Light-Weight-Easy-to-Use Logger Class

Logger.swift

//
//  Logger.swift
//
//  Created by Cyan on 2018. 9. 14..
//  Copyright © 2018 Cyan. All rights reserved.
//

import Foundation
import UIKit

/**
 Very simple easy-to-use Logger.
 */
class Logger{
    
    /**
     Represents log's type.
     */
    internal enum LogType {
        case info
        case debug
        case warning
        case error
    }
    
    /**
     Leaves log of information. prints given message in console, and writes it to log file.
     
     returns actual written log message.
     */
    @discardableResult
    class func log(info message: String, line: Int = #line, function: String = #function)-> String{
        return log(.info, message, line, function)
    }
    
    /**
     Leaves log of debug. prints given message in console, and writes it to log file.
     
     returns actual written log message.
     */
    @discardableResult
    class func log(debug message: String, line: Int = #line, function: String = #function)-> String{
        return log(.debug, message, line, function)
    }
    
    /**
     Leaves log of warning. prints given message in console, and writes it to log file.
     
     returns actual written log message.
     */
    @discardableResult
    class func log(warning message: String, line: Int = #line, function: String = #function)-> String{
        return log(.warning, message, line, function)
    }
    
    /**
     Leaves log of error. prints given message in console, and writes it to log file.
     
     returns actual written log message.
     */
    @discardableResult
    class func log(error message: String, line: Int = #line, function: String = #function)-> String{
        return log(.error, message, line, function)
    }
    
    internal class func log(_ type: LogType, _ message: String, _ line: Int, _ function: String)-> String{
        
        let now = NSDate()
        let dateFormatter = DateFormatter()
        dateFormatter.locale = NSLocale(localeIdentifier: "ko_KR") as Locale?
        dateFormatter.timeStyle = .medium
        dateFormatter.dateStyle = .medium
        
        let nowdate = dateFormatter.string(from: now as Date)
        
        var prefix: String
        
        switch type {
        case .info:
            prefix = "[INFO]"
        case .debug:
            prefix = "[DEBUG]"
        case .warning:
            prefix = "[WARN]"
        case .error:
            prefix = "[ERROR]"
        }
        
        let log = "\(prefix) : [\(nowdate)] in [\(function)], (line: \(line)) : \(message)"
        print(log)
        
        let logData = "\(log)\n".data(using: .utf8)!
        
        let directory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first! as URL
        let fileDirectory = directory.appendingPathComponent("debugLogs", isDirectory: false)
        
        DispatchQueue.global().sync {
            if !FileManager.default.fileExists(atPath: fileDirectory.path){
                let createdFile = FileManager.default.createFile(atPath: fileDirectory.path, contents: logData, attributes: nil)
            }
            
            if let fileHandle = FileHandle(forWritingAtPath: fileDirectory.path){
                defer{
                    fileHandle.closeFile()
                }
                fileHandle.seekToEndOfFile()
                fileHandle.write(logData)
            }
        }
        
        return String(data: logData, encoding: .utf8)!
    }
}