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import * as os from 'node:os';
import * as path from 'node:path';
import { delay } from '../../utils/async/delay.ts';
import { startPolling } from '../../utils/async/poll.ts';
import { withTimeout } from '../../utils/async/with-timeout.ts';
import { errorify } from '../../utils/converter/errorify.ts';
import { stringify } from '../../utils/converter/stringify.ts';
import { BaseLogger } from '../base-logger.ts';
import type { LogLevel } from '../definition.ts';
import type { EmitterFormat } from '../emitter.ts';
import { emitLine, formatSupportsArgs } from '../emitter.ts';
/**
* Configuration options for the FileLogger
*/
export type FileLoggerOptions = {
/**
* The minimum severity level for log entries (default: 'info')
*/
readonly level?: LogLevel;
/**
* The format of the emitted lines (default: 'plain')
*/
readonly format?: EmitterFormat;
/**
* Whether to omit additional args in log output (default: false).
*/
readonly omitArgs?: boolean;
/**
* The delay in milliseconds between buffer flushes (default: 20)
*/
readonly flushDelayMs?: number;
/**
* Error handler callback for file operations If not provided, errors will be thrown
*/
readonly errorHandler?: (error: unknown) => void;
/**
* Number of retries to attempt for file operations (default: 0)
*/
readonly retryLimit?: number;
/**
* Delay between retries in milliseconds (default: 500)
*/
readonly retryDelayMs?: number;
};
/**
* A simple implementation of a logger that writes log entries to a file with minimal overhead.
*
* Features:
*
* - Writes logs to a specified file in a non-blocking way
* - Creates the directory structure if it doesn't exist
* - Supports relative paths (writes to OS temp dir) and absolute paths
* - Supports home directory expansion with tilde (~)
* - Strips ANSI color codes by default
* - Includes additional arguments by default with stack traces and pretty formatting
* - Optional automatic retry for file operations when they fail
*
* @example Basic usage
*
* ```ts
* // Create a file logger with default info level
* const logger = new FileLogger('/var/log/myapp.log');
* logger.info('Application started');
*
* // Or use a filename (will be created in OS temp directory)
* const tempLogger = new FileLogger('debug.log', 'debug');
*
* // Use home directory with tilde expansion
* const homeLogger = new FileLogger('~/logs/myapp.log');
*
* // Use with configuration options
* const configuredLogger = new FileLogger({
* filePath: '/var/log/myapp.log',
* level: 'warning',
* format: 'colorful', // Preserve color codes
* omitArgs: true, // Don't include additional arguments
* errorHandler: (err) => myCustomErrorReporter(err),
* retryLimit: 3, // Retry file operations up to 3 times
* retryDelayMs: 500, // Wait 500ms between retries
* });
*
* // Log with additional arguments (objects will be pretty-printed with stack traces)
* const error = new Error('Connection failed');
* configuredLogger.error('Database operation failed', error, { requestId: '12345', userId: 'user123' });
* ```
*
* @example Using with tee for multiple outputs
*
* ```ts
* import { tee } from 'emitnlog/logger';
* import { FileLogger } from 'emitnlog/logger/node';
*
* // Create a logger that writes to both file and console
* const fileLogger = new FileLogger('/var/log/app.log');
* const consoleLogger = new ConsoleLogger();
* const logger = tee(fileLogger, consoleLogger);
*
* // All logs go to both destinations
* logger.info('This appears in console AND in the log file');
* ```
*
* @example With retry capabilities
*
* ```ts
* // Create a file logger with retry capabilities (useful for unreliable storage)
* const reliableLogger = new FileLogger({
* filePath: '/network/share/logs/app.log',
* retryLimit: 5, // Retry up to 5 times
* retryDelayMs: 1000, // Wait 1 second between retries
* errorHandler: (err) => {
* console.error('Failed to write log after multiple retries:', err);
* // Maybe notify monitoring system
* },
* });
*
* // Logs will automatically retry if the file operation fails
* reliableLogger.info('This log entry will retry if the file system is temporarily unavailable');
* ```
*/
export class FileLogger extends BaseLogger {
/**
* The full path to the log file
*/
public readonly filePath: string;
/**
* The log format
*/
private readonly format: EmitterFormat;
/**
* Whether to omit additional args in log output
*/
private readonly omitArgs: boolean;
/**
* Error handler function
*/
private readonly errorHandler: (error: unknown) => void;
/**
* The delay in milliseconds between buffer flushes
*/
private readonly flushDelayMs: number;
/**
* The maximum number of retries for file operations
*/
private readonly retryLimit: number;
/**
* The delay between retries in milliseconds
*/
private readonly retryDelayMs: number;
/**
* A promise that resolves when the previous write operation is completed
*/
private writePromise: Promise<void>;
/**
* Buffer of lines to write to the file
*/
private buffer: string[] = [];
/**
* Whether the buffer write is scheduled
*/
private flushScheduled = false;
/**
* Whether the logger is closed
*/
private closed = false;
/**
* Creates a new FileLogger that writes to a file.
