spiegel-keyman/ios/engine/KMEI/KeymanEngine/Classes/Model/LanguageResource.swift

//
//  LanguageResource.swift
//  KeymanEngine
//
//  Created by Joshua Horton on 8/16/19.
//  Copyright © 2019 SIL International. All rights reserved.
//

import Foundation

public enum LanguageResourceType {
  case keyboard, lexicalModel
}

// Subclasses must implement Equatable; Swift doesn't like it directly on the root protocol.
public protocol LanguageResourceFullID {
  var id: String { get }
  var languageID: String { get }
  var type: LanguageResourceType { get }
}

extension LanguageResourceFullID where Self: Equatable {
  public static func ==(lhs: Self, rhs: Self) -> Bool {
    return lhs.id == rhs.id && lhs.languageID == rhs.languageID && lhs.type == rhs.type
  }
}

// Alas, 'associatedtype' stuff isn't exactly generic, and it's impossible to wildcard.
// So, this supports Swift's "type erasure" pattern, acting as a "wildcarded"
// LanguageResource that doesn't care about the specific associatedtype(s) that
// specific LanguageResources use.
public protocol AnyLanguageResource {
  var id: String { get }
  var languageID: String { get }
  // Was not always tracked within KeymanEngine - is optional for legacy reasons.
  var packageID: String? { get }
  var fullID: LanguageResourceFullID { get }
  var version: String { get }

  // Used for generating QR codes.
  var sharableURL: String? { get }

  // Used during resource installation
  var fonts: [Font] { get }
  var sourceFilename: String { get }
}

// Necessary due to Swift details 'documented' at
// https://stackoverflow.com/questions/42561685/why-cant-a-get-only-property-requirement-in-a-protocol-be-satisfied-by-a-proper
public protocol LanguageResource: AnyLanguageResource {
  associatedtype FullID: LanguageResourceFullID where FullID: Equatable
  var typedFullID: FullID { get }
}

extension LanguageResource {
  // Thanks to https://stackoverflow.com/a/58774558 (on same thread mentioned above)
  // for this approach.
  public var fullID: LanguageResourceFullID {
    return typedFullID
  }
}

internal protocol KMPInitializableLanguageResource: LanguageResource {
  associatedtype Metadata: KMPResource
  init?(from metadata: Metadata, packageID: String, lgCode: String)
}