fix: preserve full permalink structure in markdown URLs (#7)

src/Router/RewriteHandler.php

@@ -99,8 +99,10 @@ public function parse_markdown_url(\WP $wp): void {
             return;
         }
 
+        $path_without_md = $matches[1];
+
         // Handle /index.md - could be front page or a page with slug "index"
-        if ($matches[1] === 'index') {
+        if ($path_without_md === 'index') {
             // First try to resolve as a regular page with slug "index"
             $clean_url = home_url('/index');
             $post_id   = url_to_postid($clean_url);
@@ -116,9 +118,19 @@ public function parse_markdown_url(\WP $wp): void {
                 }
             }
         } else {
-            // Strip .md to get the original URL path, let WordPress resolve it
-            $clean_url = home_url('/' . $matches[1]);
-            $post_id   = url_to_postid($clean_url);
+            // Try to resolve the post by replacing .md with known permalink extensions,
+            // then fall back to no extension (original behavior).
+            $extensions_to_try = array_merge( UrlConverter::PERMALINK_EXTENSIONS, [ '' ] );
+            $post_id = 0;
+
+            foreach ($extensions_to_try as $ext) {
+                $clean_url = home_url('/' . $path_without_md . $ext);
+                $post_id   = url_to_postid($clean_url);
+
+                if ($post_id) {
+                    break;
+                }
+            }
 
             if (!$post_id) {
                 return; // Let WordPress show its normal 404

src/Router/UrlConverter.php

@@ -12,6 +12,20 @@
  */
 class UrlConverter {
 
+	/**
+	 * File extensions used in permalink structures that should be replaced with .md.
+	 *
+	 * @var string[]
+	 */
+	public const PERMALINK_EXTENSIONS = [ '.html', '.htm', '.php', '.aspx', '.asp' ];
+
+	/**
+	 * Regex pattern matching any of the supported permalink extensions.
+	 *
+	 * @var string
+	 */
+	private const EXTENSION_PATTERN = '/\.(html?|php|aspx?)$/i';
+
 	/**
 	 * Convert a permalink to a markdown URL.
 	 *
@@ -30,7 +44,11 @@ public static function convert_to_markdown_url( string $permalink ): string {
 			return home_url( '/index.md' );
 		}
 
-		// Otherwise, append .md to the permalink
+		// Replace file extension with .md, or append .md if no extension
+		if ( preg_match( self::EXTENSION_PATTERN, $normalized_permalink ) ) {
+			return preg_replace( self::EXTENSION_PATTERN, '.md', $normalized_permalink );
+		}
+
 		return $normalized_permalink . '.md';
 	}
 }