/**
 * 远程播放桥接：SSE 订阅 + 命令队列 + 本地状态回传。
 */
import { API_VERSION } from "./api.js";

const API_ROOT = "/api/agv";
const REMOTE_METHODS = new Set(["playAction", "stopAction", "clearActions"]);
const CLIENT_ID = globalThis.crypto?.randomUUID?.() || `client-${Date.now()}`;

export function connectRemotePlayback(playbackApi, { onStatus } = {}) {
  let lastRevision = 0;
  let connected = false;
  let es = null;
  const queue = [];
  let draining = false;
  let applyingRemote = 0;

  function setStatus(text, kind = "idle") {
    onStatus?.({ text, kind, connected, revision: lastRevision });
  }

  function shouldSkipEcho(msg) {
    return msg?.sourceClientId && msg.sourceClientId === CLIENT_ID;
  }

  async function waitUntilReady(maxMs = 20000) {
    const start = Date.now();
    while (Date.now() - start < maxMs) {
      if (playbackApi.getState?.().ready) return true;
      await new Promise((r) => setTimeout(r, 150));
    }
    return playbackApi.getState?.().ready;
  }

  async function withRemoteApply(fn) {
    applyingRemote += 1;
    try {
      return await fn();
    } finally {
      applyingRemote -= 1;
    }
  }

  async function ensureModel(modelId) {
    if (!modelId) return true;
    const cur = playbackApi.getState?.() || {};
    if (cur.modelId === modelId && cur.ready) return true;
    const res = await playbackApi.request({
      version: API_VERSION,
      method: "clearActions",
      params: { modelId },
    });
    if (!res.ok) {
      setStatus(`远程加载失败: ${res.error?.message || "unknown"}`, "error");
      return false;
    }
    return waitUntilReady();
  }

  async function applySnapshot(state) {
    if (!state) return false;
    const revision = Number(state.revision) || 0;
    if (revision <= lastRevision) return true;

    return withRemoteApply(async () => {
      const modelId = state.modelId;
      const desired = state.activeActions || [];

      if (!(await ensureModel(modelId))) return false;

      const cur = playbackApi.getState?.() || {};
      const current = new Set(cur.activeActions || []);
      const want = new Set(desired);

      for (const id of current) {
        if (!want.has(id)) {
          const res = await playbackApi.request({
            version: API_VERSION,
            method: "stopAction",
            params: { modelId: cur.modelId || modelId, actionId: id },
          });
          if (!res.ok) {
            setStatus(`远程动作同步失败: ${res.error?.message || "unknown"}`, "error");
            return false;
          }
        }
      }
      for (const id of want) {
        if (!current.has(id)) {
          const res = await playbackApi.request({
            version: API_VERSION,
            method: "playAction",
            params: { modelId: cur.modelId || modelId, actionId: id },
          });
          if (!res.ok) {
            setStatus(`远程动作同步失败: ${res.error?.message || "unknown"}`, "error");
            return false;
          }
        }
      }

      lastRevision = revision;
      return true;
    });
  }

  async function runCommand(msg) {
    if (msg.type === "connected") {
      connected = true;
      setStatus("远程已连接", "ok");
      if (msg.state) await applySnapshot(msg.state);
      return;
    }
    if (msg.type === "ping") return;
    if (!msg.method) return;

    const revision = Number(msg.revision) || 0;
    if (revision && revision <= lastRevision) return;

    if (shouldSkipEcho(msg)) {
      if (revision) lastRevision = Math.max(lastRevision, revision);
      return;
    }

    if (msg.method === "syncState") {
      await applySnapshot(msg.state);
      return;
    }

    if (!REMOTE_METHODS.has(msg.method)) return;

    await withRemoteApply(async () => {
      const p = msg.params || {};
      if (!(await ensureModel(p.modelId || p.model))) return;
      await waitUntilReady();

      const res = await playbackApi.request({
        version: API_VERSION,
        id: msg.id,
        method: msg.method,
        params: p,
      });
      if (!res.ok) {
        setStatus(`远程命令失败: ${res.error?.message || "unknown"}`, "error");
        return;
      }
      if (revision) lastRevision = Math.max(lastRevision, revision);
    });
  }

  function enqueue(msg) {
    queue.push(msg);
    drain();
  }

  async function drain() {
    if (draining) return;
    draining = true;
    while (queue.length) {
      const msg = queue.shift();
      try {
        await runCommand(msg);
      } catch (e) {
        console.warn("[remote-bridge]", e);
        setStatus(`远程执行异常: ${e.message}`, "error");
      }
    }
    draining = false;
  }

  function connectSse() {
    if (es) es.close();
    es = new EventSource(`${API_ROOT}/events`);
    es.onmessage = (ev) => {
      try {
        enqueue(JSON.parse(ev.data));
      } catch (e) {
        console.warn("[remote-bridge] bad event", e);
      }
    };
    es.onerror = () => {
      connected = false;
      setStatus("远程连接断开，自动重连…", "warn");
    };
  }

  async function fetchServerState() {
    const res = await fetch(`${API_ROOT}/state?t=${Date.now()}`);
    const body = await res.json();
    return body.ok ? body.data : null;
  }

  async function syncFromServer() {
    try {
      const state = await fetchServerState();
      if (!state || (state.revision || 0) <= 0) return state;
      await applySnapshot(state);
      return state;
    } catch (e) {
      setStatus("远程状态同步失败", "warn");
      return null;
    }
  }

  let reportTimer = null;
  function reportLocalState() {
    if (applyingRemote > 0) return;
    clearTimeout(reportTimer);
    reportTimer = setTimeout(async () => {
      const s = playbackApi.getState?.();
      if (!s?.ready || applyingRemote > 0) return;
      try {
        await fetch(`${API_ROOT}/report`, {
          method: "POST",
          headers: { "Content-Type": "application/json" },
          body: JSON.stringify({
            clientId: CLIENT_ID,
            modelId: s.modelId,
            activeActions: s.activeActions,
          }),
        });
      } catch (_) { /* ignore */ }
    }, 250);
  }

  connectSse();
  setStatus("等待远程连接…", "idle");

  return {
    clientId: CLIENT_ID,
    fetchServerState,
    syncFromServer,
    reportLocalState,
    close: () => {
      clearTimeout(reportTimer);
      es?.close();
    },
  };
}