1 files changed, 109 insertions, 100 deletions

diff --git a/lib/diff/lcs/change.rb b/lib/diff/lcs/change.rb
index 5139821..50c1de9 100644
--- a/lib/diff/lcs/change.rb
+++ b/lib/diff/lcs/change.rb
@@ -1,59 +1,59 @@
-#! /usr/env/bin ruby
-#--
-# Copyright 2004 Austin Ziegler <diff-lcs@halostatue.ca>
-#   adapted from:
-#     Algorithm::Diff (Perl) by Ned Konz <perl@bike-nomad.com>
-#     Smalltalk by Mario I. Wolczko <mario@wolczko.com>
-#   implements McIlroy-Hunt diff algorithm
-#
-# This program is free software. It may be redistributed and/or modified under
-# the terms of the GPL version 2 (or later), the Perl Artistic licence, or the
-# Ruby licence.
-# 
-# $Id$
-#++
+# -*- ruby encoding: utf-8 -*-
 # Provides Diff::LCS::Change and Diff::LCS::ContextChange.
 
-  # Centralises the change test code in Diff::LCS::Change and
-  # Diff::LCS::ContextChange, since it's the same for both classes.
-module Diff::LCS::ChangeTypeTests
-  def deleting?
-    @action == '-'
-  end
+# Represents a simplistic (non-contextual) change. Represents the removal or
+# addition of an element from either the old or the new sequenced
+# enumerable.
+class Diff::LCS::Change
+  # The only actions valid for changes are '+' (add), '-' (delete), '='
+  # (no change), '!' (changed), '<' (tail changes from first sequence), or
+  # '>' (tail changes from second sequence). The last two ('<>') are only
+  # found with Diff::LCS::diff and Diff::LCS::sdiff.
+  VALID_ACTIONS = %W(+ - = ! > <)
 
-  def adding?
-    @action == '+'
+  def self.valid_action?(action)
+    VALID_ACTIONS.include? action
   end
 
-  def unchanged?
-    @action == '='
-  end
+  # Returns the action this Change represents.
+  attr_reader :action
 
-  def changed?
-    @action == '!'
+  # Returns the position of the Change.
+  attr_reader :position
+  # Returns the sequence element of the Change.
+  attr_reader :element
+
+  def initialize(*args)
+    @action, @position, @element = *args
+
+    unless Diff::LCS::Change.valid_action?(@action)
+      raise "Invalid Change Action '#{@action}'"
+    end
+    raise "Invalid Position Type" unless @position.kind_of? Fixnum
   end
 
-  def finished_a?
-    @action == '>'
+  def inspect
+    %Q(#<#{self.class.name}:#{__id__.to_s(16)} @action=#{action} position=#{position} element=#{element.inspect})
   end
 
-  def finished_b?
-    @action == '<'
+  def to_a
+    [ @action, @position, @element ]
   end
-end
 
-  # Represents a simplistic (non-contextual) change. Represents the removal or
-  # addition of an element from either the old or the new sequenced enumerable.
-class Diff::LCS::Change
-    # Returns the action this Change represents. Can be '+' (#adding?), '-'
-    # (#deleting?), '=' (#unchanged?), # or '!' (#changed?). When created by
-    # Diff::LCS#diff or Diff::LCS#sdiff, it may also be '>' (#finished_a?) or
-    # '<' (#finished_b?).
-  attr_reader :action
-  attr_reader :position
-  attr_reader :element
+  def self.from_a(arr)
+    arr = arr.flatten
+    case arr.size
+    when 5
+      Diff::LCS::ContextChange.new(*(arr[0...5]))
+    when 3
+      Diff::LCS::Change.new(*(arr[0...3]))
+    else
+      raise "Invalid change array format provided."
+    end
+  end
 
   include Comparable
+
   def ==(other)
     (self.action == other.action) and
     (self.position == other.position) and
@@ -67,85 +67,79 @@ class Diff::LCS::Change
     r
   end
 
-  def initialize(action, position, element)
-    @action = action
-    @position = position
-    @element = element
+  def adding?
+    @action == '+'
   end
 
-    # Creates a Change from an array produced by Change#to_a.
-  def to_a
-    [@action, @position, @element]
+  def deleting?
+    @action == '-'
   end
 
-  def self.from_a(arr)
-    Diff::LCS::Change.new(arr[0], arr[1], arr[2])
+  def unchanged?
+    @action == '='
+  end
+
+  def changed?
+    @action == '!'
   end
 
-  include Diff::LCS::ChangeTypeTests
+  def finished_a?
+    @action == '>'
+  end
+
+  def finished_b?
+    @action == '<'
+  end
 end
 
