Elf

Elf.swift

//
//  Redux.swift
//  Elf
//
//  Created by JimLai on 2019/8/18.
//  Copyright © 2019 JimLai. All rights reserved.
//

import SwiftUI

protocol Redux {
    associatedtype Store
    var binding: Binding<Store> {get}
    var store: Store {get}
    var action: Action<Store> {get}
    func effect(desc: String, _ action: Action<Store>)
}

extension Redux {
    var store: Store {
        binding.value
    }
    var action: Action<Store> {
        var s = store
        let b = Binding<Store>(get: {s}, set: {s = $0})
        return Action<Store>(binding: b)
    }
    func effect(desc: String = #function, _ action: Action<Store>) {
        binding.value = action.binding.value
    }
}

@dynamicMemberLookup
struct Action<T> {
    var binding: Binding<T>
    subscript<V>(dynamicMember kp: WritableKeyPath<T, V>) -> V {
        get {
            binding.value[keyPath: kp]
        }
        nonmutating set {
            binding.value[keyPath: kp] = newValue
            debug(kp, newValue)
        }
    }
    func map(_ transform: (Action<T>) -> Void) -> Action<T> {
        var s = binding.value
        let b = Binding<T>(get: {s}, set: {s = $0})
        let action = Action<T>(binding: b)
        transform(action)
        return action
    }
    
    func debug<V>(_ kp: WritableKeyPath<T, V>, _ v: V) {
        #if DEBUG
        let mirror = Mirror(reflecting: binding.value)
        for c in mirror.children {
            guard c.value as AnyObject === binding.value[keyPath: kp] as AnyObject else {continue}
            print("\(c.label ?? "") <- \(v)")
        }
        #endif
    }
}