import { Controller, Get, Sse, MessageEvent } from '@nestjs/common';
import { ApiTags, ApiOperation } from '@nestjs/swagger';
import { interval, map, merge, mergeMap, Observable, startWith, defer, distinctUntilChanged } from 'rxjs';
import { Public } from '../../common/decorators/public.decorator';
import { SystemService } from './system.service';
import { EventStatusService } from '../../common/services/event-status.service';
import { SseHubService } from '../../common/services/sse-hub.service';
import { SettingsService } from '../settings/settings.module';

@ApiTags('system')
@Controller('api/v1')
export class SystemController {
  constructor(
    private readonly system: SystemService,
    private readonly statusSvc: EventStatusService,
    private readonly hub: SseHubService,
    private readonly settings: SettingsService,
  ) {}

  @Public()
  @Get('bootstrap')
  @ApiOperation({ summary: 'Public bootstrap payload used by the SPA on startup' })
  bootstrap() {
    return this.system.bootstrap();
  }

  @Public()
  @Get('event/status')
  @ApiOperation({ summary: 'Event status derived from UTC timestamps' })
  eventStatus() {
    return this.statusSvc.getStatus();
  }

  @Public()
  @Get('settings/event')
  @ApiOperation({ summary: 'Public-readable event window timestamps (UTC)' })
  async settingsEvent(): Promise<{ eventStartUtc: string | null; eventEndUtc: string | null }> {
    const eventStartUtc = (await this.settings.get('eventStartUtc')) || null;
    const eventEndUtc = (await this.settings.get('eventEndUtc')) || null;
    return { eventStartUtc, eventEndUtc };
  }

  /**
   * Global event status + countdown stream.
   * Emits a FLATTENED object every second (and whenever the hub pushes).
   */
  @Public()
  @Sse('event/stream')
  eventStream(): Observable<MessageEvent> {
    const tick$ = interval(1000).pipe(
      startWith(0),
      mergeMap(() =>
        defer(() =>
          this.statusSvc.getStatus().then((s) => ({
            status: s.status,
            countdownMs: s.countdownMs,
            serverNowUtc: s.serverNowUtc,
            startUtc: s.startUtc,
            endUtc: s.endUtc,
          })),
        ),
      ),
    );
    const hub$ = this.hub.event$().pipe(
      map((payload: any) => ({
        status: payload?.status,
        countdownMs: payload?.countdownMs,
        serverNowUtc: payload?.serverNowUtc,
        startUtc: payload?.startUtc,
        endUtc: payload?.endUtc,
      })),
    );
    return merge(tick$, hub$).pipe(map((src) => ({ data: src }) as MessageEvent));
  }

  /**
   * Authenticated event status SSE.
   * Path: GET /api/v1/events/status (note the plural 'events').
   * Emits an initial state immediately on connect, then re-emits on transition
   * and on a minimum 60s tick while in 'countdown' state.
   * Protected by the global JwtAuthGuard (so unauthenticated clients get 401).
   */
  @Sse('events/status')
  eventsStatus(): Observable<MessageEvent> {
    const flat = (s: any) => ({
      state: s?.state,
      serverNowUtc: s?.serverNowUtc,
      eventStartUtc: s?.eventStartUtc,
      eventEndUtc: s?.eventEndUtc,
      secondsToStart: s?.secondsToStart,
      secondsToEnd: s?.secondsToEnd,
    });

    const initial$ = defer(() =>
      this.statusSvc.getState().then((s) => flat(s)),
    );

    const tick$ = interval(60_000).pipe(
      startWith(0),
      mergeMap(() =>
        defer(() =>
          this.statusSvc.getState().then((s) => flat(s)),
        ),
      ),
    );

    const hub$ = this.hub.event$().pipe(map((p) => flat(p)));

    return merge(initial$, tick$, hub$).pipe(
      distinctUntilChanged((a, b) => JSON.stringify(a) === JSON.stringify(b)),
      map((src) => ({ data: src }) as MessageEvent),
    );
  }

  /**
   * Live solves stream.
   * Emits a FLATTENED solve payload whenever a new solve is published.
   */
  @Public()
  @Sse('scoreboard/stream')
  scoreboardStream(): Observable<MessageEvent> {
    return this.hub.scoreboard$().pipe(
      map((s: any) => ({
        challengeId: s?.challengeId,
        userId: s?.userId,
        pointsAwarded: s?.pointsAwarded,
        rankBonus: s?.rankBonus,
        solvedAt: s?.solvedAt,
      })),
      map((src) => ({ data: src }) as MessageEvent),
    );
  }
}