@future-widget-lab/logger/src/helpers/create-logger/create-logger.helper.ts

A good enough logger for server-side oriented applications.

import log, { LogLevelDesc } from 'loglevel';

import { shouldDebug as defaultShouldDebug } from '../should-debug/should-debug.helper';
import type { ShouldDebug } from '../should-debug/should-debug.helper';

type OnMessageOptions = {
	level: LogLevelDesc;
	timestamp: string;
	payload: object;
	message: string;
};

type OnAfterMessageOptions = {
	level: LogLevelDesc;
	timestamp: string;
	payload: object;
	message: string;
};

type CreateLoggerOptions = {
	/**
	 * @description
	 * Use this to set the default log level.
	 *
	 * Note: Debug level logs are controlled via command-line arguments. Please check `allTag` and `debugArgumentName` if you wish to customize the behavior.
	 */
	level: LogLevelDesc;
	/**
	 * @description
	 * Use this to set the "catch-all" tag for debugging purposes.
	 *
	 * Defaults to "all".
	 *
	 * @example
	 * const logger = createLogger({
	 *  allTag: "all" // or any other joker string you'd like to use.
	 * });
	 *
	 * // You are able to see all the debug level logs by setting your command-line arguments to `DEBUG=all`.
	 */
	allTag?: string;
	/**
	 * @description
	 * Use this to set the name of the command-line argument which signals the debug logs should be printed.
	 *
	 * Defaults to "DEBUG".
	 *
	 * @example
	 * const logger = createLogger({
	 *  ...,
	 *  debugArgumentName: "DEBUG" // or any other string you'd like to use.
	 * });
	 *
	 * logger.debug("auth-module", { ok: true }, "Systems online.")
	 *
	 * // In order to print the log you'd need to update your command with this command-line argument `DEBUG=auth-module`.
	 */
	debugArgumentName?: string;
	/**
	 * @description
	 * Use this to set a custom function that determines if a debug level log should be printed or not.
	 */
	shouldDebug?: ShouldDebug;
	/**
	 * @description
	 * Use this to set an emoji for the debug level logs.
	 *
	 * Defaults to 🕵️.
	 */
	debugEmoji?: string;
	/**
	 * @description
	 * Use this to set an emoji for the error logs.
	 *
	 * Defaults to 📕.
	 */
	errorEmoji?: string;
	/**
	 * @description
	 * Use this to set an emoji for the info level logs.
	 *
	 * Defaults to 📘.
	 */
	infoEmoji?: string;
	/**
	 * @description
	 * Use this to set an emoji for the trace level logs.
	 *
	 * Defaults to 📓.
	 */
	traceEmoji?: string;
	/**
	 * @description
	 * Use this to set an emoji for the warn level logs.
	 *
	 * Defaults to 📒.
	 */
	warnEmoji?: string;
	/**
	 * @description
	 * Use this to have fine-graned control over the message being rendered.
	 */
	onMessage?: (options: OnMessageOptions) => string;
	/**
	 * @description
	 * Use this to perform a side-effect once the message has been printed.
	 */
	onAfterMessage?: (options: OnAfterMessageOptions) => void;
};

export const createLogger = (options: CreateLoggerOptions) => {
	const {
		level,
		allTag = 'all',
		debugArgumentName = 'DEBUG',
		shouldDebug = defaultShouldDebug,
		debugEmoji = '🕵',
		errorEmoji = '📕',
		infoEmoji = '📘',
		traceEmoji = '📓',
		warnEmoji = '📒',
		onMessage,
		onAfterMessage
	} = options;

	log.setDefaultLevel(level);

	const logger = {
		debug(tag: string, object: object, message: string) {
			if (!shouldDebug({ tag, allTag, debugArgumentName })) {
				return;
			}

			const timestamp = new Date().toISOString();

			const debugMessage = onMessage
				? onMessage({
						level: 'DEBUG',
						timestamp,
						payload: object,
						message
				  })
				: `${debugEmoji || '🕵'} [${timestamp}] [DEBUG] [${tag}] ${message}`;

			log.debug(debugMessage, object);

			onAfterMessage?.({
				level: 'DEBUG',
				timestamp,
				payload: object,
				message
			});
		},
		error(object: object, message: string) {
			const timestamp = new Date().toISOString();

			const errorMessage = onMessage
				? onMessage({
						level: 'ERROR',
						timestamp,
						payload: object,
						message
				  })
				: `${errorEmoji || '📕'} [${timestamp}] [ERROR] ${message}`;

			log.error(errorMessage, object);

			onAfterMessage?.({
				level: 'ERROR',
				timestamp,
				payload: object,
				message
			});
		},
		info(object: object, message: string) {
			const timestamp = new Date().toISOString();

			const infoMessage = onMessage
				? onMessage({
						level: 'INFO',
						timestamp,
						payload: object,
						message
				  })
				: `${infoEmoji || '📘'} [${timestamp}] [INFO] ${message}`;

			log.info(infoMessage, object);

			onAfterMessage?.({
				level: 'INFO',
				timestamp,
				payload: object,
				message
			});
		},
		trace(object: object, message: string) {
			const timestamp = new Date().toISOString();

			const traceMessage = onMessage
				? onMessage({
						level: 'TRACE',
						timestamp,
						payload: object,
						message
				  })
				: `${traceEmoji || '📓'} [${timestamp}] [TRACE] ${message}`;

			log.trace(traceMessage, object);

			onAfterMessage?.({
				level: 'TRACE',
				timestamp,
				payload: object,
				message: message
			});
		},
		warn(object: object, message: string) {
			const timestamp = new Date().toISOString();

			const warningMessage = onMessage
				? onMessage({
						level: 'WARN',
						timestamp,
						payload: object,
						message
				  })
				: `${warnEmoji || '📒'} [${timestamp}] [WARN] ${message}`;

			log.warn(warningMessage, object);

			onAfterMessage?.({
				level: 'WARN',
				timestamp,
				payload: object,
				message: warningMessage
			});
		}
	} as const;

	return logger;
};