Module: Eco::Data::FuzzyMatch::Pairing

Included in:
ClassMethods
Defined in:
lib/eco/data/fuzzy_match/pairing.rb

Instance Method Summary collapse

Instance Method Details

#paired_words(str1, str2, normalized: false) {|needle, item| ... } ⇒ Hash

Pair words using some algorithm. It does the following:

  1. It splits both strings into words.
  2. Pairs all words by using block to score the best match.
  3. Gives 0 score to those words of str2 that lost their pair (a word of str1 cannot be paired twice).
  4. Merges the Score of all the paired words of str2 against their str1 word pair.

Parameters:

  • str1 (String) —

    the string of reference.

  • str2 (String) —

    one of the haystack items.

Yields:

  • (needle, item) —

    offers a comparison algorithm between two strings.

Yield Parameters:

  • needle (String) —

    the string of reference.

  • item (String) —

    one of the haystack items.

Yield Returns:

Returns:

  • (Hash) —

    where keys are the words of str1 and their values a pair array of pair and Score



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# File 'lib/eco/data/fuzzy_match/pairing.rb', line 20

def paired_words(str1, str2, normalized: false)
  str1, str2 = normalize_string([str1, str2]) unless normalized
  return {nil => [nil, Score.new(0, 0)]} if !str2 || !str1
  return {str1 => [nil, Score.new(0, 0)]} if str1.length < 2 || str1.length < 2

  needles    = get_words(str1, normalized: true)
  haystack   = get_words(str2, normalized: true)

  ranking    = {}
  faceted    = needles.each_with_object({}) do |needle, faceted|
    faceted[needle] = haystack.map do |item|
      {
        pair:  item,
        score: yield(needle, item)
      }.tap do |result|
        ranking[item] ||= []
        if result[:score].ratio > 0.05
          ranking[item] << ({needle: needle, score: result[:score]})
        end
      end
    end.sort_by do |result|
      result[:score].ratio
    end.reverse
  end

  paired = {}
  #scores = {}
  ranking.each do |item, results|
    sorted = results.reject do |result|
      paired.key?(result[:needle])
    end.sort_by do |result|
      result[:score].ratio
    end.reverse
    if result = sorted.shift
      unless result[:score].is_a?(Eco::Data::FuzzyMatch::Score)
        raise "Parining ('#{str1}' vs '#{str2}') -> Something got sour with needle '#{result[:needle]}' and item #{item}"
      end
      paired[result[:needle]] = {
        pair:  item,
        score: result[:score]
      }
    end
  end

  pending_items   = haystack - paired.values
  faceted.reject do |needle, results|
    paired.key?(needle)
  end.each do |needle, results|
    results.select! do |result|
      pending_items.include?(result[:pair]) && result[:score].ratio > 0.05
    end
    if result = results.shift
      unless result[:score].is_a?(Eco::Data::FuzzyMatch::Score)
        raise "Parining ('#{str1}' vs '#{str2}') -> Something got sour with needle '#{needle}' and item #{result[:pair]}"
      end
      paired[needle] = result
      pending_items.delete(result[:pair])
    end
  end

  pending_needles = needles - paired.keys
  pending_needles.each do |needle|
    paired[needle] = {
      pair:  nil,
      score: Score.new(0, needle.length)
    }
  end
  paired.each_with_object({}) do |(needle, data), out|
    out[needle] = data.values_at(:pair, :score)
  end
end