labels of reference links should be case insensitive

Parsedown.php

@@ -205,7 +205,7 @@ class Parsedown
 			
 			# Quick Paragraph 
 			
-			if ($line[0] >= 'A' and $line[0] !== '_' and $line[0] !== '[')
+			if ($line[0] >= 'a' or $line[0] >= 'A' and $line[0] <= 'Z')
 			{
 				goto paragraph; # trust me 
 			}
@@ -277,13 +277,13 @@ class Parsedown
 			
 			# ~ 
 			
-			$pure_line = ltrim($line);
+			$pure_line = $line[0] !== ' ' ? $line : ltrim($line);
 			
 			# Link Reference 
 			
 			if ($pure_line[0] === '[' and preg_match('/^\[(.+?)\]:[ ]*([^ ]+)/', $pure_line, $matches))
 			{
-				$label = $matches[1];
+				$label = strtolower($matches[1]);
 				$url = trim($matches[2], '<>');
 				
 				$this->reference_map[$label] = $url;
@@ -560,7 +560,7 @@ class Parsedown
 		
 		# Inline Link / Image 
 		
-		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, $matches, PREG_SET_ORDER)) # inline 
 		{
 			foreach ($matches as $matches)
 			{

tests/data/reference_link.html

@@ -2,6 +2,7 @@
 <p>Here's <a href="http://parsedown.org">one</a> on the next line.</p>
 <p>Here's <a href="http://parsedown.org/tests/">one</a> with a different URL.</p>
 <p>Here's <a href="http://parsedown.org">one</a> with a semantic name.</p>
+<p>Here's <a href="http://parsedown.org">one</a> with an upper case label definition.</p>
 <p>Here's <a href="http://parsedown.org">one</a> with definition name on the next line.</p>
 <p>Here's [one][404] with no definition.</p>
 <p>Here's an image: <img alt="Markdown Logo" src="/md.png"></p>

tests/data/reference_link.md

@@ -13,6 +13,10 @@ Here's [one][website] with a semantic name.
 
 [website]: http://parsedown.org
 
+Here's [one][case] with an upper case label definition.
+
+[CASE]: http://parsedown.org
+
 Here's [one]
 [website] with definition name on the next line.