class WebSocket::Driver::Hybi

def self.generate_accept(key)
  Base64.strict_encode64(Digest::SHA1.digest(key + GUID))
end

def add_extension(extension)
  @extensions.add(extension)
  true
end

def binary(message)
  frame(message, :binary)
end

def check_frame_length
  length = @message ? @message.data.bytesize : 0
  if length + @frame.length > @max_length
    fail(:too_large, 'WebSocket frame length too large')
    false
  else
    true
  end
end

def close(reason = nil, code = nil)
  reason ||= ''
  code   ||= ERRORS[:normal_closure]
  if @ready_state <= 0
    @ready_state = 3
    emit(:close, CloseEvent.new(code, reason))
    true
  elsif @ready_state == 1
    frame(reason, :close, code)
    @ready_state = 2
    true
  else
    false
  end
end

def emit_frame(buffer)
  frame    = @frame
  opcode   = frame.opcode
  payload  = frame.payload = Mask.mask(buffer, @frame.masking_key)
  bytesize = payload.bytesize
  @frame = nil
  case opcode
    when OPCODES[:continuation] then
      return fail(:protocol_error, 'Received unexpected continuation frame') unless @message
      @message << frame
    when OPCODES[:text], OPCODES[:binary] then
      @message = Message.new
      @message << frame
    when OPCODES[:close] then
      code, reason = payload.unpack('S>a*') if bytesize >= 2
      reason = Driver.encode(reason || '', Encoding::UTF_8)
      unless (bytesize == 0) or
             (code && code >= MIN_RESERVED_ERROR && code <= MAX_RESERVED_ERROR) or
             ERROR_CODES.include?(code)
        code = ERRORS[:protocol_error]
      end
      if bytesize > 125 or !reason.valid_encoding?
        code = ERRORS[:protocol_error]
      end
      shutdown(code || DEFAULT_ERROR_CODE, reason || '')
    when OPCODES[:ping] then
      frame(payload, :pong)
      emit(:ping, PingEvent.new(payload))
    when OPCODES[:pong] then
      message = Driver.encode(payload, Encoding::UTF_8)
      callback = @ping_callbacks[message]
      @ping_callbacks.delete(message)
      callback.call if callback
      emit(:pong, PongEvent.new(payload))
  end
  emit_message if frame.final and MESSAGE_OPCODES.include?(opcode)
end

def emit_message
  message  = @extensions.process_incoming_message(@message)
  @message = nil
  payload = message.data
  case message.opcode
    when OPCODES[:text] then
      payload = Driver.encode(payload, Encoding::UTF_8)
      payload = nil unless payload.valid_encoding?
    when OPCODES[:binary]
      payload = payload.bytes.to_a
  end
  if payload
    emit(:message, MessageEvent.new(payload))
  else
    fail(:encoding_error, 'Could not decode a text frame as UTF-8')
  end
rescue ::WebSocket::Extensions::ExtensionError => error
  fail(:extension_error, error.message)
end

def fail(type, message)
  return if @ready_state > 1
  shutdown(ERRORS[type], message, true)
end

def frame(buffer, type = nil, code = nil)
  return queue([buffer, type, code]) if @ready_state <= 0
  return false unless @ready_state == 1
  message = Message.new
  frame   = Frame.new
  message.rsv1   = message.rsv2 = message.rsv3 = false
  message.opcode = OPCODES[type || (String === buffer ? :text : :binary)]
  payload = Driver.encode(buffer)
  payload = [code, payload].pack('S>a*') if code
  message.data = payload
  if MESSAGE_OPCODES.include?(message.opcode)
    message = @extensions.process_outgoing_message(message)
  end
  frame.final       = true
  frame.rsv1        = message.rsv1
  frame.rsv2        = message.rsv2
  frame.rsv3        = message.rsv3
  frame.opcode      = message.opcode
  frame.masked      = !!@masking
  frame.masking_key = SecureRandom.random_bytes(4) if frame.masked
  frame.length      = message.data.bytesize
  frame.payload     = message.data
  send_frame(frame)
  true
rescue ::WebSocket::Extensions::ExtensionError => error
  fail(:extension_error, error.message)
end

def handshake_response
  sec_key = @socket.env['HTTP_SEC_WEBSOCKET_KEY']
  version = @socket.env['HTTP_SEC_WEBSOCKET_VERSION']
  unless version == VERSION
    raise ProtocolError.new("Unsupported WebSocket version: #{ VERSION }")
  end
  unless sec_key
    raise ProtocolError.new('Missing handshake request header: Sec-WebSocket-Key')
  end
  @headers['Upgrade']              = 'websocket'
  @headers['Connection']           = 'Upgrade'
  @headers['Sec-WebSocket-Accept'] = Hybi.generate_accept(sec_key)
  @headers['Sec-WebSocket-Protocol'] = @protocol if @protocol
  extensions = @extensions.generate_response(@socket.env['HTTP_SEC_WEBSOCKET_EXTENSIONS'])
  @headers['Sec-WebSocket-Extensions'] = extensions if extensions
  start   = 'HTTP/1.1 101 Switching Protocols'
  headers = [start, @headers.to_s, '']
  headers.join("\r\n")
end

