another.im-ios/ConversationsClassic/AppData/Client/Client+MartinMAM.swift

import Combine
import Foundation
import GRDB
import Martin

final class ClientMartinMAM {
    private var cancellables: Set<AnyCancellable> = []

    private weak var module: MessageArchiveManagementModule?
    private var afterAvailable = true
    private var beforeAvailable = true

    init(_ xmppConnection: XMPPClient) {
        module = xmppConnection.module(.mam)
        subscribe()
    }

    private func subscribe() {
        // subscribe to archived messages
        module?.archivedMessagesPublisher
            .delay(for: 0.7, scheduler: DispatchQueue.main)
            .sink(receiveValue: { [weak self] archived in
                guard let self = self else { return }
                Task {
                    await self.handleMessage(archived)
                }
            })
            .store(in: &cancellables)
    }

    private func handleMessage(_ received: Martin.MessageArchiveManagementModule.ArchivedMessageReceived) async {
        let message = received.message
        let date = received.timestamp
        let msgId = received.messageId

        try? await Database.shared.dbQueue.write { db in
            if try Message.fetchOne(db, key: msgId) != nil {
                #if DEBUG
                    print("---")
                    print("Skipping archived message with id \(message.id ?? "???") (message exists)")
                    print("---")
                #endif
                return
            } else {
                #if DEBUG
                    print("---")
                    print("Archive message received: \(message)")
                    print("Date: \(date)")
                    print("---")
                #endif
                if var msg = Message.map(message) {
                    msg.date = received.timestamp
                    try msg.insert(db)
                }
            }
        }
    }
}