From 6f04c6ef41033546896b7ced1c75cfcdf03dfb91 Mon Sep 17 00:00:00 2001
From: viktar-b <60892287+viktar-b@users.noreply.github.com>
Date: Fri, 6 Nov 2026 09:01:37 +0000
Subject: [PATCH] fix(core): parse grouped glyph scripts in linear time

---
 .../cso-core/src/sheet-model/glyphCodeName.ts | 57 ++++++++++++++++---
 .../cso-core/tests/glyph-code-name.test.ts    | 46 +++++++++++++++
 2 files changed, 96 insertions(+), 7 deletions(-)
 create mode 100644 packages/cso-core/tests/glyph-code-name.test.ts

diff --git a/packages/cso-core/src/sheet-model/glyphCodeName.ts b/packages/cso-core/src/sheet-model/glyphCodeName.ts
index 4a736f8..78bf7f7 100644
--- a/packages/cso-core/src/sheet-model/glyphCodeName.ts
+++ b/packages/cso-core/src/sheet-model/glyphCodeName.ts
@@ -1,19 +1,62 @@
-const groupedScriptPattern = /[_^][({[]([^)}\]]+)[)}\]]/g;
 const bareScriptPattern = /[_^]([A-Za-z0-9]+)/g;
+const scriptOpeners = new Set(['(', '{', '[']);
+const scriptClosers = new Set([')', '}', ']']);
+
+const replaceGroupedScripts = (value: string): string => {
+  const parts: string[] = [];
+  let unchangedStart = 0;
+  let index = 0;
+
+  while (index < value.length) {
+    const char = value[index];
+    if (
+      (char !== '_' && char !== '^') ||
+      !scriptOpeners.has(value.charAt(index + 1))
+    ) {
+      index += 1;
+      continue;
+    }
+
+    const contentStart = index + 2;
+    let end = contentStart;
+    while (end < value.length && !scriptClosers.has(value[end])) {
+      end += 1;
+    }
+
+    // No later group can close either. Preserve the remaining input without
+    // rescanning each opening delimiter in an unmatched suffix.
+    if (end === value.length) break;
+
+    // Match the former regex: groups need content, and any closer ends them,
+    // even when delimiters are mismatched or the content contains openers.
+    if (end === contentStart) {
+      index += 1;
+      continue;
+    }
+
+    parts.push(
+      value.slice(unchangedStart, index),
+      '_',
+      value.slice(contentStart, end),
+    );
+    index = end + 1;
+    unchangedStart = index;
+  }
+
+  parts.push(value.slice(unchangedStart));
+  return parts.join('');
+};
 
 const removeNonAscii = (value: string): string =>
   [...value].filter((char) => char.charCodeAt(0) <= 127).join('');
 
 const toAsciiCodeName = (value: string): string =>
-  removeNonAscii(value)
-    .trim()
-    .normalize('NFKD')
-    .replace(groupedScriptPattern, '_$1')
+  replaceGroupedScripts(removeNonAscii(value).trim().normalize('NFKD'))
     .replace(bareScriptPattern, '_$1')
     .replace(/[{}()[\]]+/g, '_')
     .replace(/[^A-Za-z0-9_]+/g, '_')
-    .replace(/^_+|_+$/g, '')
-    .replace(/_+/g, '_');
+    .replace(/_+/g, '_')
+    .replace(/^_|_$/g, '');
 
 export const deriveGlyphCodeName = ({
   glyph,
diff --git a/packages/cso-core/tests/glyph-code-name.test.ts b/packages/cso-core/tests/glyph-code-name.test.ts
new file mode 100644
index 0000000..c2c8751
--- /dev/null
+++ b/packages/cso-core/tests/glyph-code-name.test.ts
@@ -0,0 +1,46 @@
+import { execFileSync } from 'node:child_process';
+import { expect, test } from 'vitest';
+import { deriveGlyphCodeName } from '../src/sheet-model/glyphCodeName.ts';
+
+test.each([
+  ['K_(y_1)', 'K_y_1'],
+  ['A^{2}', 'A_2'],
+  ['A_[x]', 'A_x'],
+  ['A_(x)B^{2}', 'A_xB_2'],
+  ['A_(x]B', 'A_xB'],
+  ['A_()B', 'A_B'],
+  ['A_((x))B', 'A_x_B'],
+  ['A_(x', 'A_x'],
+  ['A_()_(x)', 'A_x'],
+])('derives the code name for %s', (glyph, expected) => {
+  expect(deriveGlyphCodeName({ glyph, id: 'fallback-id' })).toBe(expected);
+});
+
+test('handles long unmatched glyphs without repeatedly scanning their suffixes', () => {
+  const moduleUrl = new URL(
+    '../src/sheet-model/glyphCodeName.ts',
+    import.meta.url,
+  );
+  // Run separately so a quadratic-time regression can be terminated even
+  // though synchronous parsing would block the test runner's own timeout.
+  const output = execFileSync(
+    process.execPath,
+    [
+      '--input-type=module',
+      '-e',
+      `
+        import { deriveGlyphCodeName } from ${JSON.stringify(moduleUrl.href)};
+        const malformed = '^(' + '^(('.repeat(100_000);
+        process.stdout.write(JSON.stringify([
+          deriveGlyphCodeName({ glyphPlaintext: malformed, glyph: 'A_(x)', id: 'fallback-id' }),
+          deriveGlyphCodeName({ glyph: malformed, id: 'fallback-id' }),
+          deriveGlyphCodeName({ id: malformed }),
+          deriveGlyphCodeName({ glyph: 'A' + malformed + 'Z', id: 'fallback-id' }),
+        ]));
+      `,
+    ],
+    { encoding: 'utf8', timeout: 5_000 },
+  );
+
+  expect(JSON.parse(output)).toEqual(['A_x', 'fallback_id', 'symbol', 'A_Z']);
+}, 10_000);