Initial allow by default trailers implementation.

Author: ioquatix

lib/protocol/http/error.rb

@@ -26,5 +26,17 @@ def initialize(key)
 			# @attribute [String] key The header key that was duplicated.
 			attr :key
 		end
+		
+		class ForbiddenTrailerError < Error
+			include BadRequest
+			
+			# @parameter key [String] The header key that was forbidden in trailers.
+			def initialize(key)
+				super("#{key} is forbidden in trailers!")
+			end
+			
+			# @attribute [String] key The header key that was forbidden in trailers.
+			attr :key
+		end
 	end
 end

lib/protocol/http/header/accept.rb

@@ -92,6 +92,10 @@ def to_s
 					join(",")
 				end
 
+				def self.trailer_forbidden?
+					false
+				end
+				
 				# Parse the `accept` header.
 				#
 				# @returns [Array(Charset)] the list of content types and their associated parameters.

lib/protocol/http/header/authorization.rb

@@ -34,6 +34,10 @@ def self.basic(username, password)
 						"Basic #{strict_base64_encoded}"
 					)
 				end
+				
+				def self.trailer_forbidden?
+					true
+				end
 			end
 		end
 	end

lib/protocol/http/header/connection.rb

@@ -50,6 +50,10 @@ def close?
 				def upgrade?
 					self.include?(UPGRADE)
 				end
+				
+				def self.trailer_forbidden?
+					true
+				end
 			end
 		end
 	end

lib/protocol/http/header/cookie.rb

@@ -23,6 +23,10 @@ def to_h
 
 					cookies.map{|cookie| [cookie.name, cookie]}.to_h
 				end
+				
+				def self.trailer_forbidden?
+					true
+				end
 			end
 
 			# The `set-cookie` header sends cookies from the server to the user agent.

lib/protocol/http/header/date.rb

@@ -25,6 +25,10 @@ def << value
 				def to_time
 					::Time.parse(self)
 				end
+				
+				def self.trailer_forbidden?
+					false
+				end
 			end
 		end
 	end

lib/protocol/http/header/etag.rb

@@ -25,6 +25,10 @@ def << value
 				def weak?
 					self.start_with?("W/")
 				end
+				
+				def self.trailer_forbidden?
+					false
+				end
 			end
 		end
 	end

lib/protocol/http/header/multiple.rb

@@ -25,6 +25,10 @@ def initialize(value)
 				def to_s
 					join("\n")
 				end
+				
+				def self.trailer_forbidden?
+					false
+				end
 			end
 		end
 	end

lib/protocol/http/header/split.rb

@@ -40,6 +40,10 @@ def to_s
 					join(",")
 				end
 
+				def self.trailer_forbidden?
+					false
+				end
+				
 				protected
 
 				def reverse_find(&block)

lib/protocol/http/header/te.rb

@@ -0,0 +1,128 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2025, by Samuel Williams.
+
+require_relative "split"
+require_relative "quoted_string"
+require_relative "../error"
+
+module Protocol
+	module HTTP
+		module Header
+			# The `te` header indicates the transfer encodings the client is willing to accept.
+			#
+			# The `te` header allows a client to indicate which transfer encodings it can handle, and in what order of preference using quality factors.
+			class TE < Split
+				ParseError = Class.new(Error)
+				
+				# Transfer encoding token pattern
+				TOKEN = /[!#$%&'*+\-.0-9A-Z^_`a-z|~]+/
+				
+				# Quality value pattern (0.0 to 1.0)
+				QVALUE = /0(\.[0-9]{0,3})?|1(\.[0]{0,3})?/
+				
+				# Pattern for parsing transfer encoding with optional quality factor
+				TRANSFER_CODING = /\A(?<name>#{TOKEN})(\s*;\s*q=(?<q>#{QVALUE}))?\z/
+				
+				# The `chunked` transfer encoding
+				CHUNKED = "chunked"
+				
+				# The `gzip` transfer encoding
+				GZIP = "gzip"
+				
+				# The `deflate` transfer encoding  
+				DEFLATE = "deflate"
+				
+				# The `compress` transfer encoding
+				COMPRESS = "compress"
+				
+				# The `identity` transfer encoding
+				IDENTITY = "identity"
+				
+				# The `trailers` pseudo-encoding indicates willingness to accept trailer fields
+				TRAILERS = "trailers"
+				
+				# A single transfer coding entry with optional quality factor
+				TransferCoding = Struct.new(:name, :q) do
+					def quality_factor
+						(q || 1.0).to_f
+					end
+					
+					def <=> other
+						other.quality_factor <=> self.quality_factor
+					end
+					
+					def to_s
+						if q && q != 1.0
+							"#{name};q=#{q}"
+						else
+							name.to_s
+						end
+					end
+				end
+				
+				# Initializes the TE header with the given value. The value is split into distinct entries and converted to lowercase for normalization.
+				#
+				# @parameter value [String | Nil] the raw header value containing transfer encodings separated by commas.
+				def initialize(value = nil)
+					super(value&.downcase)
+				end
+				
+				# Adds one or more comma-separated values to the TE header. The values are converted to lowercase for normalization.
+				#
+				# @parameter value [String] the value or values to add, separated by commas.
+				def << value
+					super(value.downcase)
+				end
+				
+				# Parse the `te` header value into a list of transfer codings with quality factors.
+				#
+				# @returns [Array(TransferCoding)] the list of transfer codings and their associated quality factors.
+				def transfer_codings
+					self.map do |value|
+						if match = value.match(TRANSFER_CODING)
+							TransferCoding.new(match[:name], match[:q])
+						else
+							raise ParseError.new("Could not parse transfer coding: #{value.inspect}")
+						end
+					end
+				end
+				
+				# @returns [Boolean] whether the `chunked` encoding is accepted.
+				def chunked?
+					self.any? {|value| value.start_with?(CHUNKED)}
+				end
+				
+				# @returns [Boolean] whether the `gzip` encoding is accepted.
+				def gzip?
+					self.any? {|value| value.start_with?(GZIP)}
+				end
+				
+				# @returns [Boolean] whether the `deflate` encoding is accepted.
+				def deflate?
+					self.any? {|value| value.start_with?(DEFLATE)}
+				end
+				
+				# @returns [Boolean] whether the `compress` encoding is accepted.
+				def compress?
+					self.any? {|value| value.start_with?(COMPRESS)}
+				end
+				
+				# @returns [Boolean] whether the `identity` encoding is accepted.
+				def identity?
+					self.any? {|value| value.start_with?(IDENTITY)}
+				end
+				
+				# @returns [Boolean] whether trailers are accepted.
+				def trailers?
+					self.any? {|value| value.start_with?(TRAILERS)}
+				end
+				
+				def self.trailer_forbidden?
+					true
+				end
+			end
+		end
+	end
+end