'use strict';

const crypto = require('crypto');
const fs = require('fs/promises');
const os = require('os');
const path = require('path');

const DEFAULT_LOCK_PATH = path.resolve(__dirname, '../../runtime/hsds/hsds_account.lock.json');
const DEFAULT_STALE_MS = Math.max(
  Number.parseInt(process.env.HSDS_ACCOUNT_LOCK_STALE_MS || '43200000', 10) || 43200000,
  60000
);

function normalizeText(value, fallback = '') {
  const text = value === undefined || value === null ? '' : String(value).trim();
  return text || fallback;
}

function isProcessAlive(pid) {
  const numericPid = Number.parseInt(pid, 10);
  if (!Number.isFinite(numericPid) || numericPid <= 0) {
    return false;
  }

  try {
    process.kill(numericPid, 0);
    return true;
  } catch (error) {
    return error?.code === 'EPERM';
  }
}

async function ensureLockDirectory(lockPath) {
  await fs.mkdir(path.dirname(lockPath), { recursive: true });
}

async function readLockPayload(lockPath) {
  try {
    const text = await fs.readFile(lockPath, 'utf8');
    return JSON.parse(text);
  } catch (_error) {
    return null;
  }
}

function isLockPayloadStale(payload) {
  if (!payload || typeof payload !== 'object') {
    return true;
  }

  if (isProcessAlive(payload.pid)) {
    return false;
  }

  const currentHostname = os.hostname();
  const lockHostname = normalizeText(payload.hostname);
  if (!lockHostname || lockHostname === currentHostname) {
    return true;
  }

  const acquiredAt = Date.parse(payload.acquiredAt || '');
  if (Number.isFinite(acquiredAt)) {
    return Date.now() - acquiredAt > DEFAULT_STALE_MS;
  }

  return true;
}

async function releaseOwnedLock(lockPath, token) {
  if (!token) {
    return;
  }

  const payload = await readLockPayload(lockPath);
  if (payload?.token !== token) {
    return;
  }

  await fs.rm(lockPath, { force: true });
}

async function acquireHsdsAccountLock(trigger = 'manual', options = {}) {
  const lockPath = path.resolve(options.lockPath || DEFAULT_LOCK_PATH);
  await ensureLockDirectory(lockPath);

  for (let attempt = 0; attempt < 2; attempt += 1) {
    const token = crypto.randomUUID();
    const payload = {
      token,
      pid: process.pid,
      hostname: os.hostname(),
      trigger: normalizeText(trigger, 'manual'),
      command: process.argv.join(' ').trim(),
      acquiredAt: new Date().toISOString(),
    };

    try {
      const handle = await fs.open(lockPath, 'wx');
      try {
        await handle.writeFile(`${JSON.stringify(payload, null, 2)}\n`, 'utf8');
      } finally {
        await handle.close();
      }

      return {
        acquired: true,
        lockPath,
        payload,
        async release() {
          await releaseOwnedLock(lockPath, token);
        },
      };
    } catch (error) {
      if (error?.code !== 'EEXIST') {
        throw error;
      }

      const holder = await readLockPayload(lockPath);
      if (isLockPayloadStale(holder)) {
        await fs.rm(lockPath, { force: true });
        continue;
      }

      return {
        acquired: false,
        lockPath,
        holder,
      };
    }
  }

  const holder = await readLockPayload(lockPath);
  return {
    acquired: false,
    lockPath,
    holder,
  };
}

async function withHsdsAccountLock(trigger, runner, options = {}) {
  const lockState = await acquireHsdsAccountLock(trigger, options);
  if (!lockState.acquired) {
    return {
      success: false,
      skipped: true,
      reason: 'hsds_account_busy',
      trigger: normalizeText(trigger, 'manual'),
      lockPath: lockState.lockPath,
      lockHolder: lockState.holder || null,
    };
  }

  try {
    return await runner();
  } finally {
    await lockState.release();
  }
}

module.exports = {
  acquireHsdsAccountLock,
  withHsdsAccountLock,
};