#!/usr/bin/env node
/**
 * systemd 服务异常退出邮件上报器。
 *
 * 两种调用：
 *   service-failure-notify.mjs --report --service pi-mail-bridge.service
 *   service-failure-notify.mjs --flush  --service pi-mail-bridge.service
 *
 * `--report` 供 ExecStopPost 使用。systemd 会把 SERVICE_RESULT / EXIT_CODE /
 * EXIT_STATUS / INVOCATION_ID 注入命令环境；正常 stop/restart 不上报，只有
 * exit-code、signal、oom-kill、timeout、watchdog 等异常结果才发信。
 *
 * Gateway 暂时不可达时，报告只把**不含密钥**的邮件 payload 落到本地 spool；
 * 下次服务启动由 `--flush` 补发。relay_key 取 systemd invocation id，立即发送与
 * 补发即使竞态也只会入库一封。
 */

import { createHash, randomUUID } from 'node:crypto';
import { mkdir, readdir, readFile, rename, rm, stat, writeFile } from 'node:fs/promises';
import { basename, join, resolve } from 'node:path';
import { fileURLToPath } from 'node:url';

const DEFAULT_GATEWAY = 'http://127.0.0.1:8180';
const DEFAULT_RECIPIENT = 'jianf@';
const DEFAULT_SPOOL = '/var/lib/agentmail/failure-spool';
const MAX_SPOOL_FILES = 100;
const REQUEST_TIMEOUT_MS = 5_000;

function argValue(argv, name) {
  const i = argv.indexOf(name);
  return i >= 0 && i + 1 < argv.length ? argv[i + 1] : '';
}

export function isAbnormalExit(env = process.env) {
  const result = String(env.SERVICE_RESULT || '').trim();
  if (result) return result !== 'success';

  const code = String(env.EXIT_CODE || '').trim();
  const status = String(env.EXIT_STATUS || '').trim();
  if (!code && !status) return false;
  return !(code === 'exited' && (status === '' || status === '0'));
}

function cleanServiceName(value, agentName) {
  const raw = String(value || '').trim();
  if (raw) return basename(raw).replace(/[^A-Za-z0-9_.@-]/g, '-').slice(0, 96);
  return `${String(agentName || 'agent').replace(/[^A-Za-z0-9_.@-]/g, '-')}-bridge`;
}

function redact(value, env) {
  let out = String(value || '');
  for (const secret of [env.AGENTMAIL_AGENT_KEY, env.AGENTMAIL_AGENT_SECRET]) {
    if (secret) out = out.split(String(secret)).join('[REDACTED]');
  }
  return out
    .replace(/Bearer\s+[A-Za-z0-9._~+\/-]+/gi, 'Bearer [REDACTED]')
    .replace(/\b(?:ak_[A-Za-z0-9_-]+|sk-[A-Za-z0-9_-]{12,})\b/g, '[REDACTED]')
    .slice(0, 1_500);
}

/**
 * 本次服务启动的短标识，用于让每封故障通知各自成会话（见 subject 处的注释）。
 *
 * 优先用 systemd 的 `INVOCATION_ID`（每次启动唯一）。它缺失时退回随机值 ——
 * 宁可每次不同，也不要因为拿不到标识而退回"主题相同 → 告警被护栏挡下"。
 */
function invocationTag(env) {
  const invocation = String(env.INVOCATION_ID || '').trim();
  if (invocation) return invocation.replace(/[^A-Za-z0-9]/g, '').slice(0, 8);
  return createHash('sha256')
    .update(`${Date.now()}:${randomUUID()}`)
    .digest('hex')
    .slice(0, 8);
}

function relayKeyFor(env, serviceName) {
  const invocation = String(env.INVOCATION_ID || '').trim();
  if (invocation) return `service-failure:${invocation}`;
  const seed = `${serviceName}:${Date.now()}:${randomUUID()}`;
  return `service-failure:${createHash('sha256').update(seed).digest('hex')}`;
}

export function buildFailurePayload({
  env = process.env,
  serviceName = '',
  reason = '',
  error = null,
  now = new Date(),
} = {}) {
  const agentName = String(env.AGENTMAIL_AGENT_NAME || 'unknown-agent').trim();
  const service = cleanServiceName(serviceName || env.AGENTMAIL_SERVICE_NAME, agentName);
  const result = String(env.SERVICE_RESULT || reason || 'unexpected-exit');
  const exitCode = String(env.EXIT_CODE || 'unknown');
  const exitStatus = String(env.EXIT_STATUS || 'unknown');
  const detail = redact(error?.stack || error?.message || error || reason, env);