-  # Represents a contextual change. Contains the position and values of the
-  # elements in the old and the new sequenced enumerables as well as the action
-  # taken.
-class Diff::LCS::ContextChange
-    # Returns the action this Change represents. Can be '+' (#adding?), '-'
-    # (#deleting?), '=' (#unchanged?), # or '!' (#changed?). When
-    # created by Diff::LCS#diff or Diff::LCS#sdiff, it may also be '>'
-    # (#finished_a?) or '<' (#finished_b?).
-  attr_reader :action
+# Represents a contextual change. Contains the position and values of the
+# elements in the old and the new sequenced enumerables as well as the action
+# taken.
+class Diff::LCS::ContextChange < Diff::LCS::Change
+  # We don't need these two values.
+  undef :position
+  undef :element
+
+  # Returns the old position being changed.
   attr_reader :old_position
-  attr_reader :old_element
+  # Returns the new position being changed.
   attr_reader :new_position
+  # Returns the old element being changed.
+  attr_reader :old_element
+  # Returns the new element being changed.
   attr_reader :new_element
 
-  include Comparable
+  def initialize(*args)
+    @action, @old_position, @old_element, @new_position, @new_element = *args
 
-  def ==(other)
-    (@action == other.action) and
-    (@old_position == other.old_position) and
-    (@new_position == other.new_position) and
-    (@old_element == other.old_element) and
-    (@new_element == other.new_element)
-  end
-
-  def inspect(*args)
-    %Q(#<#{self.class.name}:#{__id__} @action=#{action} positions=#{old_position},#{new_position} elements=#{old_element.inspect},#{new_element.inspect}>)
-  end
-
-  def <=>(other)
-    r = @action <=> other.action
-    r = @old_position <=> other.old_position if r.zero?
-    r = @new_position <=> other.new_position if r.zero?
-    r = @old_element <=> other.old_element if r.zero?
-    r = @new_element <=> other.new_element if r.zero?
-    r
+    unless Diff::LCS::Change.valid_action?(@action)
+      raise "Invalid Change Action '#{@action}'"
+    end
+    unless @old_position.nil? or @old_position.kind_of? Fixnum
+      raise "Invalid (Old) Position Type"
+    end
+    unless @new_position.nil? or @new_position.kind_of? Fixnum
+      raise "Invalid (New) Position Type"
+    end
   end
 
-  def initialize(action, old_position, old_element, new_position, new_element)
-    @action = action
-    @old_position = old_position
-    @old_element = old_element
-    @new_position = new_position
-    @new_element = new_element
+  def to_a
+    [ @action,
+      [ @old_position, @old_element ],
+      [ @new_position, @new_element ]
+    ]
   end
 
-  def to_a
-    [@action, [@old_position, @old_element], [@new_position, @new_element]]
+  def inspect(*args)
+    %Q(#<#{self.class.name}:#{__id__} @action=#{action} positions=#{old_position},#{new_position} elements=#{old_element.inspect},#{new_element.inspect}>)
   end
 
-    # Creates a ContextChange from an array produced by ContextChange#to_a.
   def self.from_a(arr)
-    if arr.size == 5
-      Diff::LCS::ContextChange.new(arr[0], arr[1], arr[2], arr[3], arr[4])
-    else
-      Diff::LCS::ContextChange.new(arr[0], arr[1][0], arr[1][1], arr[2][0],
-                                   arr[2][1])
-    end
+    Diff::LCS::Change.from_a(arr)
   end
 
-    # Simplifies a context change for use in some diff callbacks. '<' actions
-    # are converted to '-' and '>' actions are converted to '+'. 
+  # Simplifies a context change for use in some diff callbacks. '<' actions
+  # are converted to '-' and '>' actions are converted to '+'.
   def self.simplify(event)
     ea = event.to_a
 
@@ -165,5 +159,20 @@ class Diff::LCS::ContextChange
     Diff::LCS::ContextChange.from_a(ea)
   end
 
-  include Diff::LCS::ChangeTypeTests
+  def ==(other)
+    (@action == other.action) and
+    (@old_position == other.old_position) and
+    (@new_position == other.new_position) and
+    (@old_element == other.old_element) and
+    (@new_element == other.new_element)
+  end
+
+  def <=>(other)
+    r = @action <=> other.action
+    r = @old_position <=> other.old_position if r.zero?
+    r = @new_position <=> other.new_position if r.zero?
+    r = @old_element <=> other.old_element if r.zero?
+    r = @new_element <=> other.new_element if r.zero?
+    r
+  end
 end