// source-provider.js — the load-bearing abstraction.
//
// A channel is "a named thing on a guide that resolves to an HLS stream at a
// point in time." Public iptv-org streams and your future self-hosted media are
// just different SourceProviders feeding the SAME UI. Build providers against
// this contract; the UI (guide/zapper/player) only ever talks to the aggregator.

/**
 * @typedef {Object} Channel
 * @property {string} id          Namespaced id, "source:rawId" (e.g. "iptv-org:CNN.us").
 * @property {string} source      Provider id that owns this channel.
 * @property {string} name        Display name (UNTRUSTED — render as textContent only).
 * @property {number} [number]    Assigned tuning number (filled by the aggregator).
 * @property {string} [logo]      Logo URL (UNTRUSTED — scheme-allowlisted before use).
 * @property {string} [group]     Category / group-title.
 * @property {string} [country]
 * @property {string} [language]
 * @property {'live'|'vod'} kind  Always 'live' for Phase 1; self-hosted "channels" are also 'live'.
 * @property {string[]} streamUrls  Playable HLS URLs (relay-wrapped where needed), primary + fallbacks.
 * @property {string[]} [probeUrls] Raw upstream https URLs for the health prober (pre-relay).
 * @property {string} [guideId]   Key used to match EPG/program data.
 */

/**
 * @typedef {Object} Program
 * @property {string} channelId
 * @property {string} title       UNTRUSTED — textContent only.
 * @property {string} [desc]
 * @property {number} start       Epoch ms (inclusive).
 * @property {number} stop        Epoch ms (exclusive).
 */

/**
 * @typedef {Object} StreamHandle
 * @property {string} url               Playable URL handed to HLS.js (may be relay-wrapped).
 * @property {'hls'} protocol
 * @property {Object<string,string>} [headers]
 */

/**
 * The contract every source implements. Extend this or just match the shape.
 * @abstract
 */
export class SourceProvider {
  /** @type {string} stable namespace, e.g. "iptv-org" */
  get id() { throw new Error('provider must define id'); }
  /** @type {string} human label */
  get name() { return this.id; }
  /** @type {boolean} */
  get supportsGuides() { return false; }

  /** @returns {Promise<Channel[]>} */
  async listChannels() { throw new Error('not implemented'); }

  /**
   * Resolve a channel to something HLS.js can play (relay-wrapped if needed).
   * @param {string} _channelId
   * @returns {Promise<StreamHandle|null>}
   */
  async getStreamHandle(_channelId) { throw new Error('not implemented'); }

  /**
   * EPG slice for a time window. Default: none.
   * @param {string} _channelId
   * @param {{from:number,to:number}} _window
   * @returns {Promise<Program[]>}
   */
  async getPrograms(_channelId, _window) { return []; }

  /**
   * Optional liveness probe.
   * @param {string} _channelId
   * @returns {Promise<{ok:boolean, error?:string}>}
   */
  async healthCheck(_channelId) { return { ok: true }; }
}

/**
 * Merges channels from many providers behind one interface and routes
 * per-channel calls back to the owning provider by source-prefix.
 */
export class ChannelAggregator {
  constructor() {
    /** @type {Map<string, SourceProvider>} */
    this.providers = new Map();
    /** @type {Channel[]} */
    this._channels = [];
    /** @type {Map<string, Channel>} */
    this._byId = new Map();
  }

  /** @param {SourceProvider} provider */
  register(provider) {
    this.providers.set(provider.id, provider);
    return this;
  }

  /**
   * Load + merge all providers. De-dups by id, assigns sequential tuning numbers.
   * @returns {Promise<Channel[]>}
   */
  async listAllChannels() {
    const lists = await Promise.all(
      [...this.providers.values()].map(async (p) => {
        try { return await p.listChannels(); }
        catch (e) { console.warn(`[aggregator] provider ${p.id} failed:`, e); return []; }
      }),
    );
    const seen = new Set();
    /** @type {Channel[]} */
    const merged = [];
    for (const list of lists) {
      for (const ch of list) {
        if (!ch || !ch.id || seen.has(ch.id)) continue;
        seen.add(ch.id);
        merged.push(ch);
      }
    }
    // Respect any explicit number, otherwise assign by order starting at 2 (channel 1 reserved).
    let next = 2;
    const used = new Set(merged.filter((c) => Number.isFinite(c.number)).map((c) => c.number));
    for (const ch of merged) {
      if (!Number.isFinite(ch.number)) {
        while (used.has(next)) next++;
        ch.number = next;
        used.add(next);
      }
    }
    merged.sort((a, b) => a.number - b.number);
    this._channels = merged;
    this._byId = new Map(merged.map((c) => [c.id, c]));
    return merged;
  }

  /** @returns {Channel[]} */
  get channels() { return this._channels; }

  /** @param {string} id @returns {Channel|undefined} */
  getChannel(id) { return this._byId.get(id); }

  /** @param {number} number @returns {Channel|undefined} */
  getChannelByNumber(number) { return this._channels.find((c) => c.number === number); }

  /** @param {string} channelId @returns {SourceProvider|undefined} */
  _ownerOf(channelId) {
    const source = channelId.split(':', 1)[0];
    return this.providers.get(source);
  }

  /** @param {string} channelId @returns {Promise<StreamHandle|null>} */
  async getStreamHandle(channelId) {
    const owner = this._ownerOf(channelId);
    if (!owner) return null;
    return owner.getStreamHandle(channelId);
  }

  /**
   * @param {string} channelId
   * @param {{from:number,to:number}} window
   * @returns {Promise<Program[]>}
   */
  async getPrograms(channelId, window) {
    const owner = this._ownerOf(channelId);
    if (!owner) return [];
    try { return await owner.getPrograms(channelId, window); }
    catch { return []; }
  }

  /**
   * now/next helper used by the OSD banner and guide.
   * @param {string} channelId
   * @param {number} [at] epoch ms (default: now)
   * @returns {Promise<{now: Program|null, next: Program|null}>}
   */
  async nowNext(channelId, at = Date.now()) {
    const horizon = at + 6 * 3600 * 1000;
    const programs = await this.getPrograms(channelId, { from: at - 3600 * 1000, to: horizon });
    programs.sort((a, b) => a.start - b.start);
    let now = null, next = null;
    for (const p of programs) {
      if (p.start <= at && at < p.stop) now = p;
      else if (p.start > at && !next) next = p;
    }
    return { now, next };
  }
}