Sort anchors by their associatedPageIndex value

This value is always integer, so we don't have to parse things
like Roman numerals (which can exist in anchor text itself),
and we can impose meaningful order on arbitrary string anchors
(which can be surrounded by numeric anchors).

For example, anchor "pg5" can be followed by "pgimage1", then by "pg6".

We are intentionally ignoring anchors with negative numbers,
as this is a convention for anchors that are not supposed to be
in the navigation template.

extension.json

@@ -18,8 +18,7 @@
 		"MediaWiki\\PrevNextImageLinks\\AssociatedImage": "includes/AssociatedImage.php",
 		"MediaWiki\\PrevNextImageLinks\\Hooks": "includes/Hooks.php",
 		"MediaWiki\\PrevNextImageLinks\\NavigationTemplate": "includes/NavigationTemplate.php",
-		"MediaWiki\\PrevNextImageLinks\\PageFinder": "includes/PageFinder.php",
-		"MediaWiki\\PrevNextImageLinks\\RomanNumeral": "includes/util/RomanNumeral.php"
+		"MediaWiki\\PrevNextImageLinks\\PageFinder": "includes/PageFinder.php"
 	},
 	"ExtensionMessagesFiles": {
 		"PrevNextImageLinksMagic": "PrevNextImageLinks.i18n.magic.php"

includes/NavigationTemplate.php

@@ -49,7 +49,8 @@ public static function pfSubpageAnchorNavigation( Parser $parser, $pageName ) {
 
 	/**
 	 * Find all subpages of $title, find all tags like <span id="pg123"> inside each subpage,
-	 * then generate links to every #pg<number> anchor, sorted by number after "pg".
+	 * then generate links to every #pg<number> anchor,
+	 * sorted by first parameter of {{#set_associated_index:}} that is associated with this anchor.
 	 * @param PageIdentity $title
 	 * @return string|array
 	 */
@@ -59,7 +60,11 @@ protected function generate( PageIdentity $title ) {
 
 		// Find all subpages of $title.
 		$res = $dbr->newSelectQueryBuilder()
-			->select( [ 'page_title AS title', 'pp_value AS anchor' ] )
+			->select( [
+				'page_title AS title',
+				'pp_value AS anchor',
+				'pp_propname AS sortkey'
+			] )
 			->from( 'page' )
 			->join( 'page_props', null, [ 'pp_page = page_id' ] )
 			->where( [
@@ -80,29 +85,29 @@ protected function generate( PageIdentity $title ) {
 		foreach ( $res as $row ) {
 			// Strip standard prefix ("pg").
 			$shownAnchor = preg_replace( '/^pg/', '', $row->anchor );
-			$number = $this->parseAnchorNumber( $row->anchor );
-			if ( $number < 0 ) {
-				// Negative numbers (e.g. "pg-5") are NOT shown in the navigation template.
+			if ( !$shownAnchor || $shownAnchor[0] === '-' ) {
+				// Empty anchors and anchors with negative numbers (e.g. "pg-5")
+				// are NOT shown in the navigation template.
 				continue;
 			}
 
+			$sortkey = intval( preg_replace( '/^associatedPageIndex\./', '', $row->sortkey ) );
+
 			$anchorsFound[] = [
 				'title' => $row->title,
 				'anchor' => $row->anchor,
 				'text' => $shownAnchor,
-				'number' => $number
+				'sortkey' => $sortkey
 			];
 		}
 
 		uasort( $anchorsFound, static function ( $a, $b ) {
-			// Sort by number.
-			$cmp = $a['number'] - $b['number'];
+			$cmp = $a['sortkey'] - $b['sortkey'];
 			if ( $cmp !== 0 ) {
 				return $cmp;
 			}
 
-			// If numbers are the same (likely non-numeric anchors?),
-			// then sort by displayed text.
+			// If sortkeys are the same, then sort by displayed text.
 			return strcmp( $a['text'], $b['text'] );
 		} );
 
@@ -119,25 +124,4 @@ protected function generate( PageIdentity $title ) {
 		);
 		return [ $resultHtml, 'isHTML' => true ];
 	}
-
-	/**
-	 * Detect the number inside the string $anchor, e.g. "15" in "pg15" or "9" in "pg-ix".
-	 * @param string $anchor
-	 * @return int
-	 */
-	protected function parseAnchorNumber( $anchor ) {
-		// Decimal number?
-		if ( preg_match( '/\-?[0-9]+/', $anchor, $matches ) ) {
-			return (int)$matches[0];
-		}
-
-		$value = RomanNumeral::romanToInteger( $anchor );
-		if ( $value ) {
-			// Found and successfully parsed roman numeral.
-			return $value;
-		}
-
-		// Default (no number found). These anchors can still be shown.
-		return 0;
-	}
 }