Add a diff system

Thanks to https://github.com/paulgb/simplediff/

htdocs/index.php

@@ -22,7 +22,10 @@ foreach ($_GET as $k => $t)
 
         $geshi = new GeSHi($paste->content, $paste->language);
 
-	$geshi->enable_line_numbers(GESHI_FANCY_LINE_NUMBERS, 5);
+        if (!empty($kout[3]) && is_file(Paste::get_path($kout[3])))
+          $diff = new Paste($kout[3]);
+
+        $geshi->enable_line_numbers(GESHI_FANCY_LINE_NUMBERS, 5);
 
 	?>
     <div id="corps" style="text-align: center;">
@@ -33,10 +36,13 @@ foreach ($_GET as $k => $t)
       <div id="content">
        <div class="answer">
 	 <a href="/?a=<?php echo $kout[1]; ?>">Répondre</a>
-         <?php echo $paste->get_ref(); ?>
+         <?php echo $paste->get_ref(isset($diff)); ?>
        </div>
 	<?php
-	 echo $geshi->parse_code();
+         if (isset($diff))
+           echo $paste->get_diff($diff);
+         else
+           echo $geshi->parse_code();
         ?>
       </div>
     </div>

htdocs/style.css

@@ -113,3 +113,12 @@ div.answer {
     font-size: 65%;
     font-style: italic;
 }
+
+ins
+{
+    color: #00DF22;
+}
+del
+{
+    color: #DF2200;
+}

paste.class.php

@@ -166,13 +166,34 @@ class Paste
                                                  $this->date);
   }
 
-  function get_ref()
+  function get_ref($is_diff)
   {
     if (!empty($this->ref))
-      return '<a href="/?'.$this->ref.'">Voir l\'original</a>';
+    {
+      if (empty($is_diff))
+        return '<a href="/?'.$this->ref.'">Voir l\'original</a> '.
+        '<a href="/?'.$this->fileref.':'.$this->ref.'">Voir la différence</a>';
+      else
+        return '<a href="/?'.$this->fileref.'">Cacher les différences</a> ';
+    }
     else
       return "";
   }
+
+  function get_diff($diff)
+  {
+    require_once("geshi/geshi.php");
+    require_once("simplediff.php");
+
+    $geshi = new GeSHi(htmlDiff($diff->content, $this->content),
+                       $this->language);
+
+    return str_replace("&lt;ins&gt;", "<ins>",
+           str_replace("&lt;/ins&gt;", "</ins>",
+           str_replace("&lt;del&gt;", "<del>",
+           str_replace("&lt;/del&gt;", "</del>",
+                       $geshi->parse_code()))));
+  }
 }
 
 ?>

simplediff.php

@@ -0,0 +1,54 @@
+<?php
+
+/*
+	Paul's Simple Diff Algorithm v 0.1
+	(C) Paul Butler 2007 <http://www.paulbutler.org/>
+	May be used and distributed under the zlib/libpng license.
+	
+	This code is intended for learning purposes; it was written with short
+	code taking priority over performance. It could be used in a practical
+	application, but there are a few ways it could be optimized.
+	
+	Given two arrays, the function diff will return an array of the changes.
+	I won't describe the format of the array, but it will be obvious
+	if you use print_r() on the result of a diff on some test data.
+	
+	htmlDiff is a wrapper for the diff command, it takes two strings and
+	returns the differences in HTML. The tags used are <ins> and <del>,
+	which can easily be styled with CSS.  
+*/
+
+function diff($old, $new){
+	$maxlen = 0;
+	foreach($old as $oindex => $ovalue){
+		$nkeys = array_keys($new, $ovalue);
+		foreach($nkeys as $nindex){
+			$matrix[$oindex][$nindex] = isset($matrix[$oindex - 1][$nindex - 1]) ?
+				$matrix[$oindex - 1][$nindex - 1] + 1 : 1;
+			if($matrix[$oindex][$nindex] > $maxlen){
+				$maxlen = $matrix[$oindex][$nindex];
+				$omax = $oindex + 1 - $maxlen;
+				$nmax = $nindex + 1 - $maxlen;
+			}
+		}	
+	}
+	if($maxlen == 0) return array(array('d'=>$old, 'i'=>$new));
+	return array_merge(
+		diff(array_slice($old, 0, $omax), array_slice($new, 0, $nmax)),
+		array_slice($new, $nmax, $maxlen),
+		diff(array_slice($old, $omax + $maxlen), array_slice($new, $nmax + $maxlen)));
+}
+
+function htmlDiff($old, $new){
+	$ret = '';
+	$diff = diff(explode(' ', $old), explode(' ', $new));
+	foreach($diff as $k){
+		if(is_array($k))
+			$ret .= (!empty($k['d'])?"<del>".implode(' ',$k['d'])."</del> ":'').
+				(!empty($k['i'])?"<ins>".implode(' ',$k['i'])."</ins> ":'');
+		else $ret .= $k . ' ';
+	}
+	return $ret;
+}
+
+?>