//
// Copyright 2026 Novaloop AG
//
// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
// Please see LICENSE files in the repository root for full details.
//

import AsyncAlgorithms
import Combine
import SwiftUI

typealias HealthChatMemberDirectoryScreenViewModelType = StateStoreViewModelV2<HealthChatMemberDirectoryScreenViewState, HealthChatMemberDirectoryScreenViewAction>

class HealthChatMemberDirectoryScreenViewModel: HealthChatMemberDirectoryScreenViewModelType, HealthChatMemberDirectoryScreenViewModelProtocol {
    private let apiService: HealthChatAPIServiceProtocol
    private let clientProxy: ClientProxyProtocol
    private let userIndicatorController: UserIndicatorControllerProtocol
    
    private var searchQueryObservationTask: Task<Void, Never>?
    // periphery:ignore - auto cancels when reassigned
    @CancellableTask private var fetchTask: Task<Void, Never>?
    
    private let actionsSubject: PassthroughSubject<HealthChatMemberDirectoryScreenViewModelAction, Never> = .init()
    var actionsPublisher: AnyPublisher<HealthChatMemberDirectoryScreenViewModelAction, Never> {
        actionsSubject.eraseToAnyPublisher()
    }
    
    init(apiService: HealthChatAPIServiceProtocol,
         clientProxy: ClientProxyProtocol,
         mediaProvider: MediaProviderProtocol,
         userIndicatorController: UserIndicatorControllerProtocol) {
        self.apiService = apiService
        self.clientProxy = clientProxy
        self.userIndicatorController = userIndicatorController
        
        super.init(initialViewState: HealthChatMemberDirectoryScreenViewState(), mediaProvider: mediaProvider)
        
        fetchMembers()
        
        // The stream replays the current query, which the initial fetch above already covers.
        let searchQueryStream = context.observe(\.viewState.bindings.searchQuery)
            .debounce(for: .milliseconds(300))
            .removeDuplicates()
            .dropFirst()
        searchQueryObservationTask = Task { [weak self] in
            for await _ in searchQueryStream {
                self?.fetchMembers()
            }
        }
    }
    
    isolated deinit {
        searchQueryObservationTask?.cancel()
    }
    
    // MARK: - Public
    
    override func process(viewAction: HealthChatMemberDirectoryScreenViewAction) {
        switch viewAction {
        case .retry:
            state.content = .loading
            fetchMembers()
        case .selectMember(let member):
            actionsSubject.send(.selectMember(userID: member.userID))
        case .startChat(let member):
            Task { await startChat(with: member) }
        }
    }
    
    // MARK: - Private
    
    private func fetchMembers() {
        fetchTask = Task { [weak self] in
            guard let self else { return }
            
            let searchQuery = state.bindings.searchQuery
            let result = await apiService.members(searchQuery: searchQuery.isEmpty ? nil : searchQuery)
            
            guard !Task.isCancelled else { return }
            
            switch result {
            case .success(let response) where !response.isApproved:
                state.content = .pendingApproval(message: response.pendingMessage ?? HealthChatL10n.screenMemberDirectoryPendingApproval)
            case .success(let response):
                state.content = .members(response.users)
            case .failure:
                state.content = .failure
            }
        }
    }
    
    private func startChat(with member: HealthChatMember) async {
        switch clientProxy.directRoomForUserID(member.userID) {
        case .success(let roomID?):
            actionsSubject.send(.presentRoom(roomID: roomID))
        case .success(nil):
            showLoadingIndicator()
            defer { hideLoadingIndicator() }
            
            switch await clientProxy.createDirectRoom(with: member.userID, expectedRoomName: member.displayName) {
            case .success(let roomID):
                actionsSubject.send(.presentRoom(roomID: roomID))
            case .failure:
                state.bindings.alertInfo = .init(id: .failedStartingChat,
                                                 title: L10n.commonError,
                                                 message: L10n.screenStartChatErrorStartingChat)
            }
        case .failure:
            state.bindings.alertInfo = .init(id: .failedStartingChat,
                                             title: L10n.commonError,
                                             message: L10n.screenStartChatErrorStartingChat)
        }
    }
    
    // MARK: User Indicators
    
    private var loadingIndicatorIdentifier: String {
        "\(Self.self)-Loading"
    }
    
    private func showLoadingIndicator() {
        userIndicatorController.submitIndicator(UserIndicator(id: loadingIndicatorIdentifier,
                                                              type: .modal(progress: .indeterminate, interactiveDismissDisabled: false, allowsInteraction: false),
                                                              title: L10n.commonLoading,
                                                              persistent: true),
                                                delay: .milliseconds(100))
    }
    
    private func hideLoadingIndicator() {
        userIndicatorController.retractIndicatorWithId(loadingIndicatorIdentifier)
    }
}