import winston from 'winston';

export type Logger = winston.Logger;

function safeStringify(value: unknown): string {
  const seen = new WeakSet<object>();
  try {
    return JSON.stringify(value, (_key, val) => {
      if (typeof val === 'object' && val !== null) {
        if (seen.has(val)) return '[Circular]';
        seen.add(val);
      }
      if (typeof val === 'bigint') return val.toString();
      return val;
    });
  } catch (err) {
    return `[Unserializable: ${(err as Error).message}]`;
  }
}

export function createLogger(): Logger {
  return winston.createLogger({
    level: process.env.LOG_LEVEL || 'info',
    format: winston.format.combine(
      winston.format.timestamp(),
      winston.format.errors({ stack: true }),
      winston.format.json()
    ),
    transports: [
      new winston.transports.Console({
        format: winston.format.combine(
          winston.format.colorize(),
          winston.format.printf(({ level, message, timestamp, ...meta }) => {
            const metaStr = Object.keys(meta).length ? ` ${safeStringify(meta)}` : '';
            return `${timestamp} [${level}]: ${message}${metaStr}`;
          })
        ),
      }),
      new winston.transports.File({
        filename: 'logs/error.log',
        level: 'error',
      }),
      new winston.transports.File({
        filename: 'logs/combined.log',
      }),
    ],
  });
}