/**
 * ecat-bus.js — EtherCAT 总线 bootstrap / open / motor-start 唯一实现
 *
 * 设备链路（device-link 外壳 Owner）与电机传输（transport-ecat）都调用本模块，
 * 策略只保留一份：
 *   health →（未就绪）status →（未开）open 网卡 → motor/start 进 OP + 起 PDO 循环
 *
 * 红线：
 *   - DC 钉死 250µs（period_ms 默认/钳制 0.25，dc_cycle_us = max(250, round(ms*1000))）
 *   - 幂等：native/health 报 bus_open+loop 时**复用**，不再 motor/start
 *     （start 会先 loop_stop，热路径假超时 / SSC 楔死风险）
 *   - 网卡默认常量 ECAT_DEFAULT_ADAPTER 只在此定义
 */
"use strict";

/** 网卡匹配子串默认值（代码/页面/测试的唯一来源；文档漂移以此为准）。 */
export const ECAT_DEFAULT_ADAPTER = "I210";

/** 默认 PDO 周期（ms）：1ms+DC 会让发送出口回到 ~1s，必须 250µs 档。 */
export const ECAT_DEFAULT_PERIOD_MS = 0.25;

/** DC SYNC0 目标周期（µs）。 */
export const ECAT_DC_CYCLE_US = 250;

const LS_ECAT_PERIOD = "dcu_ecat_period_ms";
const LS_ECAT_SPIN = "dcu_ecat_spin";
const LS_ECAT_ADAPTER = "dcu_ecat_adapter";
const LS_PERIOD_MIG = "dcu_ecat_period_mig";

function readAdapterRaw() {
  try {
    var s = localStorage.getItem(LS_ECAT_ADAPTER);
    if (s && s.trim()) return s.trim();
  } catch (_) {}
  return ECAT_DEFAULT_ADAPTER;
}

/**
 * 构造 motor/start body：period 钳到 ≤0.5ms 且默认 0.25，DC 钉 250µs。
 * @param {{period_ms?:number, spin?:boolean|null, fromLocalStorage?:boolean}} [opts]
 */
export function resolveEcatStartBody(opts) {
  opts = opts || {};
  var body = {};
  var per = Number(opts.period_ms);
  if (!opts.fromLocalStorage && opts.period_ms == null) {
    per = ECAT_DEFAULT_PERIOD_MS;
  } else if (!(per > 0) || per > 0.5) {
    per = ECAT_DEFAULT_PERIOD_MS;
  }
  body.period_ms = per;
  body.dc_cycle_us = Math.max(ECAT_DC_CYCLE_US, Math.round(per * 1000));
  body.dc_shift_us = 0;
  var spin = opts.spin;
  if (spin == null && opts.fromLocalStorage) {
    try {
      var sp = localStorage.getItem(LS_ECAT_SPIN);
      if (sp === "0") spin = false;
      else if (sp === "1") spin = true;
    } catch (_) {}
  }
  if (spin === true || spin === false) body.spin = spin;
  return body;
}

/** 从 localStorage 解析 period；一次性清理 Python 时代误存的 "4"。 */
export function readStoredEcatPeriod() {
  try {
    if (!localStorage.getItem(LS_PERIOD_MIG)) {
      if (parseFloat(localStorage.getItem(LS_ECAT_PERIOD)) === 4) {
        localStorage.removeItem(LS_ECAT_PERIOD);
      }
      localStorage.setItem(LS_PERIOD_MIG, "1");
    }
    var v = parseFloat(localStorage.getItem(LS_ECAT_PERIOD));
    /* 用户显式设过才用；否则 0.25ms */
    if (v > 0 && v !== 1) return v;
    return ECAT_DEFAULT_PERIOD_MS;
  } catch (_) {
    return ECAT_DEFAULT_PERIOD_MS;
  }
}

