src/lib/monitoring/logger.ts

/**
 * Structured logging module for enhanced observability
 * Logs with severity levels, component tracking, and metrics
 */

type LogLevel = 'debug' | 'info' | 'warn' | 'error';

interface LogEntry {
  timestamp: string;
  level: LogLevel;
  component: string;
  message: string;
  duration?: number; // milliseconds
  error?: string;
  metadata?: Record<string, unknown>;
}

class Logger {
  private isProduction = typeof process !== 'undefined' && process.env.NODE_ENV === 'production';

  /**
   * Log a message with timestamp and component context
   */
  private log(level: LogLevel, component: string, message: string, metadata?: Record<string, unknown>) {
    const entry: LogEntry = {
      timestamp: new Date().toISOString(),
      level,
      component,
      message,
      metadata,
    };

    const prefix = `[${component}]`;
    const formattedMessage = `${prefix} ${message}`;

    const logWithMetadata = (consoleFn: typeof console.error) => {
      if (metadata && Object.keys(metadata).length > 0) {
        consoleFn(formattedMessage, metadata);
      } else {
        consoleFn(formattedMessage);
      }
    };

    switch (level) {
      case 'error':
        logWithMetadata(console.error);
        break;
      case 'warn':
        logWithMetadata(console.warn);
        break;
      case 'info':
        if (!this.isProduction) {
          logWithMetadata(console.log);
        }
        break;
      case 'debug':
        if (!this.isProduction) {
          logWithMetadata(console.debug);
        }
        break;
    }
  }

  /**
   * Log debug message (development only)
   */
  debug(component: string, message: string, metadata?: Record<string, unknown>) {
    this.log('debug', component, message, metadata);
  }

  /**
   * Log info message
   */
  info(component: string, message: string, metadata?: Record<string, unknown>) {
    this.log('info', component, message, metadata);
  }

  /**
   * Log warning message
   */
  warn(component: string, message: string, metadata?: Record<string, unknown>) {
    this.log('warn', component, message, metadata);
  }

  /**
   * Log error with optional error object
   */
  error(component: string, message: string, error?: Error | unknown, metadata?: Record<string, unknown>) {
    const errorMetadata = {
      ...metadata,
      ...(error instanceof Error && {
        errorMessage: error.message,
        errorStack: error.stack,
      }),
    };
    this.log('error', component, message, errorMetadata);
  }

  /**
   * Measure performance of an async function and log duration
   */
  async measureAsync<T>(
    component: string,
    operationName: string,
    fn: () => Promise<T>,
  ): Promise<T> {
    const start = performance.now();
    try {
      const result = await fn();
      const duration = performance.now() - start;
      this.debug(component, `${operationName} completed`, { duration: `${duration.toFixed(2)}ms` });
      return result;
    } catch (error) {
      const duration = performance.now() - start;
      this.error(component, `${operationName} failed`, error, { duration: `${duration.toFixed(2)}ms` });
      throw error;
    }
  }

  /**
   * Measure performance of a sync function and log duration
   */
  measureSync<T>(
    component: string,
    operationName: string,
    fn: () => T,
  ): T {
    const start = performance.now();
    try {
      const result = fn();
      const duration = performance.now() - start;
      this.debug(component, `${operationName} completed`, { duration: `${duration.toFixed(2)}ms` });
      return result;
    } catch (error) {
      const duration = performance.now() - start;
      this.error(component, `${operationName} failed`, error, { duration: `${duration.toFixed(2)}ms` });
      throw error;
    }
  }
}

// Export singleton instance
export const logger = new Logger();

/**
 * Helper for tracking async operation metrics
 */
export function createAsyncMetricsTracker(component: string, operationName: string) {
  const start = performance.now();
  return {
    success: (metadata?: Record<string, unknown>) => {
      const duration = performance.now() - start;
      logger.info(component, `${operationName} succeeded`, { duration: `${duration.toFixed(2)}ms`, ...metadata });
    },
    error: (error: Error | unknown, metadata?: Record<string, unknown>) => {
      const duration = performance.now() - start;
      logger.error(component, `${operationName} failed`, error, { duration: `${duration.toFixed(2)}ms`, ...metadata });
    },
  };
}