## Nim-Libp2p
## Copyright (c) 2018 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.

## This module implements MultiAddress.

{.push raises: [Defect].}

import nativesockets
import tables, strutils, stew/shims/net
import chronos
import multicodec, multihash, multibase, transcoder, vbuffer
import stew/[base58, base32, endians2, results]
from peer import PeerID
export results

type
  MAKind* = enum
    None, Fixed, Length, Path, Marker

  MAProtocol* = object
    mcodec*: MultiCodec
    size*: int
    kind: MAKind
    coder*: Transcoder

  MultiAddress* = object
    data*: VBuffer

  MaPatternOp* = enum
    Eq, Or, And

  MaPattern* = object
    operator*: MaPatternOp
    args*: seq[MaPattern]
    value*: MultiCodec

  MaPatResult* = object
    flag*: bool
    rem*: seq[MultiCodec]

  MaResult*[T] = Result[T, string]

  IpTransportProtocol* = enum
    tcpProtocol
    udpProtocol

const
  # These are needed in order to avoid an ambiguity error stemming from
  # some cint constants with the same name defined in the posix modules
  IPPROTO_TCP = Protocol.IPPROTO_TCP
  IPPROTO_UDP = Protocol.IPPROTO_UDP

proc ip4StB(s: string, vb: var VBuffer): bool =
  ## IPv4 stringToBuffer() implementation.
  try:
    var a = parseIpAddress(s)
    if a.family == IpAddressFamily.IPv4:
      vb.writeArray(a.address_v4)
      result = true
  except:
    discard

proc ip4BtS(vb: var VBuffer, s: var string): bool =
  ## IPv4 bufferToString() implementation.
  var a = IpAddress(family: IpAddressFamily.IPv4)
  if vb.readArray(a.address_v4) == 4:
    s = $a
    result = true

proc ip4VB(vb: var VBuffer): bool =
  ## IPv4 validateBuffer() implementation.
  var a = IpAddress(family: IpAddressFamily.IPv4)
  if vb.readArray(a.address_v4) == 4:
    result = true

proc ip6StB(s: string, vb: var VBuffer): bool =
  ## IPv6 stringToBuffer() implementation.
  try:
    var a = parseIpAddress(s)
    if a.family == IpAddressFamily.IPv6:
      vb.writeArray(a.address_v6)
      result = true
  except:
    discard

proc ip6BtS(vb: var VBuffer, s: var string): bool =
  ## IPv6 bufferToString() implementation.
  var a = IpAddress(family: IpAddressFamily.IPv6)
  if vb.readArray(a.address_v6) == 16:
    s = $a
    result = true

proc ip6VB(vb: var VBuffer): bool =
  ## IPv6 validateBuffer() implementation.
  var a = IpAddress(family: IpAddressFamily.IPv6)
  if vb.readArray(a.address_v6) == 16:
    result = true

proc ip6zoneStB(s: string, vb: var VBuffer): bool =
  ## IPv6 stringToBuffer() implementation.
  if len(s) > 0:
    vb.writeSeq(s)
    result = true

proc ip6zoneBtS(vb: var VBuffer, s: var string): bool =
  ## IPv6 bufferToString() implementation.
  if vb.readSeq(s) > 0:
    result = true

proc ip6zoneVB(vb: var VBuffer): bool =
  ## IPv6 validateBuffer() implementation.
  var s = ""
  if vb.readSeq(s) > 0:
    if s.find('/') == -1:
      result = true

proc portStB(s: string, vb: var VBuffer): bool =
  ## Port number stringToBuffer() implementation.
  var port: array[2, byte]
  try:
    var nport = parseInt(s)
    if (nport >= 0) and (nport < 65536):
      port[0] = cast[byte]((nport shr 8) and 0xFF)
      port[1] = cast[byte](nport and 0xFF)
      vb.writeArray(port)
      result = true
  except:
    discard

proc portBtS(vb: var VBuffer, s: var string): bool =
  ## Port number bufferToString() implementation.
  var port: array[2, byte]
  if vb.readArray(port) == 2:
    var nport = (cast[uint16](port[0]) shl 8) or cast[uint16](port[1])
    s = $nport
    result = true

proc portVB(vb: var VBuffer): bool =
  ## Port number validateBuffer() implementation.
  var port: array[2, byte]
  if vb.readArray(port) == 2:
    result = true

