import { appendFileSync, createWriteStream, existsSync, mkdirSync } from 'fs';
import { dirname } from 'path';
import { format } from 'util';
type LogLevel = 'debug' | 'info' | 'warn' | 'error';
const LEVEL_PRIORITY: Record<LogLevel, number> = {
debug: 10,
info: 20,
warn: 30,
error: 40,
};
const envLevel = (process.env.LOG_LEVEL || 'info').toLowerCase() as LogLevel;
const activeLevel = LEVEL_PRIORITY[envLevel] ? envLevel : 'info';
const destinations: NodeJS.WritableStream[] = [process.stderr];
const logFilePath = process.env.LOG_FILE;
if (logFilePath) {
try {
const parentDir = dirname(logFilePath);
if (!existsSync(parentDir)) {
mkdirSync(parentDir, { recursive: true });
}
appendFileSync(logFilePath, '');
const stream = createWriteStream(logFilePath, { flags: 'a' });
stream.on('error', (error) => {
const message = `${new Date().toISOString()} [ERROR] Log file stream error for ${logFilePath}: ${format(error)}`;
process.stderr.write(`${message}\n`);
});
destinations.push(stream);
try {
stream.write('');
} catch (error) {
const message = `${new Date().toISOString()} [ERROR] Failed to prime log file ${logFilePath}: ${format(error)}`;
process.stderr.write(`${message}\n`);
}
process.on('exit', () => {
try {
stream.end();
} catch (error) {
// noop – logging best effort on shutdown
}
});
} catch (error) {
const message = `${new Date().toISOString()} [ERROR] Failed to initialize log file ${logFilePath}: ${format(error)}`;
process.stderr.write(`${message}\n`);
}
}
function write(level: LogLevel, args: unknown[]): void {
if (LEVEL_PRIORITY[level] < LEVEL_PRIORITY[activeLevel]) {
return;
}
const message = format(...args);
const line = `${new Date().toISOString()} [${level.toUpperCase()}] ${message}\n`;
for (const destination of destinations) {
try {
destination.write(line);
} catch (error) {
// If writing to a destination fails, fall back to stderr without recursion.
if (destination !== process.stderr) {
process.stderr.write(`${new Date().toISOString()} [ERROR] Failed to write log: ${format(error)}\n`);
}
}
}
}
export const logger = {
debug: (...args: unknown[]) => write('debug', args),
info: (...args: unknown[]) => write('info', args),
warn: (...args: unknown[]) => write('warn', args),
error: (...args: unknown[]) => write('error', args),
};
