# Nim-LibP2P
# Copyright (c) 2023 Status Research & Development GmbH
# Licensed under either of
#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
#  * MIT license ([LICENSE-MIT](LICENSE-MIT))
# at your option.
# This file may not be copied, modified, or distributed except according to
# those terms.

## Tor transport implementation

when (NimMajor, NimMinor) < (1, 4):
  {.push raises: [Defect].}
else:
  {.push raises: [].}

import std/strformat
import chronos, chronicles, strutils
import stew/[byteutils, endians2, results, objects]
import ../multicodec
import transport,
      tcptransport,
      ../switch,
      ../builders,
      ../stream/[lpstream, connection, chronosstream],
      ../multiaddress,
      ../upgrademngrs/upgrade

const
  IPTcp = mapAnd(IP, mapEq("tcp"))
  IPv4Tcp = mapAnd(IP4, mapEq("tcp"))
  IPv6Tcp = mapAnd(IP6, mapEq("tcp"))
  DnsTcp = mapAnd(DNSANY, mapEq("tcp"))

  Socks5ProtocolVersion = byte(5)
  NMethods = byte(1)

type
  TorTransport* = ref object of Transport
    transportAddress: TransportAddress
    tcpTransport: TcpTransport

  Socks5AuthMethod* {.pure.} = enum
    NoAuth = 0
    GSSAPI = 1
    UsernamePassword = 2
    NoAcceptableMethod = 0xff

  Socks5RequestCommand* {.pure.} = enum
    Connect = 1, Bind = 2, UdpAssoc = 3

  Socks5AddressType* {.pure.} = enum
    IPv4 = 1, FQDN = 3, IPv6 = 4

  Socks5ReplyType* {.pure.} = enum
    Succeeded = (0, "Succeeded"), ServerFailure = (1, "Server Failure"),
    ConnectionNotAllowed = (2, "Connection Not Allowed"), NetworkUnreachable = (3, "Network Unreachable"),
    HostUnreachable = (4, "Host Unreachable"), ConnectionRefused = (5, "Connection Refused"),
    TtlExpired = (6, "Ttl Expired"), CommandNotSupported = (7, "Command Not Supported"),
    AddressTypeNotSupported = (8, "Address Type Not Supported")

  TransportStartError* = object of transport.TransportError

  Socks5Error* = object of CatchableError
  Socks5AuthFailedError* = object of Socks5Error
  Socks5VersionError* = object of Socks5Error
  Socks5ServerReplyError* = object of Socks5Error

proc new*(
  T: typedesc[TorTransport],
  transportAddress: TransportAddress,
  flags: set[ServerFlags] = {},
  upgrade: Upgrade): T {.public.} =
  ## Creates a Tor transport

  T(
    transportAddress: transportAddress,
    upgrader: upgrade,
    tcpTransport: TcpTransport.new(flags, upgrade))

proc handlesDial(address: MultiAddress): bool {.gcsafe.} =
  return Onion3.match(address) or TCP.match(address) or DNSANY.match(address)

proc handlesStart(address: MultiAddress): bool {.gcsafe.} =
  return TcpOnion3.match(address)

proc connectToTorServer(
    transportAddress: TransportAddress): Future[StreamTransport] {.async, gcsafe.} =
  let transp = await connect(transportAddress)
  try:
    discard await transp.write(@[Socks5ProtocolVersion, NMethods, Socks5AuthMethod.NoAuth.byte])
    let
      serverReply = await transp.read(2)
      socks5ProtocolVersion = serverReply[0]
      serverSelectedMethod = serverReply[1]
    if socks5ProtocolVersion != Socks5ProtocolVersion:
      raise newException(Socks5VersionError, "Unsupported socks version")
    if serverSelectedMethod != Socks5AuthMethod.NoAuth.byte:
      raise newException(Socks5AuthFailedError, "Unsupported auth method")
    return transp
  except CatchableError as err:
    await transp.closeWait()
    raise err

proc readServerReply(transp: StreamTransport) {.async, gcsafe.} =
  ## The specification for this code is defined on
  ## [link text](https://www.rfc-editor.org/rfc/rfc1928#section-5)
  ## and [link text](https://www.rfc-editor.org/rfc/rfc1928#section-6).
  let
    portNumOctets = 2
    ipV4NumOctets = 4
    ipV6NumOctets = 16
    firstFourOctets = await transp.read(4)
    socks5ProtocolVersion = firstFourOctets[0]
    serverReply = firstFourOctets[1]
  if socks5ProtocolVersion != Socks5ProtocolVersion:
    raise newException(Socks5VersionError, "Unsupported socks version")
  if serverReply != Socks5ReplyType.Succeeded.byte:
    var socks5ReplyType: Socks5ReplyType
    if socks5ReplyType.checkedEnumAssign(serverReply):
      raise newException(Socks5ServerReplyError, fmt"Server reply error: {socks5ReplyType}")
    else:
      raise newException(LPError, fmt"Unexpected server reply: {serverReply}")
  let atyp = firstFourOctets[3]
  case atyp:
    of Socks5AddressType.IPv4.byte:
      discard await transp.read(ipV4NumOctets + portNumOctets) 
    of Socks5AddressType.FQDN.byte:
      let fqdnNumOctets = await transp.read(1)
      discard await transp.read(int(uint8.fromBytes(fqdnNumOctets)) + portNumOctets)
    of Socks5AddressType.IPv6.byte:
      discard await transp.read(ipV6NumOctets + portNumOctets)
    else:
      raise newException(LPError, "Address not supported")

