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require 'locale'
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module HTTPHeaders
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# RFC2616 Accept-Language field
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# (also used in RFC2798 'preferredLanguage' LDAP attribute type)
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class AcceptLanguage
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LANG_RANGE_Q_PATTERN="([a-z]{1,8}(-[a-z]{1,8})*|\\*)(;q=(1|0\.\d+))?"
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ACCEPT_LANG_PATTERN="#{LANG_RANGE_Q_PATTERN}([ ]*,[ ]*#{LANG_RANGE_Q_PATTERN})*"
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attr_reader :sorted_language_list
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def initialize(sorted_language_list)
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# if no preference list, then assume that all languages are equally acceptable
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@sorted_language_list = sorted_language_list.empty? ? ["*"] : sorted_language_list
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end
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def self.parse(accept_language_list)
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return nil unless accept_language_list =~ Regexp.new(ACCEPT_LANG_PATTERN, Regexp::EXTENDED | Regexp::IGNORECASE)
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list = accept_language_list.split(',').collect do |lang_range_q|
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lang_range, quality = lang_range_q.split(';')
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quality ||= 1
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LanguageRange.new(lang_range, quality)
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end
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new(list.sort)
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end
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def reduce(available_language_list)
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tag_list = available_language_list.collect do |tag|
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l_tag = Locale::Tag.parse(tag).to_rfc
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match = []
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@sorted_language_list.each do |lr|
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match << lr if lr.range == "*" or
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lr.range == l_tag.to_s or
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(lr.range + "-" == l_tag.to_s[0, lr.range.size + 1])
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end
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match.sort_by {|lr| lr.range.size }
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quality = match.empty? ? 0 : match.last.quality
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LanguageRange.new(l_tag, quality)
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end
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acceptable_tag_list = tag_list.select {|lr| lr.quality != 0 }
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acceptable_tag_list.sort
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end
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end
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class LanguageRange
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include Comparable
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attr_reader :quality
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def initialize(lang_range, quality)
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@l_lang_range = (lang_range.is_a? Locale::Tag::Simple) ? lang_range : Locale::Tag.parse(lang_range).to_rfc
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@quality = quality.to_f
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end
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def range
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@l_lang_range.to_s
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end
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def <=>(lr)
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r = self.quality <=> lr.quality
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# if quality is equal, then prefer the most specific language range
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if r == 0
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self.range.size <=> lr.range.size
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else
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r
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end
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end
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end
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end
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