feat: comment collapse event (#7949)

* feat: define comment collapse event

* feat: add firing collapse events

* chore: add round-trip test

* chore: add tests for firing collapse events

* chore: format

core/comments/workspace_comment.ts

@@ -82,6 +82,15 @@ export class WorkspaceComment {
     }
   }
 
+  /** Fires a comment collapse event. */
+  private fireCollapseEvent(newCollapsed: boolean) {
+    if (eventUtils.isEnabled()) {
+      eventUtils.fire(
+        new (eventUtils.get(eventUtils.COMMENT_COLLAPSE))(this, newCollapsed),
+      );
+    }
+  }
+
   /** Sets the text of the comment. */
   setText(text: string) {
     const oldText = this.text;
@@ -107,6 +116,7 @@ export class WorkspaceComment {
   /** Sets whether the comment is collapsed or not. */
   setCollapsed(collapsed: boolean) {
     this.collapsed = collapsed;
+    this.fireCollapseEvent(collapsed);
   }
 
   /** Returns whether the comment is collapsed or not. */

core/events/events.ts

@@ -24,6 +24,10 @@ import {CommentChange, CommentChangeJson} from './events_comment_change.js';
 import {CommentCreate, CommentCreateJson} from './events_comment_create.js';
 import {CommentDelete} from './events_comment_delete.js';
 import {CommentMove, CommentMoveJson} from './events_comment_move.js';
+import {
+  CommentCollapse,
+  CommentCollapseJson,
+} from './events_comment_collapse.js';
 import {MarkerMove, MarkerMoveJson} from './events_marker_move.js';
 import {Selected, SelectedJson} from './events_selected.js';
 import {ThemeChange, ThemeChangeJson} from './events_theme_change.js';
@@ -73,6 +77,8 @@ export {CommentCreateJson};
 export {CommentDelete};
 export {CommentMove};
 export {CommentMoveJson};
+export {CommentCollapse};
+export {CommentCollapseJson};
 export {FinishedLoading};
 export {MarkerMove};
 export {MarkerMoveJson};

core/events/events_comment_collapse.ts

@@ -0,0 +1,103 @@
+/**
+ * @license
+ * Copyright 2024 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import * as registry from '../registry.js';
+import {WorkspaceComment} from '../comments/workspace_comment.js';
+import {CommentBase, CommentBaseJson} from './events_comment_base.js';
+import * as eventUtils from './utils.js';
+import type {Workspace} from '../workspace.js';
+
+export class CommentCollapse extends CommentBase {
+  override type = eventUtils.COMMENT_COLLAPSE;
+
+  constructor(
+    comment?: WorkspaceComment,
+    public newCollapsed?: boolean,
+  ) {
+    super(comment);
+
+    if (!comment) {
+      return; // Blank event to be populated by fromJson.
+    }
+  }
+
+  /**
+   * Encode the event as JSON.
+   *
+   * @returns JSON representation.
+   */
+  override toJson(): CommentCollapseJson {
+    const json = super.toJson() as CommentCollapseJson;
+    if (this.newCollapsed === undefined) {
+      throw new Error(
+        'The new collapse value undefined. Either call recordNew, or ' +
+          'call fromJson',
+      );
+    }
+    json['newCollapsed'] = this.newCollapsed;
+    return json;
+  }
+
+  /**
+   * Deserializes the JSON event.
+   *
+   * @param event The event to append new properties to. Should be a subclass
+   *     of CommentCollapse, but we can't specify that due to the fact that
+   *     parameters to static methods in subclasses must be supertypes of
+   *     parameters to static methods in superclasses.
+   * @internal
+   */
+  static fromJson(
+    json: CommentCollapseJson,
+    workspace: Workspace,
+    event?: any,
+  ): CommentCollapse {
+    const newEvent = super.fromJson(
+      json,
+      workspace,
+      event ?? new CommentCollapse(),
+    ) as CommentCollapse;
+    newEvent.newCollapsed = json.newCollapsed;
+    return newEvent;
+  }
+
+  /**
+   * Run a collapse event.
+   *
+   * @param forward True if run forward, false if run backward (undo).
+   */
+  override run(forward: boolean) {
+    const workspace = this.getEventWorkspace_();
+    if (!this.commentId) {
+      throw new Error(
+        'The comment ID is undefined. Either pass a comment to ' +
+          'the constructor, or call fromJson',
+      );
+    }
+    // TODO: Remove cast when we update getCommentById.
+    const comment = workspace.getCommentById(
+      this.commentId,
+    ) as unknown as WorkspaceComment;
+    if (!comment) {
+      console.warn(
+        "Can't collapse or uncollapse non-existent comment: " + this.commentId,
+      );
+      return;
+    }
+
+    comment.setCollapsed(forward ? !!this.newCollapsed : !this.newCollapsed);
+  }
+}
+
+export interface CommentCollapseJson extends CommentBaseJson {
+  newCollapsed: boolean;
+}
+
+registry.register(
+  registry.Type.EVENT,
+  eventUtils.COMMENT_COLLAPSE,
+  CommentCollapse,
+);

core/events/utils.ts

@@ -180,6 +180,9 @@ export const COMMENT_CHANGE = 'comment_change';
  */
 export const COMMENT_MOVE = 'comment_move';
 
+/** Type of event that moves a comment. */
+export const COMMENT_COLLAPSE = 'comment_collapse';
+
 /**
  * Name of event that records a workspace load.
  */