element-ios/RiotSwiftUI/Modules/Template/TemplateAdvancedRoomsExample/TemplateRoomChat/ViewModel/TemplateRoomChatViewModel.swift

//
// Copyright 2021 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 SwiftUI
import Combine

@available(iOS 14, *)
typealias TemplateRoomChatViewModelType = StateStoreViewModel<TemplateRoomChatViewState,
                                                              TemplateRoomChatStateAction,
                                                              TemplateRoomChatViewAction>

@available(iOS 14, *)
class TemplateRoomChatViewModel: TemplateRoomChatViewModelType, TemplateRoomChatViewModelProtocol {
    
    enum Constants {
        static let maxTimeBeforeNewBubble: TimeInterval = 5*60
    }
    // MARK: - Properties
    
    // MARK: Private
    
    private let templateRoomChatService: TemplateRoomChatServiceProtocol
    
    // MARK: Public
    
    var completion: ((TemplateRoomChatViewModelResult) -> Void)?
    
    // MARK: - Setup
    
    init(templateRoomChatService: TemplateRoomChatServiceProtocol) {
        self.templateRoomChatService = templateRoomChatService
        super.init(initialViewState: Self.defaultState(templateRoomChatService: templateRoomChatService))
        templateRoomChatService.chatMessagesSubject
            .map(Self.makeBubbles(messages:))
            .map(TemplateRoomChatStateAction.updateBubbles)
            .receive(on: DispatchQueue.main)
            .sink(receiveValue: { [weak self] action in
                self?.dispatch(action:action)
            })
            .store(in: &cancellables)
    }
    
    private static func defaultState(templateRoomChatService: TemplateRoomChatServiceProtocol) -> TemplateRoomChatViewState {
        let bubbles = makeBubbles(messages: templateRoomChatService.chatMessagesSubject.value)
        let bindings = TemplateRoomChatViewModelBindings(messageInput: "")
        return TemplateRoomChatViewState(roomName: templateRoomChatService.roomName, bubbles: bubbles, bindings: bindings)
    }
    
    private static func makeBubbles(messages: [TemplateRoomChatMessage]) -> [TemplateRoomChatBubble] {
        
        var bubbleOrder = [String]()
        var bubbleMap = [String:TemplateRoomChatBubble]()
        
        messages.enumerated().forEach { i, message in
            let messageItem = TemplateRoomChatBubbleItem(
                id: message.id,
                timestamp: message.timestamp,
                content: .message(TemplateRoomChatBubbleMessageContent(body: message.body))
            )
            if i > 0,
               let lastBubbleId = bubbleOrder.last,
               var lastBubble = bubbleMap[lastBubbleId],
               lastBubble.sender.id == message.sender.id,
               let interveningTime =  lastBubble.items.last?.timestamp.timeIntervalSince(message.timestamp),
               abs(interveningTime) < Constants.maxTimeBeforeNewBubble
            {
                let item = TemplateRoomChatBubbleItem(
                    id: message.id,
                    timestamp: message.timestamp,
                    content: .message(TemplateRoomChatBubbleMessageContent(body: message.body))
                )
                lastBubble.items.append(item)
                bubbleMap[lastBubble.id] = lastBubble
            } else {
                let bubble = TemplateRoomChatBubble(
                    id: message.id,
                    sender: message.sender,
                    items: [messageItem]
                )
                bubbleOrder.append(bubble.id)
                bubbleMap[bubble.id] = bubble
            }
        }
        return bubbleOrder.compactMap({ bubbleMap[$0] })
    }
    
    // MARK: - Public
    
    override func process(viewAction: TemplateRoomChatViewAction) {
        switch viewAction {
        case .cancel:
            cancel()
        case .done:
            done()
        case .sendMessage:
            templateRoomChatService.send(message: state.bindings.messageInput)
            dispatch(action: .clearMessageInput)
        }
    }
    
    override class func reducer(state: inout TemplateRoomChatViewState, action: TemplateRoomChatStateAction) {
        switch action {
        case .clearMessageInput:
            state.bindings.messageInput = ""
        case .updateBubbles(let bubbles):
            state.bubbles = bubbles
        }
        UILog.debug("[TemplateRoomChatViewModel] reducer with action \(action) produced state: \(state)")
    }
    
    // MARK: - Private
    
    private func done() {
        completion?(.done)
    }
    
    private func cancel() {
        completion?(.cancel)
    }
}