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# frozen_string_literal: true
# Released under the MIT License.
# Copyright, 2016, by Matthew Kerwin.
# Copyright, 2017-2024, by Samuel Williams.
require 'strscan'
require_relative 'parse_error'
require_relative 'quoted_string'
require_relative 'sort'
module HTTP
module Accept
module Encodings
# https://tools.ietf.org/html/rfc7231#section-5.3.4
CONTENT_CODING = TOKEN
# https://tools.ietf.org/html/rfc7231#section-5.3.1
QVALUE = /0(\.[0-9]{0,3})?|1(\.[0]{0,3})?/
CODINGS = /(?<encoding>#{CONTENT_CODING})(;q=(?<q>#{QVALUE}))?/
ContentCoding = Struct.new(:encoding, :q) do
def quality_factor
(q || 1.0).to_f
end
def self.parse(scanner)
return to_enum(:parse, scanner) unless block_given?
while scanner.scan(CODINGS)
yield self.new(scanner[:encoding], scanner[:q])
# Are there more?
break unless scanner.scan(/\s*,\s*/)
end
raise ParseError.new('Could not parse entire string!') unless scanner.eos?
end
end
def self.parse(text)
scanner = StringScanner.new(text)
encodings = ContentCoding.parse(scanner)
return Sort.by_quality_factor(encodings)
end
HTTP_ACCEPT_ENCODING = 'HTTP_ACCEPT_ENCODING'.freeze
WILDCARD_CONTENT_CODING = ContentCoding.new('*', nil).freeze
IDENTITY_CONTENT_CODING = ContentCoding.new('identity', nil).freeze
# Parse the list of browser preferred content codings and return ordered by priority. If no
# `Accept-Encoding:` header is specified, the behaviour is the same as if
# `Accept-Encoding: *` was provided, and if a blank `Accept-Encoding:` header value is
# specified, the behaviour is the same as if `Accept-Encoding: identity` was provided
# (according to RFC).
def self.browser_preferred_content_codings(env)
if accept_content_codings = env[HTTP_ACCEPT_ENCODING]&.strip
if accept_content_codings.empty?
# "An Accept-Encoding header field with a combined field-value that is
# empty implies that the user agent does not want any content-coding in
# response."
return [IDENTITY_CONTENT_CODING]
else
return HTTP::Accept::Encodings.parse(accept_content_codings)
end
end
# "If no Accept-Encoding field is in the request, any content-coding
# is considered acceptable by the user agent."
return [WILDCARD_CONTENT_CODING]
end
end
end
end
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