Added support for custom formatters

README.rdoc

@@ -69,9 +69,17 @@ If you would like something a little more inline...
 
 Need a different output format?  We've got a few of those too.
 
-  Differ.format(:ascii)  # <- Default
-  Differ.format(:color)
-  Differ.format(:html)
+  Differ.format = :ascii  # <- Default
+  Differ.format = :color
+  Differ.format = :html
+
+  Differ.format = MyCustomFormatModule
+
+Don't want to change the system-wide default for only a single diff output?
+Yeah, me either.
+
+  @diff = (@current - @original)
+  @diff.format_as(:color)
 
 == Copyright
 

lib/differ.rb

@@ -1,5 +1,8 @@
 require 'differ/change'
 require 'differ/diff'
+require 'differ/format/ascii'
+require 'differ/format/color'
+require 'differ/format/html'
 
 module Differ
   class << self
@@ -32,6 +35,25 @@ def diff_by_line(to, from)
       diff(to, from, "\n")
     end
 
+    def format=(f)
+      @format = format_for(f)
+    end
+
+    def format
+      return @format || Format::Ascii
+    end
+
+    def format_for(f)
+      case f
+      when Module then f
+      when :ascii then Format::Ascii
+      when :color then Format::Color
+      when :html  then Format::HTML
+      when nil    then nil
+      else raise "Unknown format type #{f.inspect}"
+      end
+    end
+
   private
     def advance(target, source)
       del, add = source.shift, target.shift

lib/differ/change.rb

@@ -18,15 +18,8 @@ def change?
       !@insert.empty? && !@delete.empty?
     end
 
-    def as_insert ; "+#{@insert.inspect}" ; end
-    def as_delete ; "-#{@delete.inspect}" ; end
-    def as_change ; "{#{@delete.inspect} >> #{@insert.inspect}}" ; end
-
     def to_s
-      (change? && self.as_change) ||
-      (insert? && self.as_insert) ||
-      (delete? && self.as_delete) ||
-      ''
+      Differ.format.format(self)
     end
     alias :inspect :to_s
 

lib/differ/diff.rb

@@ -71,6 +71,17 @@ def to_s
       @raw.to_s
     end
 
+    def format_as(f)
+      f = Differ.format_for(f)
+      @raw.inject('') do |sum, part|
+        part = case part
+        when String then part
+        when Change then f.format(part)
+        end
+        sum << part
+      end
+    end
+
   protected
     def raw_array
       @raw

lib/differ/format/ascii.rb

@@ -0,0 +1,27 @@
+module Differ
+  module Format
+    module Ascii
+      class << self
+        def format(change)
+          (change.change? && as_change(change)) ||
+          (change.delete? && as_delete(change)) ||
+          (change.insert? && as_insert(change)) ||
+          ''
+        end
+
+      private
+        def as_insert(change)
+          "{+#{change.insert.inspect}}"
+        end
+
+        def as_delete(change)
+          "{-#{change.delete.inspect}}"
+        end
+
+        def as_change(change)
+          "{#{change.delete.inspect} >> #{change.insert.inspect}}"
+        end
+      end
+    end
+  end
+end

lib/differ/format/color.rb

@@ -0,0 +1,27 @@
+module Differ
+  module Format
+    module Color
+      class << self
+        def format(change)
+          (change.change? && as_change(change)) ||
+          (change.delete? && as_delete(change)) ||
+          (change.insert? && as_insert(change)) ||
+          ''
+        end
+
+      private
+        def as_insert(change)
+          "\033[32m#{change.insert}\033[0m"
+        end
+
+        def as_delete(change)
+          "\033[31m#{change.delete}\033[0m"
+        end
+
+        def as_change(change)
+          as_delete(change) << as_insert(change)
+        end
+      end
+    end
+  end
+end

lib/differ/format/html.rb

@@ -0,0 +1,27 @@
+module Differ
+  module Format
+    module HTML
+      class << self
+        def format(change)
+          (change.change? && as_change(change)) ||
+          (change.delete? && as_delete(change)) ||
+          (change.insert? && as_insert(change)) ||
+          ''
+        end
+
+      private
+        def as_insert(change)
+          %Q{<ins class="differ">#{change.insert}</ins>}
+        end
+
+        def as_delete(change)
+          %Q{<del class="differ">#{change.delete}</del>}
+        end
+
+        def as_change(change)
+          as_delete(change) << as_insert(change)
+        end
+      end
+    end
+  end
+end

spec/differ/change_spec.rb

@@ -1,6 +1,11 @@
 require 'spec_helper'
 
 describe Differ::Change do
+  before(:each) do
+    @format = Module.new { def self.format(c); end }
+    Differ.format = @format
+  end
+
   describe '(empty)' do
     before(:each) do
       @change = Differ::Change.new()
@@ -15,6 +20,7 @@
     end
 
     it 'should stringify to ""' do
+      @format.should_receive(:format).once.and_return('')
       @change.to_s.should == ''
     end
   end
@@ -32,11 +38,6 @@
       @change.delete.should == ''
     end
 
