Add support for accept-language header.

Author: ioquatix

lib/protocol/http/header/accept_language.rb

@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2020-2023, by Samuel Williams.
+# Copyright, 2023, by Thomas Morgan.
+
+require_relative "split"
+require_relative "quoted_string"
+require_relative "../error"
+
+module Protocol
+	module HTTP
+		module Header
+			# The `accept-language` header represents a list of languages that the client can accept.
+			class AcceptLanguage < Split
+				ParseError = Class.new(Error)
+				
+				# https://tools.ietf.org/html/rfc3066#section-2.1
+				NAME = /\*|[A-Z]{1,8}(-[A-Z0-9]{1,8})*/i
+				
+				# https://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.9
+				QVALUE = /0(\.[0-9]{0,6})?|1(\.[0]{0,6})?/
+				
+				# https://greenbytes.de/tech/webdav/rfc7231.html#quality.values
+				LANGUAGE = /\A(?<name>#{NAME})(\s*;\s*q=(?<q>#{QVALUE}))?\z/
+				
+				Language = Struct.new(:name, :q) do
+					def quality_factor
+						(q || 1.0).to_f
+					end
+					
+					def <=> other
+						other.quality_factor <=> self.quality_factor
+					end
+				end
+				
+				# Parse the `accept-language` header value into a list of languages.
+				#
+				# @returns [Array(Charset)] the list of character sets and their associated quality factors.
+				def languages
+					self.map do |value|
+						if match = value.match(LANGUAGE)
+							Language.new(match[:name], match[:q])
+						else
+							raise ParseError.new("Could not parse language: #{value.inspect}")
+						end
+					end
+				end
+			end
+		end
+	end
+end

lib/protocol/http/headers.rb

@@ -5,6 +5,7 @@
 
 require_relative "header/accept_charset"
 require_relative "header/accept_encoding"
+require_relative "header/accept_language"
 require_relative "header/split"
 require_relative "header/multiple"
 require_relative "header/cookie"
@@ -282,6 +283,7 @@ def []= key, value
 
 				"accept-charset" => Header::AcceptCharset,
 				"accept-encoding" => Header::AcceptEncoding,
+				"accept-language" => Header::AcceptLanguage,
 			}.tap{|hash| hash.default = Split}
 
 			# Delete all header values for the given key, and return the merged value.

test/protocol/http/header/accept_encoding.rb

@@ -8,8 +8,8 @@
 
 describe Protocol::HTTP::Header::AcceptEncoding::Encoding do
 	it "should have default quality_factor of 1.0" do
-		charset = subject.new('utf-8', nil)
-		expect(charset.quality_factor).to be == 1.0
+		encoding = subject.new('utf-8', nil)
+		expect(encoding.quality_factor).to be == 1.0
 	end
 end
 

test/protocol/http/header/accept_language.rb

@@ -0,0 +1,96 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2016, by Matthew Kerwin.
+# Copyright, 2017-2024, by Samuel Williams.
+
+require 'protocol/http/header/accept_language'
+	
+describe Protocol::HTTP::Header::AcceptLanguage::Language do
+	it "should have default quality_factor of 1.0" do
+		language = subject.new('utf-8', nil)
+		expect(language.quality_factor).to be == 1.0
+	end
+end
+
+describe Protocol::HTTP::Header::AcceptLanguage do
+	let(:header) {subject.new(description)}
+	let(:languages) {header.languages.sort}
+	
+	with "da, en-gb;q=0.5, en;q=0.25" do
+		it "can parse languages" do
+			expect(header.length).to be == 3
+			
+			expect(languages[0].name).to be == "da"
+			expect(languages[0].quality_factor).to be == 1.0
+			
+			expect(languages[1].name).to be == "en-gb"
+			expect(languages[1].quality_factor).to be == 0.5
+			
+			expect(languages[2].name).to be == "en"
+			expect(languages[2].quality_factor).to be == 0.25
+		end
+	end
+	
+	with "en-gb;q=0.25, en;q=0.5, en-us" do
+		it "should order based on quality factor" do
+			expect(languages.collect(&:name)).to be == %w{en-us en en-gb}
+		end
+	end
+	
+	with "en-us,en-gb;q=0.8,en;q=0.6,es-419" do
+		it "should order based on quality factor" do
+			expect(languages.collect(&:name)).to be == %w{en-us es-419 en-gb en}
+		end
+	end
+	
+	with "*;q=0" do
+		it "should accept wildcard language" do
+			expect(languages[0].name).to be == "*"
+			expect(languages[0].quality_factor).to be == 0
+		end
+	end
+	
+	with "en, de;q=0.5, jp;q=0.5" do
+		it "should preserve relative order" do
+			expect(languages[0].name).to be == "en"
+			expect(languages[1].name).to be == "de"
+			expect(languages[2].name).to be == "jp"
+		end
+	end
+	
+	with "de, en-US; q=0.7, en ; q=0.3" do
+		it "should parse with optional whitespace" do
+			expect(languages[0].name).to be == "de"
+			expect(languages[1].name).to be == "en-US"
+			expect(languages[2].name).to be == "en"
+		end
+	end
+	
+	with "en;q=0.123456" do
+		it "accepts quality factors with up to 6 decimal places" do
+			expect(languages[0].name).to be == "en"
+			expect(languages[0].quality_factor).to be == 0.123456
+		end
+	end
+	
+	it "should not accept invalid input" do
+		bad_values = [
+			# Invalid quality factor:
+			"en;f=1",
+			
+			# Invalid parameter:
+			"de;fr",
+			
+			# Invalid use of separator:
+			";",
+			
+			# Empty (we ignore this one):
+			# ","
+		]
+		
+		bad_values.each do |value|
+			expect{subject.new(value).languages}.to raise_exception(subject::ParseError)
+		end
+	end
+end