Untitled

# coding: utf-8

require 'rubygems'
require 'erb'
require 'differ'


MyFormat = Differ::Format::HTML.clone

module MyFormat
  class << self
    private
    def as_change(change)
      as_delete(change) << "\n" << as_insert(change)
    end
  end
end

def diff(prev_text, new_text)
  prev, new = ERB::Util.h(prev_text), ERB::Util.h(new_text)
  differ = Differ.diff_by_line(prev, new)
  differ.format_as MyFormat
end

def diff_html(prev_text, new_text)
  String.new(<<-HTML)
<html>
<head>
<title>diff</title>
<style>
ins.differ {
  background: #cfc;
}
del.differ {
  background: #fcc;
}
</style>
</head>
<body>
<h1>diff</h1>
<pre class="diff">
#{diff(prev_text, new_text)}
</pre>
</body>
</html>
  HTML
end

if __FILE__ == $0

a =<<-EOL
いろはにほへと
ちりぬるをわか
よたれそつねな
らむうゐのおく
やまけふこえて
あさきゆめみし
ゑひもせす
EOL

b =<<-EOL
いろはにほへど
ちりぬるをわが
よたれぞつねな
らむうゐのおく
やまけふこえて
あさきゆめみじ
ゑひもせず
EOL

print diff_html(a, b)
end