element-x-ios/ElementX/Sources/Screens/ThreadTimelineScreen/ThreadTimelineScreenViewModel.swift

//
// 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 SwiftUI

typealias ThreadTimelineScreenViewModelType = StateStoreViewModel<ThreadTimelineScreenViewState, ThreadTimelineScreenViewAction>

class ThreadTimelineScreenViewModel: ThreadTimelineScreenViewModelType, ThreadTimelineScreenViewModelProtocol {
    private let roomProxy: JoinedRoomProxyProtocol
    private let userSession: UserSessionProtocol
    
    private let actionsSubject: PassthroughSubject<ThreadTimelineScreenViewModelAction, Never> = .init()
    var actionsPublisher: AnyPublisher<ThreadTimelineScreenViewModelAction, Never> {
        actionsSubject.eraseToAnyPublisher()
    }
    
    init(roomProxy: JoinedRoomProxyProtocol,
         userSession: UserSessionProtocol) {
        self.roomProxy = roomProxy
        self.userSession = userSession
        
        super.init(initialViewState: ThreadTimelineScreenViewState(roomTitle: roomProxy.infoPublisher.value.displayNameOrID,
                                                                   roomAvatar: roomProxy.infoPublisher.value.avatar), mediaProvider: userSession.mediaProvider)
        
        roomProxy.infoPublisher
            .receive(on: DispatchQueue.main)
            .sink { [weak self] roomInfo in
                self?.updateRoomInfo(roomInfo)
            }
            .store(in: &cancellables)
        
        let identityStatusChangesPublisher = roomProxy.identityStatusChangesPublisher.receive(on: DispatchQueue.main)
        Task { [weak self] in
            for await _ in identityStatusChangesPublisher.values {
                guard !Task.isCancelled else {
                    return
                }
                
                await self?.updateVerificationBadge()
            }
        }
        .store(in: &cancellables)
        
        updateRoomInfo(roomProxy.infoPublisher.value)
        Task { await updateVerificationBadge() }
    }
    
    // MARK: - Public
    
    override func process(viewAction: ThreadTimelineScreenViewAction) { }
    
    func stop() {
        // Work around QLPreviewController dismissal issues, see the InteractiveQuickLookModifier.
        state.bindings.mediaPreviewViewModel = nil
    }
    
    func displayMediaPreview(_ mediaPreviewViewModel: TimelineMediaPreviewViewModel) {
        mediaPreviewViewModel.actions.sink { [weak self] action in
            guard let self else { return }
            switch action {
            case .viewInRoomTimeline:
                fatalError("\(action) should not be visible on a thread preview.")
            case .displayMessageForwarding(let forwardingItem):
                state.bindings.mediaPreviewViewModel = nil
                // We need a small delay because we need to wait for the media preview to be fully dismissed.
                DispatchQueue.main.asyncAfter(deadline: .now() + TimelineMediaPreviewViewModel.displayMessageForwardingDelay) {
                    self.actionsSubject.send(.displayMessageForwarding(forwardingItem))
                }
            case .dismiss:
                state.bindings.mediaPreviewViewModel = nil
            }
        }
        .store(in: &cancellables)
        
        state.bindings.mediaPreviewViewModel = mediaPreviewViewModel
    }
    
    // MARK: - Private
    
    private func updateVerificationBadge() async {
        guard roomProxy.infoPublisher.value.isDM,
              let dmRecipient = roomProxy.membersPublisher.value.first(where: { $0.userID != roomProxy.ownUserID }),
              case let .success(userIdentity) = await userSession.clientProxy.userIdentity(for: dmRecipient.userID, fallBackToServer: true) else {
            state.dmRecipientDetails.verification = .notVerified
            return
        }
        
        guard let userIdentity else {
            MXLog.failure("User identity should be known at this point")
            state.dmRecipientDetails.verification = .notVerified
            return
        }
        
        state.dmRecipientDetails.verification = userIdentity.verificationState
    }
    
    private func updateRoomInfo(_ roomInfo: RoomInfoProxyProtocol) {
        state.roomTitle = roomInfo.displayNameOrID
        state.roomAvatar = roomInfo.avatar
        state.dmRecipientDetails.statusEmoji = roomInfo.statusEmoji
        
        if let powerLevels = roomInfo.powerLevels {
            state.canSendMessage = powerLevels.canOwnUser(sendMessage: .roomMessage)
        }
    }
}