import Combine
import Foundation
import Martin

final class XMPPMiddleware {
    static let shared = XMPPMiddleware()
    private let service = XMPPService(manager: Database.shared)
    private var cancellables: Set<AnyCancellable> = []

    private init() {
        service.clientState.sink { client, state in
            let jid = client.userBareJid.stringValue
            let status = ConnectionStatus.from(state)
            let action = AppAction.xmppAction(.clientConnectionChanged(jid: jid, state: status))
            DispatchQueue.main.async {
                store.dispatch(action)
            }
        }
        .store(in: &cancellables)

        service.clientMessages.sink { _, martinMessage in
            guard let message = Message.map(martinMessage) else { return }
            DispatchQueue.main.async {
                store.dispatch(.xmppAction(.xmppMessageReceived(message)))
            }
        }
        .store(in: &cancellables)
    }

    func middleware(state: AppState, action: AppAction) -> AnyPublisher<AppAction, Never> {
        switch action {
        case .accountsAction(.tryAddAccountWithCredentials):
            return Future<AppAction, Never> { [weak self] promise in
                self?.service.updateClients(for: state.accountsState.accounts)
                promise(.success(.empty))
            }
            .eraseToAnyPublisher()

        case .accountsAction(.addAccountError):
            return Future<AppAction, Never> { [weak self] promise in
                self?.service.updateClients(for: state.accountsState.accounts)
                promise(.success(.empty))
            }
            .eraseToAnyPublisher()

        case .databaseAction(.storedAccountsLoaded(let accounts)):
            return Future<AppAction, Never> { [weak self] promise in
                self?.service.updateClients(for: accounts.filter { $0.isActive && !$0.isTemp })
                promise(.success(.empty))
            }
            .eraseToAnyPublisher()

        case .rostersAction(.addRoster(let ownerJID, let contactJID, let name, let groups)):
            return Future<AppAction, Never> { [weak self] promise in
                guard let service = self?.service, let client = service.clients.first(where: { $0.connectionConfiguration.userJid.stringValue == ownerJID }) else {
                    return promise(.success(.rostersAction(.addRosterError(reason: XMPPError.item_not_found.localizedDescription))))
                }
                let module = client.modulesManager.module(RosterModule.self)
                module.addItem(jid: JID(contactJID), name: name, groups: groups, completionHandler: { result in
                    switch result {
                    case .success:
                        promise(.success(.rostersAction(.addRosterDone(jid: contactJID))))

                    case .failure(let error):
                        promise(.success(.rostersAction(.addRosterError(reason: error.localizedDescription))))
                    }
                })
            }
            .eraseToAnyPublisher()

        case .rostersAction(.deleteRoster(let ownerJID, let contactJID)):
            return Future<AppAction, Never> { [weak self] promise in
                guard let service = self?.service, let client = service.clients.first(where: { $0.connectionConfiguration.userJid.stringValue == ownerJID }) else {
                    return promise(.success(.rostersAction(.rosterDeletingFailed(reason: XMPPError.item_not_found.localizedDescription))))
                }
                let module = client.modulesManager.module(RosterModule.self)
                module.removeItem(jid: JID(contactJID), completionHandler: { result in
                    switch result {
                    case .success:
                        promise(.success(.empty))

                    case .failure(let error):
                        promise(.success(.rostersAction(.rosterDeletingFailed(reason: error.localizedDescription))))
                    }
                })
            }
            .eraseToAnyPublisher()

        case .conversationAction(.sendMessage(let from, let to, let body)):
            return Future<AppAction, Never> { [weak self] promise in
                // TODO: handle errors
                self?.service.sendMessage(from: from, to: to, body: body)
                promise(.success(.empty))
            }
            .eraseToAnyPublisher()

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