proc parseOnion3(address: MultiAddress): (byte, seq[byte], seq[byte]) {.raises: [Defect, LPError, ValueError].} =
  var addressArray = ($address).split('/')
  if addressArray.len < 2: raise newException(LPError, fmt"Onion address not supported {address}")
  addressArray = addressArray[2].split(':')
  if addressArray.len == 0: raise newException(LPError, fmt"Onion address not supported {address}")
  let
    addressStr = addressArray[0] & ".onion"
    dstAddr = @(uint8(addressStr.len).toBytes()) & addressStr.toBytes()
    dstPort = address.data.buffer[37..38]
  return (Socks5AddressType.FQDN.byte, dstAddr, dstPort)

proc parseIpTcp(address: MultiAddress): (byte, seq[byte], seq[byte]) {.raises: [Defect, LPError, ValueError].} =
  let (codec, atyp) =
    if IPv4Tcp.match(address):
      (multiCodec("ip4"), Socks5AddressType.IPv4.byte)
    elif IPv6Tcp.match(address):
      (multiCodec("ip6"), Socks5AddressType.IPv6.byte)
    else:
      raise newException(LPError, fmt"IP address not supported {address}")
  let
    dstAddr = address[codec].get().protoArgument().get()
    dstPort = address[multiCodec("tcp")].get().protoArgument().get()
  (atyp, dstAddr, dstPort)

proc parseDnsTcp(address: MultiAddress): (byte, seq[byte], seq[byte]) =
  let
    dnsAddress = address[multiCodec("dns")].get().protoArgument().get()
    dstAddr = @(uint8(dnsAddress.len).toBytes()) & dnsAddress
    dstPort = address[multiCodec("tcp")].get().protoArgument().get()
  (Socks5AddressType.FQDN.byte, dstAddr, dstPort)

proc dialPeer(
    transp: StreamTransport, address: MultiAddress) {.async, gcsafe.} =
  let (atyp, dstAddr, dstPort) =
    if Onion3.match(address):
      parseOnion3(address)
    elif IPTcp.match(address):
      parseIpTcp(address)
    elif DnsTcp.match(address):
      parseDnsTcp(address)
    else:
      raise newException(LPError, fmt"Address not supported: {address}")

  let reserved = byte(0)
  let request = @[
    Socks5ProtocolVersion,
    Socks5RequestCommand.Connect.byte,
    reserved,
    atyp] & dstAddr & dstPort
  discard await transp.write(request)
  await readServerReply(transp)

method dial*(
  self: TorTransport,
  hostname: string,
  address: MultiAddress,
  peerId: Opt[PeerId] = Opt.none(PeerId)): Future[Connection] {.async, gcsafe.} =
  ## dial a peer
  ##
  if not handlesDial(address):
    raise newException(LPError, fmt"Address not supported: {address}")
  trace "Dialing remote peer", address = $address
  let transp = await connectToTorServer(self.transportAddress)

  try:
    await dialPeer(transp, address)
    return await self.tcpTransport.connHandler(transp, Opt.none(MultiAddress), Direction.Out)
  except CatchableError as err:
    await transp.closeWait()
    raise err

method start*(
  self: TorTransport,
  addrs: seq[MultiAddress]) {.async.} =
  ## listen on the transport
  ##

  var listenAddrs: seq[MultiAddress]
  var onion3Addrs: seq[MultiAddress]
  for i, ma in addrs:
    if not handlesStart(ma):
        warn "Invalid address detected, skipping!", address = ma
        continue

    let listenAddress = ma[0..1].get()
    listenAddrs.add(listenAddress)
    let onion3 = ma[multiCodec("onion3")].get()
    onion3Addrs.add(onion3)

  if len(listenAddrs) != 0 and len(onion3Addrs) != 0:
    await procCall Transport(self).start(onion3Addrs)
    await self.tcpTransport.start(listenAddrs)
  else:
    raise newException(TransportStartError, "Tor Transport couldn't start, no supported addr was provided.")

method accept*(self: TorTransport): Future[Connection] {.async, gcsafe.} =
  ## accept a new Tor connection
  ##
  let conn = await self.tcpTransport.accept()
  conn.observedAddr = Opt.none(MultiAddress)
  return conn

method stop*(self: TorTransport) {.async, gcsafe.} =
  ## stop the transport
  ##
  await procCall Transport(self).stop() # call base
  await self.tcpTransport.stop()

method handles*(t: TorTransport, address: MultiAddress): bool {.gcsafe.} =
  if procCall Transport(t).handles(address):
    return handlesDial(address) or handlesStart(address)

type
  TorSwitch* = ref object of Switch

proc new*(
  T: typedesc[TorSwitch],
  torServer: TransportAddress,
  rng: ref HmacDrbgContext,
  addresses: seq[MultiAddress] = @[],
  flags: set[ServerFlags] = {}): TorSwitch
  {.raises: [LPError, Defect], public.} =
    var builder = SwitchBuilder.new()
        .withRng(rng)
        .withTransport(proc(upgr: Upgrade): Transport = TorTransport.new(torServer, flags, upgr))
    if addresses.len != 0:
        builder = builder.withAddresses(addresses)
    let switch = builder.withMplex()
        .withNoise()
        .build()
    let torSwitch = T(
      peerInfo: switch.peerInfo,
      ms: switch.ms,
      transports: switch.transports,
      connManager: switch.connManager,
      peerStore: switch.peerStore,
      dialer: Dialer.new(switch.peerInfo.peerId, switch.connManager, switch.transports, switch.ms, nil),
      nameResolver: nil)

    torSwitch.connManager.peerStore = switch.peerStore
    return torSwitch

method addTransport*(s: TorSwitch, t: Transport) =
  doAssert(false, "not implemented!")

method getTorTransport*(s: TorSwitch): Transport {.base.} =
  return s.transports[0]