type LogLevel = 'debug' | 'info' | 'warn' | 'error';
interface LogEntry {
timestamp: string;
level: LogLevel;
message: string;
meta?: any;
}
class Logger {
private logLevel: LogLevel;
constructor() {
this.logLevel = (process.env.LOG_LEVEL as LogLevel) || 'info';
}
private shouldLog(level: LogLevel): boolean {
const levels: Record<LogLevel, number> = {
debug: 0,
info: 1,
warn: 2,
error: 3,
};
return levels[level] >= levels[this.logLevel];
}
private formatMessage(level: LogLevel, message: string, meta?: any): string {
const entry: LogEntry = {
timestamp: new Date().toISOString(),
level,
message,
meta,
};
return JSON.stringify(entry);
}
private log(level: LogLevel, message: string, meta?: any): void {
if (!this.shouldLog(level)) return;
const formatted = this.formatMessage(level, message, meta);
// Always use stderr to avoid interfering with MCP JSON-RPC on stdout
process.stderr.write(formatted + '\n');
}
debug(message: string, meta?: any): void {
this.log('debug', message, meta);
}
info(message: string, meta?: any): void {
this.log('info', message, meta);
}
warn(message: string, meta?: any): void {
this.log('warn', message, meta);
}
error(message: string, error?: any): void {
const meta = error instanceof Error
? {
message: error.message,
stack: error.stack,
name: error.name
}
: error;
this.log('error', message, meta);
}
}
export const logger = new Logger();
