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 Future<AppAction, Never> { promise in
                let roster = state.rostersState.rosters
                    .first { $0.bareJid == chat.account && $0.contactBareJid == chat.participant }
                promise(.success(.conversationAction(.makeConversationActive(chat: chat, roster: roster))))
            }
            .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, message.contentType != .typing {
                    promise(.success(.conversationAction(.messageForCurrentConversationReceived(message))))
                } else {
                    promise(.success(.empty))
                }
            }
            .eraseToAnyPublisher()

        case .conversationAction(.messageForCurrentConversationReceived(let message)):
            return Future<AppAction, Never> { promise in
                var currentMessages = state.conversationsState.currentMessages
                currentMessages.append(message)
                promise(.success(.conversationAction(.messagesUpdated(messages: currentMessages))))
            }
            .eraseToAnyPublisher()

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