const express = require('express');
const cors = require('cors');
const path = require('path');
const fs = require('fs');

const app = express();
const PORT = process.env.PORT || 3000;

const CASDOOR_ENDPOINT  = process.env.CASDOOR_ENDPOINT  || 'https://auth.falahos.my'
const CASDOOR_CLIENT_ID = process.env.CASDOOR_CLIENT_ID || ''

app.use(cors());
app.use(express.json());

// AWS-level standard: proper static file serving with cache control
const distPath = path.join(__dirname, 'dist');
if (!fs.existsSync(distPath)) {
  console.warn(JSON.stringify({ ts: new Date().toISOString(), level: 'warn', service: 'app', msg: 'dist directory does not exist! The frontend will not be served.' }));
}

app.use(express.static(distPath, {
  maxAge: '1d', // Cache static assets for performance
  setHeaders: (res, path) => {
    if (path.endsWith('.html')) {
      // Don't cache HTML to ensure users get the latest version on reload
      res.setHeader('Cache-Control', 'no-cache, no-store, must-revalidate');
    }
  }
}));

// ── UmmahID / Casdoor auth ────────────────────────────────────────────────

function decodeJwtPayload(token) {
  try {
    const payload = token.split('.')[1]
    return JSON.parse(Buffer.from(payload, 'base64url').toString('utf-8'))
  } catch {
    return {}
  }
}

// Returns safe public config — no secrets exposed
app.get('/api/auth/config', (_req, res) => {
  if (!CASDOOR_CLIENT_ID) {
    return res.status(503).json({ error: 'CASDOOR_CLIENT_ID not configured on server' })
  }
  res.json({
    clientId:      CASDOOR_CLIENT_ID,
    endpoint:      CASDOOR_ENDPOINT,
    authorizePath: '/login/oauth/authorize',
  })
})

// PKCE token exchange — code_verifier replaces client_secret for public clients
app.post('/api/auth/token', async (req, res) => {
  const { code, codeVerifier, redirectUri } = req.body
  if (!code || !codeVerifier || !redirectUri) {
    return res.status(400).json({ error: 'Missing code, codeVerifier, or redirectUri' })
  }
  try {
    const tokenRes = await fetch(`${CASDOOR_ENDPOINT}/api/login/oauth/access_token`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({
        grant_type:    'authorization_code',
        client_id:     CASDOOR_CLIENT_ID,
        code,
        redirect_uri:  redirectUri,
        code_verifier: codeVerifier,
      }),
    })
    const data = await tokenRes.json()
    if (!tokenRes.ok || data.error) {
      return res.status(400).json({ error: data.error_description || data.error || 'Token exchange failed' })
    }
    const claims = decodeJwtPayload(data.id_token || data.access_token)
    res.json({
      accessToken: data.access_token,
      user: {
        id:       claims.sub  || claims.id       || '',
        email:    claims.email                   || '',
        fullName: claims.name || claims.preferred_username || '',
        role:     claims['falah/role'] || claims.role || 'user',
      },
    })
  } catch (err) {
    console.error(JSON.stringify({ ts: new Date().toISOString(), level: 'error', service: 'auth', msg: err.message }))
    res.status(502).json({ error: 'Could not reach Casdoor' })
  }
})

// ─────────────────────────────────────────────────────────────────────────────

app.get('/health', (_req, res) => {
  res.json({ status: 'healthy', service: 'app', version: '1.3.0', timestamp: new Date().toISOString() });
});

app.get('*', (req, res, next) => {
  const indexPath = path.join(distPath, 'index.html');
  if (fs.existsSync(indexPath)) {
    res.sendFile(indexPath, (err) => {
      if (err) {
        console.error(JSON.stringify({ ts: new Date().toISOString(), level: 'error', service: 'app', msg: 'Error sending index.html', error: err.message }));
        next(err); // Pass to global error handler
      }
    });
  } else {
    res.status(404).send('Not Found: Application build missing.');
  }
});

// Global Error Handler
app.use((err, req, res, next) => {
  console.error(JSON.stringify({ ts: new Date().toISOString(), level: 'error', service: 'app', msg: 'Unhandled error in Express', error: err.stack || err.message }));
  if (!res.headersSent) {
    res.status(500).json({ error: 'Internal Server Error' });
  }
});

const server = app.listen(PORT, () => {
  console.log(JSON.stringify({ ts: new Date().toISOString(), level: 'info', service: 'app', msg: `running on port ${PORT}` }));
});

// Graceful Shutdown for DevOps / Orchestrators (ECS, K8s, Cloud Run)
const shutdown = (signal) => {
  console.log(JSON.stringify({ ts: new Date().toISOString(), level: 'info', service: 'app', msg: `Received ${signal}. Shutting down gracefully...` }));
  server.close(() => {
    console.log(JSON.stringify({ ts: new Date().toISOString(), level: 'info', service: 'app', msg: 'Closed remaining connections.' }));
    process.exit(0);
  });
  
  // Force shutdown after 10s if connections linger
  setTimeout(() => {
    console.error(JSON.stringify({ ts: new Date().toISOString(), level: 'error', service: 'app', msg: 'Could not close connections in time, forcefully shutting down' }));
    process.exit(1);
  }, 10000);
};

process.on('SIGTERM', () => shutdown('SIGTERM'));
process.on('SIGINT', () => shutdown('SIGINT'));