DynamicLocalization.swift

import Foundation

public extension String {
    var localized: String {
        return LocalizationManager.sharedInstance.getTranslation(forText: self) ?? self
    }
}

class LocalizationManager {
    static let sharedInstance = LocalizationManager()
    
    var localizationFilePath: String?
    private lazy var localicationParsedDictionary: Dictionary<String, String> = {
        if let path = self.localizationFilePath {
            if let validFormatDictionary = NSDictionary(contentsOfFile: path) as? Dictionary<String, String> {
                return validFormatDictionary
            }
            else {
                fatalError("Invalid plist format at file path.")
            }
        }
        else {
            fatalError("Localization File Path is not set.")
        }
    }()
    
    func getTranslation(forText text: String) -> String? {
        return localicationParsedDictionary[text]
    }
    
    func updateTranslations() {
        unowned let welf = self
        let translationDownloader = API(withBaseUrl: "TODO")
        translationDownloader.get("/TODO") { err, data in
            guard err == nil else { return }
            if let translationJSONData = data {
                translationJSONData.forEach() { translationPair in
                    welf.localicationParsedDictionary[translationPair.0] = translationPair.1.stringValue
                }
                
                if let setFilePath = welf.localizationFilePath,
                    let translationsData = try? NSPropertyListSerialization.dataWithPropertyList(welf.localicationParsedDictionary,
                                                                                                 format: .XMLFormat_v1_0, options: 0) {
                    translationsData.writeToFile(setFilePath, atomically: true)
                }
            }
        }
    }
    
    init() {
        updateTranslations()
    }
}