def initialize(socket, options = {})
  super
  @extensions      = ::WebSocket::Extensions.new
  @stage           = 0
  @masking         = options[:masking]
  @protocols       = options[:protocols] || []
  @protocols       = @protocols.strip.split(/ *, */) if String === @protocols
  @require_masking = options[:require_masking]
  @ping_callbacks  = {}
  @frame = @message = nil
  return unless @socket.respond_to?(:env)
  if protos = @socket.env['HTTP_SEC_WEBSOCKET_PROTOCOL']
    protos = protos.split(/ *, */) if String === protos
    @protocol = protos.find { |p| @protocols.include?(p) }
  else
    @protocol = nil
  end
end

def parse(chunk)
  @reader.put(chunk)
  buffer = true
  while buffer
    case @stage
      when 0 then
        buffer = @reader.read(1)
        parse_opcode(buffer.getbyte(0)) if buffer
      when 1 then
        buffer = @reader.read(1)
        parse_length(buffer.getbyte(0)) if buffer
      when 2 then
        buffer = @reader.read(@frame.length_bytes)
        parse_extended_length(buffer) if buffer
      when 3 then
        buffer = @reader.read(4)
        if buffer
          @stage = 4
          @frame.masking_key = buffer
        end
      when 4 then
        buffer = @reader.read(@frame.length)
        if buffer
          @stage = 0
          emit_frame(buffer)
        end
      else
        buffer = nil
    end
  end
end

def parse_extended_length(buffer)
  @frame.length = buffer.unpack(PACK_FORMATS[buffer.bytesize]).first
  @stage = @frame.masked ? 3 : 4
  unless MESSAGE_OPCODES.include?(@frame.opcode) or @frame.length <= 125
    return fail(:protocol_error, "Received control frame having too long payload: #{ @frame.length }")
  end
  return unless check_frame_length
end

def parse_length(octet)
  @frame.masked = (octet & MASK) == MASK
  @frame.length = (octet & LENGTH)
  if @frame.length >= 0 and @frame.length <= 125
    @stage = @frame.masked ? 3 : 4
    return unless check_frame_length
  else
    @stage = 2
    @frame.length_bytes = (@frame.length == 126) ? 2 : 8
  end
  if @require_masking and not @frame.masked
    return fail(:unacceptable, 'Received unmasked frame but masking is required')
  end
end

def parse_opcode(octet)
  rsvs = [RSV1, RSV2, RSV3].map { |rsv| (octet & rsv) == rsv }
  @frame = Frame.new
  @frame.final  = (octet & FIN) == FIN
  @frame.rsv1   = rsvs[0]
  @frame.rsv2   = rsvs[1]
  @frame.rsv3   = rsvs[2]
  @frame.opcode = (octet & OPCODE)
  @stage = 1
  unless @extensions.valid_frame_rsv?(@frame)
    return fail(:protocol_error,
        "One or more reserved bits are on: reserved1 = #{ @frame.rsv1 ? 1 : 0 }" +
        ", reserved2 = #{ @frame.rsv2 ? 1 : 0 }" +
        ", reserved3 = #{ @frame.rsv3 ? 1 : 0 }")
  end
  unless OPCODES.values.include?(@frame.opcode)
    return fail(:protocol_error, "Unrecognized frame opcode: #{ @frame.opcode }")
  end
  unless MESSAGE_OPCODES.include?(@frame.opcode) or @frame.final
    return fail(:protocol_error, "Received fragmented control frame: opcode = #{ @frame.opcode }")
  end
  if @message and OPENING_OPCODES.include?(@frame.opcode)
    return fail(:protocol_error, 'Received new data frame but previous continuous frame is unfinished')
  end
end

def ping(message = '', &callback)
  @ping_callbacks[message] = callback if callback
  frame(message, :ping)
end

def pong(message = '')
  frame(message, :pong)
end

def send_frame(frame)
  length = frame.length
  values = []
  format = 'C2'
  masked = frame.masked ? MASK : 0
  values[0] = (frame.final ? FIN : 0) |
              (frame.rsv1 ? RSV1 : 0) |
              (frame.rsv2 ? RSV2 : 0) |
              (frame.rsv3 ? RSV3 : 0) |
              frame.opcode
  if length <= 125
    values[1] = masked | length
  elsif length <= 65535
    values[1] = masked | 126
    values[2] = length
    format << 'S>'
  else
    values[1] = masked | 127
    values[2] = length
    format << 'Q>'
  end
  if frame.masked
    values << frame.masking_key
    values << Mask.mask(frame.payload, frame.masking_key)
    format << 'a4a*'
  else
    values << frame.payload
    format << 'a*'
  end
  @socket.write(values.pack(format))
end

def shutdown(code, reason, error = false)
  @frame = @message = nil
  @stage = 5
  @extensions.close
  frame(reason, :close, code) if @ready_state < 2
  @ready_state = 3
  emit(:error, ProtocolError.new(reason)) if error
  emit(:close, CloseEvent.new(code, reason))
end

def version
  "hybi-#{ VERSION }"
end