//
//  SDLContext.swift
//  Tun
//
//  Created by 安礼成 on 2024/2/29.
//

import Foundation
import NetworkExtension
import NIOCore
import Combine

// 上下文环境变量，全局共享
/*
1. 处理rsa的加解密逻辑
 */

@available(macOS 14, *)
public class SDLContext {
    
    // 路由信息
    struct Route {
        let dstAddress: String
        let subnetMask: String
        
        var debugInfo: String {
            return "\(dstAddress):\(subnetMask)"
        }
    }
    
    let config: SDLConfiguration

    // nat的网络类型
    var natType: SDLNATProberActor.NatType = .blocked
    
    // AES加密，授权通过后，对象才会被创建
    var aesCipher: AESCipher
    
    // aes
    var aesKey: Data = Data()
    
    // rsa的相关配置, public_key是本地生成的
    let rsaCipher: RSACipher
    
    // 依赖的变量
    var udpHoleActor: SDLUDPHoleActor?
    var providerActor: SDLTunnelProviderActor
    var puncherActor: SDLPuncherActor
    // dns的client对象
    var dnsClientActor: SDLDNSClientActor?
    
    // 网络探测对象
    var proberActor: SDLNATProberActor?
    
    // 数据包读取任务
    private var readTask: Task<(), Never>?
    
    private var sessionManager: SessionManager
    private var arpServer: ArpServer
    
    // 记录最后发送的stunRequest的cookie
    private var lastCookie: UInt32? = 0
    
    // 网络状态变化的健康
    private var monitor: SDLNetworkMonitor?
    
    // 内部socket通讯
    private var noticeClientActor: SDLNoticeClientActor?
    
    // 流量统计
    private var flowTracer = SDLFlowTracerActor()
    private var flowTracerCancel: AnyCancellable?
    
    private let logger: SDLLogger
    private var rootTask: Task<Void, Error>?
    
    public init(provider: NEPacketTunnelProvider, config: SDLConfiguration, rsaCipher: RSACipher, aesCipher: AESCipher, logger: SDLLogger) {
        self.logger = logger
        
        self.config = config
        self.rsaCipher = rsaCipher
        self.aesCipher = aesCipher
        
        self.sessionManager = SessionManager()
        self.arpServer = ArpServer(known_macs: [:])
        self.providerActor = SDLTunnelProviderActor(provider: provider, logger: logger)
        self.puncherActor = SDLPuncherActor(querySocketAddress: config.stunSocketAddress, logger: logger)
    }
    
    public func start() async throws {
        self.rootTask = Task {
            try await withThrowingTaskGroup(of: Void.self) { group in
                group.addTask {
                    while !Task.isCancelled {
                        do {
                            try await self.startDnsClient()
                        } catch let err {
                            self.logger.log("[SDLContext] UDPHole get err: \(err)", level: .warning)
                            try await Task.sleep(for: .seconds(2))
                        }
                    }
                }
                
                group.addTask {
                    while !Task.isCancelled {
                        do {
                            try await self.startUDPHole()
                        } catch let err {
                            self.logger.log("[SDLContext] UDPHole get err: \(err)", level: .warning)
                            try await Task.sleep(for: .seconds(2))
                        }
                    }
                }
                                
                group.addTask {
                    await self.startMonitor()
                }
                
                group.addTask {
                    while !Task.isCancelled {
                        do {
                            try await self.startNoticeClient()
                        } catch let err {
                            self.logger.log("[SDLContext] noticeClient get err: \(err)", level: .warning)
                            try await Task.sleep(for: .seconds(2))
                        }
                    }
                }
                
                try await group.waitForAll()
            }
        }
        
        try await self.rootTask?.value
    }
    
    public func stop() async {
        self.rootTask?.cancel()
        self.udpHoleActor = nil
        self.noticeClientActor = nil

        self.readTask?.cancel()
    }
    
    private func startNoticeClient() async throws {
        self.noticeClientActor = try SDLNoticeClientActor(noticePort: self.config.noticePort, logger: self.logger)
        try await self.noticeClientActor?.start()
        self.logger.log("[SDLContext] notice_client task cancel", level: .warning)
    }
    
    private func startUDPHole() async throws {
        self.udpHoleActor = try SDLUDPHoleActor(logger: self.logger)
        try await self.udpHoleActor?.start()

        try await withThrowingTaskGroup(of: Void.self) { group in
            group.addTask {
                while !Task.isCancelled {
                    try Task.checkCancellation()
                    try await Task.sleep(nanoseconds: 5 * 1_000_000_000)
                    try Task.checkCancellation()
                    await self.sendStunRequest()
                }
            }
            
            group.addTask {
                if let eventStream = self.udpHoleActor?.eventStream {
                    for try await event in eventStream {
                        try Task.checkCancellation()
                        try? await self.dispatchEvent(event: event)
                    }
                }
            }
            
            if let _ = try await group.next() {
                group.cancelAll()
            }
        }
        
