express-insights/config.js

Production-ready Express middleware for backend health monitoring with metrics, HTML/JSON output, authentication, and service checks.

const validator = require('validator');

const DEFAULT_CONFIG = {
  route: '/health',
  htmlResponse: false,
  style: 'light',
  message: 'Backend Health Check',
  version: '1.0.0',
  includeNetwork: false,
  includeDisk: false,
  checks: {
    database: false,
  },
  authentication: null,
  rateLimit: null,
  enableMetrics: false,
  cors: false,
  cacheTTL: 5000,
  timeout: 5000,
  retries: 1,
  autoRefreshInterval: 30000,
  log: {
    level: 'info',
    destination: 'console',
    filePath: './health-check.log',
  },
  resourceThresholds: {
    memoryUsedPercent: 80,
    cpuLoad1Min: 2.0,
  },
};

function validateOptions(options) {
  const mergedOptions = {
    ...DEFAULT_CONFIG,
    log: { ...DEFAULT_CONFIG.log },
    resourceThresholds: { ...DEFAULT_CONFIG.resourceThresholds },
    checks: { ...DEFAULT_CONFIG.checks },
    ...options,
  };

  if (options.log) mergedOptions.log = { ...DEFAULT_CONFIG.log, ...options.log };
  if (options.resourceThresholds) mergedOptions.resourceThresholds = { ...DEFAULT_CONFIG.resourceThresholds, ...options.resourceThresholds };
  if (options.checks) mergedOptions.checks = { ...DEFAULT_CONFIG.checks, ...options.checks };

  const { route, style, log, autoRefreshInterval, resourceThresholds, cors, checks } = mergedOptions;

  if (typeof route !== 'string' || !route.startsWith('/')) throw new Error('Invalid route: must be a string starting with "/"');
  if (!['light', 'dark'].includes(style)) throw new Error('Invalid style: must be "light" or "dark"');
  if (!['info', 'warn', 'error'].includes(log.level)) throw new Error('Invalid log level: must be "info", "warn", or "error"');
  if (!['console', 'file'].includes(log.destination) && !log.customLogger) throw new Error('Invalid log destination: must be "console", "file", or provide customLogger');
  if (!Number.isInteger(autoRefreshInterval) || autoRefreshInterval < 0) throw new Error('Invalid autoRefreshInterval: must be a non-negative integer');
  if (resourceThresholds.memoryUsedPercent < 0 || resourceThresholds.memoryUsedPercent > 100) throw new Error('Invalid memoryUsedPercent threshold: must be between 0 and 100');
  if (resourceThresholds.cpuLoad1Min < 0) throw new Error('Invalid cpuLoad1Min threshold: must be non-negative');
  if (cors !== true && cors !== false && (!cors || !cors.allowedOrigins)) throw new Error('Invalid cors configuration: must be boolean or { allowedOrigins: string | string[] }');
  if (typeof checks !== 'object') throw new Error('Invalid checks configuration: must be an object');

  return mergedOptions;
}

module.exports = { DEFAULT_CONFIG, validateOptions };