Request Logging — Comprehensive Request and Response Logging

// Request logger middleware
function requestLogger(options = {}) {
  const {
    logBody = false,
    maxBodySize = 4096,
    excludePaths = ['/health', '/metrics'],
    logHeaders = true,
    sensitiveHeaders = ['authorization', 'cookie', 'x-api-key']
  } = options;

  return (req, res, next) => {
    if (excludePaths.some(p => req.path.startsWith(p))) return next();

    const startTime = Date.now();
    const requestEntry = {
      type: 'request',
      timestamp: new Date().toISOString(),
      method: req.method,
      path: req.path,
      query: req.query,
      correlationId: req.correlationId,
      userId: req.user?.id,
      userAgent: req.headers['user-agent'],
      ip: req.ip,
      contentLength: parseInt(req.headers['content-length'] || '0'),
      headers: logHeaders ? sanitizeHeaders(req.headers, sensitiveHeaders) : undefined
    };

    if (logBody && req.body) {
      requestEntry.body = truncateBody(req.body, maxBodySize);
    }

    // Capture response
    const originalEnd = res.end.bind(res);
    const chunks = [];
    res.end = function(chunk, encoding) {
      if (chunk) chunks.push(Buffer.from(chunk));
      const duration = Date.now() - startTime;

      const responseEntry = {
        type: 'response',
        statusCode: res.statusCode,
        duration,
        correlationId: req.correlationId,
        contentLength: res.getHeader('content-length') || chunks.reduce((s, c) => s + c.length, 0),
        slow: duration > (options.slowThreshold || 1000)
      };

      const logLevel = res.statusCode >= 500 ? 'error'
        : res.statusCode >= 400 ? 'warn'
        : duration > 1000 ? 'warn'
        : 'info';

      logger[logLevel]({ ...requestEntry, ...responseEntry });

      return originalEnd(chunk, encoding);
    };

    next();
  };
}