1", user_1).await.unwrap();
+
+    db.rename_channel(zed_id, user_1, "#zed-archive")
+        .await
+        .unwrap();
+
+    let zed_archive_id = zed_id;
+
+    let (channel, _) = db
+        .get_channel(zed_archive_id, user_1)
+        .await
+        .unwrap()
+        .unwrap();
+    assert_eq!(channel.name, "zed-archive");
+
+    let non_permissioned_rename = db
+        .rename_channel(zed_archive_id, user_2, "hacked-lol")
+        .await;
+    assert!(non_permissioned_rename.is_err());
+
+    let bad_name_rename = db.rename_channel(zed_id, user_1, "#").await;
+    assert!(bad_name_rename.is_err())
+}
+
+test_both_dbs!(
+    test_channels_moving,
+    test_channels_moving_postgres,
+    test_channels_moving_sqlite
+);
+
+async fn test_channels_moving(db: &Arc<Database>) {
+    let a_id = db
+        .create_user(
+            "user1@example.com",
+            false,
+            NewUserParams {
+                github_login: "user1".into(),
+                github_user_id: 5,
+                invite_count: 0,
+            },
+        )
+        .await
+        .unwrap()
+        .user_id;
+
+    let zed_id = db.create_root_channel("zed", "1", a_id).await.unwrap();
+
+    let crdb_id = db
+        .create_channel("crdb", Some(zed_id), "2", a_id)
+        .await
+        .unwrap();
+
+    let gpui2_id = db
+        .create_channel("gpui2", Some(zed_id), "3", a_id)
+        .await
+        .unwrap();
+
+    let livestreaming_id = db
+        .create_channel("livestreaming", Some(crdb_id), "4", a_id)
+        .await
+        .unwrap();
+
+    let livestreaming_dag_id = db
+        .create_channel("livestreaming_dag", Some(livestreaming_id), "5", a_id)
+        .await
+        .unwrap();
+
+    // ========================================================================
+    // sanity check
+    // Initial DAG:
+    //     /- gpui2
+    // zed -- crdb - livestreaming - livestreaming_dag
+    let result = db.get_channels_for_user(a_id).await.unwrap();
+    assert_dag(
+        result.channels,
+        &[
+            (zed_id, None),
+            (crdb_id, Some(zed_id)),
+            (gpui2_id, Some(zed_id)),
+            (livestreaming_id, Some(crdb_id)),
+            (livestreaming_dag_id, Some(livestreaming_id)),
+        ],
+    );
+
+    // Attempt to make a cycle
+    assert!(db
+        .link_channel(a_id, zed_id, livestreaming_id)
+        .await
+        .is_err());
+
+    // ========================================================================
+    // Make a link
+    db.link_channel(a_id, livestreaming_id, zed_id)
+        .await
+        .unwrap();
+
+    // DAG is now:
+    //     /- gpui2
+    // zed -- crdb - livestreaming - livestreaming_dag
+    //    \---------/
+    let result = db.get_channels_for_user(a_id).await.unwrap();
+    assert_dag(result.channels, &[
+        (zed_id, None),
+        (crdb_id, Some(zed_id)),
+        (gpui2_id, Some(zed_id)),
+        (livestreaming_id, Some(zed_id)),
+        (livestreaming_id, Some(crdb_id)),
+        (livestreaming_dag_id, Some(livestreaming_id)),
+    ]);
+
+    // ========================================================================
+    // Create a new channel below a channel with multiple parents
+    let livestreaming_dag_sub_id = db
+        .create_channel(
+            "livestreaming_dag_sub",
+            Some(livestreaming_dag_id),
+            "6",
+            a_id,
+        )
+        .await
+        .unwrap();
+
+    // DAG is now:
+    //     /- gpui2
+    // zed -- crdb - livestreaming - livestreaming_dag - livestreaming_dag_sub_id
+    //    \---------/
+    let result = db.get_channels_for_user(a_id).await.unwrap();
+    assert_dag(result.channels, &[
+        (zed_id, None),
+        (crdb_id, Some(zed_id)),
+        (gpui2_id, Some(zed_id)),
+        (livestreaming_id, Some(zed_id)),
+        (livestreaming_id, Some(crdb_id)),
+        (livestreaming_dag_id, Some(livestreaming_id)),
+        (livestreaming_dag_sub_id, Some(livestreaming_dag_id)),
+    ]);
+
+    // ========================================================================
+    // Test a complex DAG by making another link
+    let returned_channels = db
+        .link_channel(a_id, livestreaming_dag_sub_id, livestreaming_id)
+        .await
+        .unwrap();
+
+    // DAG is now:
+    //    /- gpui2                /---------------------\
+    // zed - crdb - livestreaming - livestreaming_dag - livestreaming_dag_sub_id
+    //    \--------/
+
+    // make sure we're getting just the new link
+    // Not using the assert_dag helper because we want to make sure we're returning the full data
+    pretty_assertions::assert_eq!(
+        returned_channels,
+        vec![Channel {
+            id: livestreaming_dag_sub_id,
+            name: "livestreaming_dag_sub".to_string(),
+            parent_id: Some(livestreaming_id),
+        }]
+    );
+
+    let result = db.get_channels_for_user(a_id).await.unwrap();
+    assert_dag(result.channels, &[
+        (zed_id, None),
+        (crdb_id, Some(zed_id)),
+        (gpui2_id, Some(zed_id)),
+        (livestreaming_id, Some(zed_id)),
+        (livestreaming_id, Some(crdb_id)),
+        (livestreaming_dag_id, Some(livestreaming_id)),
+        (livestreaming_dag_sub_id, Some(livestreaming_id)),
+        (livestreaming_dag_sub_id, Some(livestreaming_dag_id)),
+    ]);
+
+    // ========================================================================
+    // Test a complex DAG by making another link
+    let returned_channels = db
+        .link_channel(a_id, livestreaming_id, gpui2_id)
+        .await
+        .unwrap();
+
+    // DAG is now:
+    //    /- gpui2 -\             /---------------------\
+    // zed - crdb -- livestreaming - livestreaming_dag - livestreaming_dag_sub_id
+    //    \---------/
+
+    // Make sure that we're correctly getting the full sub-dag
+    pretty_assertions::assert_eq!(
+        returned_channels,
+        vec![
+            Channel {
+                id: livestreaming_id,
+                name: "livestreaming".to_string(),
+                parent_id: Some(gpui2_id),
+            },
+            Channel {
+                id: livestreaming_dag_id,
+                name: "livestreaming_dag".to_string(),
+                parent_id: Some(livestreaming_id),
+            },
+            Channel {
+                id: livestreaming_dag_sub_id,
+                name: "livestreaming_dag_sub".to_string(),
+                parent_id: Some(livestreaming_id),
+            },
+            Channel {
+                id: livestreaming_dag_sub_id,
+                name: "livestreaming_dag_sub".to_string(),
+                parent_id: Some(livestreaming_dag_id),
+            }
+        ]
+    );
+
+    let result = db.get_channels_for_user(a_id).await.unwrap();
+    assert_dag(result.channels, &[
+        (zed_id, None),
+        (crdb_id, Some(zed_id)),
+        (gpui2_id, Some(zed_id)),
+        (livestreaming_id, Some(gpui2_id)),
