Second Brain MCP Server

/** * Logger abstraction for MCP server * * MCP servers communicate over stdio, so we need to be careful about logging. * This logger writes to stderr to avoid polluting the protocol channel. * * Controlled via environment variables: * - SECOND_BRAIN_DEBUG=true - Enable logging (default: disabled) * - SECOND_BRAIN_LOG_LEVEL - Minimum log level (debug|info|warn|error, default: info) */ type LogLevel = 'debug' | 'info' | 'warn' | 'error'; interface LoggerConfig { enabled: boolean; minLevel: LogLevel; } const LOG_LEVELS: Record<LogLevel, number> = { debug: 0, info: 1, warn: 2, error: 3, }; class Logger { private config: LoggerConfig; constructor() { this.config = { enabled: process.env.SECOND_BRAIN_DEBUG === 'true', minLevel: this.parseLogLevel(process.env.SECOND_BRAIN_LOG_LEVEL), }; } /** * Parse log level from environment variable */ private parseLogLevel(level: string | undefined): LogLevel { if (level && level in LOG_LEVELS) { return level as LogLevel; } return 'info'; } /** * Check if a message at the given level should be logged */ private shouldLog(level: LogLevel): boolean { if (!this.config.enabled) { return false; } return LOG_LEVELS[level] >= LOG_LEVELS[this.config.minLevel]; } /** * Format a log message with timestamp and level */ private formatMessage( level: LogLevel, message: string, meta?: Record<string, unknown> ): string { const timestamp = new Date().toISOString(); const metaStr = meta ? ` ${JSON.stringify(meta)}` : ''; return `[${timestamp}] [${level.toUpperCase()}] ${message}${metaStr}`; } /** * Log a debug message */ debug(message: string, meta?: Record<string, unknown>): void { if (this.shouldLog('debug')) { console.error(this.formatMessage('debug', message, meta)); } } /** * Log an info message */ info(message: string, meta?: Record<string, unknown>): void { if (this.shouldLog('info')) { console.error(this.formatMessage('info', message, meta)); } } /** * Log a warning message */ warn(message: string, meta?: Record<string, unknown>): void { if (this.shouldLog('warn')) { console.error(this.formatMessage('warn', message, meta)); } } /** * Log an error message */ error(message: string, meta?: Record<string, unknown>): void { if (this.shouldLog('error')) { console.error(this.formatMessage('error', message, meta)); } } /** * Check if logging is enabled */ isEnabled(): boolean { return this.config.enabled; } /** * Get current configuration (for testing) */ getConfig(): LoggerConfig { return { ...this.config }; } } // Export singleton instance export const logger = new Logger(); // Export class for testing export { Logger };