import { randomUUID } from 'node:crypto';
import {
  Command,
  CommandHandler,
  ICommandHandler,
  IQueryHandler,
  Query,
  QueryBus,
  QueryHandler,
} from '@nestjs/cqrs';
import { assertThat, NotFoundError } from '@task-stream/api/shared/domain';
import {
  IssueReadModel,
  NotificationKind,
  SYSTEM_ACTOR_ID,
  SYSTEM_ACTOR_NAME,
} from '@task-stream/api/tracker/domain';
import { Notifier } from '../notifications/notifier';
import {
  IssueReminder,
  IssueRemindersRepository,
} from '../ports/issue-reminders.repository';
import { GetIssuesByIdsQuery } from '../queries/get-issues-by-ids.query';

/*
 * «Remind me on Thursday»: a person's own reminder on a ticket, told as a
 * notification (bell, push, e-mail) when its time comes. One waiting per
 * person and ticket; private, no history.
 */

/** As far ahead as a reminder goes. */
export const MAX_REMINDER_DAYS = 366;
export const MAX_REMINDER_NOTE = 280;

export class SetIssueReminderCommand extends Command<IssueReminder> {
  constructor(
    public readonly userId: string,
    public readonly issueId: string,
    /** ISO date-time. */
    public readonly at: string,
    public readonly note: string | null = null,
  ) {
    super();
  }
}

export class ClearIssueReminderCommand extends Command<void> {
  constructor(
    public readonly userId: string,
    public readonly issueId: string,
  ) {
    super();
  }
}

/** Scheduler only: tells the reminders whose time has come. */
export class SendIssueRemindersCommand extends Command<number> {
  constructor(public readonly now: string = new Date().toISOString()) {
    super();
  }
}

export class GetIssueReminderQuery extends Query<IssueReminder | null> {
  constructor(
    public readonly userId: string,
    public readonly issueId: string,
  ) {
    super();
  }
}

/** My waiting reminders with their tickets, soonest first. */
export class GetMyRemindersQuery extends Query<
  { reminder: IssueReminder; issue: IssueReadModel }[]
> {
  constructor(public readonly userId: string) {
    super();
  }
}

@CommandHandler(SetIssueReminderCommand)
export class SetIssueReminderCommandHandler
  implements ICommandHandler<SetIssueReminderCommand>
{
  constructor(
    private readonly reminders: IssueRemindersRepository,
    private readonly queryBus: QueryBus,
  ) {}

  async execute(command: SetIssueReminderCommand): Promise<IssueReminder> {
    const at = Date.parse(command.at);
    const now = Date.now();
    assertThat(!Number.isNaN(at), 'A reminder needs a date and time');
    assertThat(at > now - 60_000, 'A reminder must be in the future');
    assertThat(
      at <= now + MAX_REMINDER_DAYS * 86_400_000,
      `A reminder can be at most a year ahead`,
    );
    const note = command.note?.replace(/\s+/g, ' ').trim() || null;
    assertThat(
      !note || note.length <= MAX_REMINDER_NOTE,
      `A reminder's note takes ${MAX_REMINDER_NOTE} characters at most`,
    );
    const [issue]: IssueReadModel[] = await this.queryBus.execute(
      new GetIssuesByIdsQuery(command.userId, [command.issueId]),
    );
    // A ticket I cannot read does not exist, as far as I know.
    if (!issue || issue.trashedAt)
      throw new NotFoundError('Issue', command.issueId);
    const reminder: IssueReminder = {
      id: randomUUID(),
      userId: command.userId,
      issueId: issue.id,
      projectId: issue.projectId,
      at: new Date(at).toISOString(),
      note,
      createdAt: new Date(now).toISOString(),
      sentAt: null,
    };
    await this.reminders.save(reminder);
    return reminder;
  }
}

@CommandHandler(ClearIssueReminderCommand)
export class ClearIssueReminderCommandHandler
  implements ICommandHandler<ClearIssueReminderCommand>
{
  constructor(private readonly reminders: IssueRemindersRepository) {}

  execute(command: ClearIssueReminderCommand): Promise<void> {
    return this.reminders.remove(command.userId, command.issueId);
  }
}

@CommandHandler(SendIssueRemindersCommand)
export class SendIssueRemindersCommandHandler
  implements ICommandHandler<SendIssueRemindersCommand>
{
  constructor(
    private readonly reminders: IssueRemindersRepository,
    private readonly queryBus: QueryBus,
    private readonly notifier: Notifier,
  ) {}

  async execute(command: SendIssueRemindersCommand): Promise<number> {
    const due = await this.reminders.due(command.now, 200);
    let sent = 0;
    for (const reminder of due) {
      const [issue]: IssueReadModel[] = await this.queryBus.execute(
        new GetIssuesByIdsQuery(reminder.userId, [reminder.issueId]),
      );
      // Out of reach or in the trash by now: nothing to remind of.
      if (issue && !issue.trashedAt) {
        // Its id makes it idempotent: two instances tell it once.
        await this.notifier.send([
          {
            id: `issue-reminder:${reminder.id}`,
            userId: reminder.userId,
            kind: NotificationKind.REMINDER,
            projectId: issue.projectId,
            projectKey: issue.projectKey,
            issueId: issue.id,
            issueKey: issue.key,
            actor: { id: SYSTEM_ACTOR_ID, name: SYSTEM_ACTOR_NAME },
            summary: reminder.note
              ? `Recordatorio de ${issue.key}: ${reminder.note}`
              : `Recordatorio: ${issue.key} · ${issue.title}`,
            readAt: null,
            createdAt: command.now,
          },
        ]);
        sent++;
      }
      await this.reminders.markSent(reminder.id, command.now);
    }
    return sent;
  }
}

@QueryHandler(GetIssueReminderQuery)
export class GetIssueReminderQueryHandler
  implements IQueryHandler<GetIssueReminderQuery, IssueReminder | null>
{
  constructor(private readonly reminders: IssueRemindersRepository) {}

  execute(query: GetIssueReminderQuery): Promise<IssueReminder | null> {
    return this.reminders.waitingFor(query.userId, query.issueId);
  }
}

@QueryHandler(GetMyRemindersQuery)
export class GetMyRemindersQueryHandler
  implements
    IQueryHandler<
      GetMyRemindersQuery,
      { reminder: IssueReminder; issue: IssueReadModel }[]
    >
{
  constructor(
    private readonly reminders: IssueRemindersRepository,
    private readonly queryBus: QueryBus,
  ) {}

  async execute(
    query: GetMyRemindersQuery,
  ): Promise<{ reminder: IssueReminder; issue: IssueReadModel }[]> {
    const waiting = await this.reminders.waitingOf(query.userId);
    if (!waiting.length) return [];
    const issues: IssueReadModel[] = await this.queryBus.execute(
      new GetIssuesByIdsQuery(
        query.userId,
        waiting.map((r) => r.issueId),
      ),
    );
    const byId = new Map(
      issues.filter((i) => !i.trashedAt).map((i) => [i.id, i]),
    );
    return waiting.flatMap((reminder) => {
      const issue = byId.get(reminder.issueId);
      return issue ? [{ reminder, issue }] : [];
    });
  }
}

export const ISSUE_REMINDERS = [
  SetIssueReminderCommandHandler,
  ClearIssueReminderCommandHandler,
  SendIssueRemindersCommandHandler,
  GetIssueReminderQueryHandler,
  GetMyRemindersQueryHandler,
];