Improve splitting of hyphen-separated CFI ranges

Create a `stripCFIRange` utility which strips assertions before separating the
input. This means that hyphens inside assertions will be ignored.

src/shared/cfi.ts

@@ -34,6 +34,22 @@ function compareArrays(
   return a.length - b.length;
 }
 
+/**
+ * Split a hyphen-separated CFI range.
+ *
+ * CFI assertions are stripped in the process. If `range` does not contain a
+ * hyphen, the result will be an empty range with the end point being the same
+ * as the start point.
+ *
+ * @example
+ *   splitCFIRange("/2/4[chap-02]-/2/6[chap-03]") // returns `["/2/4", "/2/6"]`.
+ */
+export function splitCFIRange(range: string): [string, string] {
+  const rangeWithoutAssertions = stripCFIAssertions(range);
+  const [start, end] = rangeWithoutAssertions.split('-', 2);
+  return [start, end ?? start];
+}
+
 /**
  * Strip assertions from a Canonical Fragment Identifier.
  *

src/shared/test/cfi-test.js

@@ -2,6 +2,7 @@ import {
   cfiInRange,
   compareCFIs,
   documentCFI,
+  splitCFIRange,
   stripCFIAssertions,
 } from '../cfi';
 
@@ -25,6 +26,25 @@ describe('sidebar/util/cfi', () => {
     });
   });
 
+  describe('splitCFIRange', () => {
+    [
+      {
+        range: '/2/4-/4/6',
+        expected: ['/2/4', '/4/6'],
+      },
+      {
+        range: '/2/4[chap-02]-/2/6[chap-03]',
+        expected: ['/2/4', '/2/6'],
+      },
+      {
+        range: '/2/4',
+        expected: ['/2/4', '/2/4'],
+      },
+    ].forEach(({ range, expected }) => {
+      assert.deepEqual(splitCFIRange(range), expected);
+    });
+  });
+
   describe('compareCFIs', () => {
     [
       // Trivial cases

src/sidebar/helpers/annotation-segment.ts

-import { cfiInRange, stripCFIAssertions } from '../../shared/cfi';
+import {
+  cfiInRange,
+  splitCFIRange,
+  stripCFIAssertions,
+} from '../../shared/cfi';
 import type { SegmentInfo } from '../../types/annotator';
 import type { Annotation, EPUBContentSelector } from '../../types/api';
 import type { Filters } from '../store/modules/filters';
@@ -41,7 +45,7 @@ export function segmentMatchesFocusFilters(
   filters: Filters,
 ): boolean {
   if (segment.cfi && filters.cfi) {
-    const [cfiStart, cfiEnd] = filters.cfi.value.split('-');
+    const [cfiStart, cfiEnd] = splitCFIRange(filters.cfi.value);
     return cfiInRange(segment.cfi, cfiStart, cfiEnd);
   }
   if (segment.pages && filters.page) {

src/sidebar/helpers/filter-annotations.ts

-import { cfiInRange, stripCFIAssertions } from '../../shared/cfi';
+import {
+  cfiInRange,
+  splitCFIRange,
+  stripCFIAssertions,
+} from '../../shared/cfi';
 import type { Annotation } from '../../types/api';
 import { pageLabelInRange } from '../util/page-range';
 import * as unicodeUtils from '../util/unicode';
@@ -113,12 +117,11 @@ const fieldMatchers: Record<string, Matcher | Matcher<number>> = {
       //
       // If we wanted to use a more standard CFI range representation,
       // we could follow https://idpf.org/epub/linking/cfi/#sec-ranges.
-      if (cfiTerm.includes('-')) {
-        const [start, end] = cfiTerm.split('-');
+      //
+      // If `cfiTerm` does not contain a hyphen, the result will be an empty
+      // range that does not match any CFIs.
+      const [start, end] = splitCFIRange(cfiTerm);
       return cfiInRange(cfi, start, end);
-      } else {
-        return false;
-      }
     },
     normalize: (val: string) => stripCFIAssertions(val.trim()),
   },