import { unwrap, type AuthSession, type PlayContext, type RepeatMode } from '@pipu/core';
import type { PlayerState } from './types';

const LOCAL_KEY = 'pipu.player';
/** Сохраняем не больше этого числа треков очереди (лимит сервера — 500). */
const MAX_SAVED_QUEUE = 500;

export interface Saved {
  queue: string[];
  index: number;
  positionMs: number;
  context: PlayContext | null;
  volume: number;
  shuffle: boolean;
  repeat: RepeatMode;
  savedAt: string;
}

function deviceId(): string {
  try {
    let id = localStorage.getItem('pipu.device');
    if (!id) {
      id = crypto.randomUUID();
      localStorage.setItem('pipu.device', id);
    }
    return id;
  } catch {
    return 'web';
  }
}

export class PlaybackPersistence {
  private readonly device = deviceId();
  lastServerSave = 0;
  constructor(private readonly session: AuthSession, private readonly getState: () => PlayerState) {}
  snapshot(state: PlayerState): Saved {
    const ids = state.queue.map((t) => t.id);
    const start = Math.max(0, Math.min(state.index - Math.floor(MAX_SAVED_QUEUE / 2), ids.length - MAX_SAVED_QUEUE));
    return {
      queue: ids.slice(start, start + MAX_SAVED_QUEUE),
      index: state.index - start,
      positionMs: state.positionMs,
      context: state.context,
      volume: state.volume,
      shuffle: state.shuffle,
      repeat: state.repeat,
      savedAt: new Date().toISOString(),
    };
  }
  saveLocal() {
    if (!this.getState().track) return;
    try {
      localStorage.setItem(LOCAL_KEY, JSON.stringify(this.snapshot(this.getState())));
    } catch {
      // недоступное хранилище не мешает воспроизведению
    }
  }

  private saveTimer: ReturnType<typeof setTimeout> | null = null;

  saveSoon() {
    if (this.saveTimer) clearTimeout(this.saveTimer);
    this.saveTimer = setTimeout(() => this.saveServer(), 1000);
  }

  /** PUT /me/playback-state; keepalive — запрос переживёт закрытие вкладки. */
  saveServer(keepalive = false) {
    const cur = this.getState().track;
    if (!cur) return;
    this.lastServerSave = Date.now();
    this.saveLocal();
    const s = this.snapshot(this.getState());
    void this.session.client
      .PUT('/api/v1/me/playback-state', {
        body: {
          track_id: cur.id,
          position_ms: s.positionMs,
          queue: s.queue,
          queue_index: s.index,
          context: s.context ? { type: s.context.type, id: s.context.id, label: s.context.label } : undefined,
          shuffle: s.shuffle,
          repeat_mode: s.repeat,
          volume: s.volume,
          device_id: this.device,
        },
        keepalive,
      })
      .catch(() => undefined);
  }

  async restore(): Promise<Saved | null> {
    let local: Saved | null = null;
    try {
      const raw = localStorage.getItem(LOCAL_KEY);
      local = raw ? (JSON.parse(raw) as Saved) : null;
    } catch {
      local = null;
    }
    let saved = local;
    try {
      const server = unwrap(await this.session.client.GET('/api/v1/me/playback-state'));
      if (
        server.track_id &&
        server.updated_at &&
        (!local || (server.device_id !== this.device && server.updated_at > local.savedAt))
      ) {
        saved = {
          queue: server.queue,
          index: server.queue_index,
          positionMs: server.position_ms,
          context: (server.context?.type ? server.context : null) as PlayContext | null,
          volume: server.volume,
          shuffle: server.shuffle,
          repeat: server.repeat_mode,
          savedAt: server.updated_at,
        };
      }
    } catch {
      // офлайн — остаёмся с локальной копией
    }
    return saved;
  }
  dispose() {
    if (this.saveTimer) clearTimeout(this.saveTimer);
    this.saveTimer = null;
  }
}