first commit

libs/api/tracker/domain/src/lib/comment/comment.ts

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+import {
+  BusinessRuleError,
+  ForbiddenError,
+  VersionedAggregateRoot,
+  assertThat,
+} from '@task-stream/api/shared/domain';
+import { CommentAddedEvent } from '../events/comment-added.event';
+import { CommentDeletedEvent } from '../events/comment-deleted.event';
+import { CommentEditedEvent } from '../events/comment-edited.event';
+
+/** Data of a comment (what CommentAddedEvent carries). */
+export interface CommentProps {
+  id: string;
+  issueId: string;
+  projectId: string;
+  authorId: string;
+  body: string;
+  deleted: boolean;
+  createdAt: string;
+  editedAt: string | null;
+}
+
+const MAX_BODY = 20_000;
+
+/** Decisions and explanations inside a ticket. */
+export class Comment extends VersionedAggregateRoot implements CommentProps {
+  public issueId!: string;
+  public projectId!: string;
+  public authorId!: string;
+  public body!: string;
+  public deleted = false;
+  public createdAt!: string;
+  public editedAt: string | null = null;
+
+  constructor(id: string) {
+    super();
+    this.id = id;
+  }
+
+  edit(actorId: string, body: string): void {
+    this.assertAlive();
+    if (actorId !== this.authorId) {
+      throw new ForbiddenError('Only the author can edit a comment');
+    }
+    const next = validCommentBody(body);
+    if (next === this.body) return;
+    this.apply(
+      new CommentEditedEvent(
+        actorId,
+        this.id,
+        this.projectId,
+        this.issueId,
+        next,
+      ),
+    );
+  }
+
+  /** @param canModerate whether the actor manages the project (may delete others' comments). */
+  delete(actorId: string, canModerate: boolean): void {
+    this.assertAlive();
+    if (actorId !== this.authorId && !canModerate) {
+      throw new ForbiddenError(
+        'Only the author or a project admin can delete a comment',
+      );
+    }
+    this.apply(
+      new CommentDeletedEvent(actorId, this.id, this.projectId, this.issueId),
+    );
+  }
+
+  /* ---- State transitions (also replayed by loadFromHistory) ---- */
+
+  onCommentAddedEvent({ comment }: CommentAddedEvent): void {
+    Object.assign(this, comment);
+  }
+
+  onCommentEditedEvent(event: CommentEditedEvent): void {
+    this.body = event.body;
+    this.editedAt = event.occurredAt;
+  }
+
+  onCommentDeletedEvent(): void {
+    this.deleted = true;
+  }
+
+  private assertAlive(): void {
+    if (this.deleted) throw new BusinessRuleError('Comment was deleted');
+  }
+}
+
+export function validCommentBody(body: string): string {
+  const trimmed = body.trim();
+  assertThat(trimmed.length > 0, 'Comment cannot be empty');
+  assertThat(
+    trimmed.length <= MAX_BODY,
+    `Comment cannot exceed ${MAX_BODY} characters`,
+  );
+  return trimmed;
+}