/**
 * LandveX Finance — Förbättrad Health Check
 * Sprint 3: Observability
 * 
 * Kontrollerar: PostgreSQL, Redis, Disk, Ledger-tjänst, Revolut API
 */

import { financeInfo, financeError } from './logger.mjs';
import { healthCheckDuration, diskGauge } from './metrics.mjs';

let _cache = null;
let _cacheTime = 0;
const CACHE_TTL = 30000; // 30 sekunder

export async function financeHealthHandler(req, res) {
  const start = Date.now();

  // Returnera cache om giltig
  if (_cache && Date.now() - _cacheTime < CACHE_TTL) {
    return res.status(_cache.status === 'healthy' ? 200 : _cache.status === 'degraded' ? 200 : 503).json(_cache);
  }

  const checks = {};
  let status = 'healthy';

  // ── 1. PostgreSQL (Ledger DB) ──
  try {
    const { Pool } = await import('pg');
    const pool = new Pool({
      connectionString: process.env.DATABASE_URL || process.env.LEDGER_DB_URL,
      ssl: { rejectUnauthorized: false },
      max: 2,
      connectionTimeoutMillis: 3000,
    });
    const dbStart = Date.now();
    await pool.query('SELECT 1');
    const dbDur = Date.now() - dbStart;
    checks.database = { status: 'healthy', response_ms: dbDur };
    healthCheckDuration.observe({ check: 'database' }, dbDur);
    await pool.end();
  } catch (e) {
    checks.database = { status: 'unhealthy', error: e.message };
    status = 'unhealthy';
    financeError('health_check_failed', { error: e, context: { check: 'database' } });
  }

  // ── 2. Redis ──
  try {
    const { default: Redis } = await import('ioredis');
    const redis = new Redis(process.env.REDIS_URL || 'redis://localhost:6379', {
      connectTimeout: 3000,
      maxRetriesPerRequest: 1,
    });
    const redisStart = Date.now();
    await redis.ping();
    const redisDur = Date.now() - redisStart;
    checks.redis = { status: 'healthy', response_ms: redisDur };
    healthCheckDuration.observe({ check: 'redis' }, redisDur);
    redis.disconnect();
  } catch (e) {
    checks.redis = { status: 'unhealthy', error: e.message };
    if (status === 'healthy') status = 'degraded';
    financeError('health_check_failed', { error: e, context: { check: 'redis' } });
  }

  // ── 3. Disk ──
  try {
    const { statfs } = await import('fs');
    const stats = await statfs('/opt/amos/data');
    const freeGB = (stats.bavail * stats.bsize) / (1024 ** 3);
    const totalGB = (stats.blocks * stats.bsize) / (1024 ** 3);
    const usedPct = parseFloat(((totalGB - freeGB) / totalGB * 100).toFixed(1));
    const diskStatus = freeGB < 1 ? 'critical' : freeGB < 5 ? 'warning' : 'healthy';
    
    checks.disk = {
      status: diskStatus,
      free_gb: Math.round(freeGB * 100) / 100,
      total_gb: Math.round(totalGB * 100) / 100,
      used_percent: usedPct,
    };
    diskGauge.set({ path: '/opt/amos/data' }, usedPct);
    
    if (diskStatus === 'critical') status = 'unhealthy';
    else if (diskStatus === 'warning' && status === 'healthy') status = 'degraded';
  } catch (e) {
    checks.disk = { status: 'unknown', error: e.message };
  }

  // ── 4. Ledger Service (intern) ──
  try {
    const ledgerStart = Date.now();
    const ledgerBase = process.env.LEDGER_BASE || 'http://localhost:3250';
    const r = await fetch(`${ledgerBase}/health`, {
      signal: AbortSignal.timeout(3000),
    });
    const ledgerDur = Date.now() - ledgerStart;
    checks.ledger = {
      status: r.ok ? 'healthy' : 'unhealthy',
      response_ms: ledgerDur,
    };
    healthCheckDuration.observe({ check: 'ledger' }, ledgerDur);
    if (!r.ok && status === 'healthy') status = 'degraded';
  } catch (e) {
    checks.ledger = { status: 'unhealthy', error: e.message };
    if (status === 'healthy') status = 'degraded';
    financeError('health_check_failed', { error: e, context: { check: 'ledger' } });
  }

  // ── 5. Revolut API (extern) ──
  try {
    const revStart = Date.now();
    // Försök hämta token (från ledger-proxy.mjs logik)
    const revClientId = process.env.REVOLUT_CLIENT_ID;
    const revRefreshToken = process.env.REVOLUT_REFRESH_TOKEN;
    const revPrivKeyPath = process.env.REVOLUT_PRIVATE_KEY_PATH;
    
    let revStatus = 'unknown';
    let revAuth = false;
    
    if (revClientId && revRefreshToken && revPrivKeyPath) {
      // Vi försöker inte faktiskt autentisera här (tar för lång tid)
      // Utan kollar bara att konfiguration finns
      revStatus = 'configured';
      revAuth = true;
    } else {
      revStatus = 'not_configured';
    }
    
    checks.revolut = {
      status: revStatus === 'configured' ? 'healthy' : 'degraded',
      response_ms: Date.now() - revStart,
      authenticated: revAuth,
    };
    
    if (revStatus === 'not_configured' && status === 'healthy') {
      status = 'degraded';
    }
  } catch (e) {
    checks.revolut = { status: 'unhealthy', error: e.message };
  }

  const result = {
    service: 'finance',
    status,
    timestamp: new Date().toISOString(),
    response_ms: Date.now() - start,
    checks,
  };

  // Cachea resultatet
  _cache = result;
  _cacheTime = Date.now();

  financeInfo('health_check_completed', {
    duration: result.response_ms,
    context: { status, checks_count: Object.keys(checks).length },
  });

  res.status(status === 'healthy' ? 200 : status === 'degraded' ? 200 : 503).json(result);
}

// Manuell cache-invalidering (t.ex. efter deployment)
export function invalidateHealthCache() {
  _cache = null;
  _cacheTime = 0;
  financeInfo('health_cache_invalidated', {});
}