log4js exclude categories via env var

/* eslint-env node, es6 */
'use strict';



/*	@param {object|string} _logger - an instance of Log4js/object with a `log` method. If a string, should be a category (see Log4js.getLogger(category)).
	@example
		logger = require('logger').getLogger( gutil );
*/

const log4js = require('log4js');

/** Calls log4js.configure on the supplied path, 
 * but adding to the category filter's exclude list 
 * the CSV potentially stored in the env var LOG_EXC
 * Expects something like:
 log4js.configure({
	appenders: [
		{
			type: 'categoryFilter',
			exclude: ['results'],
			layout: {
				type: 'pattern',
				pattern: '%[%-10c %-5p%] %m'
			},
			appender: {
				type: 'console'
			}
		}
	],
	replaceConsole: true
});

...where config can be a path

 */
module.exports.configure = function (pathOrConfig) {
	if (process.env.LOG_EXC) {
		let exc = process.env.LOG_EXC.replace(/\s+/, '');
		if (exc.length > 0 ) {
			if (typeof pathOrConfig === 'string') {
				let configJson = require('fs').readFileSync( pathOrConfig );
				pathOrConfig = JSON.parse( configJson );
			}
			pathOrConfig.appenders.forEach( (appender) => {
				if (appender.type === 'categoryFilter') {
					appender.exclude = appender.exclude || [];
					appender.exclude.push( exc );
				}
			});
		}
	}

	log4js.configure( pathOrConfig );
};

/* @param {string|object} _logger Log4js category, or Log4js object; or object with .log method (ie gutil */
module.exports.getLogger = function (_logger) {
	var logger;
	if (_logger) {
		if (typeof _logger === 'string') {
			logger = log4js.getLogger(_logger);
		} else {
			logger = _logger;
			// If not an instanceof log4js, fake it 
			if (!logger.hasOwnProperty('setLevel')) {
				'trace,debug,warn,info,error,fatal'.split(',').forEach((i) => {
					logger[i] = logger.log;
				});
			}
		}
	} else {
		logger = log4js.getLogger(_logger);
	}

	if (logger.hasOwnProperty('setLevel')) {
		var logLevel = process.env.LOG_LEVEL || 'TRACE';
		logger.setLevel(logLevel.toUpperCase());
	}

	return logger;
};