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# 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. AKA `accept-transfer-encoding`. How we ended up with `te` instead of `accept-transfer-encoding` is a mystery lost to time.
#
# 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
# Whether this header is acceptable in HTTP trailers.
# TE headers negotiate transfer encodings and must not appear in trailers.
# @returns [Boolean] `false`, as TE headers are hop-by-hop and control message framing.
def self.trailer?
false
end
end
end
end
end
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