module Excon::SOCKS5

# File lib/excon/socks5.rb, line 44
def parse_socks5_proxy(proxy_string)
  # Support formats:
  #   host:port
  #   user:pass@host:port
  #   socks5://host:port
  #   socks5://user:pass@host:port
  proxy_string = proxy_string.to_s.sub(%r{^socks5://}, '')

  user = nil
  pass = nil

  if proxy_string.include?('@')
    auth, host_port = proxy_string.split('@', 2)
    user, pass = auth.split(':', 2)
  else
    host_port = proxy_string
  end

  host, port = host_port.split(':', 2)
  port ||= '1080'

  [host, port, user, pass]
end

# File lib/excon/socks5.rb, line 69
def socks5_authenticate
  auth_methods = if @proxy_user && @proxy_pass
    [SOCKS5_NO_AUTH, SOCKS5_AUTH_USERNAME_PASSWORD]
  else
    [SOCKS5_NO_AUTH]
  end

  greeting = [SOCKS5_VERSION, auth_methods.length, *auth_methods].pack('C*')
  @socket.write(greeting)

  response = socks5_read_exactly(2)
  version, chosen_method = response.unpack('CC')

  if version != SOCKS5_VERSION
    raise Excon::Error::Socket.new(Exception.new("SOCKS5 proxy returned invalid version: #{version}"))
  end

  case chosen_method
  when SOCKS5_NO_AUTH
    # No authentication required
  when SOCKS5_AUTH_USERNAME_PASSWORD
    unless @proxy_user && @proxy_pass
      raise Excon::Error::Socket.new(Exception.new('SOCKS5 proxy requires authentication but no credentials provided'))
    end
    socks5_username_password_auth
  when SOCKS5_NO_ACCEPTABLE_AUTH
    raise Excon::Error::Socket.new(Exception.new('SOCKS5 proxy: no acceptable authentication methods'))
  else
    raise Excon::Error::Socket.new(Exception.new("SOCKS5 proxy: unsupported authentication method #{chosen_method}"))
  end
end

# File lib/excon/socks5.rb, line 122
def socks5_connect(host, port)
  if host.bytesize > MAX_HOSTNAME_LENGTH
    raise Excon::Error::Socket.new(Exception.new("SOCKS5: hostname exceeds maximum length of #{MAX_HOSTNAME_LENGTH} bytes"))
  end

  # Build CONNECT request with domain name (let proxy resolve DNS)
  request = [SOCKS5_VERSION, SOCKS5_CMD_CONNECT, SOCKS5_RESERVED].pack('CCC')
  request += [SOCKS5_ATYP_DOMAIN, host.bytesize, host].pack('CCA*')
  request += [port.to_i].pack('n')

  @socket.write(request)

  response = socks5_read_exactly(4)
  version, reply, _, atyp = response.unpack('CCCC')

  if version != SOCKS5_VERSION
    raise Excon::Error::Socket.new(Exception.new("SOCKS5 proxy returned invalid version: #{version}"))
  end

  unless reply == SOCKS5_SUCCESS
    error_msg = SOCKS5_ERRORS[reply] || "Unknown error (#{reply})"
    raise Excon::Error::Socket.new(Exception.new("SOCKS5 proxy connect failed: #{error_msg}"))
  end

  # Read and discard bound address (not needed for CONNECT)
  socks5_read_bound_address(atyp)
end

# File lib/excon/socks5.rb, line 150
def socks5_read_bound_address(atyp)
  case atyp
  when SOCKS5_ATYP_IPV4
    socks5_read_exactly(4 + 2) # 4 bytes IP + 2 bytes port
  when SOCKS5_ATYP_DOMAIN
    domain_len = socks5_read_exactly(1).unpack1('C')
    socks5_read_exactly(domain_len + 2)
  when SOCKS5_ATYP_IPV6
    socks5_read_exactly(16 + 2) # 16 bytes IP + 2 bytes port
  else
    raise Excon::Error::Socket.new(Exception.new("SOCKS5 proxy returned unknown address type: #{atyp}"))
  end
end

# File lib/excon/socks5.rb, line 165
def socks5_read_exactly(nbytes)
  data = ''.dup
  deadline = @data[:read_timeout] ? Time.now + @data[:read_timeout] : nil

  while data.bytesize < nbytes
    if deadline
      remaining = deadline - Time.now
      if remaining <= 0
        raise Excon::Error::Timeout.new('SOCKS5 read timeout')
      end
      ready = IO.select([@socket], nil, nil, remaining)
      unless ready
        raise Excon::Error::Timeout.new('SOCKS5 read timeout')
      end
    end

    chunk = @socket.read_nonblock(nbytes - data.bytesize, exception: false)
    case chunk
    when :wait_readable
      IO.select([@socket], nil, nil, deadline ? [deadline - Time.now, 0].max : nil)
    when nil, ''
      raise Excon::Error::Socket.new(Exception.new('SOCKS5 proxy connection closed unexpectedly'))
    else
      data << chunk
    end
  end
  data
end

# File lib/excon/socks5.rb, line 102
def socks5_username_password_auth
  auth_request = [
    0x01, # auth protocol version
    @proxy_user.bytesize,
    @proxy_user,
    @proxy_pass.bytesize,
    @proxy_pass
  ].pack('CCA*CA*')

  @socket.write(auth_request)

  response = socks5_read_exactly(2)
  _, status = response.unpack('CC')

  unless status == 0x00
    raise Excon::Error::Socket.new(Exception.new('SOCKS5 proxy authentication failed'))
  end
end