/**
 * device-link.js — 全链路设备健康层（外壳 Owner + 功能页 Client）
 *
 * 问题：各页各自 fetch，只共用 IP 字符串 → 一页「已连接」一页「失败」。
 * 方案：tabs.html 常驻 Owner 轮询 ESP32 /system/status 与 EtherCAT /api/status
 *      + /api/app/load，经 BroadcastChannel('dcu-device-link') 广播快照；
 *      功能页只订阅渲染。业务命令（SPI/CAN/OTA）仍页内发，失败不得把
 *      「设备离线」灯打红——灯只认本层。
 *
 * 角色：
 *   - Owner：tabs.html 在加载本文件前设 window.__dcuDeviceLinkOwner = true
 *   - Client：任意页 import { deviceLink }
 * 独立直开页面（无外壳）时 client 收不到 snapshot，可退回本地轮询。
 */
"use strict";

var CH_NAME = "dcu-device-link";
var ESP32_FAIL_ONLINE = 3;      /* 连续失败 ≥3 判离线 */
var ESP32_POLL_MS = 1000;
var ECAT_POLL_MS = 2000;
var LS_ESP_IP = "dcu_esp_ip";
var DEFAULT_IP = "192.168.31.127";

function nowMs() { return Date.now(); }

function readIp() {
  try {
    var s = localStorage.getItem(LS_ESP_IP);
    if (s && s.trim()) return s.trim();
  } catch (_) {}
  return DEFAULT_IP;
}

function writeIp(ip) {
  if (!ip || !String(ip).trim()) return;
  try { localStorage.setItem(LS_ESP_IP, String(ip).trim()); } catch (_) {}
}

function emptySnapshot() {
  return {
    ts: 0,
    ip: readIp(),
    links: {
      esp32: { online: false, ageMs: -1, failStreak: 0 },
      ecat:  { online: false, busOpen: false, op: false, loop: false,
               loadValid: false, loadPerm: 0, ageMs: -1 },
      ble:   { online: false, deviceName: "", owner: null }
    },
    esp32Status: null
  };
}

/* ───────────────────────── Owner ───────────────────────── */

function createOwner() {
  var ch = null;
  try { ch = new BroadcastChannel(CH_NAME); } catch (_) { ch = null; }
  var snap = emptySnapshot();
  var esp32Fails = 0;
  var lastEsp32OkAt = 0;
  var esp32Timer = null;
  var ecatTimer = null;
  var stopped = false;

  function publish() {
    snap.ts = nowMs();
    snap.ip = readIp();
    if (ch) {
      try { ch.postMessage({ type: "snapshot", snap: snap }); } catch (_) {}
    }
  }

  function setEsp32(status, ok) {
    if (ok) {
      esp32Fails = 0;
      lastEsp32OkAt = nowMs();
      snap.links.esp32.online = true;
      snap.links.esp32.ageMs = 0;
      snap.esp32Status = status || null;
    } else {
      esp32Fails++;
      snap.links.esp32.failStreak = esp32Fails;
      snap.links.esp32.ageMs = lastEsp32OkAt ? (nowMs() - lastEsp32OkAt) : -1;
      if (esp32Fails >= ESP32_FAIL_ONLINE) snap.links.esp32.online = false;
    }
    snap.links.esp32.failStreak = esp32Fails;
    publish();
  }

  function pollEsp32() {
    if (stopped) return;
    var ip = readIp();
    var ac = null;
    try { ac = new AbortController(); } catch (_) {}
    var tmo = null;
    fetch("http://" + ip + "/system/status" + (window._memLayout ? "" : "?layout=1"), {
      signal: ac ? ac.signal : undefined,
      cache: "no-store"
    }).then(function (r) {
      if (!r.ok) throw new Error("HTTP " + r.status);
      return r.json();
    }).then(function (j) {
      if (ac) { clearTimeout(tmo); }
      setEsp32(j, true);
    }).catch(function () {
      if (ac) { clearTimeout(tmo); }
      setEsp32(null, false);
    }).then(function () {
      esp32Timer = setTimeout(pollEsp32, ESP32_POLL_MS);
    });
    if (ac) {
      tmo = setTimeout(function () { try { ac.abort(); } catch (_) {} }, 4000);
    }
  }

  function pollEcat() {
    if (stopped) return;
    var base = "/ecat/api/";
    var stP = fetch(base + "status", {
      method: "POST", body: "{}", cache: "no-store",
      signal: AbortSignal.timeout(4000)
    }).then(function (r) { return r.json(); }).catch(function () { return null; });
    var ldP = fetch(base + "app/load", {
      method: "POST", body: "{}", cache: "no-store",
      signal: AbortSignal.timeout(4000)
    }).then(function (r) { return r.json(); }).catch(function () { return null; });

