Move @lib/diff.rb@ to @lib/redmine/string_array_diff@ and extract @Diffable@ class to its own file (#29914, #32938).

git-svn-id: http://svn.redmine.org/redmine/trunk@21262 e93f8b46-1217-0410-a6f0-8f06a7374b81

lib/redmine/string_array_diff/diffable.rb

@@ -0,0 +1,131 @@
+# 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