Rules

interface RecommendedRules {
  "markdown/fenced-code-language": "error";
  "markdown/heading-increment": "error"; 
  "markdown/no-duplicate-definitions": "error";
  "markdown/no-empty-definitions": "error";
  "markdown/no-empty-images": "error";
  "markdown/no-empty-links": "error";
  "markdown/no-invalid-label-refs": "error";
  "markdown/no-missing-atx-heading-space": "error";
  "markdown/no-missing-label-refs": "error";
  "markdown/no-missing-link-fragments": "error";
  "markdown/no-multiple-h1": "error";
  "markdown/no-reversed-media-syntax": "error";
  "markdown/no-space-in-emphasis": "error";
  "markdown/no-unused-definitions": "error";
  "markdown/require-alt-text": "error";
  "markdown/table-column-count": "error";
}

/**
 * Require languages for fenced code blocks
 * Recommended: Yes
 */
"markdown/fenced-code-language": "error" | "warn" | "off"

<!-- ✓ Good -->
```javascript
console.log("Hello");

console.log("Hello");

#### heading-increment

Enforces heading levels increment by one (no skipping levels like H1 → H3).

```javascript { .api }
/**
 * Enforce heading levels increment by one
 * Recommended: Yes
 */
"markdown/heading-increment": "error" | "warn" | "off"

<!-- ✓ Good -->
# Main Title (H1)
## Section (H2)
### Subsection (H3)

<!-- ✗ Bad -->
# Main Title (H1)
### Subsection (H3) - skipped H2

/**
 * Disallow multiple H1 headings in the same document
 * Recommended: Yes
 */
"markdown/no-multiple-h1": "error" | "warn" | "off"

<!-- ✓ Good -->
# Main Title
## Section 1
## Section 2

<!-- ✗ Bad -->
# Main Title
# Another Main Title

/**
 * Disallow duplicate definitions
 * Recommended: Yes
 */
"markdown/no-duplicate-definitions": "error" | "warn" | "off"

<!-- ✓ Good -->
[link]: https://example.com
[another]: https://other.com

<!-- ✗ Bad -->
[link]: https://example.com
[link]: https://duplicate.com

/**
 * Disallow empty definitions
 * Recommended: Yes
 */
"markdown/no-empty-definitions": "error" | "warn" | "off"

/**
 * Disallow invalid label references
 * Recommended: Yes
 */
"markdown/no-invalid-label-refs": "error" | "warn" | "off"

/**
 * Disallow missing label references
 * Recommended: Yes
 */
"markdown/no-missing-label-refs": "error" | "warn" | "off"

/**
 * Disallow link fragments that do not reference valid headings
 * Recommended: Yes
 */
"markdown/no-missing-link-fragments": "error" | "warn" | "off"

<!-- ✓ Good -->
# Section One
[Link to section](#section-one)

<!-- ✗ Bad -->
# Section One
[Link to non-existent](#section-two)

/**
 * Disallow unused definitions
 * Recommended: Yes
 */
"markdown/no-unused-definitions": "error" | "warn" | "off"

/**
 * Disallow empty images
 * Recommended: Yes
 */
"markdown/no-empty-images": "error" | "warn" | "off"

/**
 * Disallow empty links
 * Recommended: Yes
 */
"markdown/no-empty-links": "error" | "warn" | "off"

/**
 * Require alternative text for images
 * Recommended: Yes
 */  
"markdown/require-alt-text": "error" | "warn" | "off"

<!-- ✓ Good -->
![Description of image](image.png)

<!-- ✗ Bad -->
![](image.png)

/**
 * Disallow headings without a space after the hash characters
 * Recommended: Yes
 */
"markdown/no-missing-atx-heading-space": "error" | "warn" | "off"

<!-- ✓ Good -->
# Heading with space

<!-- ✗ Bad -->
#Heading without space

/**
 * Disallow reversed link and image syntax
 * Recommended: Yes
 */
"markdown/no-reversed-media-syntax": "error" | "warn" | "off"

<!-- ✓ Good -->
![alt text](image.png)
[link text](url)

<!-- ✗ Bad -->
(image.png)[alt text]
(url)[link text]

