class WebSocket::Extensions

def activate(header)
  responses = Parser.parse_header(header)
  @sessions = []
  responses.each_offer do |name, params|
    unless record = @index[name]
      raise ExtensionError, %Q{Server sent am extension response for unknown extension "#{ name } }
    end
    ext, session = *record
    if reserved = reserved?(ext)
      raise ExtensionError, %Q{Server sent two extension responses that use the RSV#{ reserved[0] }} +
                            %Q{bit: "#{ reserved[1] }" and "#{ ext.name }"}
    end
    unless session.activate(params) == true
      raise ExtensionError, %Q{Server send unacceptable extension parameters: #{ Parser.serialize_params(name, params) }}
    end
    reserve(ext)
    @sessions.push(record)
  end
end

def add(ext)
  unless ext.respond_to?(:name) and ext.name.is_a?(String)
    raise TypeError, 'extension.name must be a string'
  end
  unless ext.respond_to?(:type) and ext.type == 'permessage'
    raise TypeError, 'extension.type must be "permessage"'
  end
  unless ext.respond_to?(:rsv1) and [true, false].include?(ext.rsv1)
    raise TypeError, 'extension.rsv1 must be true or false'
  end
  unless ext.respond_to?(:rsv2) and [true, false].include?(ext.rsv2)
    raise TypeError, 'extension.rsv2 must be true or false'
  end
  unless ext.respond_to?(:rsv3) and [true, false].include?(ext.rsv3)
    raise TypeError, 'extension.rsv3 must be true or false'
  end
  if @by_name.has_key?(ext.name)
    raise TypeError, %Q{An extension with name "#{ ext.name }" is already registered}
  end
  @by_name[ext.name] = ext
  @in_order.push(ext)
end

def close
  return unless @sessions
  @sessions.each do |ext, session|
    session.close rescue nil
  end
end

def generate_offer
  sessions = []
  offer    = []
  index    = {}
  @in_order.each do |ext|
    session = ext.create_client_session
    next unless session
    record = [ext, session]
    sessions.push(record)
    index[ext.name] = record
    offers = session.generate_offer
    offers = offers ? [offers].flatten : []
    offers.each do |off|
      offer.push(Parser.serialize_params(ext.name, off))
    end
  end
  @sessions = sessions
  @index    = index
  offer.size > 0 ? offer.join(', ') : nil
end

def generate_response(header)
  sessions = []
  response = []
  offers   = Parser.parse_header(header)
  @in_order.each do |ext|
    offer = offers.by_name(ext.name)
    next if offer.empty? or reserved?(ext)
    next unless session = ext.create_server_session(offer)
    reserve(ext)
    sessions.push([ext, session])
    response.push(Parser.serialize_params(ext.name, session.generate_response))
  end
  @sessions = sessions
  response.size > 0 ? response.join(', ') : nil
end

def initialize
  @rsv1 = @rsv2 = @rsv3 = nil
  @by_name  = {}
  @in_order = []
  @sessions = []
  @index    = {}
end

def process_incoming_message(message)
  @sessions.reverse.inject(message) do |msg, (ext, session)|
    begin
      session.process_incoming_message(msg)
    rescue => error
      raise ExtensionError, [ext.name, error.message].join(': ')
    end
  end
end

def process_outgoing_message(message)
  @sessions.inject(message) do |msg, (ext, session)|
    begin
      session.process_outgoing_message(msg)
    rescue => error
      raise ExtensionError, [ext.name, error.message].join(': ')
    end
  end
end

def reserve(ext)
  @rsv1 ||= ext.rsv1 && ext.name
  @rsv2 ||= ext.rsv2 && ext.name
  @rsv3 ||= ext.rsv3 && ext.name
end

def reserved?(ext)
  return [1, @rsv1] if @rsv1 and ext.rsv1
  return [2, @rsv2] if @rsv2 and ext.rsv2
  return [3, @rsv3] if @rsv3 and ext.rsv3
  false
end

def valid_frame_rsv(frame)
  allowed = { :rsv1 => false, :rsv2 => false, :rsv3 => false }
  if MESSAGE_OPCODES.include?(frame.opcode)
    @sessions.each do |ext, session|
      allowed[:rsv1] ||= ext.rsv1
      allowed[:rsv2] ||= ext.rsv2
      allowed[:rsv3] ||= ext.rsv3
    end
  end
  (allowed[:rsv1] || !frame.rsv1) &&
  (allowed[:rsv2] || !frame.rsv2) &&
  (allowed[:rsv3] || !frame.rsv3)
end