/**
 * shiroko-monitor 边缘探针（Cloudflare Workers）
 *
 * - scheduled：cron 每分钟触发一轮探测（HTTP 用 fetch，TCP 用 cloudflare:sockets）
 * - 状态与历史心率整体存于 KV 的 state 键（小规模单键足够，上限 25MB）
 * - /api/status、/api/monitors、/api/refresh 由本 Worker 提供，其余请求交给静态资源
 *
 * 注意：cloudflare:sockets 的 TCP 出站连接需要 Workers 付费计划；
 *       免费计划下 http 类型探测与静态面板均可正常使用，tcp 类型会返回 down。
 */

import { connect } from 'cloudflare:sockets';

const VERSION = '0.9.1';
const HISTORY_LIMIT = 48;
const UPTIME_DAYS = 90;
const USER_AGENT = 'shiroko-monitor/0.3 (lightweight uptime panel)';

// 边缘端按 UTC 日期分桶（Worker 无本地时区概念）
function dayKey(d = new Date()) {
  return d.toISOString().slice(0, 10);
}

// 只保留最近 UPTIME_DAYS 天；YYYY-MM-DD 的字典序即时间序
function pruneDaily(daily) {
  const keys = Object.keys(daily).sort();
  while (keys.length > UPTIME_DAYS) delete daily[keys.shift()];
}

export default {
  async scheduled(event, env, ctx) {
    ctx.waitUntil(runChecksDedup(env));
  },

  async fetch(request, env, ctx) {
    const url = new URL(request.url);
    if (url.pathname === '/api/status') return json(await getStatus(env, ctx));
    if (url.pathname === '/api/monitors') return json(await getMonitors(env, request.url));
    if (url.pathname === '/api/refresh') {
      // 公网上的强制探测必须显式开启，避免被任意访客当作「探测放大器」使用
      const gate = refreshGate(env, request);
      if (!gate.ok) return json({ error: gate.error }, { status: gate.status });
      return json(await runChecksDedup(env));
    }
    return env.ASSETS.fetch(request);
  },
};

// 未配置 REFRESH_TOKEN 时一律拒绝（wrangler secret put REFRESH_TOKEN 开启）；
// 比较采用等长逐字节异或，避免按字符提前返回带来的时序差异
function refreshGate(env, request) {
  const token = env.REFRESH_TOKEN;
  if (!token) return { ok: false, status: 403, error: 'refresh-disabled' };
  const url = new URL(request.url);
  const provided = request.headers.get('x-refresh-token') || url.searchParams.get('token') || '';
  if (provided.length !== token.length) return { ok: false, status: 403, error: 'refresh-forbidden' };
  let diff = 0;
  for (let i = 0; i < token.length; i++) diff |= provided.charCodeAt(i) ^ token.charCodeAt(i);
  return diff === 0 ? { ok: true } : { ok: false, status: 403, error: 'refresh-forbidden' };
}

async function probeMonitor(m) {
  if (m.type === 'tcp') return probeTcp(m);
  // 边缘端无原始 socket 读取能力（sockets API 需付费版且未覆盖测试），banner 类型请使用本地探针
  if (m.type === 'banner') return { status: 'down', latency: 0, code: null, detail: '边缘端暂不支持 banner 探测（请用本地探针）' };
  return probeHttp(m);
}

// 同隔离体内共享同一轮探测，避免并发刷新对目标重复施压（跨隔离体为 best-effort）
let inFlightRound = null;

function runChecksDedup(env) {
  if (!inFlightRound) {
    inFlightRound = runChecks(env).finally(() => {
      inFlightRound = null;
    });
  }
  return inFlightRound;
}

function json(data, init = {}) {
  return new Response(JSON.stringify(data), {
    ...init,
    headers: { 'content-type': 'application/json; charset=utf-8', 'cache-control': 'no-store', ...(init.headers ?? {}) },
  });
}

async function getMonitors(env, baseUrl) {
  const raw = await env.MONITOR_KV.get('monitors');
  if (raw) return JSON.parse(raw);
  // 未手动写入 KV 时，直接从静态资产读取仓库根目录的 monitors.json，实现零配置部署
  const res = await env.ASSETS.fetch(new URL('/monitors.json', baseUrl));
  if (res.ok) return res.json();
  return { settings: {}, monitors: [] };
}

async function getStatus(env, ctx) {
  const state = (await env.MONITOR_KV.get('state', 'json')) ?? { monitors: {}, generatedAt: null };
  if (!state.generatedAt) ctx.waitUntil(runChecks(env));
  return state;
}

