/**
 * pbl_overlay_transport.js —— 覆盖层传输层（M9 / pbl_scense_ext）
 *
 * 职责：① 契约调用（bootstrap / 意图上行 / 证据 / 反馈）；② 广播通道（SSE 优先，长轮询降级，
 * Q-OPEN-6 定稿）；③ seq 幂等去重 + 掉线补齐（get_state_snapshot + poll_events(since)）；
 * ④ 广播渲染时延预算 ≤500ms 的计时与降级。
 *
 * 纪律：本层只搬运数据并派发 pbl:broadcast-received 事件，DOM 更新由 pbl_overlay.js 负责，
 * 不触碰 scense/scense_game 渲染主循环。
 */
(function (global) {
  'use strict';

  var Core = global.PblOverlayCore;
  if (!Core) { throw new Error('pbl_overlay_core.js 必须先于 pbl_overlay_transport.js 加载'); }

  var BUDGETS = Core.BUDGETS;

  // 契约端点表（模块自动路由 /{module}/api/{name}.dspy）
  var ENDPOINTS = {
    'bootstrap':      '/pbl_scense_ext/api/pbl_overlay_bootstrap.dspy',
    'page_registry':  '/pbl_scense_ext/api/pbl_page_registry_list.dspy',
    'session_ctx':    '/pbl_scense_ext/api/pbl_session_context_get.dspy',
    'feedback_save':  '/pbl_scense_ext/api/pbl_playtest_feedback_save.dspy',
    // 运行时（pbl_runtime_ext，M11a/M11b 权威实现）
    'event_poll':     '/pbl_runtime_ext/api/pbl_runtime_event_poll.dspy',
    'broadcast_pull': '/pbl_runtime_ext/api/pbl_runtime_broadcast_pull.dspy',
    'entity_state':   '/pbl_runtime_ext/api/pbl_entity_state_get.dspy',
    'world_broadcast':'/pbl_runtime_ext/api/pbl_world_broadcast.dspy',
    // 意图上行 / 证据 / 评估（其余 pbl_* 模块契约）
    'submit_intent':  '/pbl_runtime_ext/api/pbl_world_broadcast.dspy',
    'entity_apply':   '/pbl_runtime_ext/api/pbl_entity_state_apply.dspy',
    'evidence_collect': '/pbl_evidence/api/pbl_collect_evidence.dspy',
    'artifact_create':  '/pbl_evidence/api/pbl_create_artifact.dspy',
    'artifact_submit':  '/pbl_evidence/api/pbl_submit_artifact.dspy',
    'assessment_report': '/pbl_assessment/api/pbl_assessment_report.dspy'
  };

  function apiBase() {
    // 去掉页面路由尾部，得到应用根（与 scense_game game.js 同策略，不改基线）
    return (global.__PBL_API_BASE__ || String(location.pathname).replace(/\/(pbl_overlay|game|scense_game)\/.*$/, '')).replace(/\/$/, '');
  }

  function Transport(opts) {
    opts = opts || {};
    this.sessionId = opts.session_id || null;
    this.blueprintId = opts.blueprint_id || null;
    this.lastSeq = Number(opts.since_seq || 0);
    this.pending = {};          // seq -> true（去重）
    this.sse = null;
    this.timer = null;
    this.stopped = false;
    this.cache = {};            // 断网时供降级态展示缓存数据
    this.onEvent = opts.onEvent || function () {};
    this.onDegrade = opts.onDegrade || function () {};
    this.onPerf = opts.onPerf || function () {};
  }

