import { Rule, RuleViolation } from './rule-interface';
/**
* MD049: Emphasis style
*
* This rule is triggered when the style used for emphasis (italics)
* is inconsistent. By default, this rule enforces asterisks (*) for emphasis,
* but it can be configured to enforce underscores (_) instead.
*/
export const name = 'MD049';
export const description = 'Emphasis style';
/**
* Check if a line is within a code block (fenced or indented)
* @param lines Array of all lines
* @param lineIndex Index of the line to check
* @returns True if the line is within a code block
*/
function isInCodeBlock(lines: string[], lineIndex: number): boolean {
let inFencedBlock = false;
let fenceChar = '';
// Check if current line is indented code block (4+ spaces)
const currentLine = lines[lineIndex];
if (currentLine.match(/^ /)) {
return true;
}
// Check lines before current line for fenced code blocks
for (let i = 0; i < lineIndex; i++) {
const line = lines[i].trim();
// Check for fenced code block start/end
const backtickMatch = line.match(/^`{3,}/);
const tildeMatch = line.match(/^~{3,}/);
if (backtickMatch || tildeMatch) {
const currentFence = backtickMatch ? '`' : '~';
if (!inFencedBlock) {
// Starting a fenced block
inFencedBlock = true;
fenceChar = currentFence;
} else if (fenceChar === currentFence) {
// Ending a fenced block
inFencedBlock = false;
fenceChar = '';
}
}
}
return inFencedBlock;
}
/**
* Find emphasis markers in a line, avoiding code spans
* @param line Line to search
* @returns Array of emphasis markers found
*/
function findEmphasisMarkers(line: string): Array<{ type: 'asterisk' | 'underscore'; start: number; end: number; text: string }> {
const markers: Array<{ type: 'asterisk' | 'underscore'; start: number; end: number; text: string }> = [];
let i = 0;
while (i < line.length) {
const char = line[i];
// Skip code spans
if (char === '`') {
const codeSpanStart = i;
i++;
while (i < line.length && line[i] !== '`') {
i++;
}
if (i < line.length) {
i++; // Skip closing backtick
}
continue;
}
// Look for emphasis markers
if (char === '*' || char === '_') {
const markerChar = char;
const markerStart = i;
// Skip if it's part of bold (**text** or __text__)
if (i + 1 < line.length && line[i + 1] === markerChar) {
i += 2;
continue;
}
// Look for closing marker
i++;
const textStart = i;
while (i < line.length && line[i] !== markerChar) {
i++;
}
if (i < line.length && i > textStart) {
// Found a complete emphasis
const text = line.substring(textStart, i);
// Skip if emphasis has spaces at the beginning or end (not valid emphasis)
if (text.startsWith(' ') || text.endsWith(' ')) {
i++; // Skip closing marker
continue;
}
markers.push({
type: markerChar === '*' ? 'asterisk' : 'underscore',
start: markerStart,
end: i + 1,
text
});
i++; // Skip closing marker
}
} else {
i++;
}
}
return markers;
}
/**
* Validate function to check emphasis style consistency
* @param lines Array of string lines to validate
* @param config Optional rule configuration
* @returns Array of rule violations
*/
export function validate(lines: string[], config?: any): RuleViolation[] {
const violations: RuleViolation[] = [];
const style = config?.style || 'asterisk'; // Default to asterisk
// Track what styles we've seen
const stylesFound = new Set<string>();
for (let i = 0; i < lines.length; i++) {
const line = lines[i];
// Skip code blocks
if (isInCodeBlock(lines, i)) {
continue;
}
// Find emphasis markers in this line
const markers = findEmphasisMarkers(line);
for (const marker of markers) {
stylesFound.add(marker.type);
// Check if this marker matches the configured style
if (style === 'asterisk' && marker.type === 'underscore') {
violations.push({
lineNumber: i + 1,
details: `Emphasis style should be asterisk (*) not underscore (_)`,
range: [marker.start, marker.end]
});
} else if (style === 'underscore' && marker.type === 'asterisk') {
violations.push({
lineNumber: i + 1,
details: `Emphasis style should be underscore (_) not asterisk (*)`,
range: [marker.start, marker.end]
});
}
}
}
return violations;
}
/**
* Fix emphasis style by standardizing to the configured style
* @param lines Array of string lines to fix
* @param config Optional rule configuration
* @returns Fixed lines array with consistent emphasis style
*/
export function fix(lines: string[], config?: any): string[] {
const style = config?.style || 'asterisk'; // Default to asterisk
return lines.map((line, index) => {
// Skip code blocks
if (isInCodeBlock(lines, index)) {
return line;
}
// Find emphasis markers that need to be fixed
const markers = findEmphasisMarkers(line);
let fixedLine = line;
// Process markers from right to left to avoid index shifting issues
for (let i = markers.length - 1; i >= 0; i--) {
const marker = markers[i];
// Check if this marker needs to be fixed
let shouldFix = false;
let newMarker = '';
if (style === 'asterisk' && marker.type === 'underscore') {
shouldFix = true;
newMarker = '*';
} else if (style === 'underscore' && marker.type === 'asterisk') {
shouldFix = true;
newMarker = '_';
}
if (shouldFix) {
// Replace the emphasis markers
const beforePart = fixedLine.substring(0, marker.start);
const afterPart = fixedLine.substring(marker.end);
fixedLine = beforePart + newMarker + marker.text + newMarker + afterPart;
}
}
return fixedLine;
});
}
/**
* Rule implementation for MD049
*/
export const rule: Rule = {
name,
description,
validate,
fix
};
export default rule;