+        (livestreaming_id, Some(zed_id)),
+        (livestreaming_id, Some(crdb_id)),
+        (livestreaming_dag_id, Some(livestreaming_id)),
+        (livestreaming_dag_sub_id, Some(livestreaming_id)),
+        (livestreaming_dag_sub_id, Some(livestreaming_dag_id)),
+    ]);
+
+    // ========================================================================
+    // Test unlinking in a complex DAG by removing the inner link
+    db
+        .unlink_channel(
+            a_id,
+            livestreaming_dag_sub_id,
+            Some(livestreaming_id),
+        )
+        .await
+        .unwrap();
+
+    // DAG is now:
+    //    /- gpui2 -\
+    // zed - crdb -- livestreaming - livestreaming_dag - livestreaming_dag_sub
+    //    \---------/
+
+    let result = db.get_channels_for_user(a_id).await.unwrap();
+    assert_dag(result.channels, &[
+        (zed_id, None),
+        (crdb_id, Some(zed_id)),
+        (gpui2_id, Some(zed_id)),
+        (livestreaming_id, Some(gpui2_id)),
+        (livestreaming_id, Some(zed_id)),
+        (livestreaming_id, Some(crdb_id)),
+        (livestreaming_dag_id, Some(livestreaming_id)),
+        (livestreaming_dag_sub_id, Some(livestreaming_dag_id)),
+    ]);
+
+    // ========================================================================
+    // Test unlinking in a complex DAG by removing the inner link
+    db.unlink_channel(a_id, livestreaming_id, Some(gpui2_id))
+        .await
+        .unwrap();
+
+    // DAG is now:
+    //    /- gpui2
+    // zed - crdb -- livestreaming - livestreaming_dag - livestreaming_dag_sub
+    //    \---------/
+    let result = db.get_channels_for_user(a_id).await.unwrap();
+    assert_dag(result.channels, &[
+        (zed_id, None),
+        (crdb_id, Some(zed_id)),
+        (gpui2_id, Some(zed_id)),
+        (livestreaming_id, Some(zed_id)),
+        (livestreaming_id, Some(crdb_id)),
+        (livestreaming_dag_id, Some(livestreaming_id)),
+        (livestreaming_dag_sub_id, Some(livestreaming_dag_id)),
+    ]);
+
+    // ========================================================================
+    // Test moving DAG nodes by moving livestreaming to be below gpui2
+    db.move_channel(a_id, livestreaming_id, Some(crdb_id), gpui2_id)
+        .await
+        .unwrap();
+
+    // DAG is now:
+    //    /- gpui2 -- livestreaming - livestreaming_dag - livestreaming_dag_sub
+    // zed - crdb    /
+    //    \---------/
+    let result = db.get_channels_for_user(a_id).await.unwrap();
+    assert_dag(result.channels, &[
+        (zed_id, None),
+        (crdb_id, Some(zed_id)),
+        (gpui2_id, Some(zed_id)),
+        (livestreaming_id, Some(zed_id)),
+        (livestreaming_id, Some(gpui2_id)),
+        (livestreaming_dag_id, Some(livestreaming_id)),
+        (livestreaming_dag_sub_id, Some(livestreaming_dag_id)),
+    ]);
+
+    // ========================================================================
+    // Deleting a channel should not delete children that still have other parents
+    db.delete_channel(gpui2_id, a_id).await.unwrap();
+
+    // DAG is now:
+    // zed - crdb
+    //    \- livestreaming - livestreaming_dag - livestreaming_dag_sub
+    let result = db.get_channels_for_user(a_id).await.unwrap();
+    assert_dag(result.channels, &[
+        (zed_id, None),
+        (crdb_id, Some(zed_id)),
+        (livestreaming_id, Some(zed_id)),
+        (livestreaming_dag_id, Some(livestreaming_id)),
+        (livestreaming_dag_sub_id, Some(livestreaming_dag_id)),
+    ]);
+
+    // ========================================================================
+    // Unlinking a channel from it's parent should automatically promote it to a root channel
+    db.unlink_channel(a_id, crdb_id, Some(zed_id))
+        .await
+        .unwrap();
+
+    // DAG is now:
+    // crdb
+    // zed
+    //    \- livestreaming - livestreaming_dag - livestreaming_dag_sub
+
+    let result = db.get_channels_for_user(a_id).await.unwrap();
+    assert_dag(result.channels, &[
+        (zed_id, None),
+        (crdb_id, None),
+        (livestreaming_id, Some(zed_id)),
+        (livestreaming_dag_id, Some(livestreaming_id)),
+        (livestreaming_dag_sub_id, Some(livestreaming_dag_id)),
+    ]);
+
+    // ========================================================================
+    // Unlinking a root channel should not have any effect
+    db.unlink_channel(a_id, crdb_id, None)
+        .await
+        .unwrap();
+
+    // DAG is now:
+    // crdb
+    // zed
+    //    \- livestreaming - livestreaming_dag - livestreaming_dag_sub
+    //
+    let result = db.get_channels_for_user(a_id).await.unwrap();
+    assert_dag(result.channels, &[
+        (zed_id, None),
+        (crdb_id, None),
+        (livestreaming_id, Some(zed_id)),
+        (livestreaming_dag_id, Some(livestreaming_id)),
+        (livestreaming_dag_sub_id, Some(livestreaming_dag_id)),
+    ]);
+
+    // ========================================================================
+    // You should be able to move a root channel into a non-root channel
+    db.move_channel(a_id, crdb_id, None, zed_id)
+        .await
+        .unwrap();
+
+    // DAG is now:
+    // zed - crdb
+    //    \- livestreaming - livestreaming_dag - livestreaming_dag_sub
+
+    let result = db.get_channels_for_user(a_id).await.unwrap();
+    assert_dag(result.channels, &[
+        (zed_id, None),
+        (crdb_id, Some(zed_id)),
+        (livestreaming_id, Some(zed_id)),
+        (livestreaming_dag_id, Some(livestreaming_id)),
+        (livestreaming_dag_sub_id, Some(livestreaming_dag_id)),
+    ]);
+
+
+    // ========================================================================
+    // Moving a non-root channel without a parent id should be the equivalent of a link operation
+    db.move_channel(a_id, livestreaming_id, None, crdb_id)
+        .await
+        .unwrap();
+
+    // DAG is now:
+    // zed - crdb - livestreaming - livestreaming_dag - livestreaming_dag_sub
+    //    \--------/
+
+    let result = db.get_channels_for_user(a_id).await.unwrap();
+    assert_dag(result.channels, &[
+        (zed_id, None),
+        (crdb_id, Some(zed_id)),
+        (livestreaming_id, Some(zed_id)),
+        (livestreaming_id, Some(crdb_id)),
+        (livestreaming_dag_id, Some(livestreaming_id)),
+        (livestreaming_dag_sub_id, Some(livestreaming_dag_id)),
+    ]);
+
+    // ========================================================================
+    // Deleting a parent of a DAG should delete the whole DAG:
+    db.delete_channel(zed_id, a_id).await.unwrap();
+    let result = db.get_channels_for_user(a_id).await.unwrap();
+    assert!(
+        result.channels.is_empty()
+    )
+}
+
+#[track_caller]
+fn assert_dag(actual: Vec<Channel>, expected: &[(ChannelId, Option<ChannelId>)]) {
+    let actual = actual
+        .iter()
+        .map(|channel| (channel.id, channel.parent_id))
+        .collect::<Vec<_>>();
+
+    pretty_assertions::assert_eq!(actual, expected)
+}

