another.im-ios/ConversationsClassic/AppData/Store/ConversationStore.swift

import Collections
import Combine
import Foundation
import GRDB

@MainActor
final class ConversationStore: ObservableObject {
    @Published private(set) var messages: Deque<Message> = []
    private(set) var roster: Roster

    private let client: Client
    private let blockSize = Const.messagesPageSize
    private let messagesMax = Const.messagesMaxSize

    private var messagesObservation: AnyDatabaseCancellable

    init(roster: Roster, client: Client) {
        self.client = client
        self.roster = roster

        // observe change messages in database
        messagesObservation = DatabaseRegionObservation(tracking: Message.all()).start(in: Database.shared.dbQueue) { _ in
            // Handle error
        } onChange: { _ in
            print("Messages were changed")
        }
    }
}

extension ConversationStore {
    func loadMoreBackward() async {
        // guard let lastMessage = messages.last else { return }
        // let messages = await fetchBlock(lastMessage.date, nil)
        // self.messages.append(contentsOf: messages)
    }

    func loadMoreForward() async {
        // guard let firstMessage = messages.first else { return }
        // let messages = await fetchBlock(nil, firstMessage.date)
        // self.messages.insert(contentsOf: messages, at: 0)
    }
}

extension ConversationStore {
    private func fetchBlock(_ beforeDate: Date?, _ afterDate: Date?) async -> [Message] {
        print(beforeDate, afterDate)
        return []
        // let messages = await client.fetchMessages()
        // self.messages.append(contentsOf: messages)
    }

    private func cutMessages() {
        // if messages.count > messagesMax {
        //     messages.removeFirst(messages.count - messagesMax)
        // }
    }
}