-    it 'should stringify via the #as_insert method' do
-      @change.should_receive(:as_insert).once.and_return('FORMAT')
-      @change.to_s.should == 'FORMAT'
-    end
-
     it { (@change).should be_an_insert }
   end
 
@@ -53,11 +54,6 @@
       @change.delete.should == 'bar'
     end
 
-    it 'should stringify via the #as_delete method' do
-      @change.should_receive(:as_delete).once.and_return('FORMAT')
-      @change.to_s.should == 'FORMAT'
-    end
-
     it { (@change).should be_a_delete }
   end
 
@@ -74,13 +70,13 @@
       @change.delete.should == 'bar'
     end
 
-    it 'should stringify via the #as_change method' do
-      @change.should_receive(:as_change).once.and_return('FORMAT')
-      @change.to_s.should == 'FORMAT'
-    end
-
     it { (@change).should be_an_insert }
     it { (@change).should be_a_delete }
     it { (@change).should be_a_change }
   end
+
+  it "should stringify via the current format's #format method" do
+    @format.should_receive(:format).once
+    Differ::Change.new.to_s
+  end
 end

spec/differ/diff_spec.rb

@@ -7,6 +7,10 @@
   end
 
   describe '#to_s' do
+    before(:each) do
+      @format = Differ.format
+    end
+
     it 'should concatenate the result list' do
       diff('a', 'b', 'c').to_s.should == 'abc'
     end
@@ -16,22 +20,28 @@
       diff('a', 'b', 'c').to_s.should == 'abc'
     end
 
-    it 'should delegate insertion changes to the Change class' do
+    it 'should delegate insertion changes to Differ#format' do
       i = +'b'
-      i.should_receive(:as_insert).once.and_return('!')
+      @format.should_receive(:format).once.with(i).and_return('!')
       diff('a', i, 'c').to_s.should == 'a!c'
     end
+  end
+
+  describe '#format_as' do
+    before(:each) do
+      @change = +'b'
+      Differ.format = Module.new { def self.format(c); raise :error; end }
+      @format = Module.new { def self.format(c); end }
+    end
 
-    it 'should delegate deletion changes to the Change class' do
-      d = -'b'
-      d.should_receive(:as_delete).once.and_return('!')
-      diff('a', d, 'c').to_s.should == 'a!c'
+    it 'should delegate change formatting to the given format' do
+      @format.should_receive(:format).once.with(@change).and_return('!')
+      diff('a', @change, 'c').format_as(@format).should == 'a!c'
     end
 
-    it 'should delegate replacement changes to the Change class' do
-      r = ('b' >> 'd')
-      r.should_receive(:as_change).once.and_return('!')
-      diff('a', r, 'c').to_s.should == 'a!c'
+    it 'should use Differ#format_for to grab the correct format' do
+      Differ.should_receive(:format_for).once.with(@format)
+      diff().format_as(@format)
     end
   end
 

spec/differ/format/ascii_spec.rb

@@ -0,0 +1,18 @@
+require 'spec_helper'
+
+describe Differ::Format::Ascii do
+  it 'should format inserts well' do
+    @expected = '{+"SAMPLE"}'
+    Differ::Format::Ascii.format(+'SAMPLE').should == @expected
+  end
+
+  it 'should format deletes well' do
+    @expected = '{-"SAMPLE"}'
+    Differ::Format::Ascii.format(-'SAMPLE').should == @expected
+  end
+
+  it 'should format changes well' do
+    @expected = '{"THEN" >> "NOW"}'
+    Differ::Format::Ascii.format('THEN' >> 'NOW').should == @expected
+  end
+end

spec/differ/format/color_spec.rb

@@ -0,0 +1,18 @@
+require 'spec_helper'
+
+describe Differ::Format::Color do
+  it 'should format inserts well' do
+    @expected = "\033[32mSAMPLE\033[0m"
+    Differ::Format::Color.format(+'SAMPLE').should == @expected
+  end
+
+  it 'should format deletes well' do
+    @expected = "\033[31mSAMPLE\033[0m"
+    Differ::Format::Color.format(-'SAMPLE').should == @expected
+  end
+
+  it 'should format changes well' do
+    @expected = "\033[31mTHEN\033[0m\033[32mNOW\033[0m"
+    Differ::Format::Color.format('THEN' >> 'NOW').should == @expected
+  end
+end

spec/differ/format/html_spec.rb

@@ -0,0 +1,18 @@
+require 'spec_helper'
+
+describe Differ::Format::HTML do
+  it 'should format inserts well' do
+    @expected = '<ins class="differ">SAMPLE</ins>'
+    Differ::Format::HTML.format(+'SAMPLE').should == @expected
+  end
+
+  it 'should format deletes well' do
+    @expected = '<del class="differ">SAMPLE</del>'
+    Differ::Format::HTML.format(-'SAMPLE').should == @expected
+  end
+
+  it 'should format changes well' do
+    @expected = '<del class="differ">THEN</del><ins class="differ">NOW</ins>'
+    Differ::Format::HTML.format('THEN' >> 'NOW').should == @expected
+  end
+end