feat: add heading level normalization for split markdown sections

## CHANGES

- Add `decrementHeadingLevels` helper method
- Adjust heading levels when splitting sections
- Make split sections start at h1
- Deep clone trees to avoid mutations
- Update tests for new heading levels
- Bump version to 1.2.1

Author: ksylvan

bin/md-tree.js

@@ -472,7 +472,10 @@ For more information, visit: https://github.com/ksylvan/markdown-tree-parser
     for (let i = 0; i < sections.length; i++) {
       const section = sections[i];
       const headingText = section.headingText;
-      const markdown = await this.parser.stringify(section.tree);
+
+      // Decrement heading levels by 1 so the section starts at level 1
+      const adjustedTree = this.decrementHeadingLevels(section.tree);
+      const markdown = await this.parser.stringify(adjustedTree);
 
       // Generate filename without numbered prefix
       const filename = `${this.sanitizeFilename(headingText)}.md`;
@@ -574,6 +577,30 @@ For more information, visit: https://github.com/ksylvan/markdown-tree-parser
 
     return null;
   }
+
+  // Helper method to decrement all heading levels in a tree by 1
+  decrementHeadingLevels(tree) {
+    if (!tree || !tree.children) return tree;
+
+    // Create a deep copy to avoid modifying the original tree
+    const clonedTree = JSON.parse(JSON.stringify(tree));
+
+    const decrementNode = (node) => {
+      if (node.type === 'heading' && node.depth > 1) {
+        node.depth = node.depth - 1;
+      }
+
+      if (node.children) {
+        node.children.forEach(decrementNode);
+      }
+    };
+
+    if (clonedTree.children) {
+      clonedTree.children.forEach(decrementNode);
+    }
+
+    return clonedTree;
+  }
 }
 
 // Run CLI

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@kayvan/markdown-tree-parser",
-  "version": "1.2.0",
+  "version": "1.2.1",
   "description": "A powerful JavaScript library and CLI tool for parsing and manipulating markdown files as tree structures using the remark/unified ecosystem",
   "type": "module",
   "main": "index.js",

test/test-cli.js

@@ -243,31 +243,31 @@ async function runTests() {
     const introPath = path.join(outputDir, 'introduction.md');
     const introContent = await fs.readFile(introPath, 'utf-8');
     assert(
-      introContent.includes('## Introduction'),
+      introContent.includes('# Introduction'),
       'Introduction file should have section heading'
     );
     assert(
       introContent.includes('This is the introduction section'),
       'Should have section content'
     );
     assert(
-      introContent.includes('### Background'),
+      introContent.includes('## Background'),
       'Should include subsections'
     );
 
     // Check installation.md
     const installPath = path.join(outputDir, 'installation.md');
     const installContent = await fs.readFile(installPath, 'utf-8');
     assert(
-      installContent.includes('## Installation'),
+      installContent.includes('# Installation'),
       'Installation file should have section heading'
     );
     assert(
       installContent.includes('Instructions for installation'),
       'Should have section content'
     );
     assert(
-      installContent.includes('### Prerequisites'),
+      installContent.includes('## Prerequisites'),
       'Should include subsections'
     );
     assert(