class DynarexLevenshtein

# File lib/dynarexlevenshtein.rb, line 11
def initialize(a,b)
  @distance = levenshtein(a,b)
end

# File lib/dynarexlevenshtein.rb, line 15
def levenshtein(a,b)

  a, b = [a, b].sort_by(&:length)
  n, m = a.length, b.length

  schema = 'table[title,string1,string2, distance]/rows(' + \
      (['line','label'] + (0..n).map{|x| "col%s" % x}).join(',') + ')'
  @to_dynarex = Dynarex.new(schema)

  @to_dynarex.summary[:title] = 'Calculates the Levenshtein distance between a and b.'
  @to_dynarex.summary[:string1] =  a
  @to_dynarex.summary[:string2] =  b

  current = (n+1).times.to_a

  top_label = ['0','',''] + a.split('')    
  label = [''] + b.split('')
  h = Hash[([:line, :label] + (0..n).map{|x| ("col%s" % x).to_sym})\
    .zip(top_label)]
  @to_dynarex.create h

  (1..m).each do |i|
    previous, current = current, [i]+[0]*n

    h = Hash[([:line, :label] + (0..n).map{|x| ("col%s" % x).to_sym}).zip([i.to_s, \
      label[i-1]] + previous)]
    @to_dynarex.create h

    (1..n).each do |j|
      delete, change, add = current[j-1], previous[j-1], previous[j]
      change += 1 if a[j-1] != b[i-1]
      current[j] = [add+1, delete+1, change].min
    end
  end

  h = Hash[([:line, :label] + (0..n).map{|x| ("col%s" % x).to_sym}).zip([(m+1).to_s, label[-1]] + current)]
  @to_dynarex.create h

  @to_dynarex.summary[:distance] = current[n].to_s
  current[n]
end