  const lines = [
    `**${agentName}** 的宿主服务 **${service}** 异常终止。`,
    '',
    `- 时间：${now.toISOString()}`,
    `- systemd 结果：${result}`,
    `- 退出类型：${exitCode}`,
    `- 退出状态：${exitStatus}`,
    `- invocation：${String(env.INVOCATION_ID || 'unknown')}`,
  ];
  if (detail) lines.push('', '**异常详情（已脱敏）**：', '```text', detail, '```');
  lines.push(
    '',
    'systemd 已按指数退避策略自动重启该服务；如果邮件连续出现，请检查：',
    `\`journalctl -u ${service} -n 100 --no-pager\``,
  );

  return {
    to: String(env.AGENTMAIL_FAILURE_RECIPIENT || DEFAULT_RECIPIENT),
    /*
     * 主题带上本次启动的 invocation 短号。
     *
     * 服务端按 `AutoAliasFor(收件人, 主题)` 派生会话别名，所以**主题相同 = 同一条会话**。
     * 崩溃循环下这一点会咬人：多封告警全落进同一条会话，而网关对会话内**连续**的中继
     * 邮件有 `maxRelayHops=5` 的硬上限（防两个 Agent 互相唤醒的正当护栏）→ 第 6 封起
     * 返回 403，报告只能落 spool，等下次 ExecStartPost `--flush` 才补投。
     *
     * 实测就是这样：dsh 崩溃循环时的六条告警全部 spooled，而**服务反复崩溃正是最需要
     * 告警送达的时刻**。
     *
     * 带 invocation 让每次崩溃各自成会话，因而每次都能投出去 —— 护栏不受影响
     * （它针对的是 agent↔agent 的互相唤醒，不是同一个人收多条故障通知）。
     * 副作用是崩溃循环会产生多条会话而不是一条线程；对"服务在崩"这件事，
     * 分开计数比合并成一条更容易发现问题。
     */
    subject: `[${agentName}] 桥服务异常终止 #${invocationTag(env)}`,
    body: lines.join('\n'),
    relay: 'summary',
    relay_key: relayKeyFor(env, service),
  };
}

async function postPayload(payload, env = process.env) {
  const key = String(env.AGENTMAIL_AGENT_KEY || '').trim();
  if (!key) throw new Error('AGENTMAIL_AGENT_KEY 未配置');

  const base = String(env.AGENTMAIL_GATEWAY_URL || DEFAULT_GATEWAY).replace(/\/+$/, '');
  const controller = new AbortController();
  const timer = setTimeout(() => controller.abort(), REQUEST_TIMEOUT_MS);
  try {
    const res = await fetch(`${base}/api/v1/mail/send`, {
      method: 'POST',
      headers: {
        Authorization: `Bearer ${key}`,
        'X-Agent-Name': String(env.AGENTMAIL_AGENT_NAME || ''),
        'Content-Type': 'application/json',
      },
      body: JSON.stringify(payload),
      signal: controller.signal,
    });
    const responseBody = await res.text();
    if (!res.ok) throw new Error(`Gateway HTTP ${res.status}: ${responseBody.slice(0, 300)}`);
    return responseBody;
  } finally {
    clearTimeout(timer);
  }
}

function safeAgentName(env) {
  return String(env.AGENTMAIL_AGENT_NAME || 'unknown-agent')
    .replace(/[^A-Za-z0-9_.@-]/g, '-')
    .slice(0, 96);
}

function spoolDirFor(env) {
  return join(String(env.AGENTMAIL_FAILURE_SPOOL || DEFAULT_SPOOL), safeAgentName(env));
}

function safeSpoolName(payload) {
  return `${createHash('sha256').update(String(payload.relay_key)).digest('hex')}.json`;
}

async function pruneSpool(spoolDir) {
  const names = (await readdir(spoolDir).catch(() => []))
    .filter((name) => name.endsWith('.json'));
  if (names.length <= MAX_SPOOL_FILES) return;

  const entries = await Promise.all(names.map(async (name) => ({
    name,
    mtime: (await stat(join(spoolDir, name))).mtimeMs,
  })));
  entries.sort((a, b) => a.mtime - b.mtime);
  for (const entry of entries.slice(0, entries.length - MAX_SPOOL_FILES)) {
    await rm(join(spoolDir, entry.name), { force: true });
  }
}

