Redmine/lib/redmine/string_array_diff/diffable.rb

# frozen_string_literal: true

=begin
  = Diff
  (({diff.rb})) - computes the differences between two arrays or
  strings. Copyright (C) 2001 Lars Christensen

  == Synopsis

      diff = Diff.new(a, b)
      b = a.patch(diff)

  == Class Diff
  === Class Methods
  --- Diff.new(a, b)
  --- a.diff(b)
        Creates a Diff object which represent the differences between
        ((|a|)) and ((|b|)). ((|a|)) and ((|b|)) can be either be arrays
        of any objects, strings, or object of any class that include
        module ((|Diffable|))

  == Module Diffable
  The module ((|Diffable|)) is intended to be included in any class for
  which differences are to be computed. Diffable is included into String
  and Array when (({diff.rb})) is (({require}))'d.

  Classes including Diffable should implement (({[]})) to get element at
  integer indices, (({<<})) to append elements to the object and
  (({ClassName#new})) should accept 0 arguments to create a new empty
  object.

  === Instance Methods
  --- Diffable#patch(diff)
        Applies the differences from ((|diff|)) to the object ((|obj|))
        and return the result. ((|obj|)) is not changed. ((|obj|)) and
        can be either an array or a string, but must match the object
        from which the ((|diff|)) was created.
=end

module Redmine
  module StringArrayDiff
    module Diffable
      def diff(b)
        Redmine::StringArrayDiff::Diff.new(self, b)
      end

      # Create a hash that maps elements of the array to arrays of indices
      # where the elements are found.

      def reverse_hash(range = (0...self.length))
        revmap = {}
        range.each { |i|
          elem = self[i]
          if revmap.has_key? elem
            revmap[elem].push i
          else
            revmap[elem] = [i]
          end
        }
        return revmap
      end

      def replacenextlarger(value, high = nil)
        high ||= self.length
        if self.empty? || value > self[-1]
          push value
          return high
        end
        # binary search for replacement point
        low = 0
        while low < high
          index = (high+low)/2
          found = self[index]
          return nil if value == found
          if value > found
            low = index + 1
          else
            high = index
          end
        end

        self[low] = value
        #  $stderr << "replace #{value} : 0/#{low}/#{init_high} (#{steps} steps) (#{init_high-low} off )\n"
        #  $stderr.puts self.inspect
        # gets
        # p length - low
        return low
      end

      def patch(diff)
        newary = nil
        if diff.difftype == String
          newary = diff.difftype.new('')
        else
          newary = diff.difftype.new
        end
        ai = 0
        bi = 0
        diff.diffs.each { |d|
          d.each { |mod|
            case mod[0]
            when '-'
              while ai < mod[1]
                newary << self[ai]
                ai += 1
                bi += 1
              end
              ai += 1
            when '+'
              while bi < mod[1]
                newary << self[ai]
                ai += 1
                bi += 1
              end
              newary << mod[2]
              bi += 1
            else
              raise "Unknown diff action"
            end
          }
        }
        while ai < self.length
          newary << self[ai]
          ai += 1
          bi += 1
        end
        return newary
      end
    end
  end
end