MultistoreReduxInPlayground.swift

import Foundation
import PlaygroundSupport

PlaygroundPage.current.needsIndefiniteExecution = true

// 1
struct User: Equatable {
    // 2
    struct Address: Equatable {
        var street: String
    }

    struct Phone: Equatable {
        var number: String = "+7"
    }

    // 3
    enum Role {
        // 4
        enum Permission {
            case create
            case read
            case update
            case delete
        }

        case admin
        case member
        case guest

        var permissions: [Permission] {
            switch self {
            case .admin:
                return [.create, .read, .update, .delete]
            case .member:
                return [.create, .read]
            case .guest:
                return [.read]
            }
        }
    }

    var name: String
    let email: String
    var address: Address?
    var phone: Phone = .init()
    let role: Role
}

struct Reducer<State, Action> {
    let reduce: (State, Action) -> State
}

final class Store<State: Equatable, Action> {
    private var stateGetter: (() -> State)!
    private var stateSetter: ((State) -> Void)!

    var state: State {
        get { stateGetter() }
        set { stateSetter(newValue) }
    }

    var _state: State! {
        didSet {
            listners.forEach { listner in
                listner()
            }
        }
    }

    let reducer: Reducer<State, Action>
    var listners: [() -> Void] = []

    func addListener(_ listener: @escaping () -> Void) {
        listners.append(listener)
    }

    init(
        state: State,
        reducer: Reducer<State, Action>
    ) {
        self.reducer = reducer

        self._state = state
        self.stateGetter = { [unowned self] in
            return self._state
        }
        self.stateSetter = { [unowned self] state in
            self._state = state
        }
    }

    private init(
        stateSetter: @escaping (State) -> Void,
        stateGetter: @escaping () -> State,
        reducer: Reducer<State, Action>
    ) {
        self.stateSetter = stateSetter
        self.stateGetter = stateGetter
        self.reducer = reducer
    }

    func dispatch(_ action: Action) {
        state = reducer.reduce(state, action)
    }

    func createChildStore<ChildState, ChildAction>(
        keyPath: WritableKeyPath<State, ChildState>,
        reducer: Reducer<ChildState, ChildAction>
    ) -> Store<ChildState, ChildAction> {
        let s = Store<ChildState, ChildAction>(
            stateSetter: { self.state[keyPath: keyPath] = $0 },
            stateGetter: { self.state[keyPath: keyPath] },
            reducer: reducer
        )
        addListener({ [weak s] in
            guard let s = s else { return }
            s.listners.forEach { listner in
                listner()
            }
        })
        return s
    }
}

let subReducer = Reducer<Optional<User.Address>, String>(reduce: { state, action in
    if var state = state {
        state.street += ", " + action + "sub"
        return state
    } else {
        return .init(street: "initial " + action)
    }
})

let reducer: Reducer<User, Int> = Reducer(
    reduce: { state, action in
        var state = state
        state.name += "\(action)"
        return state
    }
)

let store = Store<User, Int>(
    state: User(
        name: "",
        email: "",
        address: nil,
        role: .guest
    ),
    reducer: reducer
)

var aaa = Date().timeIntervalSince1970
let initialAAA = aaa
print(Date().timeIntervalSince1970 - aaa, "Baseline")
aaa = Date().timeIntervalSince1970
let stores = Array(0...1000).map { _ -> Store<Optional<User.Address>, String> in
    let subStore = store.createChildStore(keyPath: \.address, reducer: subReducer)
    return subStore
}

print(Date().timeIntervalSince1970 - aaa, "createChildStore")
aaa = Date().timeIntervalSince1970

var updateCount = 0
stores.first?.listners.append {
    updateCount += 1
}

print(Date().timeIntervalSince1970 - aaa, "updateCount")
aaa = Date().timeIntervalSince1970

Array(0...2).forEach { index in
    stores.first!.dispatch("\(index)")
}

print(Date().timeIntervalSince1970 - aaa, "stores.first dispatch 3")
aaa = Date().timeIntervalSince1970

Array(0...100).forEach { index in
    stores.last!.dispatch("\(index)")
}
print(Date().timeIntervalSince1970 - aaa, "stores.last dispatch 101 (* 1000)")
if Date().timeIntervalSince1970 - aaa > 1 {
    print("TOO MUCH")
}
aaa = Date().timeIntervalSince1970

stores.last!.dispatch("final")

print(Date().timeIntervalSince1970 - aaa, "stores.last dispatch final")
aaa = Date().timeIntervalSince1970

store.dispatch(1)
store.dispatch(2)
store.dispatch(3)
store.dispatch(4)

print(Date().timeIntervalSince1970 - aaa, "rootStore dispatch 1,2,3,4")
aaa = Date().timeIntervalSince1970

stores.last!.dispatch("123")

print(Date().timeIntervalSince1970 - aaa, "stores.last dispatch 123")
aaa = Date().timeIntervalSince1970

print(store.state.name)
print(store.state.address?.street ?? "null")

print("IS SUBSTORES EQUAL: ", stores.first!.state?.street ?? "null" == stores.last!.state?.street ?? "null")
print("IS SUB & STORE EQUAL: ", stores.last!.state?.street ?? "null" == store.state.address?.street ?? "null")

print(Date().timeIntervalSince1970 - initialAAA, "final")

print("Update count:", updateCount)
print("IS UPDATE COUNT 110?", updateCount == 110 ? "TRUE" : "FALSE")

//    0.0002391338348388672 Baseline
//    1.5412371158599854 createChildStore
//    0.000701904296875 updateCount
//    0.027843952178955078 stores.first dispatch 3
//    0.9228630065917969 stores.last dispatch 101 (* 1000)
//    0.009496927261352539 stores.last dispatch final
//    0.04581594467163086 rootStore dispatch 1,2,3,4
//    0.009209156036376953 stores.last dispatch 123
//    1234
//    initial 0, 1sub, 2sub, 0sub, 1sub, 2sub, 3sub, 4sub, 5sub, 6sub, 7sub, 8sub, 9sub, 10sub, 11sub, 12sub, 13sub, 14sub, 15sub, 16sub, 17sub, 18sub, 19sub, 20sub, 21sub, 22sub, 23sub, 24sub, 25sub, 26sub, 27sub, 28sub, 29sub, 30sub, 31sub, 32sub, 33sub, 34sub, 35sub, 36sub, 37sub, 38sub, 39sub, 40sub, 41sub, 42sub, 43sub, 44sub, 45sub, 46sub, 47sub, 48sub, 49sub, 50sub, 51sub, 52sub, 53sub, 54sub, 55sub, 56sub, 57sub, 58sub, 59sub, 60sub, 61sub, 62sub, 63sub, 64sub, 65sub, 66sub, 67sub, 68sub, 69sub, 70sub, 71sub, 72sub, 73sub, 74sub, 75sub, 76sub, 77sub, 78sub, 79sub, 80sub, 81sub, 82sub, 83sub, 84sub, 85sub, 86sub, 87sub, 88sub, 89sub, 90sub, 91sub, 92sub, 93sub, 94sub, 95sub, 96sub, 97sub, 98sub, 99sub, 100sub, finalsub, 123sub
//    IS SUBSTORES EQUAL:  true
//    IS SUB & STORE EQUAL:  true
//    2.5582311153411865 final
//    Update count: 110
//    IS UPDATE COUNT 110? TRUE