  /* ───────────── 1. 契约调用（POST，参数进 params_kw） ───────────── */
  Transport.prototype.call = function (name, params) {
    var url = ENDPOINTS[name];
    if (!url) { return Promise.reject({ code: 'PBL_E_NOT_FOUND', message: '未知契约 ' + name }); }
    var body = Object.assign({}, params || {});
    if (this.sessionId && body.session_id === undefined) { body.session_id = this.sessionId; }
    if (this.blueprintId && body.blueprint_id === undefined) { body.blueprint_id = this.blueprintId; }
    var ctrl = ('AbortController' in global) ? new AbortController() : null;
    var to = ctrl ? setTimeout(function () { ctrl.abort(); }, BUDGETS.intent_timeout_ms) : null;
    var self = this;
    return fetch(apiBase() + url, {
      method: 'POST',
      credentials: 'same-origin',
      headers: { 'Content-Type': 'application/json;charset=UTF-8' },
      body: JSON.stringify(body),
      signal: ctrl ? ctrl.signal : undefined
    }).then(function (r) {
      if (to) { clearTimeout(to); }
      if (r.status === 401 || r.status === 403) { return { status: 'fail', code: 'PBL_E_FORBIDDEN', message: 'HTTP ' + r.status }; }
      if (r.status === 429) { return { status: 'fail', code: 'PBL_RATE_LIMIT', message: '请求过于频繁' }; }
      if (!r.ok) { return { status: 'fail', code: 'PBL_E_NETWORK', message: 'HTTP ' + r.status }; }
      return r.json();
    }).then(function (res) {
      if (res && res.status === 'fail') {
        self.onDegrade(res.code || 'PBL_E_NETWORK', res.message || res.msg || '');
        var e = new Error(res.message || 'contract fail');
        e.code = res.code; e.payload = res;
        throw e;
      }
      self.cache[name] = { at: Date.now(), data: res };
      return res;
    }).catch(function (err) {
      if (err && err.name === 'AbortError') { self.onDegrade('PBL_E_TIMEOUT', '契约超时 ' + name); }
      else if (err && !err.code) { self.onDegrade('PBL_E_NETWORK', '网络中断'); }
      throw err;
    });
  };

  /* ───────────── 2. S1 进入世界：一次 bootstrap 拿齐上下文 ───────────── */
  Transport.prototype.bootstrap = function (extra) {
    var self = this;
    return this.call('bootstrap', Object.assign({ recent_events: 20 }, extra || {})).then(function (ctx) {
      var d = (ctx && ctx.data) || ctx || {};
      self.context = d;
      if (Array.isArray(d.recent_events)) {
        d.recent_events.forEach(function (ev) { self._accept(ev, true); });
      }
      if (d.max_seq !== undefined) { self.lastSeq = Math.max(self.lastSeq, Number(d.max_seq) || 0); }
      return d;
    });
  };

  Transport.prototype.pageRegistry = function () {
    return this.call('page_registry', { page_size: 50 }).then(function (r) {
      var d = (r && r.data) || r || {};
      return d.rows || d.data || d || [];
    });
  };

  /* ───────────── 3. S2 意图上行（前端无权威状态，仅发起） ───────────── */
  Transport.prototype.submitIntent = function (intent) {
    var payload = {
      intent_type: intent.type || 'action',
      action: intent.action || '',
      entity_id: intent.entity_id || '',
      payload_json: JSON.stringify(intent.payload || {}),
      client_ts: Date.now()
    };
    var self = this;
    Core.Bus.emit('pbl:intent-submitted', payload);
    return this.call(intent.channel || 'submit_intent', payload).then(function (r) {
      var d = (r && r.data) || r || {};
      // 服务端权威：只有回传 seq 后才允许更新覆盖层（不预测渲染）
      if (d.seq !== undefined) { self._accept({ seq: d.seq, event_type: intent.action || 'ack', payload_json: d }, true); }
      return d;
    });
  };

  /* ───────────── 4. 广播通道：SSE 优先，长轮询降级 ───────────── */
  Transport.prototype.subscribe = function () {
    var self = this;
    if (this.stopped) { return; }
    var sseUrl = apiBase() + '/pbl_runtime_ext/api/pbl_runtime_broadcast_pull.dspy?session_id=' +
                 encodeURIComponent(this.sessionId || '') + '&since_seq=' + this.lastSeq;
    var ok = false;
    if (typeof global.EventSource === 'function' && !this.sse) {
      try {
        this.sse = new global.EventSource(sseUrl);
        this.sse.onmessage = function (m) {
          var ev = null;
          try { ev = JSON.parse(m.data); } catch (e) { ev = null; }
          if (ev) { self._accept(ev); }
        };
        this.sse.onerror = function () {
          self.closeSse();
          self.onDegrade('PBL_RENDER_DEGRADED', '实时通道降级为长轮询');
          self.poll();
        };
        ok = true;
      } catch (e) { ok = false; }
    }
    if (!ok) { this.poll(); }
  };

