Class: TextAlignment::AnchorFinder

Inherits:
Object
  • Object
show all
Defined in:
lib/text_alignment/anchor_finder.rb

Instance Method Summary collapse

Constructor Details

#initialize(source_str, target_str, _size_ngram = nil, _size_window = nil) ⇒ AnchorFinder

Returns a new instance of AnchorFinder.



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# File 'lib/text_alignment/anchor_finder.rb', line 12

def initialize(source_str, target_str, _size_ngram = nil, _size_window = nil)
  @size_ngram  = _size_ngram  || TextAlignment::SIZE_NGRAM
  @size_window = _size_window || TextAlignment::SIZE_WINDOW

  @reverse = (target_str.length < source_str.length)

  @s1, @s2 = if @reverse
    [target_str.downcase, source_str.downcase]
  else
    [source_str.downcase, target_str.downcase]
  end

  # current position in s1
  @beg_s1 = 0
  @end_s1_prev = 0
  @end_s2_prev = 0
end

Instance Method Details

#get_next_anchor ⇒ Object 



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# File 'lib/text_alignment/anchor_finder.rb', line 30

def get_next_anchor
  # find the position of an anchor ngram in s1 and s2
  while @beg_s1 < (@s1.length - @size_ngram)
    anchor = @s1[@beg_s1, @size_ngram]

    # search_position = 0
    search_position = @end_s2_prev
    while @beg_s2 = @s2.index(anchor, search_position)
      # if both the begining points are sufficiantly close to the end points of the last match
      break if @end_s1_prev && (@beg_s1 - @end_s1_prev < 5) && (@beg_s2 >= @end_s2_prev) && (@beg_s2 - @end_s2_prev < 5)

      left_window_s1, left_window_s2 = get_left_windows
      break if left_window_s1 && (text_similarity(left_window_s1, left_window_s2) > TextAlignment::TEXT_SIMILARITY_TRESHOLD)

      right_window_s1, right_window_s2 = get_right_windows
      break if right_window_s2 && (text_similarity(right_window_s1, right_window_s2) > TextAlignment::TEXT_SIMILARITY_TRESHOLD)

      search_position = @beg_s2 + 1
    end

    break unless @beg_s2.nil?

    @beg_s1 += 1
  end

  return nil if @beg_s1 >= (@s1.length - @size_ngram)

  # extend the block
  b1 = @beg_s1
  b2 = @beg_s2
  while b1 >= @end_s1_prev && b2 > -1 && @s1[b1] == @s2[b2]
    b1 -= 1; b2 -= 1
  end
  b1 += 1; b2 += 1

  e1 = @beg_s1 + @size_ngram
  e2 = @beg_s2 + @size_ngram
  while @s1[e1] && @s1[e1] == @s2[e2]
    e1 += 1; e2 += 1
  end

  @end_s1_prev = e1
  @end_s2_prev = e2
  @beg_s1 = e1

  if @reverse
    {source:{begin:b2 , end:e2}, target:{begin:b1, end:e1}}
  else
    {source:{begin:b1 , end:e1}, target:{begin:b2, end:e2}}
  end
end