Bundle+InAppLanguage.swift

//
//  Bundle+InAppLanguage.swift
//
//  Created by Gabriel Chen on 2018/9/20.
//  Copyright © 2018 Gabriel Chen All rights reserved.
//

import Foundation

fileprivate var kALB = 0 // Associated Language Bundle

// MARK: ---------- Private Custom Bundle ----------

fileprivate class MyBundle: Bundle {
    
    override func localizedString(forKey key: String, value: String?, table tableName: String?) -> String {
        guard let bundle = objc_getAssociatedObject(self, &kALB) as? Bundle else {
            return super.localizedString(forKey: key, value: value, table: tableName)
        }
        
        return bundle.localizedString(forKey: key, value: value, table: tableName)
    }
    
}

// MARK: ---------- Bundle Extension ----------

extension Notification.Name {
    static let languageWasChanged = Notification.Name(rawValue: "ag_languageWasChanged")
}

extension Bundle {
    
    private static let dispatch_once: () = {
        object_setClass(Bundle.main, MyBundle.self)
    }()
    
    @discardableResult
    class func setLanguage(_ code: String) -> Bool {
        dispatch_once
        
        guard let bundlePath = Bundle.main.path(forResource: code, ofType: "lproj") else {
            return false
        }
        
        let bundle = Bundle(path: bundlePath)
        let policy = objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC
        
        objc_setAssociatedObject(Bundle.main, &kALB, bundle, policy)
        
        UserDefaults.standard.set([code], forKey: "AppleLanguages")
        
        NotificationCenter.default.post(name: .languageWasChanged, object: code)
        
        return true
    }
    
    class var language: String? {
        if let bundle = objc_getAssociatedObject(Bundle.main, &kALB) as? Bundle {
            let path = bundle.bundlePath as NSString
            
            if let fileName = path.pathComponents.last as NSString? {
                return fileName.deletingPathExtension
            }
        }
        
        return Bundle.main.preferredLocalizations.first
    }
    
}