  Transport.prototype.closeSse = function () {
    if (this.sse) { try { this.sse.close(); } catch (e) { } this.sse = null; }
  };

  /** 长轮询降级：固定节拍拉取增量（seq 单调，去重幂等） */
  Transport.prototype.poll = function () {
    var self = this;
    if (this.stopped) { return; }
    if (this.timer) { clearInterval(this.timer); }
    this.timer = setInterval(function () { self.pollOnce(); }, BUDGETS.poll_interval_ms);
    this.pollOnce();
  };

  Transport.prototype.pollOnce = function () {
    var self = this;
    return this.call('broadcast_pull', { since_seq: this.lastSeq, limit: 50 })
      .then(function (r) {
        var d = (r && r.data) || r || {};
        var evs = d.events || d.rows || [];
        for (var i = 0; i < evs.length; i++) { self._accept(evs[i]); }
        if (d.max_seq !== undefined) { self.lastSeq = Math.max(self.lastSeq, Number(d.max_seq) || 0); }
      })
      .catch(function () { self.onDegrade('PBL_E_NETWORK', '广播拉取失败，使用缓存数据'); });
  };

  /** seq 去重 + 计时（广播到达 → 交给上层渲染，≤500ms 预算） */
  Transport.prototype._accept = function (ev, silent) {
    if (!ev) { return false; }
    var seq = Number(ev.seq !== undefined ? ev.seq : (ev.event_seq || 0));
    if (seq > 0) {
      if (seq <= this.lastSeq || this.pending[seq]) { return false; }
      this.pending[seq] = true;
      this.lastSeq = Math.max(this.lastSeq, seq);
    }
    var payload = ev.payload_json;
    if (typeof payload === 'string') { try { payload = JSON.parse(payload); } catch (e) { payload = { raw: payload }; } }
    var item = {
      seq: seq,
      event_type: ev.event_type || ev.type || 'unknown',
      entity_id: ev.entity_id || (payload && payload.entity_id) || '',
      payload: payload || {},
      received_at: Core.now()
    };
    if (!silent) { Core.Bus.emit('pbl:broadcast-received', item); }
    this.onEvent(item, !!silent);
    return true;
  };

  /* ───────────── 5. 断线重连补齐（Q4：快照 + since 补发） ───────────── */
  Transport.prototype.reconnect = function () {
    var self = this;
    return this.call('entity_state', { session_id: this.sessionId })
      .then(function (r) {
        var d = (r && r.data) || r || {};
        self.snapshot = d;
        Core.Bus.emit('pbl:snapshot-applied', d);
        return self.call('event_poll', { since_event_id: self.lastSeq, limit: 100 });
      })
      .then(function (r) {
        var d = (r && r.data) || r || {};
        (d.events || d.rows || []).forEach(function (ev) { self._accept(ev); });
        self.subscribe();
        return true;
      })
      .catch(function () { self.onDegrade('PBL_E_NETWORK', '重连失败，保持只读缓存'); return false; });
  };

  /* ───────────── 6. S3/S4 产出物、证据、反馈 ───────────── */
  Transport.prototype.createArtifact = function (a) {
    return this.call('artifact_create', {
      title: a.title || '', artifact_type: a.artifact_type || 'document',
      content_txt: a.content_txt || '', session_id: this.sessionId
    });
  };
  Transport.prototype.submitArtifact = function (artifactId) {
    return this.call('artifact_submit', { artifact_id: artifactId, session_id: this.sessionId });
  };
  Transport.prototype.collectEvidence = function (e) {
    return this.call('evidence_collect', {
      evidence_type: e.evidence_type || 'artifact_version',
      source_id: e.source_id || '', session_id: this.sessionId
    });
  };
  Transport.prototype.saveFeedback = function (f) {
    return this.call('feedback_save', {
      feedback_type: f.feedback_type || 'feedback',
      rating: f.rating === undefined ? '' : f.rating,
      content_txt: f.content_txt || '',
      context_json: f.context_json || {}
    });
  };

  Transport.prototype.stop = function () {
    this.stopped = true;
    this.closeSse();
    if (this.timer) { clearInterval(this.timer); this.timer = null; }
  };

  global.PblOverlayTransport = {
    ENDPOINTS: ENDPOINTS,
    apiBase: apiBase,
    Transport: Transport
  };
})(window);