improve parsing of emphasis

Parsedown.php

@@ -629,9 +629,9 @@ class Parsedown
 
 		$index = 0;
 
-		# inline link or image (recursive)
+		# inline link / inline image (recursive)
 
-		if (strpos($text, '](') !== FALSE and preg_match_all('/(!?)(\[((?:[^\[\]]|(?2))*)\])\((.*?)\)/', $text, $matches, PREG_SET_ORDER)) # inline
+		if (strpos($text, '](') !== FALSE and preg_match_all('/(!?)(\[((?:[^\[\]]|(?2))*)\])\((.*?)\)/', $text, $matches, PREG_SET_ORDER))
 		{
 			foreach ($matches as $matches)
 			{
@@ -643,7 +643,7 @@ class Parsedown
 				{
 					$element = '<img alt="'.$matches[3].'" src="'.$url.'">';
 				}
-				else
+				else # link
 				{
 					$element_text = $this->parse_span_elements($matches[3]);
 
@@ -662,7 +662,7 @@ class Parsedown
 			}
 		}
 
-		# reference link or image (recursive)
+		# reference link / reference image (recursive)
 
 		if ($this->reference_map and strpos($text, '[') !== FALSE and preg_match_all('/(!?)\[(.+?)\](?:\n?[ ]?\[(.*?)\])?/ms', $text, $matches, PREG_SET_ORDER))
 		{
@@ -684,7 +684,7 @@ class Parsedown
 					{
 						$element = '<img alt="'.$matches[2].'" src="'.$url.'">';
 					}
-					else # anchor
+					else # link
 					{
 						$element_text = $this->parse_span_elements($matches[2]);
 
@@ -784,18 +784,15 @@ class Parsedown
 		if (strpos($text, '_') !== FALSE)
 		{
 			$text = preg_replace('/__(?=\S)([^_]+?)(?<=\S)__/s', '<strong>$1</strong>', $text, -1, $count);
-			$count or $text = preg_replace('/__(?=\S)(.+?)(?<=\S)__(?!_)/s', '<strong>$1</strong>', $text);
-
-			$text = preg_replace('/\b_(?=\S)(.+?)(?<=\S)_\b/s', '<em>$1</em>', $text);
+			$text = preg_replace('/(\b|_)_(?=\S)([^_]+?)(?<=\S)_(\b|_)/s', '$1<em>$2</em>$3', $text);
+			$text = preg_replace('/__(?=\S)([^_]+?)(?<=\S)__/s', '<strong>$1</strong>', $text, -1, $count);
 		}
 
 		if (strpos($text, '*') !== FALSE)
 		{
-			$text = preg_replace('/\*\*(?=\S)([^*]+?)(?<=\S)\*\*/s', '<strong>$1</strong>', $text, -1, $count);
-			$count or $text = preg_replace('/\*\*(?=\S)(.+?)(?<=\S)\*\*(?!\*)/s', '<strong>$1</strong>', $text);
-
-			$text = preg_replace('/\*(?=\S)([^*]+?)(?<=\S)\*/s', '<em>$1</em>', $text, -1, $count);
-			$count or $text = preg_replace('/\*(?=\S)(.+?)(?<=\S)\*(?!\*)/s', '<em>$1</em>', $text);
+			$text = preg_replace('/\*\*(?=\S)([^*]+?)(?<=\S)\*\*/s', '<strong>$1</strong>', $text);
+			$text = preg_replace('/\*(?=\S)([^*]+?)(?<=\S)\*/s', '<em>$1</em>', $text);
+			$text = preg_replace('/\*\*(?=\S)([^*]+?)(?<=\S)\*\*/s', '<strong>$1</strong>', $text);
 		}
 
 		$text = strtr($text, $map);

tests/data/em_strong.html

@@ -1,4 +1,6 @@
 <p><strong><em>em strong</em> strong</strong></p>
 <p><strong>strong <em>em strong</em></strong></p>
 <p><strong>strong <em>em strong</em> strong</strong></p>
-<p><strong>strong <em>em strong</em></strong></p>
+<p><strong><em>em strong</em> strong</strong></p>
+<p><strong>strong <em>em strong</em></strong></p>
+<p><strong>strong <em>em strong</em> strong</strong></p>

tests/data/em_strong.md

@@ -4,4 +4,8 @@ __strong _em strong___
 
 __strong _em strong_ strong__
 
-**strong *em strong***
+***em strong* strong**
+
+**strong *em strong***
+
+**strong *em strong* strong**

tests/data/emphasis.html

@@ -3,4 +3,5 @@
 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>
+<p>an empty emphasis __ ** is not an emphasis</p>
+<p>*mixed *<em>double and</em> single asterisk** spans</p>

tests/data/emphasis.md

@@ -7,4 +7,6 @@ _ this _ is not an emphasis, neither is _ this_, _this _, or _this*
 
 this_is_not_an_emphasis
 
-an empty emphasis __ ** is not an emphasis
+an empty emphasis __ ** is not an emphasis
+
+*mixed **double and* single asterisk** spans