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// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
import Foundation
import Common
/// Stores your entire app state in the form of a single data structure.
/// This state can only be modified by dispatching Actions to the store.
/// Whenever the state of the store changes, the store will notify all store subscriber.
public class Store<State: StateType>: DefaultDispatchStore {
typealias SubscriptionType = SubscriptionWrapper<State>
public var state: State {
didSet {
subscriptions.forEach {
guard $0.subscriber != nil else {
subscriptions.remove($0)
return
}
$0.newValues(oldState: oldValue, newState: state)
}
}
}
private var reducer: Reducer<State>
private var middlewares: [Middleware<State>]
private var subscriptions: Set<SubscriptionType> = []
private var actionRunning = false
private let logger: Logger
private var actionQueue: [Action] = []
private var isProcessingActions = false
public init(state: State,
reducer: @escaping Reducer<State>,
middlewares: [Middleware<State>] = [],
logger: Logger = DefaultLogger.shared) {
self.state = state
self.reducer = reducer
self.middlewares = middlewares
self.logger = logger
}
/// General subscription to app main state
public func subscribe<S: StoreSubscriber>(_ subscriber: S) where S.SubscriberStateType == State {
subscribe(subscriber, transform: nil)
}
/// Adds support to subscribe to subState parts of the store's state
public func subscribe<SubState, S: StoreSubscriber>(
_ subscriber: S,
transform: ((Subscription<State>) -> Subscription<SubState>)?
) where S.SubscriberStateType == SubState {
let originalSubscription = Subscription<State>()
let transformedSubscription = transform?(originalSubscription)
subscribe(subscriber, mainSubscription: originalSubscription, transformedSubscription: transformedSubscription)
}
public func unsubscribe(_ subscriber: any StoreSubscriber) {
if let index = subscriptions.firstIndex(where: { return $0.subscriber === subscriber }) {
subscriptions.remove(at: index)
}
}
public func unsubscribe<S: StoreSubscriber>(_ subscriber: S) where S.SubscriberStateType == State {
if let index = subscriptions.firstIndex(where: { return $0.subscriber === subscriber }) {
subscriptions.remove(at: index)
}
}
public func dispatch(_ action: Action) {
logger.log("Dispatched action: \(action.displayString())", level: .info, category: .redux)
guard Thread.isMainThread else {
DispatchQueue.main.async { [weak self] in self?.dispatch(action) }
return
}
actionQueue.append(action)
processQueuedActions()
}
private func processQueuedActions() {
guard !isProcessingActions else { return }
isProcessingActions = true
while !actionQueue.isEmpty {
let action = actionQueue.removeFirst()
executeAction(action)
}
isProcessingActions = false
}
private func executeAction(_ action: Action) {
// Each active screen state is given an opportunity to be reduced using the dispatched action
// (Note: this is true even if the action's UUID differs from the screen's window's UUID).
// Typically, reducers should compare the action's UUID to the incoming state UUID and skip
// processing for actions originating in other windows.
// Note that only reducers for active screens are processed.
let newState = reducer(state, action)
// Middlewares are all given an opportunity to respond to the action. This is only done once
// per middleware, regardless of how many active windows or screen states there are. (This
// differs slightly from reducers, which are called once for each screen.)
middlewares.forEach { middleware in
middleware(newState, action)
}
state = newState
}
private func subscribe<SubState, S: StoreSubscriber>(
_ subscriber: S,
mainSubscription: Subscription<State>,
transformedSubscription: Subscription<SubState>?
) {
let subscriptionWrapper = SubscriptionWrapper(
originalSubscription: mainSubscription,
transformedSubscription: transformedSubscription,
subscriber: subscriber
)
subscriptions.update(with: subscriptionWrapper)
mainSubscription.newValues(oldState: nil, newState: state)
}
}