mcp-ynab/src/shared/logger.js

Model Context Protocol server for YNAB integration

import { writeFile, appendFile, existsSync, mkdirSync } from 'fs';
import { promisify } from 'util';
import { resolve, dirname } from 'path';
import { fileURLToPath } from 'url';

const writeFileAsync = promisify(writeFile);
const appendFileAsync = promisify(appendFile);

const __filename = fileURLToPath(import.meta.url);
const __dirname = dirname(__filename);

class Logger {
  constructor() {
    this.logsDir = resolve(__dirname, '../../logs');
    this.logFile = resolve(this.logsDir, 'mcp-debug.log');
    // Don't check enabled in constructor - check at runtime
  }

  get enabled() {
    // Check environment variables at runtime, not construction time
    return process.env.NODE_ENV === 'development' || process.env.MCP_DEBUG === 'true';
  }

  ensureLogsDirectory() {
    if (this.enabled && !existsSync(this.logsDir)) {
      try {
        mkdirSync(this.logsDir, { recursive: true });
      } catch (error) {
        // Silently fail to avoid breaking MCP protocol
      }
    }
  }

  async log(level, message, data = null) {
    if (!this.enabled) return;

    // Ensure logs directory exists
    this.ensureLogsDirectory();

    const timestamp = new Date().toISOString();
    const logEntry = {
      timestamp,
      level,
      message,
      data,
      pid: process.pid
    };

    const logLine = JSON.stringify(logEntry) + '\n';
    
    try {
      await appendFileAsync(this.logFile, logLine);
    } catch (error) {
      // Silently fail - don't break MCP protocol
    }
  }

  async info(message, data) {
    await this.log('INFO', message, data);
  }

  async error(message, data) {
    await this.log('ERROR', message, data);
  }

  async debug(message, data) {
    await this.log('DEBUG', message, data);
  }

  async warn(message, data) {
    await this.log('WARN', message, data);
  }

  async startup(message, data) {
    await this.log('STARTUP', message, data);
  }

  async tool(toolName, params, result) {
    await this.log('TOOL', `Tool executed: ${toolName}`, {
      tool: toolName,
      params,
      success: !result?.error,
      resultSize: JSON.stringify(result).length
    });
  }
}

export default new Logger();