import Combine
import Foundation
import GRDB
import Martin

@MainActor
final class MessagesStore: ObservableObject {
    @Published private(set) var messages: [Message] = []
    @Published var replyText = ""

    private(set) var roster: Roster
    private let client: Client

    private var messagesCancellable: AnyCancellable?
    private let archiveMessageFetcher = ArchiveMessageFetcher()

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

// MARK: - Send message
extension MessagesStore {
    func sendMessage(_ message: String) {
        Task {
            var msg = Message.blank
            msg.from = roster.bareJid
            msg.to = roster.contactBareJid
            msg.body = message

            // store as pending on db, and send
            do {
                try await msg.save()
                try await client.sendMessage(msg)
                try await msg.setStatus(.sent)
            } catch {
                try? await msg.setStatus(.error)
            }
        }
    }

    func sendContact(_ jidStr: String) {
        sendMessage("contact:\(jidStr)")
    }

    func sendLocation(_ lat: Double, _ lon: Double) {
        sendMessage("geo:\(lat),\(lon)")
    }
}

// MARK: - Subscriptions
private extension MessagesStore {
    func subscribe() {
        messagesCancellable = ValueObservation.tracking(Message
            .filter(
                (Column("to") == roster.bareJid && Column("from") == roster.contactBareJid) ||
                    (Column("from") == roster.bareJid && Column("to") == roster.contactBareJid)
            )
            .order(Column("date").desc)
            .fetchAll
        )
        .publisher(in: Database.shared.dbQueue, scheduling: .immediate)
        .receive(on: DispatchQueue.main)
        .sink { _ in
        } receiveValue: { [weak self] messages in
            self?.messages = messages
            if messages.isEmpty {
                self?.requestLastArchivedMessages()
            }
        }
    }
}

// MARK: - Archived messages
extension MessagesStore {
    func requestEarliestArchivedMessages() {
        guard let beforeId = messages.last?.id else { return }
        Task {
            await archiveMessageFetcher.fetchBeforeMessages(roster, client, beforeId: beforeId)
        }
    }

    func requestLatestArchivedMessages() {
        guard let afterId = messages.first?.id else { return }
        Task {
            await archiveMessageFetcher.fetchAfterMessages(roster, client, afterId: afterId)
        }
    }

    private func requestLastArchivedMessages() {
        Task {
            await archiveMessageFetcher.fetchLastMessages(roster, client)
        }
    }
}

private actor ArchiveMessageFetcher {
    private var afterAvailable = true
    private var beforeAvailable = true
    private var isFetching = false
    private var fetchingIsPossinle = true

    func fetchLastMessages(_ roster: Roster, _ client: Client) async {
        if !fetchingIsPossinle { return }
        while isFetching {
            await Task.yield()
        }
        isFetching = true

        let query: RSM.Query = .init(lastItems: Const.mamRequestLimit)
        do {
            _ = try await client.fetchArchiveMessages(for: roster, query: query)
        } catch AppError.featureNotSupported {
            fetchingIsPossinle = false
        } catch {
            logIt(.error, "Error requesting archived messages: \(error)")
        }

        isFetching = false
    }

    func fetchBeforeMessages(_ roster: Roster, _ client: Client, beforeId: String) async {
        if !fetchingIsPossinle || !beforeAvailable { return }
        while isFetching {
            await Task.yield()
        }
        isFetching = true

        let query: RSM.Query = .init(before: beforeId, max: Const.mamRequestLimit)
        do {
            let result = try await client.fetchArchiveMessages(for: roster, query: query)
            if result.complete {
                beforeAvailable = false
            }
        } catch AppError.featureNotSupported {
            fetchingIsPossinle = false
        } catch {
            logIt(.error, "Error requesting archived messages: \(error)")
        }

        isFetching = false
    }

    func fetchAfterMessages(_ roster: Roster, _ client: Client, afterId: String) async {
        if !fetchingIsPossinle || !afterAvailable { return }
        while isFetching {
            await Task.yield()
        }
        isFetching = true

        let query: RSM.Query = .init(after: afterId, max: Const.mamRequestLimit)
        do {
            let result = try await client.fetchArchiveMessages(for: roster, query: query)
            if result.complete {
                afterAvailable = false
            }
        } catch AppError.featureNotSupported {
            fetchingIsPossinle = false
        } catch {
            logIt(.error, "Error requesting archived messages: \(error)")
        }

        isFetching = false
    }
}