import { DestroyRef, Injectable, computed, inject, signal } from '@angular/core';
import { Observable } from 'rxjs';
import {
  BoardCard,
  BoardResponse,
  CategoryColumn,
  ChallengeDetail,
  EventStatePayloadLike,
  SolveEventLivePayload,
  SolveEventPayload,
  SolveResponse,
  SolverRow,
  mergeSolveEventIntoSolvers,
  parseSolveEvent,
  sortCardsInColumn,
  sortColumnsByAbbrev,
} from './challenges.pure';
import { ChallengesApiService } from './challenges.service';
import { EventSourceLike } from '../../core/services/event-status.pure';

@Injectable({ providedIn: 'root' })
export class ChallengesStore {
  private readonly api: ChallengesApiService;
  private readonly destroyRef: DestroyRef;

  private readonly _board = signal<BoardResponse | null>(null);
  private readonly _eventState = signal<EventStatePayloadLike['state']>('unconfigured');
  private readonly _secondsToStart = signal<number | null>(null);
  private readonly _secondsToEnd = signal<number | null>(null);
  private readonly _loading = signal(false);
  private readonly _error = signal<string | null>(null);
  private readonly _tick = signal(0);
  private readonly _myUserId = signal<string | null>(null);
  private readonly _selectedDetail = signal<ChallengeDetail | null>(null);

  private readonly solveListeners = new Map<string, Set<(p: SolveEventLivePayload) => void>>();

  constructor(api?: ChallengesApiService, destroyRef?: DestroyRef) {
    this.api = api ?? inject(ChallengesApiService);
    this.destroyRef = destroyRef ?? inject(DestroyRef);
    this.destroyRef.onDestroy(() => this.stop());
  }

  readonly board = this._board.asReadonly();
  readonly loading = this._loading.asReadonly();
  readonly error = this._error.asReadonly();
  readonly eventState = this._eventState.asReadonly();
  readonly selectedChallengeDetail = this._selectedDetail.asReadonly();

  readonly sortedColumns = computed<CategoryColumn[]>(() => {
    const b = this._board();
    if (!b) return [];
    return sortColumnsByAbbrev(
      b.columns.map((col) => ({
        ...col,
        cards: sortCardsInColumn(col.cards),
      })),
    );
  });

  readonly isRunning = computed(() => this._eventState() === 'running');

  readonly countdownSeconds = computed<number | null>(() => {
    void this._tick();
    const state = this._eventState();
    if (state === 'countdown') return this._secondsToStart();
    if (state === 'running') return this._secondsToEnd();
    return null;
  });

  private intervalId: ReturnType<typeof setInterval> | null = null;
  private sse: EventSourceLike | null = null;
  private countdownZeroHandler: (() => void) | null = null;

  setMyUserId(id: string | null): string | null {
    const prev = this._myUserId();
    const hasCachedUserData = this._board() !== null || this._selectedDetail() !== null;
    if (hasCachedUserData && prev !== id) {
      this.reset();
    }
    this._myUserId.set(id);
    return prev;
  }

  reset(): void {
    this.stop();
    this._board.set(null);
    this._selectedDetail.set(null);
    this._myUserId.set(null);
    this._error.set(null);
    this._loading.set(false);
    this.countdownZeroHandler = null;
    this.solveListeners.clear();
  }

  async load(): Promise<void> {
    this._loading.set(true);
    this._error.set(null);
    try {
      const board = await new Promise<BoardResponse>((resolve, reject) => {
        this.api.getBoard().subscribe({ next: resolve, error: reject });
      });
      this._board.set(board);
    } catch (err: any) {
      this._error.set(err?.message ?? 'Failed to load challenges');
    } finally {
      this._loading.set(false);
    }
  }

  fetchEventState(): Observable<EventStatePayloadLike> {
    return this.api.getEventState();
  }

  async loadDetail(id: string): Promise<ChallengeDetail | null> {
    try {
      const detail = await new Promise<ChallengeDetail>((resolve, reject) => {
        this.api.getDetail(id).subscribe({ next: resolve, error: reject });
      });
      this._selectedDetail.set(detail);
      this.applySubmitResponse({
        status: 'solved',
        challenge: detail.challenge,
        awarded: {
          position: 0,
          basePoints: 0,
          rankBonus: 0,
          awardedPoints: 0,
          awardedAtUtc: '',
        },
        solvers: detail.solvers,
      });
      return detail;
    } catch {
      this._selectedDetail.set(null);
      return null;
    }
  }

  clearSelectedDetail(): void {
    this._selectedDetail.set(null);
  }

  registerSolveListener(challengeId: string, listener: (p: SolveEventLivePayload) => void): () => void {
    const set = this.solveListeners.get(challengeId) ?? new Set();
    set.add(listener);
    this.solveListeners.set(challengeId, set);
    return () => {
      const cur = this.solveListeners.get(challengeId);
      if (!cur) return;
      cur.delete(listener);
      if (cur.size === 0) this.solveListeners.delete(challengeId);
    };
  }

  applyStatusPayload(payload: EventStatePayloadLike): void {
    this._eventState.set(payload.state);
    this._secondsToStart.set(payload.secondsToStart);
    this._secondsToEnd.set(payload.secondsToEnd);
  }

  wireSse(createSource: () => EventSourceLike, onUnauthorized?: () => void): void {
    this.stop();
    const src = createSource();
    this.sse = src;
    // The challenges store only cares about 'solve' frames. The status stream is
    // consumed separately by EventStatusStore (via its own 'message' listener).
    // Registering on multiple event names would cause each frame to be dispatched
    // twice (the transport fan-outs to both the named listener and 'message').
    const handler = (ev: MessageEvent | Event) => this.handleSseFrame(ev);
    src.addEventListener('solve', handler);
    if (onUnauthorized) {
      src.addEventListener('unauthorized', () => {
        try {
          onUnauthorized();
        } catch {
          // ignore
        }
      });
    }
    if (!this.intervalId) {
      this.intervalId = setInterval(() => this._tick.update((v) => v + 1), 1000);
    }
    queueMicrotask(() => this.checkCountdownZero());
  }

