bundesmessenger-ios/Riot/Modules/Room/RoomInfo/RoomInfoList/RoomInfoListViewModel.swift

// File created from ScreenTemplate
// $ createScreen.sh Room2/RoomInfo RoomInfoList
/*
 Copyright 2020 New Vector Ltd
 Copyright (c) 2021 BWI GmbH
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
 
 http://www.apache.org/licenses/LICENSE-2.0
 
 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */

import Foundation

final class RoomInfoListViewModel: NSObject, RoomInfoListViewModelType {
    
    // MARK: - Properties
    
    // MARK: Private

    private let session: MXSession
    private let room: MXRoom
    
    // MARK: Public

    weak var viewDelegate: RoomInfoListViewModelViewDelegate?
    weak var coordinatorDelegate: RoomInfoListViewModelCoordinatorDelegate?
    
    private var viewData: RoomInfoListViewData {
        let encryptionImage = EncryptionTrustLevelBadgeImageHelper.roomBadgeImage(for: room.summary.roomEncryptionTrustLevel())
        let directUserPresence = session.user(withUserId: room.directUserId)?.presence ?? .unknown
        
        let basicInfoViewData = RoomInfoBasicViewData(avatarUrl: room.summary.avatar,
                                                      mediaManager: session.mediaManager,
                                                      roomId: room.roomId,
                                                      roomDisplayName: room.summary.displayname,
                                                      mainRoomAlias: room.summary.aliases?.first,
                                                      roomTopic: room.summary.topic,
                                                      encryptionImage: encryptionImage,
                                                      isEncrypted: room.summary.isEncrypted,
                                                      isDirect: room.isDirect,
                                                      directUserId: room.directUserId,
                                                      directUserPresence: directUserPresence)
        
        return RoomInfoListViewData(numberOfMembers: Int(room.summary.membersCount.joined),
                                    isEncrypted: room.summary.isEncrypted,
                                    isDirect: room.isDirect,
                                    basicInfoViewData: basicInfoViewData)
    }
    
    // MARK: - Setup
    
    init(session: MXSession, room: MXRoom) {
        self.session = session
        self.room = room
        super.init()
        startObservingSummaryChanges()
    }
    
    deinit {
        stopObservingSummaryChanges()
    }
    
    // MARK: - Public
    
    func process(viewAction: RoomInfoListViewAction) {
        switch viewAction {
        case .loadData:
            self.loadData()
        case .navigate(let target):
            self.navigate(to: target)
        case .leave:
            self.leave()
        case .cancel:
            self.coordinatorDelegate?.roomInfoListViewModelDidCancel(self)
        case .permalink:
            self.createPermalink()
        }
    }
    
    func canLeaveRoom() -> Bool {
        let myUserId = self.session.myUserId
        
        // None Admins can always leave the room
        if !self.isAdmin(self.session.myUserId) {
            return true
        }
        
        var canLeave = false
        
        // admins can only leave if there is at least one other admin
        self.room.state { (state) in
            if let members = state?.members.joinedMembers {
                for user in members where user.userId != myUserId {
                    if self.isAdmin(user.userId) {
                        canLeave = true
                        break
                    }
                }
            }
        }
        
        // A single admin can leave the room if he is the only member
        if !canLeave && self.isOnlyMember() {
            canLeave = true
        }
        
        return canLeave
    }
    
    func isDirectRoom() -> Bool {
        return room.isDirect
    }
    
    func isPersonalNotesRoom() -> Bool {
        return room.isPersonalNotesRoom()
    }

    func isOnlyMember() -> Bool {
        var memberCount = 0
        
        self.room.state { (state) in
            if let members = state?.members.joinedMembers {
                memberCount = members.count
            }
        }
        return (memberCount == 1)
    }
    
    // MARK: - Private
    
    private func isAdmin(_ userId: String) -> Bool {
        var admin = false
        
        self.room.state { (state) in
            let powerLevels = state?.powerLevels
            let userPowerLevel = powerLevels?.powerLevelOfUser(withUserID: userId)
            let roomPowerLevel = RoomPowerLevelHelper.roomPowerLevel(from: userPowerLevel ?? RoomPowerLevel.user.rawValue)
            
            if roomPowerLevel == RoomPowerLevel.admin {
                admin = true
            }
        }
        
        return admin
    }
    
    private func startObservingSummaryChanges() {
        NotificationCenter.default.addObserver(self, selector: #selector(roomSummaryUpdated(_:)), name: .mxRoomSummaryDidChange, object: room.summary)
    }
    
    private func stopObservingSummaryChanges() {
        NotificationCenter.default.removeObserver(self, name: .mxRoomSummaryDidChange, object: nil)
    }
    
    @objc private func roomSummaryUpdated(_ notification: Notification) {
        //  force update view
        self.update(viewState: .loaded(viewData: viewData))
    }
    
    private func loadData() {
        self.update(viewState: .loaded(viewData: viewData))
    }
    
    private func navigate(to target: RoomInfoListTarget) {
        self.coordinatorDelegate?.roomInfoListViewModel(self, wantsToNavigateTo: target)
    }
    
    private func leave() {
        self.stopObservingSummaryChanges()
        self.update(viewState: .loading)
        self.room.leave { (response) in
            switch response {
            case .success:
                self.coordinatorDelegate?.roomInfoListViewModelDidLeaveRoom(self)
            case .failure(let error):
                self.startObservingSummaryChanges()
                self.update(viewState: .error(error))
            }
        }
    }
    
    private func update(viewState: RoomInfoListViewState) {
        self.viewDelegate?.roomInfoListViewModel(self, didUpdateViewState: viewState)
    }
    
    private func createPermalink() {        
        if let permalink = MXTools.permalink(toRoom: self.room.roomId), let url = URL(string: permalink) {
            MXKPasteboardManager.shared.pasteboard.url = url
            self.viewDelegate?.roomInfoListViewModel(self, didUpdateViewState: .permalinkCreated)
        }
        
    }
}