import { Rule } from './rule-interface';
/**
* MD053: Link and image reference definitions should be needed
*
* This rule is triggered when a reference definition is not used by any link or image.
* Our fix will remove unused reference definitions.
*/
export const name = 'MD053';
export const description = 'Link and image reference definitions should be needed';
/**
* Fix by removing unused reference definitions
* @param lines Array of string lines to fix
* @returns Fixed lines array with only used reference definitions
*/
export function fix(lines: string[]): string[] {
// First, extract all reference link definitions and their line indices
const { definitions, definitionLines } = extractReferenceLinkDefinitions(lines);
// Find all reference usages
const usedLabels = findReferenceUsages(lines);
// Filter out lines with unused reference definitions
return lines.filter((line, index) => {
// If this is not a definition line, keep it
if (!definitionLines.includes(index)) {
return true;
}
// Find which definition this line corresponds to
const definitionMatch = line.match(/^\s*\[([^\]]+)\]:/);
if (!definitionMatch) {
return true; // Shouldn't happen, but keep the line if no match
}
const label = definitionMatch[1].trim().toLowerCase();
// Keep the line if the reference is used
return usedLabels.includes(label);
});
}
/**
* Extract reference link definitions from the document
* Returns both the definitions and their line indices
*/
function extractReferenceLinkDefinitions(lines: string[]): {
definitions: Record<string, string>,
definitionLines: number[]
} {
const definitions: Record<string, string> = {};
const definitionLines: number[] = [];
// Regular expression to match reference link definitions: [label]: url
const definitionRegex = /^\s*\[([^\]]+)\]:\s*(\S+)(?:\s+(?:"([^"]+)"|'([^']+)'|\(([^)]+)\)))?$/;
for (let i = 0; i < lines.length; i++) {
const line = lines[i];
const match = line.match(definitionRegex);
if (match) {
const label = match[1].trim();
const url = match[2];
// Store the definition (case-insensitive)
definitions[label.toLowerCase()] = url;
definitionLines.push(i);
}
}
return { definitions, definitionLines };
}
/**
* Find all reference usages in the document
* Returns an array of lowercase labels that are used
*/
function findReferenceUsages(lines: string[]): string[] {
const usedLabels: string[] = [];
// Reference link regex: [text][label] or [text][] (shortcut reference)
const refLinkRegex = /\[([^\]]+)\]\[([^\]]*)\]/g;
// Reference image regex: ![text][label] or ![text][] (shortcut reference)
const refImageRegex = /!\[([^\]]+)\]\[([^\]]*)\]/g;
for (const line of lines) {
// Find all reference links in this line
let match;
while ((match = refLinkRegex.exec(line)) !== null) {
const text = match[1];
const label = match[2] || text; // For shortcut references, label is the text
usedLabels.push(label.toLowerCase());
}
// Reset regex to search from the beginning of the line
refImageRegex.lastIndex = 0;
// Find all reference images in this line
while ((match = refImageRegex.exec(line)) !== null) {
const text = match[1];
const label = match[2] || text; // For shortcut references, label is the text
usedLabels.push(label.toLowerCase());
}
}
return usedLabels;
}
/**
* Rule implementation for MD053
*/
export const rule: Rule = {
name,
description,
fix
};
export default rule;