proc p2pStB(s: string, vb: var VBuffer): bool =
  ## P2P address stringToBuffer() implementation.
  try:
    var data = Base58.decode(s)
    var mh: MultiHash
    if MultiHash.decode(data, mh).isOk:
      vb.writeSeq(data)
      result = true
  except:
    discard

proc p2pBtS(vb: var VBuffer, s: var string): bool =
  ## P2P address bufferToString() implementation.
  var address = newSeq[byte]()
  if vb.readSeq(address) > 0:
    var mh: MultiHash
    if MultiHash.decode(address, mh).isOk:
      s = Base58.encode(address)
      result = true

proc p2pVB(vb: var VBuffer): bool =
  ## P2P address validateBuffer() implementation.
  var address = newSeq[byte]()
  if vb.readSeq(address) > 0:
    var mh: MultiHash
    if MultiHash.decode(address, mh).isOk:
      result = true

proc onionStB(s: string, vb: var VBuffer): bool =
  try:
    var parts = s.split(':')
    if len(parts) != 2:
      return false
    if len(parts[0]) != 16:
      return false
    var address = Base32Lower.decode(parts[0].toLowerAscii())
    var nport = parseInt(parts[1])
    if (nport > 0 and nport < 65536) and len(address) == 10:
      address.setLen(12)
      address[10] = cast[byte]((nport shr 8) and 0xFF)
      address[11] = cast[byte](nport and 0xFF)
      vb.writeArray(address)
      result = true
  except:
    discard

proc onionBtS(vb: var VBuffer, s: var string): bool =
  ## ONION address bufferToString() implementation.
  var buf: array[12, byte]
  if vb.readArray(buf) == 12:
    var nport = (cast[uint16](buf[10]) shl 8) or cast[uint16](buf[11])
    s = Base32Lower.encode(buf.toOpenArray(0, 9))
    s.add(":")
    s.add($nport)
    result = true

proc onionVB(vb: var VBuffer): bool =
  ## ONION address validateBuffer() implementation.
  var buf: array[12, byte]
  if vb.readArray(buf) == 12:
    result = true

proc unixStB(s: string, vb: var VBuffer): bool =
  ## Unix socket name stringToBuffer() implementation.
  if len(s) > 0:
    vb.writeSeq(s)
    result = true

proc unixBtS(vb: var VBuffer, s: var string): bool =
  ## Unix socket name bufferToString() implementation.
  s = ""
  if vb.readSeq(s) > 0:
    result = true

proc unixVB(vb: var VBuffer): bool =
  ## Unix socket name validateBuffer() implementation.
  var s = ""
  if vb.readSeq(s) > 0:
    result = true

proc dnsStB(s: string, vb: var VBuffer): bool =
  ## DNS name stringToBuffer() implementation.
  if len(s) > 0:
    vb.writeSeq(s)
    result = true

proc dnsBtS(vb: var VBuffer, s: var string): bool =
  ## DNS name bufferToString() implementation.
  s = ""
  if vb.readSeq(s) > 0:
    result = true

proc dnsVB(vb: var VBuffer): bool =
  ## DNS name validateBuffer() implementation.
  var s = ""
  if vb.readSeq(s) > 0:
    if s.find('/') == -1:
      result = true

proc mapEq*(codec: string): MaPattern =
  ## ``Equal`` operator for pattern
  result.operator = Eq
  result.value = multiCodec(codec)

proc mapOr*(args: varargs[MaPattern]): MaPattern =
  ## ``Or`` operator for pattern
  result.operator = Or
  result.args = @args

proc mapAnd*(args: varargs[MaPattern]): MaPattern =
  ## ``And`` operator for pattern
  result.operator = And
  result.args = @args

