Introduced the concepts of room summary and event brief.

ElementX/Sources/Services/Room/RoomSummary/EventBrief.swift

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+//
+//  EventBrief.swift
+//  ElementX
+//
+//  Created by Stefan Ceriu on 01/04/2022.
+//  Copyright © 2022 Element. All rights reserved.
+//
+
+import Foundation
+
+struct EventBrief {
+    let id: String
+    let senderName: String
+    let body: String
+    let htmlBody: String?
+    let date: Date
+}

ElementX/Sources/Services/Room/RoomSummary/EventBriefFactory.swift

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+//
+//  EventBriefFactory.swift
+//  ElementX
+//
+//  Created by Stefan Ceriu on 01/04/2022.
+//  Copyright © 2022 Element. All rights reserved.
+//
+
+import Foundation
+
+struct EventBriefFactory: EventBriefFactoryProtocol {
+    
+    func eventBriefForMessage(_ message: RoomMessageProtocol?) -> EventBrief? {
+        guard let message = message else {
+            return nil
+        }
+        
+        switch message {
+        case is ImageRoomMessage:
+            return nil
+        case let message as TextRoomMessage:
+            return buildEventBrief(message: message, htmlBody: message.htmlBody)
+        case let message as NoticeRoomMessage:
+            return buildEventBrief(message: message, htmlBody: message.htmlBody)
+        case let message as EmoteRoomMessage:
+            return buildEventBrief(message: message, htmlBody: message.htmlBody)
+        default:
+            fatalError("Unknown room message.")
+        }
+    }
+    
+    // MARK: - Private
+    
+    private func buildEventBrief(message: RoomMessageProtocol, htmlBody: String?) -> EventBrief {
+        return EventBrief(id: message.id,
+                          senderName: message.sender,
+                          body: message.body,
+                          htmlBody: htmlBody,
+                          date: message.originServerTs)
+    }
+}

ElementX/Sources/Services/Room/RoomSummary/EventBriefFactoryProtocol.swift

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+//
+//  EventBriefFactoryProtocol.swift
+//  ElementX
+//
+//  Created by Stefan Ceriu on 01/04/2022.
+//  Copyright © 2022 Element. All rights reserved.
+//
+
+import Foundation
+
+protocol EventBriefFactoryProtocol {
+    func eventBriefForMessage(_ message: RoomMessageProtocol?) -> EventBrief?
+}

ElementX/Sources/Services/Room/RoomSummary/MockRoomSummary.swift

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+//
+//  MockRoomSummary.swift
+//  ElementX
+//
+//  Created by Stefan Ceriu on 01/04/2022.
+//  Copyright © 2022 Element. All rights reserved.
+//
+
+import UIKit
+import Combine
+
+struct MockRoomSummary: RoomSummaryProtocol {
+    var id: String = UUID().uuidString
+    
+    var name: String?
+    
+    var topic: String?
+    
+    var isDirect: Bool = false
+    
+    var isEncrypted: Bool = false
+    
+    var isSpace: Bool = false
+    
+    var isTombstoned: Bool = false
+    
+    var displayName: String?
+    
+    var lastMessage: EventBrief?
+    
+    var avatar: UIImage?
+    
+    func loadData() {
+        
+    }
+    
+    var callbacks = PassthroughSubject<RoomSummaryCallback, Never>()
+}

