Extended logger for swift-log library (https://github.com/apple/swift-log)

LabeledStreamLogHandler.swift

//
//  LabeledStreamLogHandler.swift
//  WishBag
//
//  Created by ultraon on 15/12/19.
//  Copyright © 2019 ultraon. All rights reserved.
//

import Foundation
import Logging
import Then

let DBG: Bool = true

extension Logger: Then {}

/// Creates an instance of `Logger`.
/// - Parameters:
///   - label: a label will be used to add label/tag into log message.
///   - showLine: if `true` will add a code line number.
///
/// Usage:
/// ```swift
///  private let LOG = logger("")
///
///  struct MyStruct {
///    func myFunc() {
///      LOG.debug("My log message.")
///    }
///  }
/// ```
func logger(_ label: String, _ showLine: Bool = false) -> Logger {
    return Logger(label: label, factory: { LabeledStreamLogHandler($0, showLine) }).with {
        $0.logLevel = DBG ? .debug : .info
    }
}

private struct LabeledStreamLogHandler: LogHandler {
    
    private var delegate: LogHandler
    private let label: String
    private let showLine: Bool
    
    init(_ label: String, _ delegate: LogHandler, _ showLine: Bool = false) {
        self.label = label
        self.delegate = delegate
        self.showLine = showLine
    }
    
    init(_ label: String, _ showLine: Bool = false) {
        self.init(label, StreamLogHandler.standardOutput(label: label), showLine)
    }
    
    func log(level: Logger.Level, message: Logger.Message, metadata: Logger.Metadata?, file: String, function: String, line: UInt) {
        delegate.log(level: level, message: "\(label):\(showLine ? " L-\(line):" : "") \(message)", metadata: metadata, file: file, function: function, line: line)
    }
    
    subscript(metadataKey key: String) -> Logger.Metadata.Value? {
        get {
            return delegate[metadataKey: key]
        }
        set {
            delegate[metadataKey: key] = newValue
        }
    }
    
    var metadata: Logger.Metadata {
        get {
            return delegate.metadata
        }
        set {
            delegate.metadata = newValue
        }
    }
    
    var logLevel: Logger.Level {
        get {
            return delegate.logLevel
        }
        set {
            delegate.logLevel = newValue
        }
    }
}