mdsvex.config.js

/**
 * Source: https://github.com/melt-ui/melt-ui/blob/develop/mdsvex.config.js
 */

import { resolve } from 'path';
import { readFileSync } from 'fs';
import { fileURLToPath } from 'url';
import { visit } from 'unist-util-visit';
import { toHtml } from 'hast-util-to-html';
import rehypePrettyCode from 'rehype-pretty-code';
import { BUNDLED_LANGUAGES, getHighlighter } from 'shiki-es';
import { escapeSvelte } from '@huntabyte/mdsvex';
import katex from 'katex';

// import { highlightCode } from './src/lib/scripts/highlight.js';

const __dirname = fileURLToPath(new URL('.', import.meta.url));

const correct_hast_tree = () => (tree) => {
	visit(tree, 'text', (node) => {
		if (node.value.trim().startsWith('<')) {
			node.type = 'raw';
		}
	});
};

const inlineKatexUsingInlineCode = () => (tree) => { 
	visit(tree, 'inlineCode', (node) => {
		if (node.value.endsWith('{:eq}')) {
			node.value = node.value.replace('{:eq}', '')
			const str = katex.renderToString(node.value, {
				displayMode: false,
				leqno: false,
				fleqn: false,
				throwOnError: true,
				errorColor: '#cc0000',
				strict: 'warn',
				output: 'htmlAndMathml',
				trust: false,
				macros: { '\\f': '#1f(#2)' }
			});

			node.type = 'raw';
			node.value = '<span class="text-base mx-1">{@html `' + str + '`}</span>';
		} 
	})
}

const katex_blocks = () => (tree) => {
	visit(tree, 'code', (node) => {
		if (node.lang === 'math') {
			const str = katex.renderToString(node.value, {
				displayMode: true,
				leqno: false,
				fleqn: false,
				throwOnError: true,
				errorColor: '#cc0000',
				strict: 'warn',
				output: 'htmlAndMathml',
				trust: false,
				macros: { '\\f': '#1f(#2)' }
			});

			node.type = 'raw';
			node.value = '<span class="text-sm md:text-lg">{@html `' + str + '`}</span>';
		}
	});
};

const katex_inline = () => (tree) => {
  visit(tree, 'text', (node, index, parent) => {
    const regex = /\$\$(.*?)\$\$/g;
	  let replacedText = node.value;

    replacedText = replacedText.replace(regex, (match, equation) => {
      // Replace double backslashes with single backslashes
		const cleanedEquation = equation.replace(/\\\\/g, '\\');

      const str = katex.renderToString(cleanedEquation, {
        throwOnError: true,
        errorColor: '#cc0000',
        strict: 'warn',
        output: 'htmlAndMathml',
        trust: false,
        macros: { '\\f': '#1f(#2)' }
      });

      // Escape the HTML for Svelte
		const escapedHTML = escapeSvelte(str);


      // Wrap the rendered equation in a span
      return `<span class="text-base">{@html \`${escapedHTML}\`}</span>`;
    });

    // Replace the original text node with the modified text
    parent.children[index] = { type: 'text', value: replacedText };
  });
};


const prettyCodeOptions = {
	// theme: 'github-dark',
	theme: {
		// for dark, class name will be Moonlight II, use that class name in pre.svelte to adjust
		// any changes here, you need to change in pre.svelte as well with the same class name
		dark: JSON.parse(readFileSync(resolve(__dirname, './static/moonlight-2-theme.json'), 'utf-8')),
		// for light, class name will be min-light, use that class name in pre.svelte to adjust
		// any changes here, you need to change in pre.svelte as well with the same class name
		light: 'min-light'
	},
	keepBackground: false, // to use our own background color
	onVisitLine(node) {
		if (node.children.length === 0) {
			node.children = { type: 'text', value: ' ' };
		}
	},
	// onVisitTitle(node) {
	// 	// console.log('title:', node);
	// },
	getHighlighter: (options) => {
		return getHighlighter({
			...options,
			langs: BUNDLED_LANGUAGES.filter(({ id }) => {
				return [
					'svelte',
					'typescript',
					'html',
					'css',
					'javascript',
					'bash',
					'shell',
					'python',
					'java',
					'md',
					'go',
					'rust',
					'c',
					'cpp',
					'csharp',
					'php',
					'json',
					'yaml',
					'swift',
				].includes(id);
			})
		});
	}
};

// replaces “ and ” with " and ". useful to render {} curly braces
const replaceQuotes = () => (tree) => {
	visit(tree, 'text', (node) => {
		node.value = node.value
			.replace(/”/g, '"') // Replace curly double quotes with straight double quotes
			.replace(/“/g, '"') // Replace straight double quotes with straight double quotes
			.replace(/’/g, "'") // Replace curly single quotes with straight single quotes
			.replace(/‘/g, "'"); // Replace straight single quotes with straight single quotes
	});
};


