# 日志层（Logger）

/**
 * Simple Logger
 */


'use strict';

const chalk = require('chalk');
const moment = require('moment');

const noop = s => s;

const LOG_LEVEL = {
    'DEBUG': 1,
    'VERBOSE': 2,
    'INFO': 3,
    'IMP': 4,
    'WARN': 5,
    'ERROR': 6,
    'FATAL': 7
}

const LOG_LEVEL_LABEL = {
    1: 'DEBUG',
    2: 'VERBOSE',
    3: 'INFO',
    4: 'IMP',
    5: 'WARN',
    6: 'ERROR',
    7: 'FATAL'
};

const LOG_LEVEL_COLOR = {
    1: chalk.gray,
    2: chalk.cyan,
    3: chalk.blue,
    4: chalk.magenta,
    5: chalk.yellow,
    6: chalk.red,
    7: chalk.red
};

class Log {
    constructor(tag, identifier) {
        this.tag = tag;
        this.identifier = identifier;
    }
    /**
     * 输出日志消息
     * @private
     * @param   {LogEntry}  entry   日志
     */
    _write(entry) {
        let log = this._format(entry);
        if (entry.priority >= LOG_LEVEL.ERROR) {
            console.error(log);
        } else {
            console.log(log);
        }
    }
    /**
     * 格式化日志输出
     * @private
     * @param   {LogEntry}  entry   日志
     * @returns {String}    格式化后的日志
     */
    _format(entry) {
        if (this.formatter) {
            return this.formatter.call(this, entry);
        }
        return `[${chalk.gray(moment().format('YYYY-MM-DD HH:mm:ss'))}] ${chalk.bold(LOG_LEVEL_COLOR[entry.priority](entry.priorityLabel))}/${entry.tag || ''} ${entry.identifier ? '<' + entry.identifier + '>' : ''}${entry.message}`;
    }
    _entry(priority, message) {
        return new LogEntry(
            moment(),
            priority,
            this.tag,
            process.pid,
            this.identifier,
            message
        );
    }
    debug(message) {
        this._write(this._entry(LOG_LEVEL.DEBUG, message));
    }
    verbose(message) {
        this._write(this._entry(LOG_LEVEL.VERBOSE, message));
    }
    info(message) {
        this._write(this._entry(LOG_LEVEL.INFO, message));
    }
    important(message) {
        this._write(this._entry(LOG_LEVEL.IMP, message));
    }
    warn(message) {
        this._write(this._entry(LOG_LEVEL.WARN, message));
    }
    error(message) {
        this._write(this._entry(LOG_LEVEL.ERROR, message));
    }
    fatal(message) {
        this._write(this._entry(LOG_LEVEL.FATAL, message));
    }
    static createLogger(tag) {
        return new Log(tag);
    }
}

class LogEntry {
    constructor(timestamp, priority, tag, pid, identifier, message) {
        this.timestamp = timestamp;
        this.priority = priority;
        this.priorityLabel = LOG_LEVEL_LABEL[priority] || 'UNKNOWN';
        this.tag = tag;
        this.pid = pid;
        this.identifier = identifier;
        this.message = message;
    }
}

module.exports = Log;
module.exports.LogEntry = LogEntry;