// hotstate.js —— 热更新版本状态机（纯 fs，bootstrap 与 main 共用）。
// 维护 userData/hot/current.json：{ target, confirmed, blacklist[], attempts{} }
// - target    ：期望运行的热更版本
// - confirmed ：最近一次证明健康（渲染层成功加载）的版本 = 安全回退点
// - blacklist ：损坏版本，永不再选
// - attempts  ：未确认版本的启动尝试计数（先落盘再加载，崩溃后下次可判砖）
"use strict";
const fs = require("fs");
const path = require("path");

const MAX_TRY = 1; // 未确认版本最多尝试次数；超过即判砖回退

function statePath(hotBase) {
  return path.join(hotBase, "current.json");
}
function readState(hotBase) {
  try {
    const s = JSON.parse(fs.readFileSync(statePath(hotBase), "utf8"));
    return {
      target: s.target || null,
      confirmed: s.confirmed || null,
      blacklist: Array.isArray(s.blacklist) ? s.blacklist : [],
      attempts: s.attempts && typeof s.attempts === "object" ? s.attempts : {},
    };
  } catch {
    return { target: null, confirmed: null, blacklist: [], attempts: {} };
  }
}
function writeState(hotBase, state) {
  try {
    fs.mkdirSync(hotBase, { recursive: true });
    fs.writeFileSync(statePath(hotBase), JSON.stringify(state, null, 2));
    return true;
  } catch {
    return false; // 无写权限等 → 由调用方降级
  }
}
// 版本目录是否为可加载的完整结构
function versionUsable(hotBase, ver) {
  if (!ver) return false;
  try {
    return fs.existsSync(path.join(hotBase, ver, "electron", "main.js"));
  } catch {
    return false;
  }
}

// bootstrap 调用：决定本次启动加载哪个版本。返回版本名（字符串）或 null（=用包内）。
// 有副作用：对 pending 版本自增 attempts 并【先落盘】，超限则拉黑回退。
function chooseVersion(hotBase) {
  const state = readState(hotBase);
  let cand = state.target;
  if (!cand) return null;
  // 被拉黑或目录不可用 → 回退 confirmed
  if (state.blacklist.includes(cand) || !versionUsable(hotBase, cand)) {
    cand = state.confirmed;
  }
  if (!versionUsable(hotBase, cand)) return null; // confirmed 也没了 → 包内
  if (cand === state.confirmed) return cand; // 已确认健康，直接用
  // cand 是刚应用、尚未确认的新版本（pending）
  state.attempts[cand] = (state.attempts[cand] || 0) + 1;
  const over = state.attempts[cand] > MAX_TRY;
  if (over) {
    // 之前给过机会仍未确认 → 判砖，拉黑并回退
    if (!state.blacklist.includes(cand)) state.blacklist.push(cand);
    delete state.attempts[cand];
    state.target = state.confirmed;
    writeState(hotBase, state);
    return versionUsable(hotBase, state.confirmed) ? state.confirmed : null;
  }
  writeState(hotBase, state); // 关键：先落盘尝试计数，再返回让 bootstrap 加载
  return cand;
}

// 加载崩溃时拉黑某版本
function blacklistVersion(hotBase, ver, reason) {
  if (!ver) return;
  const state = readState(hotBase);
  if (!state.blacklist.includes(ver)) state.blacklist.push(ver);
  delete state.attempts[ver];
  if (state.target === ver) state.target = state.confirmed;
  state.lastError = { ver, reason: String(reason || "").slice(0, 500) };
  writeState(hotBase, state);
}

// 渲染层成功加载后确认健康
function confirmHealthy(hotBase, ver) {
  if (!ver) return;
  const state = readState(hotBase);
  state.confirmed = ver;
  state.target = ver;
  delete state.attempts[ver];
  state.blacklist = state.blacklist.filter((v) => v !== ver);
  writeState(hotBase, state);
}

// 应用新版本后设为 target（等重启生效）
function setTarget(hotBase, ver) {
  const state = readState(hotBase);
  state.target = ver;
  writeState(hotBase, state);
}

// 当前“有效内容版本”：优先已确认，其次包内（由调用方给 fallback）
function effectiveVersion(hotBase) {
  const state = readState(hotBase);
  return state.confirmed || null;
}

module.exports = {
  MAX_TRY, readState, writeState, versionUsable,
  chooseVersion, blacklistVersion, confirmHealthy, setTarget, effectiveVersion,
};