import { EventsHandler, IEventHandler } from '@nestjs/cqrs';
import {
  CommentAddedEvent,
  IssueAssignedEvent,
  IssueCreatedEvent,
  IssueStatusChangedEvent,
  mentionedUserIds,
  NotificationKind,
  ProjectMemberAddedEvent,
  StatusCategory,
  TrackerEvent,
  withoutMentionMarkup,
} from '@task-stream/api/tracker/domain';
import { FindCommentsRepository } from '../ports/find-comments.repository';
import { FindIssuesRepository } from '../ports/find-issues.repository';
import { FindProjectsRepository } from '../ports/find-projects.repository';
import { UserDirectory } from '../ports/user-directory';
import { NotificationDraft, Notifier } from './notifier';

/* Read by people, like the activity feed: Spanish. */

const excerpt = (text: string, max = 120) => {
  const flat = withoutMentionMarkup(text).replace(/\s+/g, ' ').trim();
  return flat.length > max ? `${flat.slice(0, max - 1)}…` : flat;
};

/**
 * Who is told what, for the events that concern someone in particular:
 * whoever is mentioned, whoever a ticket is assigned to, whoever reported or
 * works on it when it moves or gets a comment, whoever follows it, whoever
 * joins a project. The order is the order of importance: each person gets
 * one notification per event, for the first reason that applies.
 */
@EventsHandler(
  IssueCreatedEvent,
  IssueAssignedEvent,
  IssueStatusChangedEvent,
  CommentAddedEvent,
  ProjectMemberAddedEvent,
)
export class NotificationsEventHandler implements IEventHandler<TrackerEvent> {
  constructor(
    private readonly notifier: Notifier,
    private readonly findIssues: FindIssuesRepository,
    private readonly findProjects: FindProjectsRepository,
    private readonly users: UserDirectory,
    private readonly findComments: FindCommentsRepository,
  ) {}

  async handle(event: TrackerEvent): Promise<void> {
    const project = await this.findProjects.findById(event.projectId);
    if (!project) return;
    const actor = (await this.users.refs([event.actorId])).of(
      event.actorId,
    ).name;

    if (event instanceof ProjectMemberAddedEvent) {
      return this.notifier.deliver(
        event,
        {
          projectId: project.id,
          projectKey: project.key,
          issueId: null,
          issueKey: null,
        },
        [
          {
            userId: event.userId,
            kind: NotificationKind.ADDED_TO_PROJECT,
            summary: `${actor} te añadió al proyecto ${project.name} (${project.key})`,
          },
        ],
      );
    }

    const issueId =
      event instanceof CommentAddedEvent
        ? event.comment.issueId
        : event.aggregateId;
    const issue =
      event instanceof IssueCreatedEvent
        ? event.issue
        : await this.findIssues.findById(issueId);
    if (!issue) return;
    const reporterId =
      'reporterId' in issue ? issue.reporterId : issue.reporter.id;
    const assigneeId =
      'assigneeId' in issue ? issue.assigneeId : (issue.assignee?.id ?? null);
    const ticket = `${issue.key}: ${issue.title}`;
    const watcherIds =
      'watchers' in issue ? issue.watchers.map((w) => w.id) : [];
    const memberIds = new Set(project.members.map((m) => m.user.id));

    const drafts: NotificationDraft[] = [];
    if (event instanceof IssueCreatedEvent && assigneeId) {
      drafts.push({
        userId: assigneeId,
        kind: NotificationKind.ASSIGNED,
        summary: `${actor} te asignó ${ticket}`,
      });
    }
    if (event instanceof IssueAssignedEvent) {
      const assignee = event.assigneeId
        ? (await this.users.refs([event.assigneeId])).of(event.assigneeId).name
        : null;
      if (event.assigneeId) {
        drafts.push({
          userId: event.assigneeId,
          kind: NotificationKind.ASSIGNED,
          summary: `${actor} te asignó ${ticket}`,
        });
      }
      for (const userId of watcherIds) {
        drafts.push({
          userId,
          kind: NotificationKind.WATCHED,
          summary: assignee
            ? `${actor} asignó ${ticket} a ${assignee}`
            : `${actor} dejó sin asignar ${ticket}`,
        });
      }
    }
    if (event instanceof IssueStatusChangedEvent) {
      const to = event.meta?.toName ?? event.to;
      // Back from QA without passing: the one move whoever did the work must hear about.
      const failedQa =
        event.meta?.fromCategory === StatusCategory.QA &&
        event.meta?.toCategory !== StatusCategory.QA &&
        event.meta?.toCategory !== StatusCategory.DONE;
      const reason = event.reason ? `: ${excerpt(event.reason)}` : '';
      const summary = failedQa
        ? `${actor} devolvió ${ticket} desde QA${reason}`
        : `${actor} movió ${ticket} a ${to}${reason}`;
      for (const userId of [assigneeId, reporterId]) {
        if (!userId) continue;
        drafts.push({
          userId,
          kind: failedQa
            ? NotificationKind.QA_FAILED
            : NotificationKind.STATUS_CHANGED,
          summary,
        });
      }
      for (const userId of watcherIds) {
        drafts.push({ userId, kind: NotificationKind.WATCHED, summary });
      }
    }
    if (event instanceof CommentAddedEvent) {
      const said = `«${excerpt(event.comment.body)}»`;
      // Only members: a mention cannot reach someone who cannot read the ticket.
      for (const userId of mentionedUserIds(event.comment.body)) {
        if (!memberIds.has(userId)) continue;
        drafts.push({
          userId,
          kind: NotificationKind.MENTIONED,
          summary: `${actor} te mencionó en ${issue.key}: ${said}`,
        });
      }
      const answered = event.comment.replyTo
        ? await this.findComments.findById(event.comment.replyTo)
        : null;
      if (answered && !answered.deleted) {
        drafts.push({
          userId: answered.author.id,
          kind: NotificationKind.REPLIED,
          summary: `${actor} respondió a tu comentario en ${issue.key}: ${said}`,
        });
      }
      for (const userId of [assigneeId, reporterId]) {
        if (!userId) continue;
        drafts.push({
          userId,
          kind: NotificationKind.COMMENTED,
          summary: `${actor} comentó en ${issue.key}: ${said}`,
        });
      }
      for (const userId of watcherIds) {
        drafts.push({
          userId,
          kind: NotificationKind.WATCHED,
          summary: `${actor} comentó en ${issue.key}, que sigues: ${said}`,
        });
      }
    }

    await this.notifier.deliver(
      event,
      {
        projectId: project.id,
        projectKey: project.key,
        issueId: issue.id,
        issueKey: issue.key,
      },
      drafts,
    );
  }
}