    Promise.all([stP, ldP]).then(function (arr) {
      var st = arr[0], ld = arr[1];
      var e = snap.links.ecat;
      e.online = !!(st && st.ok && st.slave);
      e.busOpen = e.online;
      /* native status 不直接给 op/loop；用 load valid + slave state 粗判 */
      e.op = !!(st && st.slave && st.slave.state != null && (st.slave.state & 0x0F) === 8);
      e.loadValid = !!(ld && ld.ok && ld.valid === true
        && Number.isFinite(ld.age_ms) && ld.age_ms >= 0 && ld.age_ms <= 3000);
      e.loop = e.loadValid || e.op;
      e.loadPerm = (ld && Number.isFinite(ld.load_perm)) ? ld.load_perm : 0;
      e.ageMs = (ld && Number.isFinite(ld.age_ms)) ? ld.age_ms : -1;
      publish();
    }).catch(function () {
      /* 字段访问/异常不得让 ECAT 轮询永久停摆 */
    }).then(function () {
      if (!stopped) ecatTimer = setTimeout(pollEcat, ECAT_POLL_MS);
    });
  }

  function onMsg(ev) {
    var m = ev && ev.data;
    if (!m || !m.type) return;
    if (m.type === "hello") { publish(); return; }
    if (m.type === "set-ip") {
      writeIp(m.ip);
      /* 立刻重拉 ESP32（旧 timer 下一拍也会跟上） */
      try { fetch("http://" + readIp() + "/system/status", { cache: "no-store",
        signal: AbortSignal.timeout(2000) }).then(function (r) { return r.json(); })
        .then(function (j) { setEsp32(j, true); })
        .catch(function () { setEsp32(null, false); });
      } catch (_) {}
      return;
    }
    if (m.type === "ble-state") {
      snap.links.ble.online = !!m.online;
      snap.links.ble.deviceName = m.deviceName || "";
      snap.links.ble.owner = m.owner || (m.online ? "page" : null);
      publish();
      return;
    }
  }

  if (ch) ch.addEventListener("message", onMsg);
  pollEsp32();
  pollEcat();
  publish();

  return {
    stop: function () {
      stopped = true;
      if (esp32Timer) clearTimeout(esp32Timer);
      if (ecatTimer) clearTimeout(ecatTimer);
      if (ch) { try { ch.close(); } catch (_) {} }
    }
  };
}

/* ───────────────────────── Client ───────────────────────── */

function createClient() {
  var ch = null;
  try { ch = new BroadcastChannel(CH_NAME); } catch (_) { ch = null; }
  var listeners = [];
  var last = null;

  function emit() {
    for (var i = 0; i < listeners.length; i++) {
      try { listeners[i](last); } catch (_) {}
    }
  }

  if (ch) {
    ch.addEventListener("message", function (ev) {
      var m = ev && ev.data;
      if (!m || m.type !== "snapshot" || !m.snap) return;
      last = m.snap;
      emit();
    });
    try { ch.postMessage({ type: "hello" }); } catch (_) {}
  }

  return {
    /** 当前快照（可能为 null，Owner 尚未广播时） */
    getSnapshot: function () { return last; },
    /** 订阅快照；返回取消函数 */
    subscribe: function (fn) {
      if (typeof fn !== "function") return function () {};
      listeners.push(fn);
      if (last) { try { fn(last); } catch (_) {} }
      return function () {
        var i = listeners.indexOf(fn);
        if (i >= 0) listeners.splice(i, 1);
      };
    },
    setIp: function (ip) {
      writeIp(ip);
      if (ch) { try { ch.postMessage({ type: "set-ip", ip: readIp() }); } catch (_) {} }
    },
    getIp: function () { return readIp(); },
    reportBle: function (online, deviceName) {
      var payload = {
        type: "ble-state",
        online: !!online,
        deviceName: deviceName || "",
        owner: "iframe"
      };
      if (ch) { try { ch.postMessage(payload); } catch (_) {} }
      /* 本地立刻改一份，单页直开也能看到 */
      if (last) {
        last.links.ble.online = !!online;
        last.links.ble.deviceName = deviceName || "";
        last.links.ble.owner = online ? "iframe" : null;
        last.ts = nowMs();
        emit();
      }
    },
    /** 是否有外壳 Owner 在管（收到过 snapshot 或自身是 owner） */
    hasOwner: function () { return !!last; }
  };
}

/* ───────────────────────── bootstrap ───────────────────────── */

var deviceLink;
try {
  if (window.__dcuDeviceLinkOwner) {
    window.__dcuDeviceLinkInstance = createOwner();
  }
} catch (_) {}

deviceLink = createClient();
export { deviceLink };
export default deviceLink;