//
//  NEUDPLink.swift
//  TunnelKit
//
//  Created by Davide De Rosa on 5/23/19.
//  Copyright (c) 2024 Davide De Rosa. All rights reserved.
//
//  https://github.com/passepartoutvpn
//
//  This file is part of TunnelKit.
//
//  TunnelKit is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  TunnelKit is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with TunnelKit.  If not, see <http://www.gnu.org/licenses/>.
//

import Foundation
import NetworkExtension
import TunnelKitCore
import TunnelKitAppExtension
import TunnelKitOpenVPNCore
import TunnelKitOpenVPNProtocol

class NEUDPLink: LinkInterface {
    private let impl: NWUDPSession

    private let maxDatagrams: Int

    private let xor: XORProcessor

    init(impl: NWUDPSession, maxDatagrams: Int? = nil, xorMethod: OpenVPN.XORMethod?) {
        self.impl = impl
        self.maxDatagrams = maxDatagrams ?? 200
        xor = XORProcessor(method: xorMethod)
    }

    // MARK: LinkInterface

    let isReliable: Bool = false

    var remoteAddress: String? {
        (impl.resolvedEndpoint as? NWHostEndpoint)?.hostname
    }

    var remoteProtocol: String? {
        guard let remote = impl.resolvedEndpoint as? NWHostEndpoint else {
            return nil
        }
        return "UDP:\(remote.port)"
    }

    var packetBufferSize: Int {
        return maxDatagrams
    }

    func setReadHandler(queue: DispatchQueue, _ handler: @escaping ([Data]?, Error?) -> Void) {

        // WARNING: runs in Network.framework queue
        impl.setReadHandler({ [weak self] packets, error in
            guard let self = self else {
                return
            }
            var packetsToUse: [Data]?
            if let packets = packets {
                packetsToUse = self.xor.processPackets(packets, outbound: false)
            }
            queue.sync {
                handler(packetsToUse, error)
            }
        }, maxDatagrams: maxDatagrams)
    }

    func writePacket(_ packet: Data, completionHandler: ((Error?) -> Void)?) {
        let dataToUse = xor.processPacket(packet, outbound: true)
        impl.writeDatagram(dataToUse) { error in
            completionHandler?(error)
        }
    }

    func writePackets(_ packets: [Data], completionHandler: ((Error?) -> Void)?) {
        let packetsToUse = xor.processPackets(packets, outbound: true)
        impl.writeMultipleDatagrams(packetsToUse) { error in
            completionHandler?(error)
        }
    }
}

extension NEUDPSocket: LinkProducer {
    public func link(userObject: Any?) -> LinkInterface {
        let xorMethod = userObject as? OpenVPN.XORMethod
        return NEUDPLink(impl: impl, maxDatagrams: nil, xorMethod: xorMethod)
    }
}