    }
    
    private func startMonitor() async {
        self.monitor = SDLNetworkMonitor()
        for await event in self.monitor!.eventStream {
            switch event {
            case .changed:
                // 需要重新探测网络的nat类型
                //self.natType = await self.getNatType()
                
                self.logger.log("didNetworkPathChanged, nat type is: \(self.natType)", level: .info)
            case .unreachable:
                self.logger.log("didNetworkPathUnreachable", level: .warning)
            }
        }
    }
    
    private func startDnsClient() async throws {
        let remoteDnsServer = config.remoteDnsServer
        let dnsSocketAddress = try SocketAddress.makeAddressResolvingHost(remoteDnsServer, port: 15353)
        self.dnsClientActor = try await SDLDNSClientActor(dnsServerAddress: dnsSocketAddress, logger: self.logger)
        
        try await withThrowingTaskGroup(of: Void.self) { group in
            defer {
                self.logger.log("[SDLContext] dns client task cancel", level: .warning)
            }
            
            group.addTask {
                try await self.dnsClientActor?.start()
            }
            
            group.addTask {
                if let packetFlow = self.dnsClientActor?.packetFlow {
                    for await packet in packetFlow {
                        let nePacket = NEPacket(data: packet, protocolFamily: 2)
                        await self.providerActor.writePackets(packets: [nePacket])
                    }
                }
                
            }
            
            if let _ = try await group.next() {
                group.cancelAll()
            }
        }
    }
    
    private func handleUDPHoleReady() async throws {
        await self.puncherActor.setUDPHoleActor(udpHoleActor: self.udpHoleActor)
        
        // 开始探测nat的类型
        if let udpHoleActor = self.udpHoleActor {
            self.proberActor = SDLNATProberActor(udpHole: udpHoleActor, addressArray: self.config.stunProbeSocketAddressArray, logger: self.logger)
            self.natType = await self.proberActor!.probeNatType()
        }

        var registerSuper = SDLRegisterSuper()
        registerSuper.pktID = 0
        registerSuper.clientID = self.config.clientId
        registerSuper.networkID = self.config.networkAddress.networkId
        registerSuper.mac = self.config.networkAddress.mac
        registerSuper.ip = self.config.networkAddress.ip
        registerSuper.maskLen = UInt32(self.config.networkAddress.maskLen)
        registerSuper.hostname = self.config.hostname
        registerSuper.pubKey = self.rsaCipher.pubKey
        registerSuper.accessToken = self.config.accessToken

        await self.udpHoleActor?.send(type: .registerSuper, data: try registerSuper.serializedData(), remoteAddress: self.config.stunSocketAddress)
    }
    
    private func sendStunRequest() async {
        var stunRequest = SDLStunRequest()
        stunRequest.clientID = self.config.clientId
        stunRequest.networkID = self.config.networkAddress.networkId
        stunRequest.ip = self.config.networkAddress.ip
        stunRequest.mac = self.config.networkAddress.mac
        stunRequest.natType = UInt32(self.natType.rawValue)
        
        if let stunData = try? stunRequest.serializedData() {
            let remoteAddress = self.config.stunSocketAddress
            await self.udpHoleActor?.send(type: .stunRequest, data: stunData, remoteAddress: remoteAddress)
        }
    }
    