crates/collab/src/db/tests/db_tests.rs

@@ -877,458 +877,6 @@ async fn test_invite_codes() {
     assert!(db.has_contact(user5, user1).await.unwrap());
 }
 
-test_both_dbs!(test_channels, test_channels_postgres, test_channels_sqlite);
-
-async fn test_channels(db: &Arc<Database>) {
-    let a_id = db
-        .create_user(
-            "user1@example.com",
-            false,
-            NewUserParams {
-                github_login: "user1".into(),
-                github_user_id: 5,
-                invite_count: 0,
-            },
-        )
-        .await
-        .unwrap()
-        .user_id;
-
-    let b_id = db
-        .create_user(
-            "user2@example.com",
-            false,
-            NewUserParams {
-                github_login: "user2".into(),
-                github_user_id: 6,
-                invite_count: 0,
-            },
-        )
-        .await
-        .unwrap()
-        .user_id;
-
-    let zed_id = db.create_root_channel("zed", "1", a_id).await.unwrap();
-
-    // Make sure that people cannot read channels they haven't been invited to
-    assert!(db.get_channel(zed_id, b_id).await.unwrap().is_none());
-
-    db.invite_channel_member(zed_id, b_id, a_id, false)
-        .await
-        .unwrap();
-
-    db.respond_to_channel_invite(zed_id, b_id, true)
-        .await
-        .unwrap();
-
-    let crdb_id = db
-        .create_channel("crdb", Some(zed_id), "2", a_id)
-        .await
-        .unwrap();
-    let livestreaming_id = db
-        .create_channel("livestreaming", Some(zed_id), "3", a_id)
-        .await
-        .unwrap();
-    let replace_id = db
-        .create_channel("replace", Some(zed_id), "4", a_id)
-        .await
-        .unwrap();
-
-    let mut members = db.get_channel_members(replace_id).await.unwrap();
-    members.sort();
-    assert_eq!(members, &[a_id, b_id]);
-
-    let rust_id = db.create_root_channel("rust", "5", a_id).await.unwrap();
-    let cargo_id = db
-        .create_channel("cargo", Some(rust_id), "6", a_id)
-        .await
-        .unwrap();
-
-    let cargo_ra_id = db
-        .create_channel("cargo-ra", Some(cargo_id), "7", a_id)
-        .await
-        .unwrap();
-
-    let result = db.get_channels_for_user(a_id).await.unwrap();
-    assert_eq!(
-        result.channels,
-        vec![
-            Channel {
-                id: zed_id,
-                name: "zed".to_string(),
-                parent_id: None,
-            },
-            Channel {
-                id: crdb_id,
-                name: "crdb".to_string(),
-                parent_id: Some(zed_id),
-            },
-            Channel {
-                id: livestreaming_id,
-                name: "livestreaming".to_string(),
-                parent_id: Some(zed_id),
-            },
-            Channel {
-                id: replace_id,
-                name: "replace".to_string(),
-                parent_id: Some(zed_id),
-            },
-            Channel {
-                id: rust_id,
-                name: "rust".to_string(),
-                parent_id: None,
-            },
-            Channel {
-                id: cargo_id,
-                name: "cargo".to_string(),
-                parent_id: Some(rust_id),
-            },
-            Channel {
-                id: cargo_ra_id,
-                name: "cargo-ra".to_string(),
-                parent_id: Some(cargo_id),
-            }
-        ]
-    );
-
-    let result = db.get_channels_for_user(b_id).await.unwrap();
-    assert_eq!(
-        result.channels,
-        vec![
-            Channel {
-                id: zed_id,
-                name: "zed".to_string(),
-                parent_id: None,
-            },
-            Channel {
-                id: crdb_id,
-                name: "crdb".to_string(),
-                parent_id: Some(zed_id),
-            },
-            Channel {
-                id: livestreaming_id,
-                name: "livestreaming".to_string(),
-                parent_id: Some(zed_id),
-            },
-            Channel {
-                id: replace_id,
-                name: "replace".to_string(),
-                parent_id: Some(zed_id),
-            },
-        ]
-    );
-
-    // Update member permissions
-    let set_subchannel_admin = db.set_channel_member_admin(crdb_id, a_id, b_id, true).await;
-    assert!(set_subchannel_admin.is_err());
-    let set_channel_admin = db.set_channel_member_admin(zed_id, a_id, b_id, true).await;
-    assert!(set_channel_admin.is_ok());
-
-    let result = db.get_channels_for_user(b_id).await.unwrap();
-    assert_eq!(
-        result.channels,
-        vec![
-            Channel {
-                id: zed_id,
-                name: "zed".to_string(),
-                parent_id: None,
-            },
-            Channel {
-                id: crdb_id,
-                name: "crdb".to_string(),
-                parent_id: Some(zed_id),
-            },
-            Channel {
-                id: livestreaming_id,
-                name: "livestreaming".to_string(),
-                parent_id: Some(zed_id),
-            },
-            Channel {
-                id: replace_id,
-                name: "replace".to_string(),
-                parent_id: Some(zed_id),
-            },
-        ]
-    );
-
-    // Remove a single channel
-    db.remove_channel(crdb_id, a_id).await.unwrap();
-    assert!(db.get_channel(crdb_id, a_id).await.unwrap().is_none());
-
-    // Remove a channel tree
-    let (mut channel_ids, user_ids) = db.remove_channel(rust_id, a_id).await.unwrap();
-    channel_ids.sort();
-    assert_eq!(channel_ids, &[rust_id, cargo_id, cargo_ra_id]);
-    assert_eq!(user_ids, &[a_id]);
-
-    assert!(db.get_channel(rust_id, a_id).await.unwrap().is_none());
-    assert!(db.get_channel(cargo_id, a_id).await.unwrap().is_none());
-    assert!(db.get_channel(cargo_ra_id, a_id).await.unwrap().is_none());
-}
-
-test_both_dbs!(
-    test_joining_channels,
-    test_joining_channels_postgres,
-    test_joining_channels_sqlite
-);
-
-async fn test_joining_channels(db: &Arc<Database>) {
-    let owner_id = db.create_server("test").await.unwrap().0 as u32;
-
-    let user_1 = db
-        .create_user(
-            "user1@example.com",
-            false,
-            NewUserParams {
-                github_login: "user1".into(),
-                github_user_id: 5,
-                invite_count: 0,
-            },
-        )
-        .await
-        .unwrap()
-        .user_id;
-    let user_2 = db
-        .create_user(
-            "user2@example.com",
-            false,
-            NewUserParams {
-                github_login: "user2".into(),
-                github_user_id: 6,
-                invite_count: 0,
-            },
-        )
-        .await
-        .unwrap()
-        .user_id;
-
-    let channel_1 = db
-        .create_root_channel("channel_1", "1", user_1)
-        .await
-        .unwrap();
-    let room_1 = db.room_id_for_channel(channel_1).await.unwrap();
-
-    // can join a room with membership to its channel
-    let joined_room = db
-        .join_room(room_1, user_1, ConnectionId { owner_id, id: 1 })
-        .await
-        .unwrap();
-    assert_eq!(joined_room.room.participants.len(), 1);
-
-    drop(joined_room);
-    // cannot join a room without membership to its channel
-    assert!(db
-        .join_room(room_1, user_2, ConnectionId { owner_id, id: 1 })
-        .await
-        .is_err());
-}
-
-test_both_dbs!(
-    test_channel_invites,
-    test_channel_invites_postgres,
-    test_channel_invites_sqlite
-);
-
-async fn test_channel_invites(db: &Arc<Database>) {
-    db.create_server("test").await.unwrap();
-
-    let user_1 = db
-        .create_user(
-            "user1@example.com",
-            false,
-            NewUserParams {
-                github_login: "user1".into(),
-                github_user_id: 5,
-                invite_count: 0,
-            },
-        )
-        .await
-        .unwrap()
-        .user_id;
-    let user_2 = db
-        .create_user(
-            "user2@example.com",
-            false,
-            NewUserParams {
-                github_login: "user2".into(),
-                github_user_id: 6,
-                invite_count: 0,
-            },
-        )
-        .await
-        .unwrap()
-        .user_id;
-
-    let user_3 = db
-        .create_user(
-            "user3@example.com",
-            false,
-            NewUserParams {
-                github_login: "user3".into(),
-                github_user_id: 7,
-                invite_count: 0,
-            },
-        )
-        .await
-        .unwrap()
-        .user_id;
-
-    let channel_1_1 = db
-        .create_root_channel("channel_1", "1", user_1)
-        .await
-        .unwrap();
-
-    let channel_1_2 = db
-        .create_root_channel("channel_2", "2", user_1)
-        .await
-        .unwrap();
-
-    db.invite_channel_member(channel_1_1, user_2, user_1, false)
-        .await
-        .unwrap();
-    db.invite_channel_member(channel_1_2, user_2, user_1, false)
-        .await
-        .unwrap();
-    db.invite_channel_member(channel_1_1, user_3, user_1, true)
-        .await
-        .unwrap();
-
-    let user_2_invites = db
-        .get_channel_invites_for_user(user_2) // -> [channel_1_1, channel_1_2]
-        .await
-        .unwrap()
-        .into_iter()
-        .map(|channel| channel.id)
-        .collect::<Vec<_>>();
-
-    assert_eq!(user_2_invites, &[channel_1_1, channel_1_2]);
-
-    let user_3_invites = db
-        .get_channel_invites_for_user(user_3) // -> [channel_1_1]
-        .await
-        .unwrap()
-        .into_iter()
-        .map(|channel| channel.id)
-        .collect::<Vec<_>>();
-
-    assert_eq!(user_3_invites, &[channel_1_1]);
-
-    let members = db
-        .get_channel_member_details(channel_1_1, user_1)
-        .await
-        .unwrap();
-    assert_eq!(
-        members,
-        &[
-            proto::ChannelMember {
-                user_id: user_1.to_proto(),
-                kind: proto::channel_member::Kind::Member.into(),
-                admin: true,
-            },
-            proto::ChannelMember {
-                user_id: user_2.to_proto(),
-                kind: proto::channel_member::Kind::Invitee.into(),
-                admin: false,
-            },
-            proto::ChannelMember {
-                user_id: user_3.to_proto(),
-                kind: proto::channel_member::Kind::Invitee.into(),
-                admin: true,
-            },
-        ]
-    );
-
-    db.respond_to_channel_invite(channel_1_1, user_2, true)
-        .await
-        .unwrap();
-
-    let channel_1_3 = db
-        .create_channel("channel_3", Some(channel_1_1), "1", user_1)
-        .await
-        .unwrap();
-
-    let members = db
-        .get_channel_member_details(channel_1_3, user_1)
-        .await
-        .unwrap();
-    assert_eq!(
-        members,
-        &[
-            proto::ChannelMember {
-                user_id: user_1.to_proto(),
-                kind: proto::channel_member::Kind::Member.into(),
-                admin: true,
-            },
-            proto::ChannelMember {
-                user_id: user_2.to_proto(),
-                kind: proto::channel_member::Kind::AncestorMember.into(),
-                admin: false,
-            },
-        ]
-    );
-}
-
-test_both_dbs!(
-    test_channel_renames,
-    test_channel_renames_postgres,
-    test_channel_renames_sqlite
-);
-
-async fn test_channel_renames(db: &Arc<Database>) {
-    db.create_server("test").await.unwrap();
-
-    let user_1 = db
-        .create_user(
-            "user1@example.com",
-            false,
-            NewUserParams {
-                github_login: "user1".into(),
-                github_user_id: 5,
-                invite_count: 0,
-            },
-        )
-        .await
-        .unwrap()
-        .user_id;
-
-    let user_2 = db
-        .create_user(
-            "user2@example.com",
-            false,
-            NewUserParams {
-                github_login: "user2".into(),
-                github_user_id: 6,
-                invite_count: 0,
-            },
-        )
-        .await
-        .unwrap()
-        .user_id;
-
-    let zed_id = db.create_root_channel("zed", "1", user_1).await.unwrap();
-
-    db.rename_channel(zed_id, user_1, "#zed-archive")
-        .await
-        .unwrap();
-
-    let zed_archive_id = zed_id;
-
-    let (channel, _) = db
-        .get_channel(zed_archive_id, user_1)
-        .await
-        .unwrap()
-        .unwrap();
-    assert_eq!(channel.name, "zed-archive");
-
-    let non_permissioned_rename = db
-        .rename_channel(zed_archive_id, user_2, "hacked-lol")
-        .await;
-    assert!(non_permissioned_rename.is_err());
-
-    let bad_name_rename = db.rename_channel(zed_id, user_1, "#").await;
-    assert!(bad_name_rename.is_err())
-}
-
 #[gpui::test]
 async fn test_multiple_signup_overwrite() {
     let test_db = TestDb::postgres(build_background_executor());

