discourse/lib/text_sentinel.rb

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#
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# Given a string, tell us whether or not is acceptable.
#
class TextSentinel
attr_accessor :text
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def initialize(text, opts=nil)
@opts = opts || {}
@text = text.encode('UTF-8', invalid: :replace, undef: :replace, replace: '') if text.present?
end
def self.non_symbols_regexp
/[\ -\/\[-\`\:-\@\{-\~]/m
end
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def self.body_sentinel(text)
TextSentinel.new(text, min_entropy: SiteSetting.body_min_entropy)
end
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def self.title_sentinel(text)
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TextSentinel.new(text,
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min_entropy: SiteSetting.title_min_entropy,
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max_word_length: SiteSetting.max_word_length)
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end
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# Entropy is a number of how many unique characters the string needs.
def entropy
return 0 if @text.blank?
@entropy ||= @text.strip.each_char.to_a.uniq.size
end
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def valid?
# Blank strings are not valid
return false if @text.blank? || @text.strip.blank?
# Entropy check if required
return false if @opts[:min_entropy].present? && (entropy < @opts[:min_entropy])
# We don't have a comprehensive list of symbols, but this will eliminate some noise
non_symbols = @text.gsub(TextSentinel.non_symbols_regexp, '').size
return false if non_symbols == 0
# Don't allow super long strings without spaces
return false if @opts[:max_word_length] && @text =~ /\w{#{@opts[:max_word_length]},}(\s|$)/
# We don't allow all upper case content in english
return false if (@text =~ /[A-Z]+/) && (@text == @text.upcase)
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# It is valid
true
end
end