Dynamic dependency injection

DomainContext.swift

//
//  DomainContext.swift
//
//  Copyright (c) 2019 Jason Jobe. All rights reserved.
//  https://gist.github.com/wildthink/fa824de45aacc2fed89aae0fe2cf0370
//
//  Created by Jason Jobe on 5/11/15.
//  Derived from Relay.swift
//  Copyright (c) 2015, 2016 Jason Jobe. All rights reserved.
//  https://gist.github.com/wildthink/acfdf82c2625dc73ad6e42d399d91846
//

/* Example usage
 protocol MyProtocol {
    func someClassOrProtocolFunction (some:Int, args:[String])
 }

 relay (MyProtocol.self) {
    $0.someClassOrProtocolFunction(some, args)
 }
 relay { (target: MyProtocol) in
    target.someClassOrProtocolFunction(some, args)
 }

 Domain Chain Resolution

    View -> Controller -> WindowController -> [nextResponder] -> NSApp -> AppDelegate
*/

import Foundation

#if os(iOS)
import UIKit.UIResponder
public typealias Responder = UIResponder
public typealias Application = UIApplication
public typealias Controller = UIViewController
#else
import AppKit.NSResponder
public typealias Responder = NSResponder
public typealias Application = NSApplication
public typealias Controller = NSViewController
#endif


@objc public protocol DomainContext: class {
    func domainContext(type: AnyClass, chain: NSMutableArray?) -> Any?
}

extension Responder: DomainContext {

    public func domainContext(type ac: AnyClass, chain: NSMutableArray?) -> Any? {
        chain?.add(self)
        if self.isKind(of: ac) { return self }
        return nextResponder?.domainContext(type: ac, chain: chain)
    }
}

extension Application {

    public override func domainContext(type ac: AnyClass, chain: NSMutableArray?) -> Any? {
        chain?.add(self)
        if self.isKind(of: ac) { return self }

        if let r = delegate as? DomainContext { return r.domainContext(type:ac, chain: chain) }
        // In case the delegate is not a DomainContext
        if (delegate?.isKind(of: ac) ?? false) {
            chain?.add(delegate as Any)
            return delegate
        }
        return nil
    }
}

#if os(macOS)
extension NSWindowController {

    public override func domainContext(type ac: AnyClass, chain: NSMutableArray?) -> Any? {
        chain?.add(self)
        if self.isKind(of: ac) { return self }
        if let dc = nextResponder?.domainContext(type: ac, chain: chain) { return dc }
        return NSApp.domainContext(type: ac, chain: chain)
    }
}
#endif

extension Controller {

    public override func domainContext(type ac: AnyClass, chain: NSMutableArray?) -> Any? {
        chain?.add(self)
        if self.isKind(of: ac) { return self }
        return parent?.domainContext(type: ac, chain: chain)
            ?? nextResponder?.domainContext(type: ac, chain: chain)
    }
}


// Mark - Swifty API

// public extension NSObjectProtocol where Self: Controller {

extension DomainContext {
    func domain<C: AnyObject>(as type: C.Type, chain: NSMutableArray? = nil) -> C? {
        return domainContext(type: C.self, chain: chain) as? C
    }
    func relay <T: AnyObject> (_ type: T.Type, call: (T) -> Void) -> Void {
        if let target = domain(as: T.self) { call (target) }
    }
    func recall <T: AnyObject, R> (_ type: T.Type, call: (T) -> R?) -> R? {
        if let target = domain(as: T.self) { return call (target) }
        return nil
    }
}