import Combine

final class ConversationMiddleware {
    static let shared = ConversationMiddleware()

    func middleware(state: AppState, action: AppAction) -> AnyPublisher<AppAction, Never> {
        switch action {
        case .chatsAction(.chatStarted(let chat)):
            return Just(AppAction.conversationAction(.makeConversationActive(chat: chat))).eraseToAnyPublisher()

        case .conversationAction(.makeConversationActive):
            return Just(AppAction.changeFlow(.conversation)).eraseToAnyPublisher()

        case .xmppAction(.xmppMessageReceived(let message)):
            return Future<AppAction, Never> { promise in
                let currentChat = state.conversationsState.currentChat
                if message.from == currentChat?.participant, message.to == currentChat?.account {
                    promise(.success(.conversationAction(.messageForCurrentConversationReceived(message))))
                } else {
                    promise(.success(.empty))
                }
            }
            .eraseToAnyPublisher()

        default:
            return Empty().eraseToAnyPublisher()
        }
    }
}