const
  TranscoderIP4* = Transcoder(
    stringToBuffer: ip4StB,
    bufferToString: ip4BtS,
    validateBuffer: ip4VB
  )
  TranscoderIP6* = Transcoder(
    stringToBuffer: ip6StB,
    bufferToString: ip6BtS,
    validateBuffer: ip6VB
  )
  TranscoderIP6Zone* = Transcoder(
    stringToBuffer: ip6zoneStB,
    bufferToString: ip6zoneBtS,
    validateBuffer: ip6zoneVB
  )
  TranscoderUnix* = Transcoder(
    stringToBuffer: unixStB,
    bufferToString: unixBtS,
    validateBuffer: unixVB
  )
  TranscoderP2P* = Transcoder(
    stringToBuffer: p2pStB,
    bufferToString: p2pBtS,
    validateBuffer: p2pVB
  )
  TranscoderPort* = Transcoder(
    stringToBuffer: portStB,
    bufferToString: portBtS,
    validateBuffer: portVB
  )
  TranscoderOnion* = Transcoder(
    stringToBuffer: onionStB,
    bufferToString: onionBtS,
    validateBuffer: onionVB
  )
  TranscoderDNS* = Transcoder(
    stringToBuffer: dnsStB,
    bufferToString: dnsBtS,
    validateBuffer: dnsVB
  )
  ProtocolsList = [
    MAProtocol(
      mcodec: multiCodec("ip4"), kind: Fixed, size: 4,
      coder: TranscoderIP4
    ),
    MAProtocol(
      mcodec: multiCodec("tcp"), kind: Fixed, size: 2,
      coder: TranscoderPort
    ),
    MAProtocol(
      mcodec: multiCodec("udp"), kind: Fixed, size: 2,
      coder: TranscoderPort
    ),
    MAProtocol(
      mcodec: multiCodec("ip6"), kind: Fixed, size: 16,
      coder: TranscoderIP6
    ),
    MAProtocol(
      mcodec: multiCodec("dccp"), kind: Fixed, size: 2,
      coder: TranscoderPort
    ),
    MAProtocol(
      mcodec: multiCodec("sctp"), kind: Fixed, size: 2,
      coder: TranscoderPort
    ),
    MAProtocol(
      mcodec: multiCodec("udt"), kind: Marker, size: 0
    ),
    MAProtocol(
      mcodec: multiCodec("utp"), kind: Marker, size: 0
    ),
    MAProtocol(
      mcodec: multiCodec("http"), kind: Marker, size: 0
    ),
    MAProtocol(
      mcodec: multiCodec("https"), kind: Marker, size: 0
    ),
    MAProtocol(
      mcodec: multiCodec("quic"), kind: Marker, size: 0
    ),
    MAProtocol(
      mcodec: multiCodec("ip6zone"), kind: Length, size: 0,
      coder: TranscoderIP6Zone
    ),
    MAProtocol(
      mcodec: multiCodec("onion"), kind: Fixed, size: 10,
      coder: TranscoderOnion
    ),
    MAProtocol(
      mcodec: multiCodec("ws"), kind: Marker, size: 0
    ),
    MAProtocol(
      mcodec: multiCodec("ipfs"), kind: Length, size: 0,
      coder: TranscoderP2P
    ),
    MAProtocol(
      mcodec: multiCodec("p2p"), kind: Length, size: 0,
      coder: TranscoderP2P
    ),
    MAProtocol(
      mcodec: multiCodec("unix"), kind: Path, size: 0,
      coder: TranscoderUnix
    ),
    MAProtocol(
      mcodec: multiCodec("dns4"), kind: Length, size: 0,
      coder: TranscoderDNS
    ),
    MAProtocol(
      mcodec: multiCodec("dns6"), kind: Length, size: 0,
      coder: TranscoderDNS
    ),
    MAProtocol(
      mcodec: multiCodec("dnsaddr"), kind: Length, size: 0,
      coder: TranscoderDNS
    ),
    MAProtocol(
      mcodec: multiCodec("p2p-circuit"), kind: Marker, size: 0
    ),
    MAProtocol(
      mcodec: multiCodec("p2p-websocket-star"), kind: Marker, size: 0
    ),
    MAProtocol(
      mcodec: multiCodec("p2p-webrtc-star"), kind: Marker, size: 0
    ),
    MAProtocol(
      mcodec: multiCodec("p2p-webrtc-direct"), kind: Marker, size: 0
    )
  ]

  DNS4* = mapEq("dns4")
  DNS6* = mapEq("dns6")
  IP4* = mapEq("ip4")
  IP6* = mapEq("ip6")
  DNS* = mapOr(mapEq("dnsaddr"), DNS4, DNS6)
  IP* = mapOr(IP4, IP6)
  TCP* = mapOr(mapAnd(DNS, mapEq("tcp")), mapAnd(IP, mapEq("tcp")))
  UDP* = mapOr(mapAnd(DNS, mapEq("udp")), mapAnd(IP, mapEq("udp")))
  UTP* = mapAnd(UDP, mapEq("utp"))
  QUIC* = mapAnd(UDP, mapEq("quic"))
  UNIX* = mapEq("unix")

  Unreliable* = mapOr(UDP)

