import { CommandHandler, EventPublisher, ICommandHandler } from '@nestjs/cqrs';
import { BusinessRuleError } from '@task-stream/api/shared/domain';
import {
  CommentFactory,
  SYSTEM_ACTOR_ID,
} from '@task-stream/api/tracker/domain';
import { AddCommentCommand } from './add-comment.command';
import { CommandResult, ack } from './command-result';
import { WriteAccess } from './write-access';

@CommandHandler(AddCommentCommand)
export class AddCommentCommandHandler
  implements ICommandHandler<AddCommentCommand>
{
  constructor(
    private readonly access: WriteAccess,
    private readonly commentFactory: CommentFactory,
    private readonly eventPublisher: EventPublisher,
  ) {}

  async execute(command: AddCommentCommand): Promise<CommandResult> {
    // TaskStream itself (alerts that repeat) is no member; only internal
    // commands act as it, never a request from outside.
    const issue =
      command.actorId === SYSTEM_ACTOR_ID
        ? await this.access.issue(command.issueId)
        : (await this.access.issueForReporter(command.issueId, command.actorId))
            .issue;
    if (issue.trashedAt)
      throw new BusinessRuleError(
        `${issue.key} is in the trash: restore it to change it`,
      );
    const comment = this.commentFactory.create({
      issueId: issue.id,
      projectId: issue.projectId,
      authorId: command.actorId,
      body: command.body,
      replyTo: command.replyTo
        ? await this.threadOf(command.replyTo, issue.id)
        : null,
      poll: command.poll,
    });

    this.eventPublisher.mergeObjectContext(comment);
    await comment.commitAndWait();
    return ack(comment);
  }

  /**
   * The top-level comment a reply hangs from: one level only, so answering
   * a reply joins its thread.
   */
  private async threadOf(commentId: string, issueId: string): Promise<string> {
    const parent = await this.access.comment(commentId);
    if (parent.issueId !== issueId)
      throw new BusinessRuleError('A reply must be on the same ticket');
    return parent.replyTo ?? parent.id;
  }
}