import { Rule } from './rule-interface';
/**
* MD036: Emphasis used instead of a heading
*
* This rule identifies when emphasis markers like bold or italic are used to create
* a heading-like structure, when it would be better to use actual heading syntax.
*
* For example, the following should be converted to a proper heading:
* **This is a heading**
*
* It should become:
* ## This is a heading
*/
export const name = 'MD036';
export const description = 'Emphasis used instead of a heading';
/**
* Configuration options for MD036
*/
interface MD036Config {
punctuation?: string; // Regex to match punctuation that indicates the emphasis is not a heading (default: ".,;:!?")
}
/**
* Fix instances where emphasis is used instead of a heading
* @param lines Array of string lines to fix
* @param config Optional configuration object
* @returns Fixed lines array with proper headings
*/
export function fix(lines: string[], config?: MD036Config): string[] {
if (lines.length === 0) return lines;
// Default configuration
const punctuationRegex = config?.punctuation
? new RegExp(`[${config.punctuation}]$`)
: /[.,;:!?]$/;
const result: string[] = [];
let inCodeBlock = false;
let inList = false;
// Regular expressions for different emphasis styles
const boldRegex = /^\s*(\*\*|__)(.*?)(\*\*|__)\s*$/;
const italicRegex = /^\s*(\*|_)(.*?)(\*|_)\s*$/;
// Helper to check if a line is a potential heading
function isEmphasisHeading(line: string): { isHeading: boolean; content: string; level: number } {
// Don't convert if we're in a code block or list
if (inCodeBlock || inList) {
return { isHeading: false, content: '', level: 0 };
}
// Check for bold emphasis (**text** or __text__)
const boldMatch = line.match(boldRegex);
if (boldMatch) {
const content = boldMatch[2].trim();
// Skip lines with terminal punctuation or that are too short
if (punctuationRegex.test(content) || content.length < 2) {
return { isHeading: false, content: '', level: 0 };
}
return { isHeading: true, content, level: 2 }; // Bold = h2
}
// Check for italic emphasis (*text* or _text_)
const italicMatch = line.match(italicRegex);
if (italicMatch) {
const content = italicMatch[2].trim();
// Skip lines with terminal punctuation or that are too short
if (punctuationRegex.test(content) || content.length < 2) {
return { isHeading: false, content: '', level: 0 };
}
return { isHeading: true, content, level: 3 }; // Italic = h3
}
return { isHeading: false, content: '', level: 0 };
}
// Process each line
for (let i = 0; i < lines.length; i++) {
const line = lines[i];
const trimmed = line.trim();
// Track code blocks
if (trimmed.startsWith('```') || trimmed.startsWith('~~~')) {
inCodeBlock = !inCodeBlock;
result.push(line);
continue;
}
// Track lists (simple detection)
if (trimmed.match(/^[-+*](\s+|$)/) || trimmed.match(/^\d+\.(\s+|$)/)) {
inList = true;
result.push(line);
continue;
} else if (trimmed === '' && inList) {
inList = false;
result.push(line);
continue;
} else if (inList) {
result.push(line);
continue;
}
// Check if this line is an emphasis heading
const { isHeading, content, level } = isEmphasisHeading(line);
if (isHeading) {
// Convert to a proper heading
const indentation = line.match(/^\s*/)?.[0] || '';
result.push(`${indentation}${'#'.repeat(level)} ${content}`);
// If the next line isn't blank, add a blank line
if (i < lines.length - 1 && lines[i + 1].trim() !== '') {
result.push('');
}
} else {
result.push(line);
}
}
return result;
}
/**
* Rule implementation for MD036
*/
export const rule: Rule = {
name,
description,
fix
};
export default rule;