  Reliable* = mapOr(TCP, UTP, QUIC)

  IPFS* = mapAnd(Reliable, mapEq("p2p"))

  HTTP* = mapOr(
    mapAnd(TCP, mapEq("http")),
    mapAnd(IP, mapEq("http")),
    mapAnd(DNS, mapEq("http"))
  )

  HTTPS* = mapOr(
    mapAnd(TCP, mapEq("https")),
    mapAnd(IP, mapEq("https")),
    mapAnd(DNS, mapEq("https"))
  )

  WebRTCDirect* = mapOr(
    mapAnd(HTTP, mapEq("p2p-webrtc-direct")),
    mapAnd(HTTPS, mapEq("p2p-webrtc-direct"))
  )

proc initMultiAddressCodeTable(): Table[MultiCodec,
                                        MAProtocol] {.compileTime.} =
  result = initTable[MultiCodec, MAProtocol]()
  for item in ProtocolsList:
    result[item.mcodec] = item

const
  CodeAddresses = initMultiAddressCodeTable()

proc trimRight(s: string, ch: char): string =
  ## Consume trailing characters ``ch`` from string ``s`` and return result.
  var m = 0
  for i in countdown(s.high, 0):
    if s[i] == ch:
      inc(m)
    else:
      break
  result = s[0..(s.high - m)]

proc shcopy*(m1: var MultiAddress, m2: MultiAddress) =
  shallowCopy(m1.data.buffer, m2.data.buffer)
  m1.data.offset = m2.data.offset
  m1.data.length = m2.data.length

proc protoCode*(ma: MultiAddress): MaResult[MultiCodec] =
  ## Returns MultiAddress ``ma`` protocol code.
  var header: uint64
  var vb: MultiAddress
  shcopy(vb, ma)
  if vb.data.readVarint(header) == -1:
    err("multiaddress: Malformed binary address!")
  else:
    let proto = CodeAddresses.getOrDefault(MultiCodec(header))
    if proto.kind == None:
      err("multiaddress: Unsupported protocol '" & $header & "'")
    else:
      ok(proto.mcodec)

proc protoName*(ma: MultiAddress): MaResult[string] =
  ## Returns MultiAddress ``ma`` protocol name.
  var header: uint64
  var vb: MultiAddress
  shcopy(vb, ma)
  if vb.data.readVarint(header) == -1:
    err("multiaddress: Malformed binary address!")
  else:
    let proto = CodeAddresses.getOrDefault(MultiCodec(header))
    if proto.kind == None:
      err("multiaddress: Unsupported protocol '" & $header & "'")
    else:
      ok($(proto.mcodec))

proc protoArgument*(ma: MultiAddress, value: var openarray[byte]): MaResult[int] =
  ## Returns MultiAddress ``ma`` protocol argument value.
  ##
  ## If current MultiAddress do not have argument value, then result will be
  ## ``0``.
  var header: uint64
  var vb: MultiAddress
  var buffer: seq[byte]
  shcopy(vb, ma)
  if vb.data.readVarint(header) == -1:
    err("multiaddress: Malformed binary address!")
  else:
    let proto = CodeAddresses.getOrDefault(MultiCodec(header))
    if proto.kind == None:
      err("multiaddress: Unsupported protocol '" & $header & "'")
    else:
      var res: int
      if proto.kind == Fixed:
        res = proto.size
        if  len(value) >= res and
            vb.data.readArray(value.toOpenArray(0, proto.size - 1)) != proto.size:
          err("multiaddress: Decoding protocol error")
        else:
          ok(res)
      elif proto.kind in {Length, Path}:
        if vb.data.readSeq(buffer) == -1:
          err("multiaddress: Decoding protocol error")
        else:
          res = len(buffer)
          if len(value) >= res:
            copyMem(addr value[0], addr buffer[0], res)
          ok(res)
      else:
        ok(res)

proc protoAddress*(ma: MultiAddress): MaResult[seq[byte]] =
  ## Returns MultiAddress ``ma`` protocol address binary blob.
  ##
  ## If current MultiAddress do not have argument value, then result array will
  ## be empty.
  var buffer = newSeq[byte](len(ma.data.buffer))
  let res = ? protoArgument(ma, buffer)
  buffer.setLen(res)
  ok(buffer)

proc getPart(ma: MultiAddress, index: int): MaResult[MultiAddress] =
  var header: uint64
  var data = newSeq[byte]()
  var offset = 0
  var vb = ma
  var res: MultiAddress
  res.data = initVBuffer()
  while offset <= index:
    if vb.data.readVarint(header) == -1:
      return err("multiaddress: Malformed binary address!")

