'use strict';

const express = require('express');
const { execFile } = require('child_process');
const path = require('path');
const { pool } = require('../lib/db');

const router = express.Router();

/** Server start time — captured once at module load */
const SERVER_START = Date.now();

// ─── Helpers ─────────────────────────────────────────────────────────────────

/**
 * Run a shell command and resolve with its stdout, or reject on error.
 * @param {string} cmd
 * @param {string[]} args
 * @param {number} timeoutMs
 * @returns {Promise<string>}
 */
function runCommand(cmd, args, timeoutMs = 3000) {
  return new Promise((resolve, reject) => {
    execFile(cmd, args, { timeout: timeoutMs }, (err, stdout) => {
      if (err) return reject(err);
      resolve(stdout.trim());
    });
  });
}

/**
 * Parse `df -h` output for a given mount point.
 * Returns { used, total, percent } or null.
 * @param {string} mountPoint
 * @returns {Promise<{ used: string, total: string, percent: string } | null>}
 */
async function checkDisk(mountPoint) {
  try {
    const out = await runCommand('df', ['-h', mountPoint]);
    // Header line + data line
    const lines = out.split('\n').filter(Boolean);
    const dataLine = lines[lines.length - 1];
    // Columns: Filesystem  Size  Used  Avail  Use%  Mounted
    const parts = dataLine.split(/\s+/);
    if (parts.length < 6) return null;
    return {
      used: parts[2],
      total: parts[1],
      percent: parts[4], // e.g. "72%"
    };
  } catch {
    return null;
  }
}

/**
 * Determine overall status from individual checks.
 * Any "outage" → overall "outage"; any "degraded" → "degraded"; else "operational".
 * @param {{ status: string }[]} checks
 * @returns {'operational' | 'degraded' | 'outage'}
 */
function computeOverall(checks) {
  if (checks.some(c => c.status === 'outage')) return 'outage';
  if (checks.some(c => c.status === 'degraded')) return 'degraded';
  return 'operational';
}

// ─── Route: GET /status (serve HTML page) ────────────────────────────────────

router.get('/', (req, res) => {
  res.sendFile(path.resolve(__dirname, '../public/status.html'));
});

// ─── Route: GET /status/api ───────────────────────────────────────────────────

router.get('/api', async (req, res) => {
  const checks = [];

  // 1. Web server — always operational if we reached this handler
  checks.push({ name: 'Веб-сервер', status: 'operational', latency: 0 });

  // 2. Database — SELECT 1
  {
    const t0 = Date.now();
    try {
      await pool.execute('SELECT 1');
      checks.push({ name: 'База данных', status: 'operational', latency: Date.now() - t0 });
    } catch {
      checks.push({ name: 'База данных', status: 'outage', latency: Date.now() - t0 });
    }
  }

  // 3. FFmpeg
  {
    const t0 = Date.now();
    try {
      await runCommand('which', ['ffmpeg']);
      checks.push({ name: 'FFmpeg', status: 'operational', latency: Date.now() - t0 });
    } catch {
      checks.push({ name: 'FFmpeg', status: 'degraded', latency: Date.now() - t0 });
    }
  }

  // 4. Disk /
  {
    const disk = await checkDisk('/');
    if (disk) {
      const pct = parseInt(disk.percent, 10);
      const status = pct >= 95 ? 'outage' : pct >= 85 ? 'degraded' : 'operational';
      checks.push({
        name: 'Диск / (NVMe)',
        status,
        detail: `${disk.percent} использовано (${disk.used} / ${disk.total})`,
      });
    } else {
      checks.push({ name: 'Диск / (NVMe)', status: 'degraded', detail: 'Не удалось проверить' });
    }
  }

  // 5. Disk /mnt/webdata
  {
    const disk = await checkDisk('/mnt/webdata');
    if (disk) {
      const pct = parseInt(disk.percent, 10);
      const status = pct >= 95 ? 'outage' : pct >= 85 ? 'degraded' : 'operational';
      checks.push({
        name: 'Диск /mnt/webdata',
        status,
        detail: `${disk.percent} использовано (${disk.used} / ${disk.total})`,
      });
    } else {
      // Mount point may not exist on dev — treat as degraded, not outage
      checks.push({ name: 'Диск /mnt/webdata', status: 'degraded', detail: 'Не смонтирован' });
    }
  }

  const mem = process.memoryUsage();

  res.json({
    overall: computeOverall(checks),
    uptime: Math.floor((Date.now() - SERVER_START) / 1000),
    checks,
    server: {
      node: process.version,
      memory: {
        rss: Math.round(mem.rss / 1024 / 1024) + 'MB',
        heap:
          Math.round(mem.heapUsed / 1024 / 1024) +
          '/' +
          Math.round(mem.heapTotal / 1024 / 1024) +
          'MB',
      },
      pid: process.pid,
    },
    timestamp: new Date().toISOString(),
  });
});

module.exports = router;