flow like the river

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

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+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+    value: true
+});
+exports.default = minifyCss;
+
+var _cssnano = require('cssnano');
+
+var _cssnano2 = _interopRequireDefault(_cssnano);
+
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+
+/** Minify CSS with cssnano */
+function minifyCss(tree, options, cssnanoOptions) {
+    var promises = [];
+    tree.walk(function (node) {
+        if (node.tag === 'style' && node.content && node.content.length) {
+            promises.push(processStyleNode(node, cssnanoOptions));
+        } else if (node.attrs && node.attrs.style) {
+            promises.push(processStyleAttr(node, cssnanoOptions));
+        }
+
+        return node;
+    });
+
+    return Promise.all(promises).then(function () {
+        return tree;
+    });
+}
+
+function processStyleNode(styleNode, cssnanoOptions) {
+    return _cssnano2.default.process(Array.isArray(styleNode.content) ? styleNode.content.join(' ') : styleNode.content, cssnanoOptions).then(function (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;}
+    var wrapperStart = 'a{';
+    var wrapperEnd = '}';
+    var wrappedStyle = wrapperStart + (node.attrs.style || '') + wrapperEnd;
+
+    return _cssnano2.default.process(wrappedStyle, cssnanoOptions).then(function (result) {
+        var 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);
+    });
+}