import {
  ChangeDetectionStrategy,
  Component,
  DestroyRef,
  OnDestroy,
  OnInit,
  ViewChild,
  computed,
  effect,
  inject,
  signal,
} from '@angular/core';
import { CommonModule } from '@angular/common';
import { AuthService } from '../../core/services/auth.service';
import { AuthenticatedEventSourceService } from '../../core/services/authenticated-event-source.service';
import { EventStatusStore } from '../../core/services/event-status.store';
import { ChallengesStore } from './challenges.store';
import { CategoryColumnComponent } from './category-column.component';
import { ChallengeModalComponent } from './challenge-modal.component';
import { SolverRow, formatDdHhMm } from './challenges.pure';

@Component({
  selector: 'app-challenges-page',
  standalone: true,
  changeDetection: ChangeDetectionStrategy.OnPush,
  imports: [CommonModule, CategoryColumnComponent, ChallengeModalComponent],
  styles: [`
    :host { display: block; }
    .wrap { padding: 12px 0; }
    .grid {
      display: flex; gap: 12px;
      overflow-x: auto; overflow-y: visible;
      padding-bottom: 12px;
    }
    .gate {
      display: flex; align-items: center; justify-content: center;
      min-height: 240px; flex-direction: column; gap: 8px;
      padding: 32px;
    }
    .gate h2 { margin: 0; }
    .countdown {
      font-variant-numeric: tabular-nums; font-size: 28px; font-weight: 700;
      letter-spacing: 0.04em;
    }
    .label { opacity: 0.7; }
    .error { color: var(--color-danger, #ef4444); }
  `],
  template: `
    <section class="wrap" data-testid="challenges-page">
      <ng-container *ngIf="isRunning(); else gate">
        <h2>Challenges</h2>
        <div class="grid" data-testid="challenges-grid">
          <app-category-column
            *ngFor="let col of store.sortedColumns(); trackBy: trackByCol"
            [column]="col"
            (openCard)="openChallenge($event)"
          ></app-category-column>
        </div>
      </ng-container>

      <ng-template #gate>
        <div class="gate" data-testid="challenges-gate">
          <h2 *ngIf="eventState() === 'countdown'">Event starts in</h2>
          <h2 *ngIf="eventState() === 'stopped'">Event ended</h2>
          <h2 *ngIf="eventState() === 'unconfigured'">Awaiting configuration</h2>
          <div class="countdown" data-testid="challenges-countdown">
            {{ countdownText() }}
          </div>
          <div class="label" *ngIf="eventState() === 'countdown'">The board will be available once the event is running.</div>
          <div class="label" *ngIf="eventState() === 'stopped'">The board is closed.</div>
        </div>
      </ng-template>

      <div class="error" *ngIf="store.error() as e">{{ e }}</div>

      <app-challenge-modal
        *ngIf="selectedCard() as card"
        #modal
        [card]="card"
        [initialSolvers]="selectedSolvers()"
        [canSubmit]="canSubmit()"
        [noticeOverride]="modalNotice()"
        (close)="closeChallenge()"
        (submitted)="onSubmitted()"
      ></app-challenge-modal>
    </section>
  `,
})
export class ChallengesPage implements OnInit, OnDestroy {
  readonly store = inject(ChallengesStore);
  private readonly eventStatus = inject(EventStatusStore);
  private readonly auth = inject(AuthService);
  private readonly authenticatedEventSource = inject(AuthenticatedEventSourceService);
  private readonly destroyRef = inject(DestroyRef);

  @ViewChild('modal') modalRef?: ChallengeModalComponent;

  readonly eventState = this.eventStatus.state;
  readonly secondsToStart = this.eventStatus.secondsToStartPublic;
  readonly secondsToEnd = this.eventStatus.secondsToEndPublic;

  readonly isRunning = computed(() => this.eventState() === 'running');
  readonly canSubmit = computed(() => this.eventStatus.state() === 'running');
  readonly modalNotice = computed(() =>
    this.eventStatus.state() === 'running'
      ? null
      : 'Submissions are only accepted while the event is running.',
  );

  readonly countdownText = computed(() => {
    const s = this.eventState();
    if (s === 'countdown') {
      return formatDdHhMm(this.secondsToStart() ?? 0);
    }
    if (s === 'running') {
      return formatDdHhMm(this.secondsToEnd() ?? 0);
    }
    if (s === 'stopped') return 'Event ended';
    return '';
  });

  readonly selectedCard = signal<ReturnType<ChallengesStore['findCard']>>(null);
  readonly selectedSolvers = signal<SolverRow[]>([]);

  private sseWired = false;
  private currentSolveUnsub: (() => void) | null = null;

  constructor() {
    this.destroyRef.onDestroy(() => this.store.stop());
    const unsubscribeReload = this.eventStatus.subscribeReloadAtCountdownZero(() => {
      if (typeof window !== 'undefined') window.location.reload();
    });
    this.destroyRef.onDestroy(() => unsubscribeReload());
  }

  ngOnInit(): void {
    const user = this.auth.currentUser();
    if (user?.id) this.store.setMyUserId(user.id);
    void this.store.load();

    // REST snapshot first so the page has synchronous state even if the SSE
    // stream hasn't delivered its first frame yet (e.g. slow networks, mobile).
    this.store.fetchEventState().subscribe({
      next: (payload) => this.eventStatus.applyServerStatus(payload),
      error: () => undefined,
    });

    if (!this.sseWired) {
      this.sseWired = true;
      this.store.wireSse(
        () => this.authenticatedEventSource.open('/api/v1/events'),
      );
    }
  }

  ngOnDestroy(): void {
    this.store.stop();
    this.currentSolveUnsub?.();
  }

  trackByCol = (_idx: number, col: { id: string }) => col.id;

  openChallenge(id: string): void {
    const card = this.store.findCard(id);
    this.selectedCard.set(card);
    this.selectedSolvers.set([]);
    this.currentSolveUnsub?.();
    this.currentSolveUnsub = this.store.registerSolveListener(id, (payload) => {
      this.modalRef?.applyLiveSolve(payload);
    });
    void this.store.loadDetail(id).then((detail) => {
      if (!detail) return;
      if (this.selectedCard()?.id !== id) return;
      this.selectedSolvers.set(detail.solvers);
    });
  }

  closeChallenge(): void {
    this.selectedCard.set(null);
    this.selectedSolvers.set([]);
    this.currentSolveUnsub?.();
    this.currentSolveUnsub = null;
    this.store.clearSelectedDetail();
  }

  onSubmitted(): void {
    // No-op: the store already mutated the board; the modal updates itself.
  }
}