async function probeHttp(m) {
  const started = Date.now();
  const timeoutMs = (m.timeout ?? 10) * 1000;
  try {
    // redirect: manual —— 保留 3xx 原始状态码交给 expectStatus 判定
    const res = await fetch(m.url, {
      method: m.method || 'GET',
      redirect: 'manual',
      signal: AbortSignal.timeout(timeoutMs),
      headers: { 'user-agent': USER_AGENT, accept: '*/*' },
    });
    const latency = Date.now() - started;
    const expect = m.expectStatus ?? [200];
    const ok = expect.includes(res.status);
    return {
      status: ok ? 'up' : 'down',
      latency,
      code: res.status,
      detail: ok ? `HTTP ${res.status}` : `HTTP ${res.status}（期望 ${expect.join('/')}）`,
    };
  } catch (err) {
    const latency = Date.now() - started;
    return {
      status: 'down',
      latency,
      code: 0,
      detail: err.name === 'TimeoutError' ? `请求超时（>${timeoutMs / 1000}s）` : String(err.cause?.code || err.message),
    };
  }
}

async function probeTcp(m) {
  const started = Date.now();
  const timeoutMs = (m.timeout ?? 10) * 1000;
  try {
    const socket = connect({ hostname: m.host, port: m.port });
    const timer = setTimeout(() => socket.close(), timeoutMs);
    await Promise.race([
      socket.opened,
      new Promise((_, reject) => setTimeout(() => reject(new Error('TCP 连接超时')), timeoutMs)),
    ]);
    clearTimeout(timer);
    socket.close();
    return { status: 'up', latency: Date.now() - started, code: null, detail: `TCP ${m.host}:${m.port} 可连接` };
  } catch (err) {
    return { status: 'down', latency: Date.now() - started, code: null, detail: String(err?.message || err) };
  }
}

async function runChecks(env) {
  const config = await getMonitors(env, new URL('http://placeholder/'));
  const state = (await env.MONITOR_KV.get('state', 'json')) ?? { monitors: {} };
  const monitors = state.monitors ?? {};
  const redact = config.settings?.redactDetails === true;
  let up = 0;
  let down = 0;
  let pending = 0;
  let latencySum = 0;
  let latencyCount = 0;

  await Promise.all(
    (config.monitors ?? []).map(async (m) => {
      const prev = monitors[m.id];
      const r = await probeMonitor(m);
      r.checkedAt = new Date().toISOString();
      const history = [...(prev?.history ?? []), { t: r.checkedAt, ok: r.status === 'up', ms: r.latency ?? 0 }].slice(-HISTORY_LIMIT);

      const daily = { ...(prev?.daily ?? {}) };
      const key = dayKey();
      const bucket = daily[key] ?? (daily[key] = { total: 0, up: 0 });
      bucket.total++;
      if (r.status === 'up') bucket.up++;
      pruneDaily(daily);

      monitors[m.id] = {
        status: r.status,
        latency: r.latency,
        code: r.code,
        detail: redact ? (r.status === 'up' ? '正常' : '异常') : r.detail,
        lastCheck: r.checkedAt,
        history,
        daily,
      };
      if (r.status === 'up') {
        up++;
        latencySum += r.latency ?? 0;
        latencyCount++;
      } else {
        down++;
      }
    })
  );

  let uptimeUp = 0;
  let uptimeTotal = 0;
  for (const m of Object.values(monitors)) {
    for (const bucket of Object.values(m.daily ?? {})) {
      uptimeTotal += bucket.total ?? 0;
      uptimeUp += bucket.up ?? 0;
    }
  }

  // 与本地探针保持同一份快照口径：dataUpdatedAt / updateIntervalSec / dataFilter
  // 面板据此把倒计时对齐服务端节奏，并按同一过滤口径展示
  const filter = ['both', 'config', 'uptimerobot'].includes(config.settings?.dataFilter) ? config.settings.dataFilter : 'both';
  const intervals = [];
  if (filter !== 'uptimerobot') {
    for (const m of config.monitors ?? []) {
      const n = Number(m.interval);
      if (Number.isFinite(n) && n > 0) intervals.push(n);
    }
  }

  const next = {
    prober: `shiroko-monitor-worker/${VERSION}`,
    demo: false,
    generatedAt: new Date().toISOString(),
    // state.generatedAt 是上一轮探测完成的时间，即「数据最后变更时刻」
    dataUpdatedAt: state.generatedAt ?? new Date().toISOString(),
    updateIntervalSec: Math.max(5, Math.round(intervals.length ? Math.min(...intervals) : 60)),
    dataFilter: filter,
    stats: {
      total: (config.monitors ?? []).length,
      up,
      down,
      pending,
      avgLatency: latencyCount ? Math.round(latencySum / latencyCount) : null,
      avgUptime90: uptimeTotal ? Math.round((uptimeUp / uptimeTotal) * 1000) / 10 : null,
    },
    sources: {},
    monitors,
  };
  await env.MONITOR_KV.put('state', JSON.stringify(next));
  return next;
}