# all files / http-proxy-middleware/lib/ logger.js

100% Statements 70/70
94.74% Branches 36/38
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     var util = require('util');
    var _ = require('lodash');

    var loggerInstance;

    var defaultProvider = {
        log: console.log,
        debug: console.log,    // use .log(); since console does not have .debug()
        info: console.info,
        warn: console.warn,
        error: console.error
    };

    // log level 'weight'
    var LEVELS = {
        debug: 10,
        info: 20,
        warn: 30,
        error: 50,
        silent: 80
    };

    module.exports = {
        // singleton
        getInstance: function() {
            if (!loggerInstance) {
                loggerInstance = new Logger();
            }

            return loggerInstance;
        },
        getArrow: getArrow
    };

    function Logger() {
        var logLevel;
        var provider;

        var api = {
            log: log,
            debug: debug,
            info: info,
            warn: warn,
            error: error,
            setLevel: function(v) {
                Eif (isValidLevel(v)) {
                    logLevel = v;
                }
            },
            setProvider: function(fn) {
                Eif (fn && isValidProvider(fn)) {
                    provider = fn(defaultProvider);
                }
            }
        };

        init();

        return api;

        function init() {
            api.setLevel('info');
            api.setProvider(function() {
                return defaultProvider;
            });
        }

        // log will log messages, regardless of logLevels
        function log() {
            provider.log(_interpolate.apply(null, arguments));
        }

        function debug() {
            if (_showLevel('debug')) {
                provider.debug(_interpolate.apply(null, arguments));
            }
        }

        function info() {
            if (_showLevel('info')) {
                provider.info(_interpolate.apply(null, arguments));
            }
        }

        function warn() {
            if (_showLevel('warn')) {
                provider.warn(_interpolate.apply(null, arguments));
            }
        }

        function error() {
            if (_showLevel('error')) {
                provider.error(_interpolate.apply(null, arguments));
            }
        }

        /**
         * Decide to log or not to log, based on the log levels 'weight'
         * @param  {String}  showLevel [debug, info, warn, error, silent]
         * @return {Boolean}
         */
        function _showLevel(showLevel) {
            var result = false;
            var currentLogLevel = LEVELS[logLevel];

            if (currentLogLevel && (currentLogLevel <= LEVELS[showLevel])) {
                result = true;
            }

            return result;
        }

        // make sure logged messages and its data are return interpolated
        // make it possible for additional log data, such date/time or custom prefix.
        function _interpolate() {
            var fn = _.spread(util.format);
            var result = fn(_.slice(arguments));

            return result;
        }

        function isValidProvider(fnProvider) {
            var result = true;

            if (fnProvider && !_.isFunction(fnProvider)) {
                throw new Error('[HPM] Log provider config error. Expecting a function.');
            }

            return result;
        }

        function isValidLevel(levelName) {
            var validLevels = _.keys(LEVELS);
            var isValid = _.includes(validLevels, levelName);

            if (!isValid) {
                throw new Error('[HPM] Log level error. Invalid logLevel.');
            }

            return isValid;
        }
    }

    /**
     * -> normal proxy
     * => proxyTable
     * ~> pathRewrite
     * ≈> proxyTable + pathRewrite
     */
    function getArrow(originalPath, newPath, originalTarget, newTarget) {
        var arrow = ['>'];
        var isNewTarget = (originalTarget !== newTarget); // router
        var isNewPath = (originalPath !== newPath); // pathRewrite

        if (isNewPath && !isNewTarget) {arrow.unshift('~');} else if (!isNewPath && isNewTarget) {arrow.unshift('=');} else if (isNewPath && isNewTarget) {arrow.unshift('≈');} else {arrow.unshift('-');}

        return arrow.join('');
    }