SingleFile/lib/single-file/modules/css-rules-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";

const DEBUG = false;

export {
	process
};

function process(stylesheets, styles, mediaAllInfo) {
	const stats = { processed: 0, discarded: 0 };
	let sheetIndex = 0;
	stylesheets.forEach(stylesheetInfo => {
		if (!stylesheetInfo.scoped) {
			const cssRules = stylesheetInfo.stylesheet.children;
			if (cssRules) {
				stats.processed += cssRules.getSize();
				stats.discarded += cssRules.getSize();
				let mediaInfo;
				if (stylesheetInfo.mediaText && stylesheetInfo.mediaText != "all") {
					mediaInfo = mediaAllInfo.medias.get("style-" + sheetIndex + "-" + stylesheetInfo.mediaText);
				} else {
					mediaInfo = mediaAllInfo;
				}
				processRules(cssRules, sheetIndex, mediaInfo);
				stats.discarded -= cssRules.getSize();
			}
		}
		sheetIndex++;
	});
	let startTime;
	if (DEBUG) {
		startTime = Date.now();
		log("  -- STARTED processStyleAttribute");
	}
	styles.forEach(style => processStyleAttribute(style, mediaAllInfo));
	if (DEBUG) {
		log("  -- ENDED   processStyleAttribute delay =", Date.now() - startTime);
	}
	return stats;
}

function processRules(cssRules, sheetIndex, mediaInfo) {
	let mediaRuleIndex = 0, startTime;
	if (DEBUG && cssRules.getSize() > 1) {
		startTime = Date.now();
		log("  -- STARTED processRules", "rules.length =", cssRules.getSize());
	}
	const removedCssRules = [];
	for (let cssRule = cssRules.head; cssRule; cssRule = cssRule.next) {
		const ruleData = cssRule.data;
		if (ruleData.block && ruleData.block.children && ruleData.prelude && ruleData.prelude.children) {
			if (ruleData.type == "Atrule" && ruleData.name == "media") {
				const mediaText = cssTree.generate(ruleData.prelude);
				processRules(ruleData.block.children, sheetIndex, mediaInfo.medias.get("rule-" + sheetIndex + "-" + mediaRuleIndex + "-" + mediaText));
				if (!ruleData.prelude.children.getSize() || !ruleData.block.children.getSize()) {
					removedCssRules.push(cssRule);
				}
				mediaRuleIndex++;
			} else if (ruleData.type == "Rule") {
				const ruleInfo = mediaInfo.rules.get(ruleData);
				const pseudoSelectors = mediaInfo.pseudoRules.get(ruleData);
				if (!ruleInfo && !pseudoSelectors) {
					removedCssRules.push(cssRule);
				} else if (ruleInfo) {
					processRuleInfo(ruleData, ruleInfo, pseudoSelectors);
					if (!ruleData.prelude.children.getSize() || !ruleData.block.children.getSize()) {
						removedCssRules.push(cssRule);
					}
				}
			}
		} else {
			if (!ruleData || ruleData.type == "Raw" || (ruleData.type == "Rule" && (!ruleData.prelude || ruleData.prelude.type == "Raw"))) {
				removedCssRules.push(cssRule);
			}
		}
	}
	removedCssRules.forEach(cssRule => cssRules.remove(cssRule));
	if (DEBUG && cssRules.getSize() > 1) {
		log("  -- ENDED   processRules delay =", Date.now() - startTime);
	}
}

function processRuleInfo(ruleData, ruleInfo, pseudoSelectors) {
	const removedDeclarations = [];
	const removedSelectors = [];
	let pseudoSelectorFound;
	for (let selector = ruleData.prelude.children.head; selector; selector = selector.next) {
		const selectorText = cssTree.generate(selector.data);
		if (pseudoSelectors && pseudoSelectors.has(selectorText)) {
			pseudoSelectorFound = true;
		}
		if (!ruleInfo.matchedSelectors.has(selectorText) && (!pseudoSelectors || !pseudoSelectors.has(selectorText))) {
			removedSelectors.push(selector);
		}
	}
	if (!pseudoSelectorFound) {
		for (let declaration = ruleData.block.children.tail; declaration; declaration = declaration.prev) {
			if (!ruleInfo.declarations.has(declaration.data)) {
				removedDeclarations.push(declaration);
			}
		}
	}
	removedDeclarations.forEach(declaration => ruleData.block.children.remove(declaration));
	removedSelectors.forEach(selector => ruleData.prelude.children.remove(selector));
}

function processStyleAttribute(styleData, mediaAllInfo) {
	const removedDeclarations = [];
	const styleInfo = mediaAllInfo.matchedStyles.get(styleData);
	if (styleInfo) {
		let propertyFound;
		for (let declaration = styleData.children.head; declaration && !propertyFound; declaration = declaration.next) {
			if (!styleInfo.declarations.has(declaration.data)) {
				removedDeclarations.push(declaration);
			}
		}
		removedDeclarations.forEach(declaration => styleData.children.remove(declaration));
	}
}

function log(...args) {
	console.log("S-File <css-min>", ...args); // eslint-disable-line no-console
}