Proposed changes editor features (#18373)

This PR adds some more functionality to the Proposed Changes Editor
view, which we'll be using in
https://github.com/zed-industries/zed/pull/18240 for allowing the
assistant to propose changes to a set of buffers.

* Add an `Apply All` button, and fully implement applying of changes to
the base buffer
* Make the proposed changes editor searchable
* Fix a bug in branch buffers' diff state management

Release Notes:

- N/A

crates/editor/src/proposed_changes_editor.rs

@@ -6,10 +6,13 @@ use language::{Buffer, BufferEvent, Capability};
 use multi_buffer::{ExcerptRange, MultiBuffer};
 use project::Project;
 use smol::stream::StreamExt;
-use std::{ops::Range, time::Duration};
+use std::{any::TypeId, ops::Range, time::Duration};
 use text::ToOffset;
 use ui::prelude::*;
-use workspace::Item;
+use workspace::{
+    searchable::SearchableItemHandle, Item, ItemHandle as _, ToolbarItemEvent, ToolbarItemLocation,
+    ToolbarItemView,
+};
 
 pub struct ProposedChangesEditor {
     editor: View<Editor>,
@@ -23,6 +26,10 @@ pub struct ProposedChangesBuffer<T> {
     pub ranges: Vec<Range<T>>,
 }
 
+pub struct ProposedChangesEditorToolbar {
+    current_editor: Option<View<ProposedChangesEditor>>,
+}
+
 impl ProposedChangesEditor {
     pub fn new<T: ToOffset>(
         buffers: Vec<ProposedChangesBuffer<T>>,
@@ -96,6 +103,17 @@ impl ProposedChangesEditor {
             self.recalculate_diffs_tx.unbounded_send(buffer).ok();
         }
     }
+
+    fn apply_all_changes(&self, cx: &mut ViewContext<Self>) {
+        let buffers = self.editor.read(cx).buffer.read(cx).all_buffers();
+        for branch_buffer in buffers {
+            if let Some(base_buffer) = branch_buffer.read(cx).diff_base_buffer() {
+                base_buffer.update(cx, |base_buffer, cx| {
+                    base_buffer.merge(&branch_buffer, None, cx)
+                });
+            }
+        }
+    }
 }
 
 impl Render for ProposedChangesEditor {
@@ -122,4 +140,66 @@ impl Item for ProposedChangesEditor {
     fn tab_content_text(&self, _cx: &WindowContext) -> Option<SharedString> {
         Some("Proposed changes".into())
     }
+
+    fn as_searchable(&self, _: &View<Self>) -> Option<Box<dyn SearchableItemHandle>> {
+        Some(Box::new(self.editor.clone()))
+    }
+
+    fn act_as_type<'a>(
+        &'a self,
+        type_id: TypeId,
+        self_handle: &'a View<Self>,
+        _: &'a AppContext,
+    ) -> Option<gpui::AnyView> {
+        if type_id == TypeId::of::<Self>() {
+            Some(self_handle.to_any())
+        } else if type_id == TypeId::of::<Editor>() {
+            Some(self.editor.to_any())
+        } else {
+            None
+        }
+    }
+}
+
+impl ProposedChangesEditorToolbar {
+    pub fn new() -> Self {
+        Self {
+            current_editor: None,
+        }
+    }
+
+    fn get_toolbar_item_location(&self) -> ToolbarItemLocation {
+        if self.current_editor.is_some() {
+            ToolbarItemLocation::PrimaryRight
+        } else {
+            ToolbarItemLocation::Hidden
+        }
+    }
+}
+
+impl Render for ProposedChangesEditorToolbar {
+    fn render(&mut self, _cx: &mut ViewContext<Self>) -> impl IntoElement {
+        let editor = self.current_editor.clone();
+        Button::new("apply-changes", "Apply All").on_click(move |_, cx| {
+            if let Some(editor) = &editor {
+                editor.update(cx, |editor, cx| {
+                    editor.apply_all_changes(cx);
+                });
+            }
+        })
+    }
+}
+
+impl EventEmitter<ToolbarItemEvent> for ProposedChangesEditorToolbar {}
+
+impl ToolbarItemView for ProposedChangesEditorToolbar {
+    fn set_active_pane_item(
+        &mut self,
+        active_pane_item: Option<&dyn workspace::ItemHandle>,
+        _cx: &mut ViewContext<Self>,
+    ) -> workspace::ToolbarItemLocation {
+        self.current_editor =
+            active_pane_item.and_then(|item| item.downcast::<ProposedChangesEditor>());
+        self.get_toolbar_item_location()
+    }
 }