ElementX/Sources/Services/Room/RoomSummary/RoomSummary.swift

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+//
+//  RoomSummary.swift
+//  ElementX
+//
+//  Created by Stefan Ceriu on 01/04/2022.
+//  Copyright © 2022 Element. All rights reserved.
+//
+
+import Foundation
+import UIKit
+import Combine
+
+class RoomSummary: RoomSummaryProtocol {
+    private let roomProxy: RoomProxyProtocol
+    private let mediaProvider: MediaProviderProtocol
+    private let eventBriefFactory: EventBriefFactoryProtocol
+    
+    private var hasLoadedData = false
+    private var roomUpdateListeners = Set<AnyCancellable>()
+    
+    var id: String {
+        roomProxy.id
+    }
+    
+    var name: String? {
+        roomProxy.name
+    }
+    
+    var topic: String? {
+        roomProxy.topic
+    }
+    
+    var isDirect: Bool {
+        roomProxy.isDirect
+    }
+    
+    var isEncrypted: Bool {
+        roomProxy.isEncrypted
+    }
+    
+    var isSpace: Bool {
+        roomProxy.isSpace
+    }
+    
+    var isTombstoned: Bool {
+        roomProxy.isTombstoned
+    }
+    
+    private(set) var displayName: String? {
+        didSet {
+            self.callbacks.send(.updatedData)
+        }
+    }
+    
+    private(set) var lastMessage: EventBrief? {
+        didSet {
+            self.callbacks.send(.updatedData)
+        }
+    }
+    
+    private(set) var avatar: UIImage? {
+        didSet {
+            self.callbacks.send(.updatedData)
+        }
+    }
+    
+    let callbacks = PassthroughSubject<RoomSummaryCallback, Never>()
+    
+    init(roomProxy: RoomProxyProtocol, mediaProvider: MediaProviderProtocol, eventBriefFactory: EventBriefFactoryProtocol) {
+        self.roomProxy = roomProxy
+        self.mediaProvider = mediaProvider
+        self.eventBriefFactory = eventBriefFactory
+        
+        lastMessage = eventBriefFactory.eventBriefForMessage(roomProxy.messages.last)
+        
+        roomProxy.callbacks.sink { [weak self] callback in
+            guard let self = self else {
+                return
+            }
+            
+            switch callback {
+            case .updatedMessages:
+                self.lastMessage = self.eventBriefFactory.eventBriefForMessage(self.roomProxy.messages.last)
+            }
+        }
+        .store(in: &roomUpdateListeners)
+    }
+    
+    func loadData() {
+        if hasLoadedData {
+            return
+        }
+        
+        loadDisplayName()
+        loadLastMessage()
+        loadAvatar()
+        
+        hasLoadedData = true
+    }
+    
+    // MARK: - Private
+    
+    private func loadDisplayName() {
+        roomProxy.displayName { [weak self] result in
+            guard let self = self else { return }
+            
+            switch result {
+            case .success(let displayName):
+                self.displayName = displayName
+            case .failure(let error):
+                MXLog.error("Failed fetching room display name with error: \(error)")
+            }
+        }
+    }
+    
+    private func loadLastMessage() {
+        if roomProxy.messages.last == nil {
+            roomProxy.paginateBackwards(count: 1) { [weak self] result in
+                guard let self = self else { return }
+                
+                switch result {
+                case .success:
+                    self.lastMessage = self.eventBriefFactory.eventBriefForMessage(self.roomProxy.messages.last)
+                case .failure(let error):
+                    MXLog.error("Failed back paginating with error: \(error)")
+                }
+            }
+        }
+    }
+    
+    private func loadAvatar() {
+        if let avatarURL = roomProxy.avatarURL {
+            mediaProvider.loadImageFromURL(avatarURL) { [weak self] result in
+                guard let self = self else { return }
+                
+                switch result {
+                case .success(let image):
+                    self.avatar = image
+                case .failure(let error):
+                    MXLog.error("Failed fetching room avatar with error: \(error)")
+                }
+            }
+        }
+    }
+}

ElementX/Sources/Services/Room/RoomSummary/RoomSummaryProtocol.swift

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+//
+//  RoomSummaryProtocol.swift
+//  ElementX
+//
+//  Created by Stefan Ceriu on 01/04/2022.
+//  Copyright © 2022 Element. All rights reserved.
+//
+
+import UIKit
+import Combine
+
+enum RoomSummaryCallback {
+    case updatedData
+}
+
+protocol RoomSummaryProtocol {
+    var id: String { get }
+    var name: String? { get }
+    var topic: String? { get }
+    var isDirect: Bool { get }
+    var isEncrypted: Bool { get }
+    var isSpace: Bool { get }
+    var isTombstoned: Bool { get }
+    
+    var displayName: String? { get }
+    var lastMessage: EventBrief? { get }
+    var avatar: UIImage? { get }
+    
+    var callbacks: PassthroughSubject<RoomSummaryCallback, Never> { get }
+    
+    func loadData()
+}