implement URL auto-linking

Parsedown.php

@@ -733,29 +733,35 @@ class Parsedown
 			}
 		}
 
-		# automatic link
-
-		if (strpos($text, '<') !== FALSE and preg_match_all('/<((https?|ftp|dict):[^\^\s]+?)>/i', $text, $matches, PREG_SET_ORDER))
+		if (strpos($text, '://') !== FALSE)
 		{
-			foreach ($matches as $matches)
+			switch (TRUE)
 			{
-				$url = $matches[1];
+				case preg_match_all('{<(https?:[/]{2}[^\s]+)>}i', $text, $matches, PREG_SET_ORDER):
+				case preg_match_all('{\b(https?:[/]{2}[^\s]+)\b}i', $text, $matches, PREG_SET_ORDER):
 
-				strpos($url, '&') !== FALSE and $url = preg_replace('/&(?!#?\w+;)/', '&amp;', $url);
+					foreach ($matches as $matches)
+					{
+						$url = $matches[1];
 
-				$element = '<a href=":href">:text</a>';
-				$element = str_replace(':text', $url, $element);
-				$element = str_replace(':href', $url, $element);
+						strpos($url, '&') !== FALSE and $url = preg_replace('/&(?!#?\w+;)/', '&amp;', $url);
 
-				# ~
+						$element = '<a href=":href">:text</a>';
+						$element = str_replace(':text', $url, $element);
+						$element = str_replace(':href', $url, $element);
 
-				$code = "\x1A".'$'.$index;
+						# ~
 
-				$text = str_replace($matches[0], $code, $text);
+						$code = "\x1A".'$'.$index;
 
-				$map[$code] = $element;
+						$text = str_replace($matches[0], $code, $text);
 
-				$index ++;
+						$map[$code] = $element;
+
+						$index ++;
+					}
+
+					break;
 			}
 		}
 
@@ -766,10 +772,15 @@ class Parsedown
 
 		# ~
 
+		if (strpos($text, '~~') !== FALSE)
+		{
+			$text = preg_replace('/~~(?=\S)(.+?)(?<=\S)~~/s', '<del>$1</del>', $text);
+		}
+
 		if (strpos($text, '_') !== FALSE)
 		{
 			$text = preg_replace('/__(?=\S)(.+?)(?<=\S)__(?!_)/s', '<strong>$1</strong>', $text);
-			$text = preg_replace('/_(?=\S)(.+?)(?<=\S)_/s', '<em>$1</em>', $text);
+			$text = preg_replace('/\b_(?=\S)(.+?)(?<=\S)_\b/s', '<em>$1</em>', $text);
 		}
 
 		if (strpos($text, '*') !== FALSE)

README.md

@@ -1,8 +1,8 @@
 ## Parsedown
 
-Parsedown is a Markdown parser for PHP. It is fast, consistent and easy to use.
+Fast, consistent and easy to use [Markdown][1] parser for PHP.
 
-[Home](http://parsedown.org)  · [Demo](http://parsedown.org/explorer/) · [Tests](http://parsedown.org/tests/)
+[Home](http://parsedown.org) · [Demo](http://parsedown.org/explorer/) · [Tests](http://parsedown.org/tests/)
 
 ### Installation
 
@@ -17,3 +17,5 @@ $result = Parsedown::instance()->parse($text);
 
 echo $result; # prints: <p>Hello <strong>Parsedown</strong>!</p>
 ```
+
+[1]: http://daringfireball.net/projects/markdown/

tests/data/emphasis.html

@@ -2,4 +2,5 @@
 <p><em>multiline
 emphasis</em></p>
 <p>_ this _ is not an emphasis, neither is _ this_, _this _, or _this*</p>
+<p>this_is_not_an_emphasis</p>
 <p>an empty emphasis __ ** is not an emphasis</p>

tests/data/emphasis.md

@@ -5,4 +5,6 @@ emphasis_
 
 _ this _ is not an emphasis, neither is _ this_, _this _, or _this*
 
+this_is_not_an_emphasis
+
 an empty emphasis __ ** is not an emphasis

tests/data/strikethrough.html

@@ -0,0 +1,3 @@
+<p><del>strikethrough</del></p>
+<p>in the <del>middle</del> of a sentence</p>
+<p>in the middle of a w<del>or</del>d</p>

tests/data/strikethrough.md

@@ -0,0 +1,5 @@
+~~strikethrough~~
+
+in the ~~middle~~ of a sentence
+
+in the middle of a w~~or~~d

tests/data/url_autolinking.html

@@ -0,0 +1 @@
+<p>Here's an autolink <a href="http://example.com">http://example.com</a>.</p>

tests/data/url_autolinking.md

@@ -0,0 +1 @@
+Here's an autolink http://example.com.