crates/collab/src/rpc.rs

@@ -2,7 +2,10 @@ mod connection_pool;
 
 use crate::{
     auth,
-    db::{self, ChannelId, ChannelsForUser, Database, ProjectId, RoomId, ServerId, User, UserId},
+    db::{
+        self, Channel, ChannelId, ChannelsForUser, Database, ProjectId, RoomId, ServerId, User,
+        UserId,
+    },
     executor::Executor,
     AppState, Result,
 };
@@ -243,7 +246,7 @@ impl Server {
             .add_request_handler(remove_contact)
             .add_request_handler(respond_to_contact_request)
             .add_request_handler(create_channel)
-            .add_request_handler(remove_channel)
+            .add_request_handler(delete_channel)
             .add_request_handler(invite_channel_member)
             .add_request_handler(remove_channel_member)
             .add_request_handler(set_channel_member_admin)
@@ -255,6 +258,9 @@ impl Server {
             .add_request_handler(get_channel_members)
             .add_request_handler(respond_to_channel_invite)
             .add_request_handler(join_channel)
+            .add_request_handler(link_channel)
+            .add_request_handler(unlink_channel)
+            .add_request_handler(move_channel)
             .add_request_handler(follow)
             .add_message_handler(unfollow)
             .add_message_handler(update_followers)
@@ -2227,23 +2233,23 @@ async fn create_channel(
     Ok(())
 }
 
-async fn remove_channel(
-    request: proto::RemoveChannel,
-    response: Response<proto::RemoveChannel>,
+async fn delete_channel(
+    request: proto::DeleteChannel,
+    response: Response<proto::DeleteChannel>,
     session: Session,
 ) -> Result<()> {
     let db = session.db().await;
 
     let channel_id = request.channel_id;
     let (removed_channels, member_ids) = db
-        .remove_channel(ChannelId::from_proto(channel_id), session.user_id)
+        .delete_channel(ChannelId::from_proto(channel_id), session.user_id)
         .await?;
     response.send(proto::Ack {})?;
 
     // Notify members of removed channels
     let mut update = proto::UpdateChannels::default();
     update
-        .remove_channels
+        .delete_channels
         .extend(removed_channels.into_iter().map(|id| id.to_proto()));
 
     let connection_pool = session.connection_pool().await;
@@ -2303,7 +2309,7 @@ async fn remove_channel_member(
         .await?;
 
     let mut update = proto::UpdateChannels::default();
-    update.remove_channels.push(channel_id.to_proto());
+    update.delete_channels.push(channel_id.to_proto());
 
     for connection_id in session
         .connection_pool()
@@ -2387,6 +2393,126 @@ async fn rename_channel(
     Ok(())
 }
 
+async fn link_channel(
+    request: proto::LinkChannel,
+    response: Response<proto::LinkChannel>,
+    session: Session,
+) -> Result<()> {
+    let db = session.db().await;
+    let channel_id = ChannelId::from_proto(request.channel_id);
+    let to = ChannelId::from_proto(request.to);
+    let channels_to_send = db.link_channel(session.user_id, channel_id, to).await?;
+
+    let members = db.get_channel_members(to).await?;
+    let connection_pool = session.connection_pool().await;
+    let update = proto::UpdateChannels {
+        channels: channels_to_send
+            .into_iter()
+            .map(|channel| proto::Channel {
+                id: channel.id.to_proto(),
+                name: channel.name,
+                parent_id: channel.parent_id.map(ChannelId::to_proto),
+            })
+            .collect(),
+        ..Default::default()
+    };
+    for member_id in members {
+        for connection_id in connection_pool.user_connection_ids(member_id) {
+            session.peer.send(connection_id, update.clone())?;
+        }
+    }
+
+    response.send(Ack {})?;
+
+    Ok(())
+}
+
+async fn unlink_channel(
+    request: proto::UnlinkChannel,
+    response: Response<proto::UnlinkChannel>,
+    session: Session,
+) -> Result<()> {
+    let db = session.db().await;
+    let channel_id = ChannelId::from_proto(request.channel_id);
+    let from = request.from.map(ChannelId::from_proto);
+    db.unlink_channel(session.user_id, channel_id, from).await?;
+
+    if let Some(from_parent) = from {
+        let members = db.get_channel_members(from_parent).await?;
+        let update = proto::UpdateChannels {
+            delete_channel_edge: vec![proto::ChannelEdge {
+                channel_id: channel_id.to_proto(),
+                parent_id: from_parent.to_proto(),
+            }],
+            ..Default::default()
+        };
+        let connection_pool = session.connection_pool().await;
+        for member_id in members {
+            for connection_id in connection_pool.user_connection_ids(member_id) {
+                session.peer.send(connection_id, update.clone())?;
+            }
+        }
+    }
+
+    response.send(Ack {})?;
+
+    Ok(())
+}
+
+async fn move_channel(
+    request: proto::MoveChannel,
+    response: Response<proto::MoveChannel>,
+    session: Session,
+) -> Result<()> {
+    let db = session.db().await;
+    let channel_id = ChannelId::from_proto(request.channel_id);
+    let from_parent = request.from.map(ChannelId::from_proto);
+    let to = ChannelId::from_proto(request.to);
+    let channels_to_send: Vec<Channel> = db
+        .move_channel(session.user_id, channel_id, from_parent, to)
+        .await?;
+
+    if let Some(from_parent) = from_parent {
+        let members = db.get_channel_members(from_parent).await?;
+        let update = proto::UpdateChannels {
+            delete_channel_edge: vec![proto::ChannelEdge {
+                channel_id: channel_id.to_proto(),
+                parent_id: from_parent.to_proto(),
+            }],
+            ..Default::default()
+        };
+        let connection_pool = session.connection_pool().await;
+        for member_id in members {
+            for connection_id in connection_pool.user_connection_ids(member_id) {
+                session.peer.send(connection_id, update.clone())?;
+            }
+        }
+    }
+
+    let members = db.get_channel_members(to).await?;
+    let connection_pool = session.connection_pool().await;
+    let update = proto::UpdateChannels {
+        channels: channels_to_send
+            .into_iter()
+            .map(|channel| proto::Channel {
+                id: channel.id.to_proto(),
+                name: channel.name,
+                parent_id: channel.parent_id.map(ChannelId::to_proto),
+            })
+            .collect(),
+        ..Default::default()
+    };
+    for member_id in members {
+        for connection_id in connection_pool.user_connection_ids(member_id) {
+            session.peer.send(connection_id, update.clone())?;
+        }
+    }
+
+    response.send(Ack {})?;
+
+    Ok(())
+}
+
 async fn get_channel_members(
     request: proto::GetChannelMembers,
     response: Response<proto::GetChannelMembers>,