    private func dispatchEvent(event: SDLUDPHoleActor.UDPHoleEvent) async throws {
        switch event {
        case .ready:
            try await self.handleUDPHoleReady()
        case .message(let remoteAddress, let message):
            switch message {
            case .registerSuperAck(let registerSuperAck):
                await self.handleRegisterSuperAck(registerSuperAck: registerSuperAck)
            case .registerSuperNak(let registerSuperNak):
                await self.handleRegisterSuperNak(nakPacket: registerSuperNak)
            case .peerInfo(let peerInfo):
                await self.puncherActor.handlePeerInfo(peerInfo: peerInfo)
            case .event(let event):
                try await self.handleEvent(event: event)
            case .stunProbeReply(let probeReply):
                await self.proberActor?.handleProbeReply(reply: probeReply)
            case .data(let data):
                try await self.handleData(data: data)
            case .register(let register):
                try await self.handleRegister(remoteAddress: remoteAddress, register: register)
            case .registerAck(let registerAck):
                await self.handleRegisterAck(remoteAddress: remoteAddress, registerAck: registerAck)
            }
        }
    }
    
    private func handleRegisterSuperAck(registerSuperAck: SDLRegisterSuperAck) async {
        // 需要对数据通过rsa的私钥解码
        let aesKey = try! self.rsaCipher.decode(data: Data(registerSuperAck.aesKey))
        
        self.logger.log("[SDLContext] get registerSuperAck, aes_key len: \(aesKey.count)", level: .info)
        // 服务器分配的tun网卡信息
        do {
            let ipAddress = try await self.providerActor.setNetworkSettings(networkAddress: self.config.networkAddress, dnsServer: SDLDNSClientActor.Helper.dnsServer)
            await self.noticeClientActor?.send(data: NoticeMessage.ipAdress(ip: ipAddress))
            
            self.startReader()
        } catch let err {
            self.logger.log("[SDLContext] setTunnelNetworkSettings get error: \(err)", level: .error)
            exit(-1)
        }
        
        self.aesKey = aesKey
    }

    private func handleRegisterSuperNak(nakPacket: SDLRegisterSuperNak) async {
        let errorMessage = nakPacket.errorMessage
        guard let errorCode = SDLNAKErrorCode(rawValue: UInt8(nakPacket.errorCode)) else {
            return
        }
        
        switch errorCode {
        case .invalidToken, .nodeDisabled:
            let alertNotice = NoticeMessage.alert(alert: errorMessage)
            await self.noticeClientActor?.send(data: alertNotice)
            exit(-1)
        case .noIpAddress, .networkFault, .internalFault:
            let alertNotice = NoticeMessage.alert(alert: errorMessage)
            await self.noticeClientActor?.send(data: alertNotice)
        }
        self.logger.log("[SDLContext] Get a SuperNak message exit", level: .warning)
        
    }
    
    private func handleEvent(event: SDLEvent) async throws {
        switch event {
        case .natChanged(let natChangedEvent):
            let dstMac = natChangedEvent.mac
            self.logger.log("[SDLContext] natChangedEvent, dstMac: \(dstMac)", level: .info)
            await sessionManager.removeSession(dstMac: dstMac)
        case .sendRegister(let sendRegisterEvent):
            self.logger.log("[SDLContext] sendRegisterEvent, ip: \(sendRegisterEvent)", level: .debug)
            let address = SDLUtil.int32ToIp(sendRegisterEvent.natIp)
            if let remoteAddress = try? SocketAddress.makeAddressResolvingHost(address, port: Int(sendRegisterEvent.natPort)) {
                // 发送register包
                var register = SDLRegister()
                register.networkID = self.config.networkAddress.networkId
                register.srcMac = self.config.networkAddress.mac
                register.dstMac = sendRegisterEvent.dstMac
                await self.udpHoleActor?.send(type: .register, data: try register.serializedData(), remoteAddress: remoteAddress)
            }
            
        case .networkShutdown(let shutdownEvent):
            let alertNotice = NoticeMessage.alert(alert: shutdownEvent.message)
            await self.noticeClientActor?.send(data: alertNotice)
            exit(-1)
        }
    }
    
    private func handleRegister(remoteAddress: SocketAddress, register: SDLRegister) async throws {
        let networkAddr = config.networkAddress
        self.logger.log("register packet: \(register), network_address: \(networkAddr)", level: .debug)
        