    let proto = CodeAddresses.getOrDefault(MultiCodec(header))
    if proto.kind == None:
      return err("multiaddress: Unsupported protocol '" & $header & "'")

    elif proto.kind == Fixed:
      data.setLen(proto.size)
      if vb.data.readArray(data) != proto.size:
        return err("multiaddress: Decoding protocol error")

      if offset == index:
        res.data.writeVarint(header)
        res.data.writeArray(data)
        res.data.finish()
    elif proto.kind in {Length, Path}:
      if vb.data.readSeq(data) == -1:
        return err("multiaddress: Decoding protocol error")

      if offset == index:
        res.data.writeVarint(header)
        res.data.writeSeq(data)
        res.data.finish()
    elif proto.kind == Marker:
      if offset == index:
        res.data.writeVarint(header)
        res.data.finish()
    inc(offset)
  ok(res)

proc `[]`*(ma: MultiAddress, i: int): MaResult[MultiAddress] {.inline.} =
  ## Returns part with index ``i`` of MultiAddress ``ma``.
  ma.getPart(i)

iterator items*(ma: MultiAddress): MaResult[MultiAddress] =
  ## Iterates over all addresses inside of MultiAddress ``ma``.
  var header: uint64
  var data = newSeq[byte]()
  var vb = ma
  while true:
    if vb.data.isEmpty():
      break

    var res = MultiAddress(data: initVBuffer())
    if vb.data.readVarint(header) == -1:
      yield err(MaResult[MultiAddress], "Malformed binary address!")

    let proto = CodeAddresses.getOrDefault(MultiCodec(header))
    if proto.kind == None:
      yield err(MaResult[MultiAddress], "Unsupported protocol '" & $header & "'")

    elif proto.kind == Fixed:
      data.setLen(proto.size)
      if vb.data.readArray(data) != proto.size:
        yield err(MaResult[MultiAddress], "Decoding protocol error")

      res.data.writeVarint(header)
      res.data.writeArray(data)
    elif proto.kind in {Length, Path}:
      if vb.data.readSeq(data) == -1:
        yield err(MaResult[MultiAddress], "Decoding protocol error")

      res.data.writeVarint(header)
      res.data.writeSeq(data)
    elif proto.kind == Marker:
      res.data.writeVarint(header)
    res.data.finish()
    yield ok(MaResult[MultiAddress], res)

proc contains*(ma: MultiAddress, codec: MultiCodec): MaResult[bool] {.inline.} =
  ## Returns ``true``, if address with MultiCodec ``codec`` present in
  ## MultiAddress ``ma``.
  for item in ma.items:
    let code = ?(?item).protoCode()
    if code == codec:
      return ok(true)
  ok(false)

proc `[]`*(ma: MultiAddress, codec: MultiCodec): MaResult[MultiAddress] {.inline.} =
  ## Returns partial MultiAddress with MultiCodec ``codec`` and present in
  ## MultiAddress ``ma``.
  for item in ma.items:
    if ?(?item).protoCode == codec:
      return item
  err("multiaddress: Codec is not present in address")

proc toString*(value: MultiAddress): MaResult[string] =
  ## Return string representation of MultiAddress ``value``.
  var header: uint64
  var vb = value
  var parts = newSeq[string]()
  var part: string
  var res: string
  while true:
    if vb.data.isEmpty():
      break
    if vb.data.readVarint(header) == -1:
      return err("multiaddress: Malformed binary address!")
    let proto = CodeAddresses.getOrDefault(MultiCodec(header))
    if proto.kind == None:
      return err("multiaddress: Unsupported protocol '" & $header & "'")
    if proto.kind in {Fixed, Length, Path}:
      if isNil(proto.coder.bufferToString):
        return err("multiaddress: Missing protocol '" & $(proto.mcodec) & "' coder")
      if not proto.coder.bufferToString(vb.data, part):
        return err("multiaddress: Decoding protocol error")
      parts.add($(proto.mcodec))
      if proto.kind == Path and part[0] == '/':
        parts.add(part[1..^1])
      else:
        parts.add(part)
    elif proto.kind == Marker:
      parts.add($(proto.mcodec))
  if len(parts) > 0:
    res = "/" & parts.join("/")
  ok(res)