crates/collab/src/tests/channel_tests.rs

@@ -874,6 +874,143 @@ async fn test_lost_channel_creation(
     );
 }
 
+#[gpui::test]
+async fn test_channel_moving(deterministic: Arc<Deterministic>, cx_a: &mut TestAppContext) {
+    deterministic.forbid_parking();
+    let mut server = TestServer::start(&deterministic).await;
+    let client_a = server.create_client(cx_a, "user_a").await;
+
+    let channel_a_id = client_a
+        .channel_store()
+        .update(cx_a, |channel_store, cx| {
+            channel_store.create_channel("channel-a", None, cx)
+        })
+        .await
+        .unwrap();
+    let channel_b_id = client_a
+        .channel_store()
+        .update(cx_a, |channel_store, cx| {
+            channel_store.create_channel("channel-b", Some(channel_a_id), cx)
+        })
+        .await
+        .unwrap();
+    let channel_c_id = client_a
+        .channel_store()
+        .update(cx_a, |channel_store, cx| {
+            channel_store.create_channel("channel-c", Some(channel_b_id), cx)
+        })
+        .await
+        .unwrap();
+
+    // Current shape:
+    // a - b - c
+    deterministic.run_until_parked();
+    assert_channels(
+        client_a.channel_store(),
+        cx_a,
+        &[
+            ExpectedChannel {
+                id: channel_a_id,
+                name: "channel-a".to_string(),
+                depth: 0,
+                user_is_admin: true,
+            },
+            ExpectedChannel {
+                id: channel_b_id,
+                name: "channel-b".to_string(),
+                depth: 1,
+                user_is_admin: true,
+            },
+            ExpectedChannel {
+                id: channel_c_id,
+                name: "channel-c".to_string(),
+                depth: 2,
+                user_is_admin: true,
+            },
+        ],
+    );
+
+    client_a
+        .channel_store()
+        .update(cx_a, |channel_store, cx| {
+            channel_store.move_channel(channel_c_id, Some(channel_b_id), channel_a_id, cx)
+        })
+        .await
+        .unwrap();
+
+    // Current shape:
+    //   /- c
+    // a -- b
+    deterministic.run_until_parked();
+    assert_channels(
+        client_a.channel_store(),
+        cx_a,
+        &[
+            ExpectedChannel {
+                id: channel_a_id,
+                name: "channel-a".to_string(),
+                depth: 0,
+                user_is_admin: true,
+            },
+            ExpectedChannel {
+                id: channel_b_id,
+                name: "channel-b".to_string(),
+                depth: 1,
+                user_is_admin: true,
+            },
+            ExpectedChannel {
+                id: channel_c_id,
+                name: "channel-c".to_string(),
+                depth: 1,
+                user_is_admin: true,
+            },
+        ],
+    );
+
+    client_a
+        .channel_store()
+        .update(cx_a, |channel_store, cx| {
+            channel_store.link_channel(channel_c_id, channel_b_id, cx)
+        })
+        .await
+        .unwrap();
+
+    // Current shape:
+    //   /------\
+    // a -- b -- c
+    deterministic.run_until_parked();
+    assert_channels(
+        client_a.channel_store(),
+        cx_a,
+        &[
+            ExpectedChannel {
+                id: channel_a_id,
+                name: "channel-a".to_string(),
+                depth: 0,
+                user_is_admin: true,
+            },
+            ExpectedChannel {
+                id: channel_b_id,
+                name: "channel-b".to_string(),
+                depth: 1,
+                user_is_admin: true,
+            },
+            ExpectedChannel {
+                id: channel_c_id,
+                name: "channel-c".to_string(),
+                depth: 2,
+                user_is_admin: true,
+            },
+            ExpectedChannel {
+                id: channel_c_id,
+                name: "channel-c".to_string(),
+                depth: 1,
+                user_is_admin: true,
+            },
+        ],
+    );
+}
+
 #[derive(Debug, PartialEq)]
 struct ExpectedChannel {
     depth: usize,
@@ -920,5 +1057,5 @@ fn assert_channels(
             })
             .collect::<Vec<_>>()
     });
-    assert_eq!(actual, expected_channels);
+    pretty_assertions::assert_eq!(actual, expected_channels);
 }

crates/collab_ui/src/collab_panel.rs

@@ -4,7 +4,7 @@ mod panel_settings;
 
 use anyhow::Result;
 use call::ActiveCall;
-use channel::{Channel, ChannelEvent, ChannelId, ChannelStore};
+use channel::{Channel, ChannelEvent, ChannelId, ChannelPath, ChannelStore};
 use client::{proto::PeerId, Client, Contact, User, UserStore};
 use context_menu::{ContextMenu, ContextMenuItem};
 use db::kvp::KEY_VALUE_STORE;
@@ -35,7 +35,7 @@ use panel_settings::{CollaborationPanelDockPosition, CollaborationPanelSettings}
 use project::{Fs, Project};
 use serde_derive::{Deserialize, Serialize};
 use settings::SettingsStore;
-use std::{borrow::Cow, mem, sync::Arc};
+use std::{borrow::Cow, hash::Hash, mem, sync::Arc};
 use theme::{components::ComponentExt, IconButton};
 use util::{iife, ResultExt, TryFutureExt};
 use workspace::{
@@ -54,37 +54,59 @@ use self::contact_finder::ContactFinder;
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
 struct RemoveChannel {
-    channel_id: u64,
+    channel_id: ChannelId,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
 struct ToggleCollapse {
-    channel_id: u64,
+    location: ChannelLocation<'static>,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
 struct NewChannel {
-    channel_id: u64,
+    location: ChannelLocation<'static>,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
 struct InviteMembers {
-    channel_id: u64,
+    channel_id: ChannelId,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
 struct ManageMembers {
-    channel_id: u64,
+    channel_id: ChannelId,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
 struct RenameChannel {
-    channel_id: u64,
+    location: ChannelLocation<'static>,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
 struct OpenChannelBuffer {
-    channel_id: u64,
+    channel_id: ChannelId,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
+struct LinkChannel {
+    channel_id: ChannelId,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
+struct MoveChannel {
+    channel_id: ChannelId,
+    parent_id: Option<ChannelId>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
+struct PutChannel {
+    to: ChannelId,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
+struct UnlinkChannel {
+    channel_id: ChannelId,
+    parent_id: Option<ChannelId>,
 }
 
 actions!(
@@ -107,12 +129,40 @@ impl_actions!(
         ManageMembers,
         RenameChannel,
         ToggleCollapse,
-        OpenChannelBuffer
+        OpenChannelBuffer,
+        LinkChannel,
+        MoveChannel,
+        PutChannel,
+        UnlinkChannel
     ]
 );
 
 const COLLABORATION_PANEL_KEY: &'static str = "CollaborationPanel";
 
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
+pub struct ChannelLocation<'a> {
+    channel: ChannelId,
+    path: Cow<'a, ChannelPath>,
+}
+
+impl From<(ChannelId, ChannelPath)> for ChannelLocation<'static> {
+    fn from(value: (ChannelId, ChannelPath)) -> Self {
+        ChannelLocation {
+            channel: value.0,
+            path: Cow::Owned(value.1),
+        }
+    }
+}
+
+impl<'a> From<(ChannelId, &'a ChannelPath)> for ChannelLocation<'a> {
+    fn from(value: (ChannelId, &'a ChannelPath)) -> Self {
+        ChannelLocation {
+            channel: value.0,
+            path: Cow::Borrowed(value.1),
+        }
+    }
+}
+
 pub fn init(_client: Arc<Client>, cx: &mut AppContext) {
     settings::register::<panel_settings::CollaborationPanelSettings>(cx);
     contact_finder::init(cx);
@@ -135,16 +185,65 @@ pub fn init(_client: Arc<Client>, cx: &mut AppContext) {
     cx.add_action(CollabPanel::collapse_selected_channel);
     cx.add_action(CollabPanel::expand_selected_channel);
     cx.add_action(CollabPanel::open_channel_buffer);
+
+    cx.add_action(
+        |panel: &mut CollabPanel, action: &LinkChannel, _: &mut ViewContext<CollabPanel>| {
+            panel.link_or_move = Some(ChannelCopy::Link(action.channel_id));
+        },
+    );
+
+    cx.add_action(
+        |panel: &mut CollabPanel, action: &MoveChannel, _: &mut ViewContext<CollabPanel>| {
+            panel.link_or_move = Some(ChannelCopy::Move {
+                channel_id: action.channel_id,
+                parent_id: action.parent_id,
+            });
+        },
+    );
+
+    cx.add_action(
+        |panel: &mut CollabPanel, action: &PutChannel, cx: &mut ViewContext<CollabPanel>| {
+            if let Some(copy) = panel.link_or_move.take() {
+                match copy {
+                    ChannelCopy::Move {
+                        channel_id,
+                        parent_id,
+                    } => panel.channel_store.update(cx, |channel_store, cx| {
+                        channel_store
+                            .move_channel(channel_id, parent_id, action.to, cx)
+                            .detach_and_log_err(cx)
+                    }),
+                    ChannelCopy::Link(channel) => {
+                        panel.channel_store.update(cx, |channel_store, cx| {
+                            channel_store
+                                .link_channel(channel, action.to, cx)
+                                .detach_and_log_err(cx)
+                        })
+                    }
+                }
+            }
+        },
+    );
+
+    cx.add_action(
+        |panel: &mut CollabPanel, action: &UnlinkChannel, cx: &mut ViewContext<CollabPanel>| {
+            panel.channel_store.update(cx, |channel_store, cx| {
+                channel_store
+                    .unlink_channel(action.channel_id, action.parent_id, cx)
+                    .detach_and_log_err(cx)
+            })
+        },
+    );
 }
 
