#
#                            Fuzzy String Match
#
#   Copyright 2010-2011 Kiyoka Nishiyama
#
#   Licensed under the Apache License, Version 2.0 (the "License");
#   you may not use this file except in compliance with the License.
#   You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#   Unless required by applicable law or agreed to in writing, software
#   distributed under the License is distributed on an "AS IS" BASIS,
#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#   See the License for the specific language governing permissions and
#   limitations under the License.
#
module FuzzyStringMatch
  class JaroWinklerPure
    THRESHOLD = 0.7

    def pure?
      true
    end

    def getDistance( s1, s2 )
      a1 = s1.split( // )
      a2 = s2.split( // )

      if s1.size > s2.size
        (max,min) = a1,a2
      else
        (max,min) = a2,a1
      end

      range = [ (max.size / 2 - 1), 0 ].max
      indexes = Array.new( min.size, -1 )
      flags   = Array.new( max.size, false )

      matches = 0;
      (0 ... min.size).each { |mi|
        c1 = min[mi]
        xi = [mi - range, 0].max
        xn = [mi + range + 1, max.size].min

        (xi ... xn).each { |i|
          if (not flags[i]) && ( c1 == max[i] )
            indexes[mi] = i
            flags[i] = true
            matches += 1
            break
          end
        }
      }

      ms1 = Array.new( matches, nil )
      ms2 = Array.new( matches, nil )

      si = 0
      (0 ... min.size).each { |i|
        if (indexes[i] != -1)
          ms1[si] = min[i]
          si += 1
        end
      }

      si = 0
      (0 ... max.size).each { |i|
        if flags[i]
          ms2[si] = max[i]
          si += 1
        end
      }

      transpositions = 0
      (0 ... ms1.size).each { |mi|
        if ms1[mi] != ms2[mi]
          transpositions += 1
        end
      }

      prefix = 0
      (0 ... min.size).each { |mi|
        if s1[mi] == s2[mi]
          prefix += 1
        else
          break
        end
      }

      if 0 == matches
        0.0
      else
        m = matches.to_f
        t = (transpositions/ 2)
        j = ((m / s1.size) + (m / s2.size) + ((m - t) / m)) / 3.0;
        return j < THRESHOLD ? j : j + [0.1, 1.0 / max.size].min * prefix * (1 - j)
      end
    end
  end
end