        // 判断目标地址是否是tun的网卡地址, 并且是在同一个网络下
        if register.dstMac == networkAddr.mac && register.networkID == networkAddr.networkId {
            // 回复ack包
            var registerAck = SDLRegisterAck()
            registerAck.networkID = networkAddr.networkId
            registerAck.srcMac = networkAddr.mac
            registerAck.dstMac = register.srcMac
            
            await self.udpHoleActor?.send(type: .registerAck, data: try registerAck.serializedData(), remoteAddress: remoteAddress)
            // 这里需要建立到来源的会话, 在复杂网络下，通过super-node查询到的nat地址不一定靠谱，需要通过udp包的来源地址作为nat地址
            let session = Session(dstMac: register.srcMac, natAddress: remoteAddress)
            await self.sessionManager.addSession(session: session)
        } else {
            self.logger.log("SDLContext didReadRegister get a invalid packet, because dst_ip not matched: \(register.dstMac)", level: .warning)
        }
    }
    
    private func handleRegisterAck(remoteAddress: SocketAddress, registerAck: SDLRegisterAck) async {
        // 判断目标地址是否是tun的网卡地址, 并且是在同一个网络下
        let networkAddr = config.networkAddress
        if registerAck.dstMac == networkAddr.mac && registerAck.networkID == networkAddr.networkId {
            let session = Session(dstMac: registerAck.srcMac, natAddress: remoteAddress)
            await self.sessionManager.addSession(session: session)
        } else {
            self.logger.log("SDLContext didReadRegisterAck get a invalid packet, because dst_mac not matched: \(registerAck.dstMac)", level: .warning)
        }
    }
    
    private func handleData(data: SDLData) async throws {
        let mac = LayerPacket.MacAddress(data: data.dstMac)
        
        let networkAddr = config.networkAddress
        guard (data.dstMac == networkAddr.mac || mac.isBroadcast() || mac.isMulticast()) else {
            return
        }
        
        guard let decyptedData = try? self.aesCipher.decypt(aesKey: self.aesKey, data: Data(data.data)) else {
            return
        }
        
        let layerPacket = try LayerPacket(layerData: decyptedData)
        
        await self.flowTracer.inc(num: decyptedData.count, type: .inbound)
        // 处理arp请求
        switch layerPacket.type {
        case .arp:
            // 判断如果收到的是arp请求
            if let arpPacket = ARPPacket(data: layerPacket.data)  {
                if arpPacket.targetIP == networkAddr.ip {
                    switch arpPacket.opcode {
                    case .request:
                        self.logger.log("[SDLContext] get arp request packet", level: .debug)
                        let response = ARPPacket.arpResponse(for: arpPacket, mac: networkAddr.mac, ip: networkAddr.ip)
                        await self.routeLayerPacket(dstMac: arpPacket.senderMAC, type: .arp, data: response.marshal())
                    case .response:
                        self.logger.log("[SDLContext] get arp response packet", level: .debug)
                        await self.arpServer.append(ip: arpPacket.senderIP, mac: arpPacket.senderMAC)
                    }
                } else {
                    self.logger.log("[SDLContext] get invalid arp packet: \(arpPacket), target_ip: \(SDLUtil.int32ToIp(arpPacket.targetIP)), net ip: \(SDLUtil.int32ToIp(networkAddr.ip))", level: .debug)
                }
            } else {
                self.logger.log("[SDLContext] get invalid arp packet", level: .debug)
            }
        case .ipv4:
            guard let ipPacket = IPPacket(layerPacket.data), ipPacket.header.destination == networkAddr.ip else {
                return
            }
            let packet = NEPacket(data: ipPacket.data, protocolFamily: 2)
            await self.providerActor.writePackets(packets: [packet])
        default:
            self.logger.log("[SDLContext] get invalid packet", level: .debug)
        }
    }
        
    
    // 流量统计
//    public func flowReportTask() {
//        Task {
//            // 每分钟汇报一次
//            self.flowTracerCancel = Timer.publish(every: 60.0, on: .main, in: .common).autoconnect()
//                .sink { _ in
//                    Task {
//                        let (forwardNum, p2pNum, inboundNum) = await self.flowTracer.reset()
//                        await self.superClient?.flowReport(forwardNum: forwardNum, p2pNum: p2pNum, inboundNum: inboundNum)
//                    }
//                }
//        }
//    }
    
    // 开始读取数据, 用单独的线程处理packetFlow
    private func startReader() {
        //  停止之前的任务
        self.readTask?.cancel()
        
        // 开启新的任务
        self.readTask = Task(priority: .high) {
            repeat {
                let packets = await self.providerActor.readPackets()
                let ipPackets = packets.compactMap { IPPacket($0) }
                await self.batchProcessPackets(batchSize: 20, packets: ipPackets)
            } while true
        }
    }
    