proc `$`*(value: MultiAddress): string {.raises: [Defect, ResultError[string]].} =
  ## Return string representation of MultiAddress ``value``.
  value.toString().tryGet()

proc protocols*(value: MultiAddress): MaResult[seq[MultiCodec]] =
  ## Returns list of protocol codecs inside of MultiAddress ``value``.
  var res = newSeq[MultiCodec]()
  for item in value.items():
    res.add(?(?item).protoCode())
  ok(res)

proc hex*(value: MultiAddress): string =
  ## Return hexadecimal string representation of MultiAddress ``value``.
  $(value.data)

proc write*(vb: var VBuffer, ma: MultiAddress) {.inline.} =
  ## Write MultiAddress value ``ma`` to buffer ``vb``.
  vb.writeArray(ma.data.buffer)

proc encode*(mbtype: typedesc[MultiBase], encoding: string,
             ma: MultiAddress): string {.inline.} =
  ## Get MultiBase encoded representation of ``ma`` using encoding
  ## ``encoding``.
  result = MultiBase.encode(encoding, ma.data.buffer)

proc validate*(ma: MultiAddress): bool =
  ## Returns ``true`` if MultiAddress ``ma`` is valid.
  var header: uint64
  var vb: MultiAddress
  shcopy(vb, ma)
  while true:
    if vb.data.isEmpty():
      break
    if vb.data.readVarint(header) == -1:
      return false
    let proto = CodeAddresses.getOrDefault(MultiCodec(header))
    if proto.kind == None:
      return false
    if proto.kind in {Fixed, Length, Path}:
      if isNil(proto.coder.validateBuffer):
        return false
      if not proto.coder.validateBuffer(vb.data):
        return false
    else:
      discard
  result = true

proc init*(
    mtype: typedesc[MultiAddress], protocol: MultiCodec,
    value: openarray[byte] = []): MaResult[MultiAddress] =
  ## Initialize MultiAddress object from protocol id ``protocol`` and array
  ## of bytes ``value``.
  let proto = CodeAddresses.getOrDefault(protocol)
  if proto.kind == None:
    err("multiaddress: Protocol not found")
  else:
    var res: MultiAddress
    res.data = initVBuffer()
    res.data.writeVarint(cast[uint64](proto.mcodec))
    case proto.kind
    of Fixed, Length, Path:
      if len(value) == 0:
        err("multiaddress: Value must not be empty array")
      else:
        if proto.kind == Fixed:
          res.data.writeArray(value)
        else:
          res.data.writeSeq(value)
        res.data.finish()
        ok(res)
    of Marker:
      if len(value) != 0:
        err("multiaddress: Value must be empty for markers")
      else:
        res.data.finish()
        ok(res)
    of None:
      raiseAssert "None checked above"

proc init*(mtype: typedesc[MultiAddress], protocol: MultiCodec, value: PeerID): MaResult[MultiAddress] {.inline.} =
  ## Initialize MultiAddress object from protocol id ``protocol`` and peer id
  ## ``value``.
  init(mtype, protocol, value.data)

proc init*(mtype: typedesc[MultiAddress], protocol: MultiCodec, value: int): MaResult[MultiAddress] =
  ## Initialize MultiAddress object from protocol id ``protocol`` and integer
  ## ``value``. This procedure can be used to instantiate ``tcp``, ``udp``,
  ## ``dccp`` and ``sctp`` MultiAddresses.
  var allowed = [multiCodec("tcp"), multiCodec("udp"), multiCodec("dccp"),
                 multiCodec("sctp")]
  if protocol notin allowed:
    err("multiaddress: Incorrect protocol for integer value")
  else:
    let proto = CodeAddresses.getOrDefault(protocol)
    var res: MultiAddress
    res.data = initVBuffer()
    res.data.writeVarint(cast[uint64](proto.mcodec))
    if value < 0 or value > 65535:
      err("multiaddress: Incorrect integer value")
    else:
      res.data.writeArray(toBytesBE(cast[uint16](value)))
      res.data.finish()
      ok(res)

proc getProtocol(name: string): MAProtocol {.inline.} =
  let mc = MultiCodec.codec(name)
  if mc != InvalidMultiCodec:
    result = CodeAddresses.getOrDefault(mc)

