mip-validator/src/logger.js

MIP validator

/*
 * Logger constructor
 * @param {String} id trace ID of the logger instance, typically use module ID
 */
function Logger(id) {
    if (!isString(id)) {
        throw new Error(`invalid logger id: ${id}`)
    }
    var debugEnabled = match(process.env.DEBUG, id)
    return {
        debug: debugEnabled ? createWith(console.log.bind(console), id) : () => false,
        log: createWith(console.log.bind(console), id),
        warn: createWith(console.warn.bind(console), id),
        error: createWith(console.error.bind(console), id),
        info: createWith(console.info.bind(console), id)
    }
}

function isString(obj) {
    return (typeof obj === 'string' || obj instanceof String)
}

/*
 * match id with DEBUG switch
 * @param {string} root DEBUG switch
 * @param {String} path trace ID
 */
function match(root, path) {
    if (!root) return false
    root = String(root).split(':').filter(x => x.length)
    path = path.split(':').filter(x => x.length)
    for (var i = 0; i < root.length; i++) {
        if (path[i] !== root[i]) return false
    }
    return true
}

/*
 * create logger method with STDOUT instance and trace ID
 * @param {Function} output STDOUT instance
 * @param {String} id trace ID
 * legal:
 *      createWith(console.log.bind(console), 'mip:cache:getCache')
 */
function createWith(output, id) {
    return function() {
        var str = `[${timestamp()}][${id}] `
        str += format.apply(exports, arguments)
        output(str)
        return str
    }
}

/*
 * Pad number to 2-digit.
 * @param {Number} n The number
 * @return {String} 2-digit number string
 * legal:
 *      pad(2)      // 02
 *      pad(22)     // 22
 */
function pad(n) {
    return n < 10 ? '0' + n.toString(10) : n.toString(10)
}

/*
 * Generate a timestamp from current time
 * @return {String} the timestamp string
 * legal:
 *      timestamp()    // "2016/09/27-17:31:22"
 */
function timestamp() {
    var d = new Date()
    var date = [pad(d.getFullYear()),
        pad(d.getMonth() + 1),
        pad(d.getDate())
    ].join('/')
    var time = [pad(d.getHours()),
        pad(d.getMinutes()),
        pad(d.getSeconds())
    ].join(':')
    return date + '-' + time
}

var formatRegExp = /%[sdjJ%]/g

/*
 * format arguments to a single string
 * @param {String} f Optional, the format string
 * @return {String} the formated string
 * legal:
 *      format('%s', 'foo', 'bar')  // foo bar
 *      format('%d', '200', 'bar')  // 200 bar
 *      format('%j', {foo: 'bar'}, 'bar')
 *                                  // {"foo":"bar"}bar
 *      format('%j', {foo: 'bar'}, 'bar')
 *                                  // \n{\n    "foo": "bar"\n}\nbar
 *      format('foo', 'bar')        // foo bar
 */
function format(f) {
    var i = 0
    var args = arguments
    var len = args.length
    var str = ''
    if (isString(f)) {
        i++
        str += f.replace(formatRegExp, function(x) {
            switch (x) {
            case '%%':
                return '%'
            case '%s':
                return String(args[i++])
            case '%d':
                return Number(args[i++])
            case '%j':
                try {
                    return JSON.stringify(args[i++])
                } catch (_) {
                    return '[Circular]'
                }
            case '%J':
                try {
                    return '\n' + JSON.stringify(args[i++], null, 4) + '\n'
                } catch (_) {
                    return '\n[Circular]\n'
                }
            }
        })
    }
    for (var x = args[i]; i < len; x = args[++i]) {
        str += ' ' + x
    }
    return str
}

module.exports = Logger