discourse/lib/text_sentinel.rb

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# Whe use ActiveSupport mb_chars from here to properly support non ascii downcase
# TODO remove when ruby 2.4 lands
require 'active_support/core_ext/string/multibyte'
#
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# Given a string, tell us whether or not is acceptable.
#
class TextSentinel
attr_accessor :text
ENTROPY_SCALE ||= 0.7
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def initialize(text, opts = nil)
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@opts = opts || {}
@text = text.to_s.encode('UTF-8', invalid: :replace, undef: :replace, replace: '')
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end
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def self.body_sentinel(text, opts = {})
entropy = SiteSetting.body_min_entropy
if opts[:private_message]
scale_entropy = SiteSetting.min_private_message_post_length.to_f / SiteSetting.min_post_length.to_f
entropy = (entropy * scale_entropy).to_i
entropy = (SiteSetting.min_private_message_post_length.to_f * ENTROPY_SCALE).to_i if entropy > SiteSetting.min_private_message_post_length
else
entropy = (SiteSetting.min_post_length.to_f * ENTROPY_SCALE).to_i if entropy > SiteSetting.min_post_length
end
TextSentinel.new(text, min_entropy: entropy)
end
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def self.title_sentinel(text)
entropy = if SiteSetting.min_topic_title_length > SiteSetting.title_min_entropy
SiteSetting.title_min_entropy
else
(SiteSetting.min_topic_title_length.to_f * ENTROPY_SCALE).to_i
end
TextSentinel.new(text, min_entropy: entropy, max_word_length: SiteSetting.title_max_word_length)
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end
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# Entropy is a number of how many unique characters the string needs.
# Non-ASCII characters are weighted heavier since they contain more "information"
def entropy
chars = @text.to_s.strip.split('')
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@entropy ||= chars.pack('M*' * chars.size).gsub("\n", '').split('=').uniq.size
end
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def valid?
@text.present? &&
seems_meaningful? &&
seems_pronounceable? &&
seems_unpretentious? &&
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seems_quiet?
end
private
def symbols_regex
/[\ -\/\[-\`\:-\@\{-\~]/m
end
def seems_meaningful?
# Minimum entropy if entropy check required
@opts[:min_entropy].blank? || (entropy >= @opts[:min_entropy])
end
def seems_pronounceable?
# At least some non-symbol characters
# (We don't have a comprehensive list of symbols, but this will eliminate some noise)
@text.gsub(symbols_regex, '').size > 0
end
def seems_unpretentious?
# Don't allow super long words if there is a word length maximum
@opts[:max_word_length].blank? || @text.split(/\s|\/|-|\.|:/).map(&:size).max <= @opts[:max_word_length]
end
def seems_quiet?
# We don't allow all upper case content
SiteSetting.allow_uppercase_posts || @text == @text.mb_chars.downcase.to_s || @text != @text.mb_chars.upcase.to_s
end
end