/** @description 只读健康：bus_open + loop = 后台 PDO 循环在跑。 */
export async function isEcatBusHealthy(ecatPost) {
  try {
    var h = await ecatPost("native/health", {}, 2500);
    return !!(h && h.ok && h.bus_open && h.loop);
  } catch (_) {
    return false;
  }
}

/**
 * 确保网卡已打开。已连接则复用，不重复 open。
 * @param {(path:string,body?:object,timeoutMs?:number)=>Promise<any>} ecatPost
 * @param {string} [adapter]
 */
export async function openEcatAdapter(ecatPost, adapter) {
  var substr = (adapter && String(adapter).trim()) || readAdapterRaw() || ECAT_DEFAULT_ADAPTER;
  var st = await ecatPost("status", {}, 6000);
  if (st && st.ok === true) return st;
  var r = await ecatPost("open", { substr: substr }, 20000);
  if (!r || r.ok !== true) {
    var msg = (r && r.log && r.log.length) ? r.log.join(" / ") : "打开网卡失败";
    var err = new Error(msg);
    err.transient = false;
    throw err;
  }
  return r;
}

/**
 * 启动 OP + PDO 循环。force=false 且总线已健康则跳过 start。
 * @returns {Promise<{reused:boolean, result?:object}>}
 */
export async function startEcatMotorLoop(ecatPost, opts) {
  opts = opts || {};
  if (!opts.force && await isEcatBusHealthy(ecatPost)) {
    return { reused: true };
  }
  var body;
  if (opts.body) body = opts.body;
  else if (opts.fromLocalStorage) {
    body = resolveEcatStartBody({ fromLocalStorage: true, period_ms: readStoredEcatPeriod() });
  } else {
    body = resolveEcatStartBody({ period_ms: opts.period_ms, spin: opts.spin });
  }
  var r = await ecatPost("motor/start", body, 30000);
  if (r && r.ok === false) {
    throw new Error((r.log && r.log.join(" / ")) || "motor/start 失败");
  }
  return { reused: false, result: r || {}, body: body };
}

/**
 * 完整 bootstrap：health → open → motor/start。
 * @param {{
 *   ecatPost: (path:string,body?:object,timeoutMs?:number)=>Promise<any>,
 *   adapter?: string, period_ms?: number, spin?: boolean|null, force?: boolean,
 *   fromLocalStorage?: boolean,
 * }} opts
 * @returns {Promise<{ok:true, reused:boolean, result?:object}>}
 */
export async function runEcatBootstrap(opts) {
  var ecatPost = opts.ecatPost;
  if (await isEcatBusHealthy(ecatPost) && !opts.force) {
    return { ok: true, reused: true };
  }
  await openEcatAdapter(ecatPost, opts.adapter);
  var st = await startEcatMotorLoop(ecatPost, {
    force: true,
    period_ms: opts.period_ms,
    spin: opts.spin,
    fromLocalStorage: opts.fromLocalStorage,
    body: opts.body,
  });
  return { ok: true, reused: false, result: st.result };
}

/**
 * DC/周期自愈：被配错（free-run 或 ≥1ms）时拉回 250µs。
 * @returns {Promise<object|null>} null=无需修复
 */
export async function repairEcatDc(ecatPost) {
  var h = await ecatPost("native/health", {}, 2000).catch(function () { return null; });
  if (!h || !h.ok) return null;
  var dcs = Number(h.dc_cycle_us);
  var per = Number(h.period_ms);
  if (h.dc === 1 && dcs === ECAT_DC_CYCLE_US &&
      (h.period_ms == null || Math.abs(per - ECAT_DEFAULT_PERIOD_MS) < 0.001)) {
    return null;
  }
  return ecatPost("motor/start", {
    period_ms: ECAT_DEFAULT_PERIOD_MS,
    dc_cycle_us: ECAT_DC_CYCLE_US,
    dc_shift_us: 0,
  }, 30000);
}

/** @description 读当前网卡子串（localStorage → 默认 I210）。 */
export function getEcatAdapterOrDefault() {
  return readAdapterRaw();
}