  /** Exposed for tests; safe to call externally as it is read-only on state. */
  handleSseFrame(ev: MessageEvent | Event): void {
    const me = ev as MessageEvent;
    if (me.type !== 'solve') return;
    try {
      const raw = typeof me.data === 'string' ? JSON.parse(me.data) : me.data;
      if (!raw) return;
      const payload = parseSolveEvent(raw);
      this.applySolveEvent(payload);
      const listeners = this.solveListeners.get(payload.challengeId);
      if (listeners) {
        for (const fn of listeners) {
          try { fn(payload); } catch { /* ignore */ }
        }
      }
    } catch {
      // ignore malformed frame
    }
  }

  onCountdownZero(handler: () => void): void {
    this.countdownZeroHandler = handler;
  }

  private checkCountdownZero(): void {
    const state = this._eventState();
    if (state === 'countdown') {
      const s = this._secondsToStart();
      if (s !== null && s <= 0 && this.countdownZeroHandler) {
        this.countdownZeroHandler();
      }
    } else if (state === 'running') {
      const s = this._secondsToEnd();
      if (s !== null && s <= 0 && this.countdownZeroHandler) {
        this.countdownZeroHandler();
      }
    }
    if (this.intervalId) {
      setTimeout(() => this.checkCountdownZero(), 1000);
    }
  }

  applySolveEvent(payload: SolveEventLivePayload): void {
    const board = this._board();
    const me = this._myUserId();
    const isMine = me !== null && payload.playerId === me;
    if (board) {
      const updated: BoardResponse = {
        ...board,
        columns: board.columns.map((col) => ({
          ...col,
          cards: col.cards.map((card): BoardCard => {
            if (card.id !== payload.challengeId) return card;
            return {
              ...card,
              livePoints: payload.livePoints ?? card.livePoints,
              solveCount: payload.solveCount ?? card.solveCount + 1,
              solvedByMe: isMine ? true : card.solvedByMe,
            };
          }),
        })),
        solvedChallengeIds: isMine && !board.solvedChallengeIds.includes(payload.challengeId)
          ? [...board.solvedChallengeIds, payload.challengeId]
          : board.solvedChallengeIds,
        perChallengeLivePoints: payload.livePoints != null
          ? { ...board.perChallengeLivePoints, [payload.challengeId]: payload.livePoints }
          : board.perChallengeLivePoints,
      };
      this._board.set(updated);
    }
    const detail = this._selectedDetail();
    if (detail && detail.challenge.id === payload.challengeId) {
      const livePoints = payload.livePoints ?? detail.challenge.livePoints;
      const solveCount = payload.solveCount ?? detail.challenge.solveCount + 1;
      this._selectedDetail.set({
        challenge: {
          ...detail.challenge,
          livePoints,
          solveCount,
          solvedByMe: isMine ? true : detail.challenge.solvedByMe,
        },
        solvers: mergeSolveEventIntoSolvers(detail.solvers, payload),
      });
    }
  }

  applySubmitResponse(response: SolveResponse): void {
    const board = this._board();
    if (board) {
      const updated: BoardResponse = {
        ...board,
        columns: board.columns.map((col) => ({
          ...col,
          cards: col.cards.map((card): BoardCard => {
            if (card.id !== response.challenge.id) return card;
            return {
              ...card,
              livePoints: response.challenge.livePoints,
              solveCount: response.challenge.solveCount,
              solvedByMe: response.challenge.solvedByMe,
            };
          }),
        })),
        solvedChallengeIds: response.challenge.solvedByMe && !board.solvedChallengeIds.includes(response.challenge.id)
          ? [...board.solvedChallengeIds, response.challenge.id]
          : board.solvedChallengeIds,
        perChallengeLivePoints: {
          ...board.perChallengeLivePoints,
          [response.challenge.id]: response.challenge.livePoints,
        },
      };
      this._board.set(updated);
    }
  }

  findCard(id: string): BoardCard | null {
    const board = this._board();
    if (!board) return null;
    for (const col of board.columns) {
      const card = col.cards.find((c) => c.id === id);
      if (card) return card;
    }
    return null;
  }

  stop(): void {
    if (this.sse) {
      try {
        this.sse.close();
      } catch {
        // ignore
      }
      this.sse = null;
    }
    if (this.intervalId) {
      clearInterval(this.intervalId);
      this.intervalId = null;
    }
  }

  async submit(challengeId: string, flag: string): Promise<SolveResponse> {
    return new Promise<SolveResponse>((resolve, reject) => {
      this.api.submit(challengeId, flag).subscribe({
        next: (resp) => {
          this.applySubmitResponse(resp);
          resolve(resp);
        },
        error: (err) => reject(err),
      });
    });
  }

  buildSolversFromResponse(solvers: SolverRow[]): SolverRow[] {
    return [...solvers].sort((a, b) => {
      const at = new Date(a.solvedAtUtc).getTime();
      const bt = new Date(b.solvedAtUtc).getTime();
      return at - bt;
    }).map((s, idx) => ({ ...s, position: idx + 1 }));
  }

  mergeLiveSolver(solvers: SolverRow[], payload: SolveEventPayload): SolverRow[] {
    return mergeSolveEventIntoSolvers(solvers, payload);
  }
}