proc init*(mtype: typedesc[MultiAddress], value: string): MaResult[MultiAddress] =
  ## Initialize MultiAddress object from string representation ``value``.
  var parts = value.trimRight('/').split('/')
  if len(parts[0]) != 0:
    err("multiaddress: Invalid MultiAddress, must start with `/`")
  else:
    var offset = 1
    var res: MultiAddress
    res.data = initVBuffer()
    while offset < len(parts):
      let part = parts[offset]
      let proto = getProtocol(part)
      if proto.kind == None:
        return err("multiaddress: Unsupported protocol '" & part & "'")
      else:
        if proto.kind in {Fixed, Length, Path}:
          if isNil(proto.coder.stringToBuffer):
            return err("multiaddress: Missing protocol '" & part & "' transcoder")

          if offset + 1 >= len(parts):
            return err("multiaddress: Missing protocol '" & part & "' argument")

        if proto.kind in {Fixed, Length}:
          res.data.write(proto.mcodec)
          let res = proto.coder.stringToBuffer(parts[offset + 1], res.data)
          if not res:
            return err("multiaddress: Error encoding `" & part & "/" &  parts[offset + 1] & "`")
          offset += 2

        elif proto.kind == Path:
          var path = "/" & (parts[(offset + 1)..^1].join("/"))
          res.data.write(proto.mcodec)
          if not proto.coder.stringToBuffer(path, res.data):
            return err("multiaddress: Error encoding `" & part & "/" &  path & "`")

          break
        elif proto.kind == Marker:
          res.data.write(proto.mcodec)
          offset += 1
    res.data.finish()
    ok(res)


proc init*(mtype: typedesc[MultiAddress], data: openarray[byte]): MaResult[MultiAddress] =
  ## Initialize MultiAddress with array of bytes ``data``.
  if len(data) == 0:
    err("multiaddress: Address could not be empty!")
  else:
    var res: MultiAddress
    res.data = initVBuffer()
    res.data.buffer.setLen(len(data))
    copyMem(addr res.data.buffer[0], unsafeAddr data[0], len(data))
    if not res.validate():
      err("multiaddress: Incorrect MultiAddress!")
    else:
      ok(res)

proc init*(mtype: typedesc[MultiAddress]): MultiAddress =
  ## Initialize empty MultiAddress.
  result.data = initVBuffer()

proc init*(mtype: typedesc[MultiAddress],
           address: ValidIpAddress,
           protocol: IpTransportProtocol,
           port: Port): MultiAddress =
  let
    familyProto = case address.family
      of IpAddressFamily.IPv4: getProtocol("ip4")
      of IpAddressFamily.IPv6: getProtocol("ip6")

    protoProto = case protocol
      of tcpProtocol: getProtocol("tcp")
      of udpProtocol: getProtocol("udp")

  var data = initVBuffer()
  data.write(familyProto.mcodec)
  var written = familyProto.coder.stringToBuffer($address, data)
  doAssert written, "Merely writing a string to a buffer should always be possible"
  data.write(protoProto.mcodec)
  written = protoProto.coder.stringToBuffer($port, data)
  doAssert written, "Merely writing a string to a buffer should always be possible"
  data.finish()

  MultiAddress(data: data)

proc init*(mtype: typedesc[MultiAddress], address: TransportAddress,
           protocol = IPPROTO_TCP): MaResult[MultiAddress] =
  ## Initialize MultiAddress using chronos.TransportAddress (IPv4/IPv6/Unix)
  ## and protocol information (UDP/TCP).
  var res: MultiAddress
  res.data = initVBuffer()
  let protoProto = case protocol
                   of IPPROTO_TCP: getProtocol("tcp")
                   of IPPROTO_UDP: getProtocol("udp")
                   else: return err("multiaddress: protocol should be either TCP or UDP")
  if address.family == AddressFamily.IPv4:
    res.data.write(getProtocol("ip4").mcodec)
    res.data.writeArray(address.address_v4)
    res.data.write(protoProto.mcodec)
    discard protoProto.coder.stringToBuffer($address.port, res.data)
  elif address.family == AddressFamily.IPv6:
    res.data.write(getProtocol("ip6").mcodec)
    res.data.writeArray(address.address_v6)
    res.data.write(protoProto.mcodec)
    discard protoProto.coder.stringToBuffer($address.port, res.data)
  elif address.family == AddressFamily.Unix:
    res.data.write(getProtocol("unix").mcodec)
    res.data.writeSeq(address.address_un)
  res.data.finish()
  ok(res)

