1 files changed, 195 insertions, 0 deletions
diff --git a/lib/redmine/string_array_diff/diff.rb b/lib/redmine/string_array_diff/diff.rb
new file mode 100644
index 000000000..4b54fb740
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+++ b/lib/redmine/string_array_diff/diff.rb
@@ -0,0 +1,195 @@
+# 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
+    class Diff
+      VERSION = 0.3
+
+      def Diff.lcs(a, b)
+        astart = 0
+        bstart = 0
+        afinish = a.length-1
+        bfinish = b.length-1
+        mvector = []
+
+        # First we prune off any common elements at the beginning
+        while (astart <= afinish) && (bstart <= afinish) && (a[astart] == b[bstart])
+          mvector[astart] = bstart
+          astart += 1
+          bstart += 1
+        end
+
+        # now the end
+        while (astart <= afinish) && (bstart <= bfinish) && (a[afinish] == b[bfinish])
+          mvector[afinish] = bfinish
+          afinish -= 1
+          bfinish -= 1
+        end
+
+        bmatches = b.reverse_hash(bstart..bfinish)
+        thresh = []
+        links = []
+
+        (astart..afinish).each { |aindex|
+          aelem = a[aindex]
+          next unless bmatches.has_key? aelem
+          k = nil
+          bmatches[aelem].reverse_each { |bindex|
+            if k && (thresh[k] > bindex) && (thresh[k-1] < bindex)
+              thresh[k] = bindex
+            else
+              k = thresh.replacenextlarger(bindex, k)
+            end
+            links[k] = [ (k==0) ? nil : links[k-1], aindex, bindex ] if k
+          }
+        }
+
+        if !thresh.empty?
+          link = links[thresh.length-1]
+          while link
+            mvector[link[1]] = link[2]
+            link = link[0]
+          end
+        end
+
+        return mvector
+      end
+
+      def makediff(a, b)
+        mvector = Diff.lcs(a, b)
+        ai = bi = 0
+        while ai < mvector.length
+          bline = mvector[ai]
+          if bline
+            while bi < bline
+              discardb(bi, b[bi])
+              bi += 1
+            end
+            match(ai, bi)
+            bi += 1
+          else
+            discarda(ai, a[ai])
+          end
+          ai += 1
+        end
+        while ai < a.length
+          discarda(ai, a[ai])
+          ai += 1
+        end
+        while bi < b.length
+          discardb(bi, b[bi])
+          bi += 1
+        end
+        match(ai, bi)
+        1
+      end
+
+      def compactdiffs
+        diffs = []
+        @diffs.each { |df|
+          i = 0
+          curdiff = []
+          while i < df.length
+            whot = df[i][0]
+            s = @isstring ? df[i][2].chr : [df[i][2]]
+            p = df[i][1]
+            last = df[i][1]
+            i += 1
+            while df[i] && df[i][0] == whot && df[i][1] == last+1
+              s << df[i][2]
+              last  = df[i][1]
+              i += 1
+            end
+            curdiff.push [whot, p, s]
+          end
+          diffs.push curdiff
+        }
+        return diffs
+      end
+
+      attr_reader :diffs, :difftype
+
+      def initialize(diffs_or_a, b = nil, isstring = nil)
+        if b.nil?
+          @diffs = diffs_or_a
+          @isstring = isstring
+        else
+          @diffs = []
+          @curdiffs = []
+          makediff(diffs_or_a, b)
+          @difftype = diffs_or_a.class
+        end
+      end
+
+      def match(ai, bi)
+        @diffs.push @curdiffs unless @curdiffs.empty?
+        @curdiffs = []
+      end
+
+      def discarda(i, elem)
+        @curdiffs.push ['-', i, elem]
+      end
+
+      def discardb(i, elem)
+        @curdiffs.push ['+', i, elem]
+      end
+
+      def compact
+        return Diff.new(compactdiffs)
+      end
+
+      def compact!
+        @diffs = compactdiffs
+      end
+
+      def inspect
+        @diffs.inspect
+      end
+    end
+  end
+end
+
+class Array
+  include Redmine::StringArrayDiff::Diffable
+end
+
+class String
+  include Redmine::StringArrayDiff::Diffable
+end