Merge frontmatter/splitter: splitFrontmatter function with 18 tests

test/frontmatter.test.ts

@@ -1,7 +1,180 @@
 import { describe, it, expect } from 'vitest';
+import { splitFrontmatter } from '../src/frontmatter/parse.js';
 
-describe('Frontmatter', () => {
-  it('placeholder — parse and serialize', () => {
-    expect(true).toBe(true);
+describe('splitFrontmatter', () => {
+  // ─── Standard frontmatter ────────────────────────────────────────────
+
+  it('extracts YAML data and markdown content from standard frontmatter', () => {
+    const input = `---
+title: Hello
+status: pending
+---
+# Heading
+
+Some content here.
+`;
+
+    const result = splitFrontmatter(input);
+    expect(result).not.toBeNull();
+    expect(result!.data).toBe('title: Hello\nstatus: pending');
+    expect(result!.content).toBe('# Heading\n\nSome content here.\n');
+  });
+
+  it('handles multi-line YAML data', () => {
+    const input = `---
+title: My Task
+depends_on:
+  - task-a
+  - task-b
+---
+Content here`;
+
+    const result = splitFrontmatter(input);
+    expect(result).not.toBeNull();
+    expect(result!.data).toBe('title: My Task\ndepends_on:\n  - task-a\n  - task-b');
+    expect(result!.content).toBe('Content here');
+  });
+
+  // ─── Empty frontmatter ───────────────────────────────────────────────
+
+  it('returns empty data and content for "---\\n---"', () => {
+    const result = splitFrontmatter('---\n---');
+    expect(result).not.toBeNull();
+    expect(result!.data).toBe('');
+    expect(result!.content).toBe('');
+  });
+
+  it('returns empty data with trailing content after empty frontmatter', () => {
+    const result = splitFrontmatter('---\n---\nSome content');
+    expect(result).not.toBeNull();
+    expect(result!.data).toBe('');
+    expect(result!.content).toBe('Some content');
+  });
+
+  // ─── No frontmatter ──────────────────────────────────────────────────
+
+  it('returns null when there is no frontmatter at all', () => {
+    const result = splitFrontmatter('Hello world\nNo frontmatter here');
+    expect(result).toBeNull();
+  });
+
+  it('returns null when file starts with text (no opening ---)', () => {
+    const result = splitFrontmatter('Some text\n---\nMore text');
+    expect(result).toBeNull();
+  });
+
+  it('returns null when opening --- exists but no closing delimiter', () => {
+    const result = splitFrontmatter('---\ntitle: Hello\nNo closing delimiter');
+    expect(result).toBeNull();
+  });
+
+  // ─── 4+ dashes are NOT delimiters ────────────────────────────────────
+
+  it('returns null when opening delimiter is 4+ dashes (----)', () => {
+    const result = splitFrontmatter('----\ntitle: Hello\n----\nContent');
+    expect(result).toBeNull();
+  });
+
+  it('does not treat ---- as a closing delimiter', () => {
+    const input = `---
+title: Hello
+----
+Content after four dashes`;
+    const result = splitFrontmatter(input);
+    // No valid closing delimiter found (---- doesn't count)
+    expect(result).toBeNull();
+  });
+
+  it('does not treat 5 dashes as a closing delimiter', () => {
+    const input = `---
+title: Hello
+-----
+Content`;
+    const result = splitFrontmatter(input);
+    expect(result).toBeNull();
+  });
+
+  // ─── Dashes in content body (shouldn't be treated as delimiters) ─────
+
+  it('ignores --- in the content body after valid frontmatter', () => {
+    const input = `---
+title: Hello
+---
+Some text
+
+---
+More text
+`;
+
+    const result = splitFrontmatter(input);
+    expect(result).not.toBeNull();
+    expect(result!.data).toBe('title: Hello');
+    expect(result!.content).toBe('Some text\n\n---\nMore text\n');
+  });
+
+  it('handles horizontal rule (---) in content', () => {
+    const input = `---
+title: Hello
+---
+Paragraph above
+
+---
+
+Paragraph below
+`;
+
+    const result = splitFrontmatter(input);
+    expect(result).not.toBeNull();
+    expect(result!.data).toBe('title: Hello');
+    expect(result!.content).toBe('Paragraph above\n\n---\n\nParagraph below\n');
+  });
+
+  // ─── BOM handling ─────────────────────────────────────────────────────
+
+  it('handles UTF-8 BOM at start of file', () => {
+    const input = '\uFEFF---\ntitle: Hello\n---\nContent';
+    const result = splitFrontmatter(input);
+    expect(result).not.toBeNull();
+    expect(result!.data).toBe('title: Hello');
+    expect(result!.content).toBe('Content');
+  });
+
+  // ─── Edge cases ──────────────────────────────────────────────────────
+
+  it('file with only "---\\n---"', () => {
+    const result = splitFrontmatter('---\n---');
+    expect(result).not.toBeNull();
+    expect(result!.data).toBe('');
+    expect(result!.content).toBe('');
+  });
+
+  it('content body starts after closing ---\\n', () => {
+    const input = `---
+key: value
+---
+Body starts here`;
+    const result = splitFrontmatter(input);
+    expect(result).not.toBeNull();
+    expect(result!.content).toBe('Body starts here');
+  });
+
+  it('content is empty string when closing --- is at end of file with no trailing newline', () => {
+    const result = splitFrontmatter('---\nkey: value\n---');
+    expect(result).not.toBeNull();
+    expect(result!.data).toBe('key: value');
+    expect(result!.content).toBe('');
+  });
+
+  it('handles leading whitespace on first line before ---', () => {
+    const input = '  ---\ntitle: Hello\n---\nContent';
+    const result = splitFrontmatter(input);
+    expect(result).not.toBeNull();
+    expect(result!.data).toBe('title: Hello');
+    expect(result!.content).toBe('Content');
+  });
+
+  it('returns null if only opening --- with no newline', () => {
+    const result = splitFrontmatter('---');
+    expect(result).toBeNull();
   });
 });