Write initial plugin structure

lib/index.js

@@ -0,0 +1,42 @@
+const minimatch = require('minimatch');
+const purifyCSS = require('purify-css');
+
+const plugin = (options) => {
+  const {content, css, output} = options;
+  // Delete options that conflict with running in Metalsmith
+  delete options.content;
+  delete options.css;
+  delete options.output;
+
+  return function(files, metalsmith, done) {
+    // Stringify HTML & other structural markup
+    const fileNames = Object.keys(files);
+    const filteredFiles = [...content].reduce((filteredFiles, filename) => {
+      return filteredFiles.concat(
+        minimatch.match(fileNames, filename, { matchBase: true })
+      );
+    }, []);
+
+    const structure = [...filteredFiles].reduce((structure, filename) => {
+      structure.push(files[filename].contents.toString());
+      return structure;
+    }, []).toString();
+
+    // Stringify CSS
+    const styles = [...css].reduce((styles, filename) => {
+      styles.push(files[filename].contents.toString());
+      return styles;
+    }, []).toString();
+
+    // Pass code and CSS to Purify
+    purifyCSS(structure, styles, options, (results) => {
+      files[output] = {
+        contents: new Buffer(results)
+      }
+    });
+
+    done();
+  }
+}
+
+module.exports = plugin;