add static gzip/brotli utility

compress.mjs

@@ -0,0 +1,38 @@
+import { promises as fs } from 'fs';
+import zlib from 'zlib';
+import { promisify } from 'util';
+import { iterate } from 'glob';
+
+const formats = [{
+	extension: '.gz',
+	compress: promisify(zlib.gzip),
+	options: {
+		level: zlib.constants.Z_BEST_COMPRESSION
+	}
+}, {
+	extension: '.br',
+	compress: promisify(zlib.brotliCompress),
+	options: {
+		params: {
+			[zlib.constants.BROTLI_PARAM_QUALITY]: zlib.constants.BROTLI_MAX_QUALITY
+		}
+	}
+}];
+
+let totalSize = 0;
+const compressedSizes = {};
+
+console.log('compressing static files...')
+
+for await (const file of iterate('.next/static/{chunks,css}/**/*.{js,css}')) {
+	const data = await fs.readFile(file);
+	totalSize += data.length;
+	for (const format of formats) {
+		const compressed = await format.compress(data, format.options);
+		compressedSizes[format.extension] = (compressedSizes[format.extension] ?? 0) + compressed.length;
+		await fs.writeFile(`${file}${format.extension}`, compressed);
+	}
+}
+
+Object.entries(compressedSizes).forEach(([ext, size]) =>
+	console.log(`  ${ext.slice(1)}: ${((1 - size / totalSize) * 100).toFixed(1)}% reduction (${Math.floor(totalSize / 1000)}kB -> ${Math.floor(size / 1000)}kB)`))