 #[derive(Debug)]
 pub enum ChannelEditingState {
     Create {
-        parent_id: Option<u64>,
+        location: Option<ChannelLocation<'static>>,
         pending_name: Option<String>,
     },
     Rename {
-        channel_id: u64,
+        location: ChannelLocation<'static>,
         pending_name: Option<String>,
     },
 }
@@ -158,10 +257,36 @@ impl ChannelEditingState {
     }
 }
 
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+enum ChannelCopy {
+    Move {
+        channel_id: u64,
+        parent_id: Option<u64>,
+    },
+    Link(u64),
+}
+
+impl ChannelCopy {
+    fn channel_id(&self) -> u64 {
+        match self {
+            ChannelCopy::Move { channel_id, .. } => *channel_id,
+            ChannelCopy::Link(channel_id) => *channel_id,
+        }
+    }
+
+    fn is_move(&self) -> bool {
+        match self {
+            ChannelCopy::Move { .. } => true,
+            ChannelCopy::Link(_) => false,
+        }
+    }
+}
+
 pub struct CollabPanel {
     width: Option<f32>,
     fs: Arc<dyn Fs>,
     has_focus: bool,
+    link_or_move: Option<ChannelCopy>,
     pending_serialization: Task<Option<()>>,
     context_menu: ViewHandle<ContextMenu>,
     filter_editor: ViewHandle<Editor>,
@@ -177,7 +302,7 @@ pub struct CollabPanel {
     list_state: ListState<Self>,
     subscriptions: Vec<Subscription>,
     collapsed_sections: Vec<Section>,
-    collapsed_channels: Vec<ChannelId>,
+    collapsed_channels: Vec<ChannelLocation<'static>>,
     workspace: WeakViewHandle<Workspace>,
     context_menu_on_selected: bool,
 }
@@ -185,7 +310,7 @@ pub struct CollabPanel {
 #[derive(Serialize, Deserialize)]
 struct SerializedCollabPanel {
     width: Option<f32>,
-    collapsed_channels: Option<Vec<ChannelId>>,
+    collapsed_channels: Option<Vec<ChannelLocation<'static>>>,
 }
 
 #[derive(Debug)]
@@ -229,6 +354,7 @@ enum ListEntry {
     Channel {
         channel: Arc<Channel>,
         depth: usize,
+        path: ChannelPath,
     },
     ChannelNotes {
         channel_id: ChannelId,
@@ -353,10 +479,15 @@ impl CollabPanel {
                                 cx,
                             )
                         }
-                        ListEntry::Channel { channel, depth } => {
+                        ListEntry::Channel {
+                            channel,
+                            depth,
+                            path,
+                        } => {
                             let channel_row = this.render_channel(
                                 &*channel,
                                 *depth,
+                                path.to_owned(),
                                 &theme.collab_panel,
                                 is_selected,
                                 cx,
@@ -425,6 +556,7 @@ impl CollabPanel {
             let mut this = Self {
                 width: None,
                 has_focus: false,
+                link_or_move: None,
                 fs: workspace.app_state().fs.clone(),
                 pending_serialization: Task::ready(None),
                 context_menu: cx.add_view(|cx| ContextMenu::new(view_id, cx)),
@@ -512,7 +644,13 @@ impl CollabPanel {
                 .log_err()
                 .flatten()
             {
-                Some(serde_json::from_str::<SerializedCollabPanel>(&panel)?)
+                match serde_json::from_str::<SerializedCollabPanel>(&panel) {
+                    Ok(panel) => Some(panel),
+                    Err(err) => {
+                        log::error!("Failed to deserialize collaboration panel: {}", err);
+                        None
+                    }
+                }
             } else {
                 None
             };
@@ -702,28 +840,24 @@ impl CollabPanel {
                     executor.clone(),
                 ));
                 if let Some(state) = &self.channel_editing_state {
-                    if matches!(
-                        state,
-                        ChannelEditingState::Create {
-                            parent_id: None,
-                            ..
-                        }
-                    ) {
+                    if matches!(state, ChannelEditingState::Create { location: None, .. }) {
                         self.entries.push(ListEntry::ChannelEditor { depth: 0 });
                     }
                 }
                 let mut collapse_depth = None;
                 for mat in matches {
-                    let (depth, channel) =
-                        channel_store.channel_at_index(mat.candidate_id).unwrap();
+                    let (channel, path) = channel_store.channel_at_index(mat.candidate_id).unwrap();
+                    let depth = path.len() - 1;
 
-                    if collapse_depth.is_none() && self.is_channel_collapsed(channel.id) {
+                    let location: ChannelLocation<'_> = (channel.id, path).into();
+
+                    if collapse_depth.is_none() && self.is_channel_collapsed(&location) {
                         collapse_depth = Some(depth);
                     } else if let Some(collapsed_depth) = collapse_depth {
                         if depth > collapsed_depth {
                             continue;
                         }
-                        if self.is_channel_collapsed(channel.id) {
+                        if self.is_channel_collapsed(&location) {
                             collapse_depth = Some(depth);
                         } else {
                             collapse_depth = None;
@@ -731,18 +865,21 @@ impl CollabPanel {
                     }
 
                     match &self.channel_editing_state {
-                        Some(ChannelEditingState::Create { parent_id, .. })
-                            if *parent_id == Some(channel.id) =>
-                        {
+                        Some(ChannelEditingState::Create {
+                            location: parent_id,
+                            ..
+                        }) if *parent_id == Some(location) => {
                             self.entries.push(ListEntry::Channel {
                                 channel: channel.clone(),
                                 depth,
+                                path: path.clone(),
                             });
                             self.entries
                                 .push(ListEntry::ChannelEditor { depth: depth + 1 });
                         }
-                        Some(ChannelEditingState::Rename { channel_id, .. })
-                            if *channel_id == channel.id =>
+                        Some(ChannelEditingState::Rename { location, .. })
+                            if location.channel == channel.id
+                                && location.path == Cow::Borrowed(path) =>
                         {
                             self.entries.push(ListEntry::ChannelEditor { depth });
                         }
@@ -750,6 +887,7 @@ impl CollabPanel {
                             self.entries.push(ListEntry::Channel {
                                 channel: channel.clone(),
                                 depth,
+                                path: path.clone(),
                             });
                         }
                     }
@@ -1546,14 +1684,21 @@ impl CollabPanel {
         &self,
         channel: &Channel,
         depth: usize,
+        path: ChannelPath,
         theme: &theme::CollabPanel,
         is_selected: bool,
         cx: &mut ViewContext<Self>,
     ) -> AnyElement<Self> {
         let channel_id = channel.id;
         let has_children = self.channel_store.read(cx).has_children(channel_id);
-        let disclosed =
-            has_children.then(|| !self.collapsed_channels.binary_search(&channel_id).is_ok());
+
+        let disclosed = {
+            let location = ChannelLocation {
+                channel: channel_id,
+                path: Cow::Borrowed(&path),
+            };
+            has_children.then(|| !self.collapsed_channels.binary_search(&location).is_ok())
+        };
 
         let is_active = iife!({
             let call_channel = ActiveCall::global(cx)
@@ -1567,7 +1712,7 @@ impl CollabPanel {
 
         const FACEPILE_LIMIT: usize = 3;
 
-        MouseEventHandler::new::<Channel, _>(channel.id as usize, cx, |state, cx| {
+        MouseEventHandler::new::<Channel, _>(id(&path) as usize, cx, |state, cx| {
             Flex::<Self>::row()
                 .with_child(
                     Svg::new("icons/hash.svg")
@@ -1618,8 +1763,13 @@ impl CollabPanel {
                 })
                 .align_children_center()
                 .styleable_component()
-                .disclosable(disclosed, Box::new(ToggleCollapse { channel_id }))
-                .with_id(channel_id as usize)
+                .disclosable(
+                    disclosed,
+                    Box::new(ToggleCollapse {
+                        location: (channel_id, path.clone()).into(),
+                    }),
+                )
+                .with_id(id(&path) as usize)
                 .with_style(theme.disclosure.clone())
                 .element()
                 .constrained()
@@ -1635,7 +1785,11 @@ impl CollabPanel {
             this.join_channel(channel_id, cx);
         })
         .on_click(MouseButton::Right, move |e, this, cx| {
-            this.deploy_channel_context_menu(Some(e.position), channel_id, cx);
+            this.deploy_channel_context_menu(
+                Some(e.position),
+                &(channel_id, path.clone()).into(),
+                cx,
+            );
         })
         .with_cursor_style(CursorStyle::PointingHand)
         .into_any()
@@ -1882,11 +2036,20 @@ impl CollabPanel {
     fn deploy_channel_context_menu(
         &mut self,
         position: Option<Vector2F>,
-        channel_id: u64,
+        location: &ChannelLocation<'static>,
         cx: &mut ViewContext<Self>,
     ) {
         self.context_menu_on_selected = position.is_none();
 
