SingleFile/src/single-file/modules/css-medias-alt-minifier.js

/*
 * Copyright 2010-2020 Gildas Lormeau
 * contact : gildas.lormeau <at> gmail.com
 * 
 * This file is part of SingleFile.
 *
 *   The code in this file is free software: you can redistribute it and/or 
 *   modify it under the terms of the GNU Affero General Public License 
 *   (GNU AGPL) as published by the Free Software Foundation, either version 3
 *   of the License, or (at your option) any later version.
 * 
 *   The code in this file is distributed in the hope that it will be useful, 
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of 
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero 
 *   General Public License for more details.
 *
 *   As additional permission under GNU AGPL version 3 section 7, you may 
 *   distribute UNMODIFIED VERSIONS OF THIS file without the copy of the GNU 
 *   AGPL normally required by section 4, provided you include this license 
 *   notice and a URL through which recipients can access the Corresponding 
 *   Source.
 */

import * as cssTree from "./../vendor/css-tree.js";
import * as mediaQueryParser from "./../vendor/css-media-query-parser.js";
import { flatten } from "./../single-file-helper.js";

const helper = {
	flatten
};

const MEDIA_ALL = "all";
const MEDIA_SCREEN = "screen";

export {
	process
};

function process(stylesheets) {
	const stats = { processed: 0, discarded: 0 };
	stylesheets.forEach((stylesheetInfo, element) => {
		if (matchesMediaType(stylesheetInfo.mediaText || MEDIA_ALL, MEDIA_SCREEN) && stylesheetInfo.stylesheet.children) {
			const removedRules = processRules(stylesheetInfo.stylesheet.children, stats);
			removedRules.forEach(({ cssRules, cssRule }) => cssRules.remove(cssRule));
		} else {
			stylesheets.delete(element);
		}
	});
	return stats;
}

function processRules(cssRules, stats, removedRules = []) {
	for (let cssRule = cssRules.head; cssRule; cssRule = cssRule.next) {
		const ruleData = cssRule.data;
		if (ruleData.type == "Atrule" && ruleData.name == "media" && ruleData.block && ruleData.block.children && ruleData.prelude && ruleData.prelude.children) {
			stats.processed++;
			if (matchesMediaType(cssTree.generate(ruleData.prelude), MEDIA_SCREEN)) {
				processRules(ruleData.block.children, stats, removedRules);
			} else {
				removedRules.push({ cssRules, cssRule });
				stats.discarded++;
			}
		}
	}
	return removedRules;
}

function matchesMediaType(mediaText, mediaType) {
	const foundMediaTypes = helper.flatten(mediaQueryParser.parseMediaList(mediaText).map(node => getMediaTypes(node, mediaType)));
	return foundMediaTypes.find(mediaTypeInfo => (!mediaTypeInfo.not && (mediaTypeInfo.value == mediaType || mediaTypeInfo.value == MEDIA_ALL))
		|| (mediaTypeInfo.not && (mediaTypeInfo.value == MEDIA_ALL || mediaTypeInfo.value != mediaType)));
}

function getMediaTypes(parentNode, mediaType, mediaTypes = []) {
	parentNode.nodes.map((node, indexNode) => {
		if (node.type == "media-query") {
			return getMediaTypes(node, mediaType, mediaTypes);
		} else {
			if (node.type == "media-type") {
				const nodeMediaType = { not: Boolean(indexNode && parentNode.nodes[0].type == "keyword" && parentNode.nodes[0].value == "not"), value: node.value };
				if (!mediaTypes.find(mediaType => nodeMediaType.not == mediaType.not && nodeMediaType.value == mediaType.value)) {
					mediaTypes.push(nodeMediaType);
				}
			}
		}
	});
	if (!mediaTypes.length) {
		mediaTypes.push({ not: false, value: MEDIA_ALL });
	}
	return mediaTypes;
}