SingleFile/lib/single-file/modules/html-images-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 srcsetParser from "./../vendor/html-srcset-parser.js";

const EMPTY_IMAGE = "data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==";

export {
	process
};

function process(doc) {
	doc.querySelectorAll("picture").forEach(pictureElement => {
		const imgElement = pictureElement.querySelector("img");
		if (imgElement) {
			let { src, srcset } = getImgSrcData(imgElement);
			if (!src) {
				const data = getSourceSrcData(Array.from(pictureElement.querySelectorAll("source")).reverse());
				src = data.src;
				if (!srcset) {
					srcset = data.srcset;
				}
			}
			setSrc({ src, srcset }, imgElement, pictureElement);
		}
	});
	doc.querySelectorAll(":not(picture) > img[srcset]").forEach(imgElement => setSrc(getImgSrcData(imgElement), imgElement));
}

function getImgSrcData(imgElement) {
	let src = imgElement.getAttribute("src");
	if (src == EMPTY_IMAGE) {
		src = null;
	}
	let srcset = getSourceSrc(imgElement.getAttribute("srcset"));
	if (srcset == EMPTY_IMAGE) {
		srcset = null;
	}
	return { src, srcset };
}

function getSourceSrcData(sources) {
	let source = sources.find(source => source.src);
	let src = source && source.src;
	let srcset = source && source.srcset;
	if (!src) {
		source = sources.find(source => getSourceSrc(source.src));
		src = source && source.src;
		if (src == EMPTY_IMAGE) {
			src = null;
		}
	}
	if (!srcset) {
		source = sources.find(source => getSourceSrc(source.srcset));
		srcset = source && source.srcset;
		if (srcset == EMPTY_IMAGE) {
			srcset = null;
		}
	}
	return { src, srcset };
}

function setSrc(srcData, imgElement, pictureElement) {
	if (srcData.src) {
		imgElement.setAttribute("src", srcData.src);
		imgElement.setAttribute("srcset", "");
		imgElement.setAttribute("sizes", "");
	} else {
		imgElement.setAttribute("src", EMPTY_IMAGE);
		if (srcData.srcset) {
			imgElement.setAttribute("srcset", srcData.srcset);
		} else {
			imgElement.setAttribute("srcset", "");
			imgElement.setAttribute("sizes", "");
		}
	}
	if (pictureElement) {
		pictureElement.querySelectorAll("source").forEach(sourceElement => sourceElement.remove());
	}
}

function getSourceSrc(sourceSrcSet) {
	if (sourceSrcSet) {
		const srcset = srcsetParser.process(sourceSrcSet);
		if (srcset.length) {
			return (srcset.find(srcset => srcset.url)).url;
		}
	}
}