export async function spoolPayload(payload, env = process.env) {
  // 每个 Agent 独立目录：否则 pi 启动时可能拿自己的密钥去补发 dsh 的报告，
  // 发件身份与正文主体会错位，relay_key 的幂等范围也变了。
  const spoolDir = spoolDirFor(env);
  await mkdir(spoolDir, { recursive: true, mode: 0o700 });
  const target = join(spoolDir, safeSpoolName(payload));
  const temp = `${target}.${process.pid}.${randomUUID()}.tmp`;
  await writeFile(temp, `${JSON.stringify({ payload }, null, 2)}\n`, { mode: 0o600 });
  await rename(temp, target);
  await pruneSpool(spoolDir);
  return target;
}

export async function notifyCrash(reason, error, options = {}) {
  const env = options.env || process.env;
  const payload = buildFailurePayload({
    env,
    serviceName: options.serviceName,
    reason,
    error,
    now: options.now,
  });
  try {
    await postPayload(payload, env);
    return { sent: true, spooled: false, payload };
  } catch (sendError) {
    if (options.spool === false) throw sendError;
    const path = await spoolPayload(payload, env);
    return { sent: false, spooled: true, path, payload, error: sendError };
  }
}

export async function flushSpool(env = process.env) {
  const spoolDir = spoolDirFor(env);
  const names = (await readdir(spoolDir).catch(() => []))
    .filter((name) => name.endsWith('.json'))
    .sort();
  let sent = 0;
  let failed = 0;

  for (const name of names) {
    const path = join(spoolDir, name);
    try {
      const record = JSON.parse(await readFile(path, 'utf8'));
      await postPayload(record.payload, env);
      await rm(path, { force: true });
      sent++;
    } catch {
      failed++;
    }
  }
  return { total: names.length, sent, failed };
}

/**
 * 把发送失败翻译成一句能定位原因的话。
 *
 * `postPayload` 对非 2xx 抛的是 `Gateway HTTP <status>: <body>` —— 里面已经带着
 * 状态码与响应体，直接打出来就够定位了。只有 fetch 本身抛（DNS/连接/超时）才真的是
 * 「不可达」，此时按名字区分开。
 */
function describeSendError(error) {
  const message = String(error?.message || error || '');
  const httpMatch = message.match(/^Gateway HTTP (\d{3}): ([\s\S]*)$/);
  if (httpMatch) {
    return `网关可达，但返回 HTTP ${httpMatch[1]}：${httpMatch[2].slice(0, 300)}`;
  }
  if (error?.name === 'AbortError') return '请求超时（网关未在限定时间内响应）';
  if (/fetch failed|ECONNREFUSED|ENOTFOUND|EHOSTUNREACH/i.test(message)) {
    return `网关不可达：${message}`;
  }
  return message || '未知错误';
}

async function main(argv = process.argv.slice(2), env = process.env) {
  const serviceName = argValue(argv, '--service');
  if (argv.includes('--flush')) {
    const result = await flushSpool(env);
    if (result.sent || result.failed) {
      console.error(`[agentmail-failure-notify] spool: sent=${result.sent} failed=${result.failed}`);
    }
    return;
  }
  if (!argv.includes('--report')) throw new Error('需要 --report 或 --flush');
  if (!isAbnormalExit(env)) return;

  if (argv.includes('--dry-run')) {
    console.log(JSON.stringify(buildFailurePayload({ env, serviceName }), null, 2));
    return;
  }

  const result = await notifyCrash(env.SERVICE_RESULT || 'unexpected-exit', null, {
    env,
    serviceName,
  });
  if (result.sent) {
    console.error(`[agentmail-failure-notify] ${serviceName} 异常已上报`);
    return;
  }
  /*
   * 区分「连不上」与「连上了但被拒」。
   *
   * 原先两种情况都打印「Gateway 不可达」。实测代价：切换插件时 dsh 进了崩溃循环，
   * 通知脚本连打六条「Gateway 不可达」并写进 spool —— 而网关**一直在正常服务**
   * （NRestarts=0），真实响应是 **HTTP 403**（同一会话连续中继邮件撞上防互相唤醒
   * 的跳数上限，`maxRelayHops=5`）。
   *
   * 那句话会把人送去查网络，而问题在策略层。故障通知本身给出误导性诊断，
   * 是「静默失败」的另一种形态。
   */
  console.error(
    `[agentmail-failure-notify] ${serviceName} 异常上报失败，报告已暂存 ${result.path}`
  );
  console.error(`[agentmail-failure-notify] 原因：${describeSendError(result.error)}`);
}

const isCLI = process.argv[1] && resolve(process.argv[1]) === fileURLToPath(import.meta.url);
if (isCLI) {
  main().catch((error) => {
    console.error(`[agentmail-failure-notify] ${error?.message || error}`);
    process.exitCode = 1;
  });
}