    // 批量分发ip数据包
    private func batchProcessPackets(batchSize: Int, packets: [IPPacket]) async {
        for startIndex in stride(from: 0, to: packets.count, by: batchSize) {
            let endIndex = Swift.min(startIndex + batchSize, packets.count)
            
            let chunkPackets = packets[startIndex..<endIndex]
            await withTaskGroup(of: Void.self) { group  in
                for packet in chunkPackets {
                    group.addTask {
                        await self.dealPacket(packet: packet)
                    }
                }
            }
        }
    }
    
    // 处理读取的每个数据包
    private func dealPacket(packet: IPPacket) async {
        let networkAddr = self.config.networkAddress
        if SDLDNSClientActor.Helper.isDnsRequestPacket(ipPacket: packet) {
            let destIp = packet.header.destination_ip
            self.logger.log("[DNSQuery] destIp: \(destIp), int: \(packet.header.destination.asIpAddress())", level: .debug)
            await self.dnsClientActor?.forward(ipPacket: packet)
            return
        }
        
        let dstIp = packet.header.destination
        // 本地通讯, 目标地址是本地服务器的ip地址
        if dstIp == networkAddr.ip {
            let nePacket = NEPacket(data: packet.data, protocolFamily: 2)
            await self.providerActor.writePackets(packets: [nePacket])
            return
        }
        
        // 查找arp缓存中是否有目标mac地址
        if let dstMac = await self.arpServer.query(ip: dstIp) {
            await self.routeLayerPacket(dstMac: dstMac, type: .ipv4, data: packet.data)
        }
        else {
            self.logger.log("[SDLContext] dstIp: \(dstIp.asIpAddress()) arp query not found, broadcast", level: .debug)
            // 构造arp广播
            let arpReqeust = ARPPacket.arpRequest(senderIP: networkAddr.ip, senderMAC: networkAddr.mac, targetIP: dstIp)
            await self.routeLayerPacket(dstMac: ARPPacket.broadcastMac , type: .arp, data: arpReqeust.marshal())
        }
    }
    
    private func routeLayerPacket(dstMac: Data, type: LayerPacket.PacketType, data: Data) async {
        let networkAddr = self.config.networkAddress
        // 将数据封装层2层的数据包
        let layerPacket = LayerPacket(dstMac: dstMac, srcMac: networkAddr.mac, type: type, data: data)
        guard let encodedPacket = try? self.aesCipher.encrypt(aesKey: self.aesKey, data: layerPacket.marshal()) else {
            return
        }
        
        // 构造数据包
        var dataPacket = SDLData()
        dataPacket.networkID = networkAddr.networkId
        dataPacket.srcMac = networkAddr.mac
        dataPacket.dstMac = dstMac
        dataPacket.ttl = 255
        dataPacket.data = encodedPacket
        
        let data = try! dataPacket.serializedData()
        // 广播地址不要去尝试打洞
        if ARPPacket.isBroadcastMac(dstMac) {
            // 通过super_node进行转发
            await self.udpHoleActor?.send(type: .data, data: data, remoteAddress: self.config.stunSocketAddress)
        }
        else {
            // 通过session发送到对端
            if let session = await self.sessionManager.getSession(toAddress: dstMac) {
                self.logger.log("[SDLContext] send packet by session: \(session)", level: .debug)
                await self.udpHoleActor?.send(type: .data, data: data, remoteAddress: session.natAddress)
                await self.flowTracer.inc(num: data.count, type: .p2p)
            }
            else {
                // 通过super_node进行转发
                await self.udpHoleActor?.send(type: .data, data: data, remoteAddress: self.config.stunSocketAddress)
                // 流量统计
                await self.flowTracer.inc(num: data.count, type: .forward)
                // 尝试打洞
                await self.puncherActor.submitRegisterRequest(request: .init(srcMac: networkAddr.mac, dstMac: dstMac, networkId: networkAddr.networkId))
            }
        }
    }
    
    deinit {
        self.rootTask?.cancel()
        self.udpHoleActor = nil
        self.dnsClientActor = nil
    }
}

private extension UInt32 {
    // 转换成ip地址
    func asIpAddress() -> String {
        return SDLUtil.int32ToIp(self)
    }
}