Add encoding sniffing

Author: boarwell

lib/core/index.js

@@ -12,6 +12,8 @@ const version = require('../../package.json').version;
 const status = require('./status-handlers');
 const generateEtag = require('./etag');
 const optsParser = require('./opts');
+const htmlEncodingSniffer = require('html-encoding-sniffer');
+const { Readable } = require('stream');
 
 let httpServerCore = null;
 
@@ -234,8 +236,12 @@ module.exports = function createMiddleware(_dir, _options) {
       let cacheControl = cache;
       let stream = null;
       if (contentType && isTextFile(contentType)) {
-        // Assume text types are utf8
-        contentType += '; charset=UTF-8';
+        const htmlBytes = fs.readFileSync(file);
+        const sniffedEncoding = htmlEncodingSniffer(htmlBytes, {
+          defaultEncoding: 'UTF-8'
+        });
+        contentType += `; charset=${sniffedEncoding}`;
+        stream = Readable.from(htmlBytes)
       }
 
       if (file === gzippedFile) { // is .gz picked up
@@ -317,7 +323,10 @@ module.exports = function createMiddleware(_dir, _options) {
         return;
       }
 
-      stream = fs.createReadStream(file);
+      // stream may already have been assigned during encoding sniffing.
+      if (stream === null) {
+        stream = fs.createReadStream(file);
+      }
 
       stream.pipe(res);
       stream.on('error', (err) => {