Extend Location sorting to support page index

Author: cdrini

src/sidebar/helpers/annotation-metadata.ts

@@ -291,6 +291,11 @@ type LocationKey = {
    * (ie. chapter).
    */
   position?: number;
+
+  /**
+   * Page index within the document.
+   */
+  pageIndex?: number;
 };
 
 /**
@@ -305,6 +310,7 @@ export function location(annotation: Annotation): LocationKey {
 
   let cfi;
   let position;
+  let pageIndex;
 
   // nb. We ignore the possibility of an annotation having multiple targets here.
   // h and the client only support one.
@@ -313,10 +319,12 @@ export function location(annotation: Annotation): LocationKey {
       position = selector.start;
     } else if (selector.type === 'EPUBContentSelector' && selector.cfi) {
       cfi = selector.cfi;
+    } else if (selector.type === 'PageSelector') {
+      pageIndex = selector.index;
     }
   }
 
-  return { cfi, position };
+  return { cfi, position, pageIndex };
 }
 
 /**

src/sidebar/helpers/thread-sorters.ts

@@ -91,11 +91,23 @@ export const sorters = {
       return 1;
     }
 
-    // If the chapter number is the same or for other document types, compare
-    // the text position instead. Missing positions sort after any present
-    // positions.
-    const aPos = aLocation.position ?? Number.MAX_SAFE_INTEGER;
-    const bPos = bLocation.position ?? Number.MAX_SAFE_INTEGER;
-    return Math.sign(aPos - bPos);
+    // If the chapter number is the same or for other document types, and
+    // at least one of the annotations has text position info, compare
+    // that instead. Missing positions sort after any present positions.
+    if (typeof aLocation.position === 'number' || typeof bLocation.position === 'number') {
+      const aPos = aLocation.position ?? Number.MAX_SAFE_INTEGER;
+      const bPos = bLocation.position ?? Number.MAX_SAFE_INTEGER;
+      return Math.sign(aPos - bPos);
+    }
+
+    // If text positions aren't specified, check for page numbers.
+    if (typeof aLocation.pageIndex === 'number' || typeof bLocation.pageIndex === 'number') {
+      const aPage = aLocation.pageIndex ?? Number.MAX_SAFE_INTEGER;
+      const bPage = bLocation.pageIndex ?? Number.MAX_SAFE_INTEGER;
+      return Math.sign(aPage - bPage);
+    }
+
+    // If nothing matches
+    return 0;
   },
 } satisfies Record<string, SortFunction>;