index.js

import getCustomProperties from './lib/get-custom-properties';
import importCustomPropertiesFromSources from './lib/import-from';
import parser from 'postcss-value-parser';
import transformAST from './lib/transform';

module.exports = (opts = {}) => {
	// how unresolved functions and arguments should be handled (default: "throw")
	const unresolvedOpt = String(Object(opts).unresolved || 'throw').toLowerCase();

	// how transformed colors will be produced in CSS
	const stringifierOpt = Object(opts).stringifier || (color => color.toLegacy());

	// sources to import custom selectors from
	const importFrom = [].concat(Object(opts).importFrom || []);

	// whether var() within color-mod() should use Custom Properties or var() fallback
	const transformVarsOpt = 'transformVars' in Object(opts) ? opts.transformVars : true;

	// promise any custom selectors are imported
	const customPropertiesPromise = importCustomPropertiesFromSources(importFrom);

	return {
		postcssPlugin: 'postcss-color-mod-function',
		async Once (root, { result }) {
			const customProperties = Object.assign(
				await customPropertiesPromise,
				getCustomProperties(root, { preserve: true })
			);

			root.walkDecls(decl => {
				const originalValue = decl.value;

				if (colorModFunctionMatch.test(originalValue)) {
					const ast = parser(originalValue);

					transformAST(ast, {
						unresolved: unresolvedOpt,
						stringifier: stringifierOpt,
						transformVars: transformVarsOpt,
						decl,
						result,
						customProperties
					});

					const modifiedValue = parser.stringify(ast);

					if (originalValue !== modifiedValue) {
						decl.value = modifiedValue;
					}
				}
			});
		}
	};
};

module.exports.postcss = true;

const colorModFunctionMatch = /(^|[^\w-])color-mod\(/i;