Add roles and permissions screen (#2505)

The screen hasn't been added to the flows yet.

ElementX/Sources/Screens/RoomRolesAndPermissionsScreen/RoomRolesAndPermissionsScreenViewModel.swift

@@ -0,0 +1,63 @@
+//
+// Copyright 2022 New Vector Ltd
+//
+// 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 Combine
+import SwiftUI
+
+typealias RoomRolesAndPermissionsScreenViewModelType = StateStoreViewModel<RoomRolesAndPermissionsScreenViewState, RoomRolesAndPermissionsScreenViewAction>
+
+class RoomRolesAndPermissionsScreenViewModel: RoomRolesAndPermissionsScreenViewModelType, RoomRolesAndPermissionsScreenViewModelProtocol {
+    private let roomProxy: RoomProxyProtocol
+    private var actionsSubject: PassthroughSubject<RoomRolesAndPermissionsScreenViewModelAction, Never> = .init()
+    
+    var actions: AnyPublisher<RoomRolesAndPermissionsScreenViewModelAction, Never> {
+        actionsSubject.eraseToAnyPublisher()
+    }
+
+    init(roomProxy: RoomProxyProtocol) {
+        self.roomProxy = roomProxy
+        super.init(initialViewState: RoomRolesAndPermissionsScreenViewState())
+        
+        roomProxy.members.sink { [weak self] members in
+            self?.updateMembers(members)
+        }
+        .store(in: &cancellables)
+        
+        updateMembers(roomProxy.members.value)
+    }
+    
+    // MARK: - Public
+    
+    override func process(viewAction: RoomRolesAndPermissionsScreenViewAction) {
+        MXLog.info("View model: received view action: \(viewAction)")
+        
+        switch viewAction {
+        case .editRoles(let role):
+            actionsSubject.send(.editRoles(role))
+        case .editPermissions(let permissionsGroup):
+            actionsSubject.send(.editPermissions(permissionsGroup))
+        case .reset:
+            break
+        }
+    }
+    
+    // MARK: - Members
+    
+    private func updateMembers(_ members: [RoomMemberProxyProtocol]) {
+        state.administratorCount = members.filter { $0.role == .administrator }.count
+        state.moderatorCount = members.filter { $0.role == .moderator }.count
+    }
+}