flow like the river

BACK_BACK/node_modules/htmlnano/lib/modules/minifyCss.js

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+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = minifyCss;
+
+var _helpers = require("../helpers");
+
+var _cssnano = _interopRequireDefault(require("cssnano"));
+
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+
+const postcssOptions = {
+  // Prevent the following warning from being shown:
+  // > Without `from` option PostCSS could generate wrong source map and will not find Browserslist config.
+  // > Set it to CSS file path or to `undefined` to prevent this warning.
+  from: undefined
+};
+/** Minify CSS with cssnano */
+
+function minifyCss(tree, options, cssnanoOptions) {
+  let promises = [];
+  tree.walk(node => {
+    if ((0, _helpers.isStyleNode)(node)) {
+      promises.push(processStyleNode(node, cssnanoOptions));
+    } else if (node.attrs && node.attrs.style) {
+      promises.push(processStyleAttr(node, cssnanoOptions));
+    }
+
+    return node;
+  });
+  return Promise.all(promises).then(() => tree);
+}
+
+function processStyleNode(styleNode, cssnanoOptions) {
+  let css = (0, _helpers.extractCssFromStyleNode)(styleNode); // Improve performance by avoiding calling stripCdata again and again
+
+  let isCdataWrapped = false;
+
+  if (css.includes('CDATA')) {
+    const strippedCss = stripCdata(css);
+    isCdataWrapped = css !== strippedCss;
+    css = strippedCss;
+  }
+
+  return _cssnano.default.process(css, postcssOptions, cssnanoOptions).then(result => {
+    if (isCdataWrapped) {
+      return styleNode.content = ['<![CDATA[' + result + ']]>'];
+    }
+
+    return styleNode.content = [result.css];
+  });
+}
+
+function processStyleAttr(node, cssnanoOptions) {
+  // CSS "color: red;" is invalid. Therefore it should be wrapped inside some selector:
+  // a{color: red;}
+  const wrapperStart = 'a{';
+  const wrapperEnd = '}';
+  const wrappedStyle = wrapperStart + (node.attrs.style || '') + wrapperEnd;
+  return _cssnano.default.process(wrappedStyle, postcssOptions, cssnanoOptions).then(result => {
+    const minifiedCss = result.css; // Remove wrapperStart at the start and wrapperEnd at the end of minifiedCss
+
+    node.attrs.style = minifiedCss.substring(wrapperStart.length, minifiedCss.length - wrapperEnd.length);
+  });
+}
+
+function stripCdata(css) {
+  const leftStrippedCss = css.replace('<![CDATA[', '');
+
+  if (leftStrippedCss === css) {
+    return css;
+  }
+
+  const strippedCss = leftStrippedCss.replace(']]>', '');
+  return leftStrippedCss === strippedCss ? css : strippedCss;
+}