refactor(core): Extract thought parsing logic into a dedicated utility (#9503)

packages/core/src/utils/thoughtUtils.test.ts

@@ -0,0 +1,80 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect } from 'vitest';
+import { parseThought } from './thoughtUtils.js';
+
+describe('parseThought', () => {
+  it.each([
+    {
+      name: 'a standard thought with subject and description',
+      rawText: '**Subject:** This is the description.',
+      expected: {
+        subject: 'Subject:',
+        description: 'This is the description.',
+      },
+    },
+    {
+      name: 'leading and trailing whitespace in the raw string',
+      rawText: '  **Subject** description with spaces   ',
+      expected: { subject: 'Subject', description: 'description with spaces' },
+    },
+    {
+      name: 'whitespace surrounding the subject content',
+      rawText: '** Subject  **',
+      expected: { subject: 'Subject', description: '' },
+    },
+    {
+      name: 'a thought with only a subject',
+      rawText: '**Only Subject**',
+      expected: { subject: 'Only Subject', description: '' },
+    },
+    {
+      name: 'a thought with only a description (no subject)',
+      rawText: 'This is just a description.',
+      expected: { subject: '', description: 'This is just a description.' },
+    },
+    {
+      name: 'an empty string input',
+      rawText: '',
+      expected: { subject: '', description: '' },
+    },
+    {
+      name: 'newlines within the subject and description',
+      rawText:
+        '**Multi-line\nSubject**\nHere is a description\nspread across lines.',
+      expected: {
+        subject: 'Multi-line\nSubject',
+        description: 'Here is a description\nspread across lines.',
+      },
+    },
+    {
+      name: 'only the first subject if multiple are present',
+      rawText: '**First** some text **Second**',
+      expected: { subject: 'First', description: 'some text **Second**' },
+    },
+    {
+      name: 'text before and after the subject',
+      rawText: 'Prefix text **Subject** Suffix text.',
+      expected: {
+        subject: 'Subject',
+        description: 'Prefix text  Suffix text.',
+      },
+    },
+    {
+      name: 'an unclosed subject tag',
+      rawText: 'Text with **an unclosed subject',
+      expected: { subject: '', description: 'Text with **an unclosed subject' },
+    },
+    {
+      name: 'an empty subject tag',
+      rawText: 'A thought with **** in the middle.',
+      expected: { subject: '', description: 'A thought with  in the middle.' },
+    },
+  ])('should correctly parse $name', ({ rawText, expected }) => {
+    expect(parseThought(rawText)).toEqual(expected);
+  });
+});

packages/core/src/utils/thoughtUtils.ts

@@ -0,0 +1,54 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+export type ThoughtSummary = {
+  subject: string;
+  description: string;
+};
+
+const START_DELIMITER = '**';
+const END_DELIMITER = '**';
+
+/**
+ * Parses a raw thought string into a structured ThoughtSummary object.
+ *
+ * Thoughts are expected to have a bold "subject" part enclosed in double
+ * asterisks (e.g., **Subject**). The rest of the string is considered
+ * the description. This function only parses the first valid subject found.
+ *
+ * @param rawText The raw text of the thought.
+ * @returns A ThoughtSummary object. If no valid subject is found, the entire
+ * string is treated as the description.
+ */
+export function parseThought(rawText: string): ThoughtSummary {
+  const startIndex = rawText.indexOf(START_DELIMITER);
+  if (startIndex === -1) {
+    // No start delimiter found, the whole text is the description.
+    return { subject: '', description: rawText.trim() };
+  }
+
+  const endIndex = rawText.indexOf(
+    END_DELIMITER,
+    startIndex + START_DELIMITER.length,
+  );
+  if (endIndex === -1) {
+    // Start delimiter found but no end delimiter, so it's not a valid subject.
+    // Treat the entire string as the description.
+    return { subject: '', description: rawText.trim() };
+  }
+
+  const subject = rawText
+    .substring(startIndex + START_DELIMITER.length, endIndex)
+    .trim();
+
+  // The description is everything before the start delimiter and after the end delimiter.
+  const description = (
+    rawText.substring(0, startIndex) +
+    rawText.substring(endIndex + END_DELIMITER.length)
+  ).trim();
+
+  return { subject, description };
+}