/**
 * Disallow spaces around emphasis markers
 * Recommended: Yes
 */
"markdown/no-space-in-emphasis": "error" | "warn" | "off"

<!-- ✓ Good -->
*italic text*
**bold text**

<!-- ✗ Bad -->
* italic text *
** bold text **

/**
 * Disallow data rows in a GitHub Flavored Markdown table from having more cells than the header row
 * Recommended: Yes
 */
"markdown/table-column-count": "error" | "warn" | "off"

<!-- ✓ Good -->
| Name | Age |
|------|-----|
| John | 25  |

<!-- ✗ Bad -->
| Name | Age |
|------|-----|
| John | 25  | Extra |

/**
 * Disallow bare URLs
 * Recommended: No
 */
"markdown/no-bare-urls": "error" | "warn" | "off"

<!-- ✓ Good -->
[Example](https://example.com)

<!-- ✗ Bad (when rule is enabled) -->
https://example.com

/**
 * Disallow duplicate headings in the same document
 * Recommended: No
 */
"markdown/no-duplicate-headings": "error" | "warn" | "off"

/**
 * Disallow HTML tags
 * Recommended: No
 * Options: { allowed?: string[], allowedIgnoreCase?: boolean }
 */
"markdown/no-html": "error" | "warn" | "off" | ["error", {
  allowed?: string[];
  allowedIgnoreCase?: boolean;
}]

// Disallow all HTML
"markdown/no-html": "error"

// Allow specific HTML tags
"markdown/no-html": ["error", {
  allowed: ["br", "strong", "em"]
}]

// Allow specific tags (case insensitive)
"markdown/no-html": ["error", {
  allowed: ["BR", "STRONG"],
  allowedIgnoreCase: true
}]

/**
 * Base rule definition for Markdown rules
 */
interface MarkdownRuleDefinition<Options = {}> {
  meta: {
    type: "problem" | "suggestion" | "layout";
    docs: {
      description: string;
      recommended: boolean;
      url?: string;
    };
    fixable?: "code" | "whitespace";
    schema?: JSONSchema7 | JSONSchema7[];
    messages: { [messageId: string]: string };
  };
  create(context: RuleContext): MarkdownRuleVisitor;
}

/**
 * Rule context with Markdown-specific methods
 */
interface RuleContext {
  report(descriptor: ReportDescriptor): void;
  getSourceCode(): MarkdownSourceCode;
  // ... other ESLint context methods
}

/**
 * Rule visitor for Markdown AST nodes
 */
interface MarkdownRuleVisitor {
  root?(node: Root): void;
  heading?(node: Heading): void;
  paragraph?(node: Paragraph): void;
  link?(node: Link): void;
  image?(node: Image): void;
  code?(node: Code): void;
  html?(node: Html): void;
  table?(node: Table): void;
  // ... exit handlers with :exit suffix
}

/**
 * Options for no-html rule
 */
interface NoHtmlOptions {
  allowed?: string[];
  allowedIgnoreCase?: boolean;
}

/**
 * Generic rule configuration
 */
type RuleConfig<T = any> = 
  | "off" 
  | "warn" 
  | "error" 
  | ["off"] 
  | ["warn"] 
  | ["error"] 
  | ["warn", T] 
  | ["error", T];

import markdown from "@eslint/markdown";

export default [
    {
        files: ["**/*.md"],
        plugins: { markdown },
        language: "markdown/gfm",
        rules: {
            // Enable specific rules
            "markdown/no-html": "error",
            "markdown/no-bare-urls": "warn",
            
            // Configure rule with options
            "markdown/no-html": ["error", {
                allowed: ["br", "strong", "em"],
                allowedIgnoreCase: true
            }],
            
            // Disable specific rules
            "markdown/no-duplicate-headings": "off"
        }
    }
];

export default [
    // Default rules for all Markdown files
    {
        files: ["**/*.md"],
        plugins: { markdown },
        language: "markdown/commonmark",
        rules: {
            "markdown/no-html": "error"
        }
    },
    // Allow HTML in README files
    {
        files: ["README.md", "**/README.md"],
        rules: {
            "markdown/no-html": "off"
        }
    }
];