/** @type {import('mdsvex').MdsvexOptions} */
export const mdsvexOptions = {
	extensions: ['.md', '.svx'],
	layout: {
		_: resolve('./src/lib/components/markdown/layout.svelte'), // default or fallback layout
		// about: resolve('./src/lib/components/markdown/about-layout.svelte') // named layout
	},
	// comment if not working
	// highlight: {
	// 	highlighter: highlightCode
	// },
	remarkPlugins: [katex_blocks, katex_inline, inlineKatexUsingInlineCode, replaceQuotes],
	rehypePlugins:  [
		rehypeCustomComponents,
		rehypeComponentPreToPre,
		[rehypePrettyCode, prettyCodeOptions],
		rehypeHandleMetadata,
		rehypeRenderCode,
		rehypePreToComponentPre,
		correct_hast_tree,
	]
};

function rehypeCustomComponents() {
	return async (tree) => {
		const hTags = [
			'Components.h1',
			'Components.h2',
			'Components.h3',
			'Components.h4',
			'Components.h5',
			'Components.h6'
		];

		visit(tree, (node) => {
			// Check h tags, and pass some extra parameters to the custom components.
			if (node?.type === 'element' && hTags.includes(node?.tagName)) {
				node.properties['id'] = node.children[0].value.split(' ').join('-').toLowerCase();
				node.properties['headerTag'] = node.tagName.split('.')[1];
			}
		});
	};
}

function rehypeComponentPreToPre() {
	return async (tree) => {
		// Replace `Component.pre` tags with regular `pre` tags.
		// This enables us to use rehype-pretty-code with our custom `pre` component.
		visit(tree, (node) => {
			// if (node?.data && 'meta' in node?.data) {
			// 	console.log('node:', node, '\n');
			// 	console.log('data:', node?.data, '\n-------------------------');
			// }

			if (node?.type === 'element' && node?.tagName === 'Components.pre') {
				node.tagName = 'pre';
			}
		});
	};
}

/**
 * Escapes the html string of code blocks so we can pass
 * it on to our custom `Component.pre` element.
 */
// function escapeHtml(html) {
// 	return html
// 		.replaceAll('&', '&amp;')
// 		.replaceAll('<', '&lt;')
// 		.replaceAll('>', '&gt;')
// 		.replaceAll('"', '&quot;')
// 		.replaceAll("'", '&#039;');
// }

function rehypePreToComponentPre() {
	return async (tree) => {
		/**
		 * Replace `pre` tags with our custom `Component.pre` tags.
		 * This enables us to use rehype-pretty-code with our custom `pre` component.
		 * We also add the raw html string as a parameter for the copy button.
		 */
		visit(tree, (node) => {
			if (node?.type === 'element' && node?.tagName === 'pre') {
				node.tagName = 'Components.pre';

				// if (node?.children.length > 0) {
				// 	console.log('\n\nnode:', node);
				// 	console.log('\n\nnode.children[0]:', node?.children[0], '\n------------------------');
				// }
				// 	const value = node.children[0].value.trim();
				// 	const rawHTMLString = value.substring(8, value.length - 2);
				// 	node.properties['rawHTMLString'] = escapeHtml(rawHTMLString);
			}
		});
	};
}

function rehypeHandleMetadata() {
	return async (tree) => {
		visit(tree, (node) => {
			if (node?.type === 'element' && node?.tagName === 'div') {
				if (!('data-rehype-pretty-code-fragment' in node.properties)) {
					return;
				}

				const titleElement = node.children[0];
				const preElement = node.children.at(-1);
				// console.log(preElement)
				// console.log(preElement.properties)
				preElement.properties['__title__'] = titleElement.children[0].value;
				// console.log(preElement.properties)

				if (
					preElement.tagName !== 'pre' ||
					!('data-rehype-pretty-code-title' in titleElement.properties)
				) {
					return;
				}

				if (titleElement.children.length > 0 && 'value' in titleElement.children[0]) {
					preElement.properties['__title__'] = titleElement.children[0].value;
					node.children.shift();
				}
			}
		});
	};
}

function rehypeRenderCode() {
	return async (tree) => {
		visit(tree, (node) => {
			if (
				node?.type === 'element' &&
				(node?.tagName === 'Components.pre' || node?.tagName === 'pre')
			) {
				const codeEl = node.children[0];
				if (codeEl.tagName !== 'code') {
					return;
				}

				const codeString = tabsToSpaces(
					toHtml(codeEl, {
						allowDangerousCharacters: true,
						allowDangerousHtml: true
					})
				);

				codeEl.type = 'raw';
				codeEl.value = `{@html \`${escapeSvelte(codeString)}\`}`;
			}
		});
	};
}

/**
 *
 * @param {string} code
 * @returns {string}
 */
function tabsToSpaces(code) {
	return code.replaceAll('	', '  ');
}