*
* @param filePathOrOptions Either a string path to the log file, or a configuration object
* @param level The minimum severity level for log entries (default: 'info')
* @param format - The format of the emitted lines (default: 'plain')
*/
public constructor(
filePathOrOptions: string | ({ readonly filePath: string } & FileLoggerOptions),
level?: LogLevel,
format?: EmitterFormat,
) {
const isString = typeof filePathOrOptions === 'string';
const logLevel = level ?? (isString ? undefined : filePathOrOptions.level);
const logFormat = format ?? (isString ? undefined : filePathOrOptions.format) ?? 'plain';
const filePath = isString ? filePathOrOptions : filePathOrOptions.filePath;
const omitArgs = isString ? false : (filePathOrOptions.omitArgs ?? false);
const flushDelayMs = isString ? 20 : (filePathOrOptions.flushDelayMs ?? 20);
const retryLimit = isString ? 0 : (filePathOrOptions.retryLimit ?? 0);
const retryDelayMs = isString ? 500 : (filePathOrOptions.retryDelayMs ?? 500);
const errorHandler = isString ? undefined : filePathOrOptions.errorHandler;
super(logLevel);
if (!filePath) {
throw new Error('File path is required');
}
this.format = logFormat;
this.omitArgs = omitArgs;
this.flushDelayMs = flushDelayMs;
this.retryLimit = retryLimit;
this.retryDelayMs = retryDelayMs;
this.errorHandler =
errorHandler ??
((error) => {
throw errorify(error);
});
if (filePath.includes(path.sep)) {
if (filePath.length > 1 && filePath.startsWith('~')) {
this.filePath = path.join(os.homedir(), filePath.substring(1));
} else {
this.filePath = filePath;
}
} else {
this.filePath = path.join(os.tmpdir(), filePath);
}
this.writePromise = this.createLogDirectory().catch(this.errorHandler);
}
protected override emitLine(level: LogLevel, message: string, args: readonly unknown[]): void {
if (this.closed) {
return;
}
if (this.omitArgs) {
args = [];
}
if (this.format !== 'colorful') {
message = message.replace(/\x1B(?:[@-Z\\-_]|\[[0-?]*[ -/]*[@-~])/g, '');
}
const content = emitLine(level, message, args, this.format);
this.buffer.push(content);
if (!formatSupportsArgs(this.format) && args.length) {
this.buffer.push('args:');
for (let i = 0; i < args.length; i++) {
const arg = args[i];
const formattedArg = stringify(arg, { includeStack: true, pretty: true, maxDepth: 3 });
this.buffer.push(`[${i}] ${formattedArg}`);
}
this.buffer.push('');
}
this.flush();
}
private async createLogDirectory(): Promise<void> {
const dir = path.dirname(this.filePath);
await fs.mkdir(dir, { recursive: true });
}
private async appendFile(content: string): Promise<void> {
if (this.retryLimit <= 0) {
await fs.appendFile(this.filePath, content, 'utf8');
return;
}
const { wait } = startPolling(
async () => {
try {
await fs.appendFile(this.filePath, content, 'utf8');
return true;
} catch {
return false;
}
},
this.retryDelayMs,
{ retryLimit: this.retryLimit, interrupt: (result) => result, invokeImmediately: true },
);
const result = await wait;
Iif (result !== true) {
throw new Error(`Failed to write to log file ${this.filePath} after ${this.retryLimit} attempts`);
}
}
/**
* Flushes the buffer to the file.
*/
public flush(): void {
if (this.flushScheduled) {
return;
}
if (!this.buffer.length) {
this.flushScheduled = false;
return;
}
this.flushScheduled = true;
this.writePromise = this.writePromise
.then(() => delay(this.flushDelayMs))
.then(async () => {
const linesToWrite = this.buffer.splice(0).join('\n') + '\n';
this.flushScheduled = false;
await this.appendFile(linesToWrite).catch(this.errorHandler);
});
}
/**
* Closes the logger by flushes the buffer to the file.
*/
public close(timeoutMs?: number): Promise<void> {
Eif (!this.closed) {
this.closed = true;
this.flush();
}
return timeoutMs !== undefined ? withTimeout(this.writePromise, timeoutMs) : this.writePromise;
}
}
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