//
// Copyright 2025 Element Creations Ltd.
// Copyright 2022-2025 New Vector Ltd.
//
// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
// Please see LICENSE files in the repository root for full details.
//

import Combine
import MatrixRustSDK
import SwiftUI

typealias InviteUsersScreenViewModelType = StateStoreViewModel<InviteUsersScreenViewState, InviteUsersScreenViewAction>

class InviteUsersScreenViewModel: InviteUsersScreenViewModelType, InviteUsersScreenViewModelProtocol {
    private let roomType: InviteUsersScreenRoomType
    private let userDiscoveryService: UserDiscoveryServiceProtocol
    private let userIndicatorController: UserIndicatorControllerProtocol
    private let appSettings: AppSettings
    
    private var suggestedUsers = [UserProfileProxy]()
    
    private let actionsSubject: PassthroughSubject<InviteUsersScreenViewModelAction, Never> = .init()
    var actions: AnyPublisher<InviteUsersScreenViewModelAction, Never> {
        actionsSubject.eraseToAnyPublisher()
    }
    
    private let selectedUsers: CurrentValuePublisher<[UserProfileProxy], Never>?
    
    init(userSession: UserSessionProtocol,
         selectedUsers: CurrentValuePublisher<[UserProfileProxy], Never>?,
         roomType: InviteUsersScreenRoomType,
         userDiscoveryService: UserDiscoveryServiceProtocol,
         userIndicatorController: UserIndicatorControllerProtocol,
         appSettings: AppSettings) {
        self.roomType = roomType
        self.userDiscoveryService = userDiscoveryService
        self.userIndicatorController = userIndicatorController
        self.appSettings = appSettings
        self.selectedUsers = selectedUsers
        
        super.init(initialViewState: InviteUsersScreenViewState(selectedUsers: selectedUsers?.value ?? [],
                                                                isCreatingRoom: roomType.isCreatingRoom),
                   mediaProvider: userSession.mediaProvider)
                
        setupSubscriptions()
        fetchMembersIfNeeded()
        
        Task {
            suggestedUsers = await userSession.clientProxy.recentConversationCounterparts()
            
            if state.usersSection.type == .suggestions {
                state.usersSection = .init(type: .suggestions, users: suggestedUsers)
            }
        }
    }
    
    // MARK: - Public
    
    override func process(viewAction: InviteUsersScreenViewAction) {
        switch viewAction {
        case .cancel:
            actionsSubject.send(.dismiss)
        case .proceed:
            switch roomType {
            case .draft:
                actionsSubject.send(.proceed(selectedUsers: state.selectedUsers))
            case .room(let roomProxy):
                inviteUsers(state.selectedUsers.map(\.userID), roomProxy: roomProxy)
            }
        case .toggleUser(let user):
            toggleUser(user)
        }
    }

    // MARK: - Private
    
    private func toggleUser(_ user: UserProfileProxy) {
        if state.selectedUsers.contains(user) {
            state.scrollToLastID = nil
            state.selectedUsers.removeAll(where: { $0.userID == user.userID })
        } else {
            state.scrollToLastID = user.userID
            state.selectedUsers.append(user)
        }
    }
    
    private func inviteUsers(_ users: [String], roomProxy: JoinedRoomProxyProtocol) {
        if appSettings.enableKeyShareOnInvite {
            showLoader(title: L10n.screenRoomDetailsInvitePeoplePreparing,
                       message: L10n.screenRoomDetailsInvitePeopleDontClose)
        } else {
            showLoader()
        }
        
        Task {
            defer {
                hideLoader()
                actionsSubject.send(.dismiss)
            }
            
            let result: Result<Void, RoomProxyError> = await withTaskGroup(of: Result<Void, RoomProxyError>.self) { group in
                for user in users {
                    group.addTask {
                        await roomProxy.invite(userID: user)
                    }
                }
                
                return await group.first { inviteResult in
                    inviteResult.isFailure
                } ?? .success(())
            }
            
            guard case .failure = result else {
                return
            }
            
            userIndicatorController.alertInfo = .init(id: .init(),
                                                      title: L10n.commonUnableToInviteTitle,
                                                      message: L10n.commonUnableToInviteMessage)
        }
    }
    
    private func buildMembershipStateIfNeeded(members: [RoomMemberProxyProtocol]) {
        showLoader()
        
        Task.detached { [members] in
            // accessing RoomMember's properties is very slow. We need to do it in a background thread.
            let membershipState = members
                .reduce(into: [String: MembershipState]()) { partialResult, member in
                    partialResult[member.userID] = member.membership
                }
            
            Task { @MainActor in
                self.state.membershipState = membershipState
                self.hideLoader()
            }
        }
    }
    
    // periphery:ignore - automatically cancelled when set to nil
    @CancellableTask
    private var fetchUsersTask: Task<Void, Never>?
    
    private func setupSubscriptions() {
        context.$viewState
            .map(\.bindings.searchQuery)
            .debounceTextQueriesAndRemoveDuplicates()
            .sink { [weak self] _ in
                self?.fetchUsers()
            }
            .store(in: &cancellables)
        
        if let selectedUsers {
            selectedUsers
                .sink { [weak self] users in
                    self?.state.selectedUsers = users
                }
                .store(in: &cancellables)
        }
    }
    
    private func fetchMembersIfNeeded() {
        guard case let .room(roomProxy) = roomType else {
            return
        }
        
        Task {
            showLoader()
            await roomProxy.updateMembers()
            hideLoader()
        }
        
        roomProxy.membersPublisher
            .filter { !$0.isEmpty }
            .first()
            .receive(on: DispatchQueue.main)
            .sink { [weak self] members in
                self?.buildMembershipStateIfNeeded(members: members)
            }
            .store(in: &cancellables)
    }
    
    private func fetchUsers() {
        guard searchQuery.count >= 3 else {
            state.usersSection = .init(type: .suggestions, users: suggestedUsers)
            return
        }
        
        state.isSearching = true
        
        fetchUsersTask = Task {
            let result = await userDiscoveryService.searchProfiles(with: searchQuery)
            
            guard !Task.isCancelled else { return }
            
            state.isSearching = false
            
            switch result {
            case .success(let users):
                state.usersSection = .init(type: .searchResult, users: users)
            case .failure:
                break
            }
        }
    }
        
    private var searchQuery: String {
        context.searchQuery
    }
    
    private let userIndicatorID = UUID().uuidString
    
    private func showLoader(title: String = L10n.commonLoading,
                            message: String? = nil) {
        userIndicatorController.submitIndicator(UserIndicator(id: userIndicatorID,
                                                              type: .modal,
                                                              title: title,
                                                              message: message,
                                                              persistent: true),
                                                delay: .milliseconds(200))
    }
    
    private func hideLoader() {
        userIndicatorController.retractIndicatorWithId(userIndicatorID)
    }
}

private extension InviteUsersScreenRoomType {
    var isCreatingRoom: Bool {
        switch self {
        case .draft:
            return true
        case .room:
            return false
        }
    }
}