import Combine

final class ChatsMiddleware {
    static let shared = ChatsMiddleware()

    func middleware(state: AppState, action: AppAction) -> AnyPublisher<AppAction, Never> {
        switch action {
        case .databaseAction(.storedChatsLoaded(let chats)):
            return Just(.chatsAction(.chatsListUpdated(chats: chats)))
                .eraseToAnyPublisher()

        case .chatsAction(.startChat(accountJid: let accountJid, participantJid: let participantJid)):
            return Future<AppAction, Never> { promise in
                if let exist = state.chatsState.chats.first(where: { $0.account == accountJid && $0.participant == participantJid }) {
                    // open existing chat
                    promise(.success(.chatsAction(.chatStarted(chat: exist))))
                } else {
                    // create new chat
                    promise(.success(.chatsAction(.createNewChat(accountJid: accountJid, participantJid: participantJid))))
                }
            }
            .eraseToAnyPublisher()

        case .chatsAction(.chatCreated(let chat)):
            return Just(.chatsAction(.chatStarted(chat: chat)))
                .eraseToAnyPublisher()

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