import { Rule } from './rule-interface';
/**
* MD024: Multiple headings with the same content
*
* This rule is triggered when multiple headings in the document have the same text content.
* The rule can be configured to allow this behavior for siblings (headings at the same level)
* while still preventing duplicate headings across different levels.
*/
export const name = 'MD024';
export const description = 'Multiple headings with the same content';
/**
* Configuration options for MD024
*/
interface MD024Config {
allow_different_nesting?: boolean; // Allow headings with same content if they have different nesting (default: false)
siblings_only?: boolean; // Only check sibling headings (default: false)
}
/**
* Interface for tracking headings with their level and content
*/
interface HeadingInfo {
level: number;
content: string;
index: number;
section?: number[]; // Track section numbering (e.g., [2, 1] for heading 2.1)
}
/**
* Fix markdown content to make heading content unique
* @param lines Array of string lines to fix
* @param config Optional configuration object
* @returns Fixed lines array with unique heading content
*/
export function fix(lines: string[], config?: MD024Config): string[] {
if (lines.length === 0) return lines;
// Default configuration
const allowDifferentNesting = config?.allow_different_nesting || false;
const siblingsOnly = config?.siblings_only || false;
// Track all headings
const headings: HeadingInfo[] = [];
// Helper to extract heading level and content from a line
function parseHeading(line: string): HeadingInfo | null {
// ATX style heading (# Heading)
const atxMatch = line.match(/^(#{1,6})\s+(.+?)(?:\s+#*)?$/);
if (atxMatch) {
return {
level: atxMatch[1].length,
content: atxMatch[2].trim(),
index: -1, // Will be set when processing
};
}
return null;
}
// First pass: collect all headings and track their positions
for (let i = 0; i < lines.length; i++) {
const heading = parseHeading(lines[i]);
if (heading) {
heading.index = i;
headings.push(heading);
}
}
// Add section numbering to help track hierarchy
let currentSection: number[] = [];
for (let i = 0; i < headings.length; i++) {
const heading = headings[i];
// Update section tracking
while (currentSection.length >= heading.level) {
currentSection.pop();
}
while (currentSection.length < heading.level - 1) {
currentSection.push(0);
}
if (currentSection.length < heading.level) {
currentSection.push(1);
} else {
currentSection[currentSection.length - 1]++;
}
heading.section = [...currentSection];
}
// Second pass: identify duplicate headings and modify them
const result = [...lines];
const seenHeadings: Map<string, Set<string>> = new Map();
for (const heading of headings) {
const { level, content, index, section } = heading;
// Key to check against depends on configuration
let key = content.toLowerCase();
if (allowDifferentNesting || siblingsOnly) {
// For allow_different_nesting or siblings_only, also consider the heading's location
if (allowDifferentNesting) {
// Consider full path (different nesting allowed)
key = section?.join('.') + ':' + key;
} else if (siblingsOnly) {
// Consider only parent section (siblings only)
key = section?.slice(0, -1).join('.') + ':' + level + ':' + key;
}
}
// Track seen headings by key
if (!seenHeadings.has(key)) {
seenHeadings.set(key, new Set([content]));
} else {
const headingSet = seenHeadings.get(key)!;
// If we've seen this heading before, modify it to make it unique
if (headingSet.has(content)) {
// Use section numbering to make the heading unique
const sectionLabel = section?.join('.') || '';
const newContent = `${content} (${sectionLabel})`;
// Update the line with the new heading content
const line = result[index];
if (line.endsWith('#')) {
// For closed ATX headings (# Heading #)
result[index] = line.replace(/^(#{1,6}\s+)(.+?)(\s+#*)?$/, `$1${newContent}$3`);
} else {
// For regular ATX headings (# Heading)
result[index] = line.replace(/^(#{1,6}\s+)(.+?)$/, `$1${newContent}`);
}
// Add the new content to the set to avoid duplicates
headingSet.add(newContent);
} else {
// First time seeing this exact content in this context
headingSet.add(content);
}
}
}
return result;
}
/**
* Rule implementation for MD024
*/
export const rule: Rule = {
name,
description,
fix
};
export default rule;
