Lay the groundwork for collaborating on assistant panel (#13991)

This pull request introduces collaboration for the assistant panel by
turning `Context` into a CRDT. `ContextStore` is responsible for sending
and applying operations, as well as synchronizing missed changes while
the connection was lost.

Contexts are shared on a per-project basis, and only the host can share
them for now. Shared contexts can be accessed via the `History` tab in
the assistant panel.

<img width="1819" alt="image"
src="https://github.com/zed-industries/zed/assets/482957/c7ae46d2-cde3-4b03-b74a-6e9b1555c154">


Please note that this doesn't implement following yet, which is
scheduled for a subsequent pull request.

Release Notes:

- N/A

crates/assistant/src/assistant.rs

@@ -1,7 +1,8 @@
 pub mod assistant_panel;
 pub mod assistant_settings;
 mod completion_provider;
-mod context_store;
+mod context;
+pub mod context_store;
 mod inline_assistant;
 mod model_selector;
 mod prompt_library;
@@ -16,8 +17,9 @@ use assistant_settings::{AnthropicModel, AssistantSettings, CloudModel, OllamaMo
 use assistant_slash_command::SlashCommandRegistry;
 use client::{proto, Client};
 use command_palette_hooks::CommandPaletteFilter;
-pub(crate) use completion_provider::*;
-pub(crate) use context_store::*;
+pub use completion_provider::*;
+pub use context::*;
+pub use context_store::*;
 use fs::Fs;
 use gpui::{actions, AppContext, Global, SharedString, UpdateGlobal};
 use indexed_docs::IndexedDocsRegistry;
@@ -57,10 +59,14 @@ actions!(
     ]
 );
 
-#[derive(
-    Copy, Clone, Debug, Default, Eq, PartialEq, PartialOrd, Ord, Hash, Serialize, Deserialize,
-)]
-struct MessageId(usize);
+#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
+pub struct MessageId(clock::Lamport);
+
+impl MessageId {
+    pub fn as_u64(self) -> u64 {
+        self.0.as_u64()
+    }
+}
 
 #[derive(Clone, Copy, Serialize, Deserialize, Debug, Eq, PartialEq)]
 #[serde(rename_all = "lowercase")]
@@ -71,8 +77,26 @@ pub enum Role {
 }
 
 impl Role {
-    pub fn cycle(&mut self) {
-        *self = match self {
+    pub fn from_proto(role: i32) -> Role {
+        match proto::LanguageModelRole::from_i32(role) {
+            Some(proto::LanguageModelRole::LanguageModelUser) => Role::User,
+            Some(proto::LanguageModelRole::LanguageModelAssistant) => Role::Assistant,
+            Some(proto::LanguageModelRole::LanguageModelSystem) => Role::System,
+            Some(proto::LanguageModelRole::LanguageModelTool) => Role::System,
+            None => Role::User,
+        }
+    }
+
+    pub fn to_proto(&self) -> proto::LanguageModelRole {
+        match self {
+            Role::User => proto::LanguageModelRole::LanguageModelUser,
+            Role::Assistant => proto::LanguageModelRole::LanguageModelAssistant,
+            Role::System => proto::LanguageModelRole::LanguageModelSystem,
+        }
+    }
+
+    pub fn cycle(self) -> Role {
+        match self {
             Role::User => Role::Assistant,
             Role::Assistant => Role::System,
             Role::System => Role::User,
@@ -151,11 +175,7 @@ pub struct LanguageModelRequestMessage {
 impl LanguageModelRequestMessage {
     pub fn to_proto(&self) -> proto::LanguageModelRequestMessage {
         proto::LanguageModelRequestMessage {
-            role: match self.role {
-                Role::User => proto::LanguageModelRole::LanguageModelUser,
-                Role::Assistant => proto::LanguageModelRole::LanguageModelAssistant,
-                Role::System => proto::LanguageModelRole::LanguageModelSystem,
-            } as i32,
+            role: self.role.to_proto() as i32,
             content: self.content.clone(),
             tool_calls: Vec::new(),
             tool_call_id: None,
@@ -222,19 +242,48 @@ pub struct LanguageModelChoiceDelta {
     pub finish_reason: Option<String>,
 }
 
-#[derive(Clone, Debug, Serialize, Deserialize)]
-struct MessageMetadata {
-    role: Role,
-    status: MessageStatus,
-}
-
-#[derive(Clone, Debug, Serialize, Deserialize)]
-enum MessageStatus {
+#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
+pub enum MessageStatus {
     Pending,
     Done,
     Error(SharedString),
 }
 
+impl MessageStatus {
+    pub fn from_proto(status: proto::ContextMessageStatus) -> MessageStatus {
+        match status.variant {
+            Some(proto::context_message_status::Variant::Pending(_)) => MessageStatus::Pending,
+            Some(proto::context_message_status::Variant::Done(_)) => MessageStatus::Done,
+            Some(proto::context_message_status::Variant::Error(error)) => {
+                MessageStatus::Error(error.message.into())
+            }
+            None => MessageStatus::Pending,
+        }
+    }
+
+    pub fn to_proto(&self) -> proto::ContextMessageStatus {
+        match self {
+            MessageStatus::Pending => proto::ContextMessageStatus {
+                variant: Some(proto::context_message_status::Variant::Pending(
+                    proto::context_message_status::Pending {},
+                )),
+            },
+            MessageStatus::Done => proto::ContextMessageStatus {
+                variant: Some(proto::context_message_status::Variant::Done(
+                    proto::context_message_status::Done {},
+                )),
+            },
+            MessageStatus::Error(message) => proto::ContextMessageStatus {
+                variant: Some(proto::context_message_status::Variant::Error(
+                    proto::context_message_status::Error {
+                        message: message.to_string(),
+                    },
+                )),
+            },
+        }
+    }
+}
+
 /// The state pertaining to the Assistant.
 #[derive(Default)]
 struct Assistant {
@@ -287,6 +336,7 @@ pub fn init(fs: Arc<dyn Fs>, client: Arc<Client>, cx: &mut AppContext) {
     })
     .detach();
 
+    context_store::init(&client);
     prompt_library::init(cx);
     completion_provider::init(client.clone(), cx);
     assistant_slash_command::init(cx);