1 files changed, 69 insertions, 0 deletions
diff --git a/scripts/frontend/startup_css/get_startup_css.js b/scripts/frontend/startup_css/get_startup_css.js
new file mode 100644
index 00000000000..10e8371df8c
--- /dev/null
+++ b/scripts/frontend/startup_css/get_startup_css.js
@@ -0,0 +1,69 @@
+const fs = require('fs');
+const cheerio = require('cheerio');
+const { mergeWith, isArray } = require('lodash');
+const { PurgeCSS } = require('purgecss');
+const purgeHtml = require('purgecss-from-html');
+const { cleanCSS } = require('./clean_css');
+const { HTML_TO_REMOVE } = require('./constants');
+const { die } = require('./utils');
+
+const cleanHtml = (html) => {
+  const $ = cheerio.load(html);
+
+  HTML_TO_REMOVE.forEach((selector) => {
+    $(selector).remove();
+  });
+
+  return $.html();
+};
+
+const mergePurgeCSSOptions = (...options) =>
+  mergeWith(...options, (objValue, srcValue) => {
+    if (isArray(objValue)) {
+      return objValue.concat(srcValue);
+    }
+
+    return undefined;
+  });
+
+const getStartupCSS = async ({ htmlPaths, cssPaths, purgeOptions }) => {
+  const content = htmlPaths.map((htmlPath) => {
+    if (!fs.existsSync(htmlPath)) {
+      die(`Could not find fixture "${htmlPath}". Have you run the fixtures?`);
+    }
+
+    const rawHtml = fs.readFileSync(htmlPath);
+    const html = cleanHtml(rawHtml);
+
+    return { raw: html, extension: 'html' };
+  });
+
+  const purgeCSSResult = await new PurgeCSS().purge({
+    content,
+    css: cssPaths,
+    ...mergePurgeCSSOptions(
+      {
+        fontFace: true,
+        variables: true,
+        keyframes: true,
+        blocklist: [/:hover/, /:focus/, /-webkit-/, /-moz-focusring-/, /-ms-expand/],
+        safelist: {
+          standard: ['brand-header-logo'],
+        },
+        // By default, PurgeCSS ignores special characters, but our utilities use "!"
+        defaultExtractor: (x) => x.match(/[\w-!]+/g),
+        extractors: [
+          {
+            extractor: purgeHtml,
+            extensions: ['html'],
+          },
+        ],
+      },
+      purgeOptions,
+    ),
+  });
+
+  return purgeCSSResult.map(({ css }) => cleanCSS(css)).join('\n');
+};
+
+module.exports = { getStartupCSS };