import { Inject, Injectable } from '@nestjs/common';
import { ISSUE_STATUSES, type IssueStatusValue } from '../../../../issue/domain/value-objects/issue-status.vo.js';
import {
  ISSUE_HISTORY_REPOSITORY,
  type IIssueHistoryRepository,
} from '../../../domain/repositories/issue-history.repository.interface.js';
import { StatsPeriod } from '../../../domain/value-objects/stats-period.vo.js';
import { DailyIssueStatsDayDto, DailyIssueStatsDto, IssueStatusCounts } from '../../dto/daily-issue-stats.dto.js';
import { GetDailyIssueStatsQuery } from './get-daily-issue-stats.query.js';

/**
 * Статистика задач по дням, считается по истории изменений (issue_change).
 * Видимость — как у списка задач: только задачи, где пользователь reporter/assignee/наблюдатель.
 */
@Injectable()
export class GetDailyIssueStatsUseCase {
  constructor(
    @Inject(ISSUE_HISTORY_REPOSITORY)
    private readonly historyRepository: IIssueHistoryRepository,
  ) {}

  async execute(query: GetDailyIssueStatsQuery): Promise<DailyIssueStatsDto> {
    const period = StatsPeriod.create({ from: query.from, to: query.to, timeZone: query.timeZone });
    const range = {
      userId: query.userId,
      projectId: query.projectId,
      from: period.from,
      to: period.to,
      timeZone: period.timeZone,
    };

    const [events, statuses] = await Promise.all([
      this.historyRepository.countDailyEvents(range),
      this.historyRepository.countDailyStatuses(range),
    ]);

    // Каждый день периода попадает в ответ, даже если в нём ничего не было
    const days = new Map<string, DailyIssueStatsDayDto>(
      period.days.map((date) => [
        date,
        { date, created: 0, transitions: emptyStatusCounts(), byStatus: emptyStatusCounts() },
      ]),
    );

    for (const event of events) {
      const day = days.get(event.date);
      if (!day) continue;

      if (event.kind === 'created') {
        day.created += event.count;
      } else if (isKnownStatus(event.status)) {
        day.transitions[event.status] += event.count;
      }
    }

    for (const entry of statuses) {
      const day = days.get(entry.date);
      if (day && isKnownStatus(entry.status)) {
        day.byStatus[entry.status] += entry.count;
      }
    }

    return { from: period.from, to: period.to, timeZone: period.timeZone, days: [...days.values()] };
  }
}

function emptyStatusCounts(): IssueStatusCounts {
  return Object.fromEntries(ISSUE_STATUSES.map((status) => [status.alias, 0])) as IssueStatusCounts;
}

function isKnownStatus(status: string): status is IssueStatusValue {
  return ISSUE_STATUSES.some((known) => known.alias === status);
}