+        let operation_details = self.link_or_move.as_ref().and_then(|link_or_move| {
+            let channel_name = self
+                .channel_store
+                .read(cx)
+                .channel_for_id(link_or_move.channel_id())
+                .map(|channel| channel.name.clone())?;
+            Some((channel_name, link_or_move.is_move()))
+        });
+
         self.context_menu.update(cx, |context_menu, cx| {
             context_menu.set_position_mode(if self.context_menu_on_selected {
                 OverlayPositionMode::Local
@@ -1894,27 +2057,112 @@ impl CollabPanel {
                 OverlayPositionMode::Window
             });
 
-            let expand_action_name = if self.is_channel_collapsed(channel_id) {
+            let mut items = Vec::new();
+
+            if let Some((channel_name, is_move)) = operation_details {
+                items.push(ContextMenuItem::action(
+                    format!(
+                        "{} '#{}' here",
+                        if is_move { "Move" } else { "Link" },
+                        channel_name
+                    ),
+                    PutChannel {
+                        to: location.channel,
+                    },
+                ));
+                items.push(ContextMenuItem::Separator)
+            }
+
+            let expand_action_name = if self.is_channel_collapsed(&location) {
                 "Expand Subchannels"
             } else {
                 "Collapse Subchannels"
             };
 
-            let mut items = vec![
-                ContextMenuItem::action(expand_action_name, ToggleCollapse { channel_id }),
-                ContextMenuItem::action("Open Notes", OpenChannelBuffer { channel_id }),
-            ];
+            items.extend([
+                ContextMenuItem::action(
+                    expand_action_name,
+                    ToggleCollapse {
+                        location: location.clone(),
+                    },
+                ),
+                ContextMenuItem::action(
+                    "Open Notes",
+                    OpenChannelBuffer {
+                        channel_id: location.channel,
+                    },
+                ),
+            ]);
+
+            if self.channel_store.read(cx).is_user_admin(location.channel) {
+                let parent_id = location.path.parent_id();
 
-            if self.channel_store.read(cx).is_user_admin(channel_id) {
                 items.extend([
                     ContextMenuItem::Separator,
-                    ContextMenuItem::action("New Subchannel", NewChannel { channel_id }),
-                    ContextMenuItem::action("Rename", RenameChannel { channel_id }),
+                    ContextMenuItem::action(
+                        "New Subchannel",
+                        NewChannel {
+                            location: location.clone(),
+                        },
+                    ),
+                    ContextMenuItem::action(
+                        "Rename",
+                        RenameChannel {
+                            location: location.clone(),
+                        },
+                    ),
                     ContextMenuItem::Separator,
-                    ContextMenuItem::action("Invite Members", InviteMembers { channel_id }),
-                    ContextMenuItem::action("Manage Members", ManageMembers { channel_id }),
+                ]);
+
+                items.push(ContextMenuItem::action(
+                    if parent_id.is_some() {
+                        "Unlink from parent"
+                    } else {
+                        "Unlink from root"
+                    },
+                    UnlinkChannel {
+                        channel_id: location.channel,
+                        parent_id,
+                    },
+                ));
+
+                items.extend([
+                    ContextMenuItem::action(
+                        "Link this channel",
+                        LinkChannel {
+                            channel_id: location.channel,
+                        },
+                    ),
+                    ContextMenuItem::action(
+                        "Move this channel",
+                        MoveChannel {
+                            channel_id: location.channel,
+                            parent_id,
+                        },
+                    ),
+                ]);
+
+                items.extend([
                     ContextMenuItem::Separator,
-                    ContextMenuItem::action("Delete", RemoveChannel { channel_id }),
+                    ContextMenuItem::action(
+                        "Invite Members",
+                        InviteMembers {
+                            channel_id: location.channel,
+                        },
+                    ),
+                    ContextMenuItem::action(
+                        "Manage Members",
+                        ManageMembers {
+                            channel_id: location.channel,
+                        },
+                    ),
+                    ContextMenuItem::Separator,
+                    ContextMenuItem::action(
+                        "Delete",
+                        RemoveChannel {
+                            channel_id: location.channel,
+                        },
+                    ),
                 ]);
             }
 
@@ -2040,7 +2288,7 @@ impl CollabPanel {
         if let Some(editing_state) = &mut self.channel_editing_state {
             match editing_state {
                 ChannelEditingState::Create {
-                    parent_id,
+                    location,
                     pending_name,
                     ..
                 } => {
@@ -2053,13 +2301,17 @@ impl CollabPanel {
 
                     self.channel_store
                         .update(cx, |channel_store, cx| {
-                            channel_store.create_channel(&channel_name, *parent_id, cx)
+                            channel_store.create_channel(
+                                &channel_name,
+                                location.as_ref().map(|location| location.channel),
+                                cx,
+                            )
                         })
                         .detach();
                     cx.notify();
                 }
                 ChannelEditingState::Rename {
-                    channel_id,
+                    location,
                     pending_name,
                 } => {
                     if pending_name.is_some() {
@@ -2070,7 +2322,7 @@ impl CollabPanel {
 
                     self.channel_store
                         .update(cx, |channel_store, cx| {
-                            channel_store.rename(*channel_id, &channel_name, cx)
+                            channel_store.rename(location.channel, &channel_name, cx)
                         })
                         .detach();
                     cx.notify();
@@ -2097,38 +2349,58 @@ impl CollabPanel {
         _: &CollapseSelectedChannel,
         cx: &mut ViewContext<Self>,
     ) {
-        let Some(channel_id) = self.selected_channel().map(|channel| channel.id) else {
+        let Some((channel_id, path)) = self
+            .selected_channel()
+            .map(|(channel, parent)| (channel.id, parent))
+        else {
             return;
         };
 
-        if self.is_channel_collapsed(channel_id) {
+        let path = path.to_owned();
+
+        if self.is_channel_collapsed(&(channel_id, path.clone()).into()) {
             return;
         }
 
-        self.toggle_channel_collapsed(&ToggleCollapse { channel_id }, cx)
+        self.toggle_channel_collapsed(
+            &ToggleCollapse {
+                location: (channel_id, path).into(),
+            },
+            cx,
+        )
     }
 
     fn expand_selected_channel(&mut self, _: &ExpandSelectedChannel, cx: &mut ViewContext<Self>) {
-        let Some(channel_id) = self.selected_channel().map(|channel| channel.id) else {
+        let Some((channel_id, path)) = self
+            .selected_channel()
+            .map(|(channel, parent)| (channel.id, parent))
+        else {
             return;
         };
 
-        if !self.is_channel_collapsed(channel_id) {
+        let path = path.to_owned();
+
+        if !self.is_channel_collapsed(&(channel_id, path.clone()).into()) {
             return;
         }
 
-        self.toggle_channel_collapsed(&ToggleCollapse { channel_id }, cx)
+        self.toggle_channel_collapsed(
+            &ToggleCollapse {
+                location: (channel_id, path).into(),
+            },
+            cx,
+        )
     }
 
     fn toggle_channel_collapsed(&mut self, action: &ToggleCollapse, cx: &mut ViewContext<Self>) {
-        let channel_id = action.channel_id;
+        let location = action.location.clone();
 
-        match self.collapsed_channels.binary_search(&channel_id) {
+        match self.collapsed_channels.binary_search(&location) {
             Ok(ix) => {
                 self.collapsed_channels.remove(ix);
             }
             Err(ix) => {
-                self.collapsed_channels.insert(ix, channel_id);
+                self.collapsed_channels.insert(ix, location);
             }
         };
         self.serialize(cx);
@@ -2137,8 +2409,8 @@ impl CollabPanel {
         cx.focus_self();
     }
 