proc isEmpty*(ma: MultiAddress): bool =
  ## Returns ``true``, if MultiAddress ``ma`` is empty or non initialized.
  result = len(ma.data) == 0

proc concat*(m1, m2: MultiAddress): MaResult[MultiAddress] =
  var res: MultiAddress
  res.data = initVBuffer()
  res.data.buffer = m1.data.buffer & m2.data.buffer
  if not res.validate():
    err("multiaddress: Incorrect MultiAddress!")
  else:
    ok(res)

proc append*(m1: var MultiAddress, m2: MultiAddress): MaResult[void] =
  m1.data.buffer &= m2.data.buffer
  if not m1.validate():
    err("multiaddress: Incorrect MultiAddress!")
  else:
    ok()

proc `&`*(m1, m2: MultiAddress): MultiAddress {.raises: [Defect, ResultError[string]].} =
  ## Concatenates two addresses ``m1`` and ``m2``, and returns result.
  ##
  ## This procedure performs validation of concatenated result and can raise
  ## exception on error.
  concat(m1, m2).tryGet()

proc `&=`*(m1: var MultiAddress, m2: MultiAddress) {.raises: [Defect, ResultError[string]].} =
  ## Concatenates two addresses ``m1`` and ``m2``.
  ##
  ## This procedure performs validation of concatenated result and can raise
  ## exception on error.
  ##
  m1.append(m2).tryGet()

proc isWire*(ma: MultiAddress): bool =
  ## Returns ``true`` if MultiAddress ``ma`` is one of:
  ## - {IP4}/{TCP, UDP}
  ## - {IP6}/{TCP, UDP}
  ## - {UNIX}/{PATH}
  var
    state = 0
  try:
    for rpart in ma.items():
      if rpart.isErr():
        return false
      let part = rpart.get()

      if state == 0:
        let rcode = part.protoCode()
        if rcode.isErr():
          return false
        let code = rcode.get()

        if code == multiCodec("ip4") or code == multiCodec("ip6"):
          inc(state)
          continue
        elif code == multiCodec("unix"):
          result = true
          break
        else:
          result = false
          break
      elif state == 1:
        let rcode = part.protoCode()
        if rcode.isErr():
          return false
        let code = rcode.get()

        if code == multiCodec("tcp") or code == multiCodec("udp"):
          inc(state)
          result = true
        else:
          result = false
          break
      else:
        result = false
        break
  except:
    result = false

proc matchPart(pat: MaPattern, protos: seq[MultiCodec]): MaPatResult =
  var empty: seq[MultiCodec]
  var pcs = protos
  if pat.operator == Or:
    for a in pat.args:
      let res = a.matchPart(pcs)
      if res.flag:
        return MaPatResult(flag: true, rem: res.rem)
    result = MaPatResult(flag: false, rem: empty)
  elif pat.operator == And:
    if len(pcs) < len(pat.args):
      return MaPatResult(flag: false, rem: empty)
    for i in 0..<len(pat.args):
      let res = pat.args[i].matchPart(pcs)
      if not res.flag:
        return MaPatResult(flag: false, rem: res.rem)
      pcs = res.rem
    result = MaPatResult(flag: true, rem: pcs)
  elif pat.operator == Eq:
    if len(pcs) == 0:
      return MaPatResult(flag: false, rem: empty)
    if pcs[0] == pat.value:
      return MaPatResult(flag: true, rem: pcs[1..^1])
    result = MaPatResult(flag: false, rem: empty)

proc match*(pat: MaPattern, address: MultiAddress): bool =
  ## Match full ``address`` using pattern ``pat`` and return ``true`` if
  ## ``address`` satisfies pattern.
  let protos = address.protocols()
  if protos.isErr():
    return false
  let res = matchPart(pat, protos.get())
  res.flag and (len(res.rem) == 0)

proc matchPartial*(pat: MaPattern, address: MultiAddress): bool =
  ## Match prefix part of ``address`` using pattern ``pat`` and return
  ## ``true`` if ``address`` starts with pattern.
  let protos = address.protocols()
  if protos.isErr():
    return false
  let res = matchPart(pat, protos.get())
  res.flag

proc `$`*(pat: MaPattern): string =
  ## Return pattern ``pat`` as string.
  var sub = newSeq[string]()
  for a in pat.args:
    sub.add($a)
  if pat.operator == And:
    result = sub.join("/")
  elif pat.operator == Or:
    result = "(" & sub.join("|") & ")"
  elif pat.operator == Eq:
    result = $pat.value