-    fn is_channel_collapsed(&self, channel: ChannelId) -> bool {
-        self.collapsed_channels.binary_search(&channel).is_ok()
+    fn is_channel_collapsed(&self, location: &ChannelLocation) -> bool {
+        self.collapsed_channels.binary_search(location).is_ok()
     }
 
     fn leave_call(cx: &mut ViewContext<Self>) {
@@ -2163,7 +2435,7 @@ impl CollabPanel {
 
     fn new_root_channel(&mut self, cx: &mut ViewContext<Self>) {
         self.channel_editing_state = Some(ChannelEditingState::Create {
-            parent_id: None,
+            location: None,
             pending_name: None,
         });
         self.update_entries(false, cx);
@@ -2181,9 +2453,9 @@ impl CollabPanel {
 
     fn new_subchannel(&mut self, action: &NewChannel, cx: &mut ViewContext<Self>) {
         self.collapsed_channels
-            .retain(|&channel| channel != action.channel_id);
+            .retain(|channel| *channel != action.location);
         self.channel_editing_state = Some(ChannelEditingState::Create {
-            parent_id: Some(action.channel_id),
+            location: Some(action.location.to_owned()),
             pending_name: None,
         });
         self.update_entries(false, cx);
@@ -2201,16 +2473,16 @@ impl CollabPanel {
     }
 
     fn remove(&mut self, _: &Remove, cx: &mut ViewContext<Self>) {
-        if let Some(channel) = self.selected_channel() {
+        if let Some((channel, _)) = self.selected_channel() {
             self.remove_channel(channel.id, cx)
         }
     }
 
     fn rename_selected_channel(&mut self, _: &menu::SecondaryConfirm, cx: &mut ViewContext<Self>) {
-        if let Some(channel) = self.selected_channel() {
+        if let Some((channel, parent)) = self.selected_channel() {
             self.rename_channel(
                 &RenameChannel {
-                    channel_id: channel.id,
+                    location: (channel.id, parent.to_owned()).into(),
                 },
                 cx,
             );
@@ -2219,12 +2491,15 @@ impl CollabPanel {
 
     fn rename_channel(&mut self, action: &RenameChannel, cx: &mut ViewContext<Self>) {
         let channel_store = self.channel_store.read(cx);
-        if !channel_store.is_user_admin(action.channel_id) {
+        if !channel_store.is_user_admin(action.location.channel) {
             return;
         }
-        if let Some(channel) = channel_store.channel_for_id(action.channel_id).cloned() {
+        if let Some(channel) = channel_store
+            .channel_for_id(action.location.channel)
+            .cloned()
+        {
             self.channel_editing_state = Some(ChannelEditingState::Rename {
-                channel_id: action.channel_id,
+                location: action.location.to_owned(),
                 pending_name: None,
             });
             self.channel_name_editor.update(cx, |editor, cx| {
@@ -2266,18 +2541,22 @@ impl CollabPanel {
     }
 
     fn show_inline_context_menu(&mut self, _: &menu::ShowContextMenu, cx: &mut ViewContext<Self>) {
-        let Some(channel) = self.selected_channel() else {
+        let Some((channel, path)) = self.selected_channel() else {
             return;
         };
 
-        self.deploy_channel_context_menu(None, channel.id, cx);
+        self.deploy_channel_context_menu(None, &(channel.id, path.to_owned()).into(), cx);
     }
 
-    fn selected_channel(&self) -> Option<&Arc<Channel>> {
+    fn selected_channel(&self) -> Option<(&Arc<Channel>, &ChannelPath)> {
         self.selection
             .and_then(|ix| self.entries.get(ix))
             .and_then(|entry| match entry {
-                ListEntry::Channel { channel, .. } => Some(channel),
+                ListEntry::Channel {
+                    channel,
+                    path: parent,
+                    ..
+                } => Some((channel, parent)),
                 _ => None,
             })
     }
@@ -2657,13 +2936,17 @@ impl PartialEq for ListEntry {
             ListEntry::Channel {
                 channel: channel_1,
                 depth: depth_1,
+                path: parent_1,
             } => {
                 if let ListEntry::Channel {
                     channel: channel_2,
                     depth: depth_2,
+                    path: parent_2,
                 } = other
                 {
-                    return channel_1.id == channel_2.id && depth_1 == depth_2;
+                    return channel_1.id == channel_2.id
+                        && depth_1 == depth_2
+                        && parent_1 == parent_2;
                 }
             }
             ListEntry::ChannelNotes { channel_id } => {
@@ -2726,3 +3009,26 @@ fn render_icon_button(style: &IconButton, svg_path: &'static str) -> impl Elemen
         .contained()
         .with_style(style.container)
 }
+
+/// Hash a channel path to a u64, for use as a mouse id
+/// Based on the Fowler–Noll–Vo hash:
+/// https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
+fn id(path: &[ChannelId]) -> u64 {
+    // I probably should have done this, but I didn't
+    // let hasher = DefaultHasher::new();
+    // let path = path.hash(&mut hasher);
+    // let x = hasher.finish();
+
+    const OFFSET: u64 = 14695981039346656037;
+    const PRIME: u64 = 1099511628211;
+
+    let mut hash = OFFSET;
+    for id in path.iter() {
+        for id in id.to_ne_bytes() {
+            hash = hash ^ (id as u64);
+            hash = (hash as u128 * PRIME as u128) as u64;
+        }
+    }
+
+    hash
+}

crates/rpc/proto/zed.proto

@@ -141,7 +141,7 @@ message Envelope {
         RespondToChannelInvite respond_to_channel_invite = 123;
         UpdateChannels update_channels = 124;
         JoinChannel join_channel = 125;
-        RemoveChannel remove_channel = 126;
+        DeleteChannel delete_channel = 126;
         GetChannelMembers get_channel_members = 127;
         GetChannelMembersResponse get_channel_members_response = 128;
         SetChannelMemberAdmin set_channel_member_admin = 129;
@@ -155,7 +155,10 @@ message Envelope {
         RemoveChannelBufferCollaborator remove_channel_buffer_collaborator = 136;
         UpdateChannelBufferCollaborator update_channel_buffer_collaborator = 139;
         RejoinChannelBuffers rejoin_channel_buffers = 140;
-        RejoinChannelBuffersResponse rejoin_channel_buffers_response = 141; // Current max
+        RejoinChannelBuffersResponse rejoin_channel_buffers_response = 141;
+        LinkChannel link_channel = 142;
+        UnlinkChannel unlink_channel = 143;
+        MoveChannel move_channel = 144; // Current max
     }
 }
 
@@ -945,11 +948,17 @@ message LspDiskBasedDiagnosticsUpdated {}
 
 message UpdateChannels {
     repeated Channel channels = 1;
-    repeated uint64 remove_channels = 2;
-    repeated Channel channel_invitations = 3;
-    repeated uint64 remove_channel_invitations = 4;
-    repeated ChannelParticipants channel_participants = 5;
-    repeated ChannelPermission channel_permissions = 6;
+    repeated ChannelEdge delete_channel_edge = 2;
+    repeated uint64 delete_channels = 3;
+    repeated Channel channel_invitations = 4;
+    repeated uint64 remove_channel_invitations = 5;
+    repeated ChannelParticipants channel_participants = 6;
+    repeated ChannelPermission channel_permissions = 7;
+}
+
+message ChannelEdge {
+    uint64 channel_id = 1;
+    uint64 parent_id = 2;
 }
 
 message ChannelPermission {
@@ -966,7 +975,7 @@ message JoinChannel {
     uint64 channel_id = 1;
 }
 
-message RemoveChannel {
+message DeleteChannel {
     uint64 channel_id = 1;
 }
 
@@ -1021,6 +1030,22 @@ message RenameChannel {
     string name = 2;
 }
 
+message LinkChannel {
+    uint64 channel_id = 1;
+    uint64 to = 2;
+}
+
+message UnlinkChannel {
+    uint64 channel_id = 1;
+    optional uint64 from = 2;
+}
+
+message MoveChannel {
+    uint64 channel_id = 1;
+    optional uint64 from = 2;
+    uint64 to = 3;
+}
+
 message JoinChannelBuffer {
     uint64 channel_id = 1;
 }

crates/rpc/src/proto.rs

@@ -237,7 +237,10 @@ messages!(
     (UpdateBuffer, Foreground),
     (UpdateBufferFile, Foreground),
     (UpdateContacts, Foreground),
-    (RemoveChannel, Foreground),
+    (DeleteChannel, Foreground),
+    (MoveChannel, Foreground),
+    (LinkChannel, Foreground),
+    (UnlinkChannel, Foreground),
     (UpdateChannels, Foreground),
     (UpdateDiagnosticSummary, Foreground),
     (UpdateFollowers, Foreground),
@@ -315,9 +318,12 @@ request_messages!(
     (SetChannelMemberAdmin, Ack),
     (GetChannelMembers, GetChannelMembersResponse),
     (JoinChannel, JoinRoomResponse),
-    (RemoveChannel, Ack),
+    (DeleteChannel, Ack),
     (RenameProjectEntry, ProjectEntryResponse),
     (RenameChannel, ChannelResponse),
+    (LinkChannel, Ack),
+    (UnlinkChannel, Ack),
+    (MoveChannel, Ack),
     (SaveBuffer, BufferSaved),
     (SearchProject, SearchProjectResponse),
     (ShareProject, ShareProjectResponse),