feat: Replace file extension instead of appending .webp

Author: Simone Sestito

README.md

@@ -26,6 +26,15 @@ After:
 
 > npm i posthtml posthtml-webp
 
+## Plugin options
+`replaceExtension` (boolean)
+
+**Default:** false
+
+Replace the extension of the source image with .webp instead of appending .webp to the original filename
+
+**Example**: image.jpg => image.webp (instead of image.jpg.webp)
+
 ## Usage
 
 ``` js
@@ -34,7 +43,7 @@ const posthtml = require('posthtml');
 const posthtmlWebp = require('posthtml-webp');
 
 posthtml()
-    .use(posthtmlWebp())
+    .use(posthtmlWebp(/* Plugin options */))
     .process(html/*, options */)
     .then(result => fs.writeFileSync('./after.html', result.html));
 ```

lib/index.js

@@ -1,26 +1,51 @@
 'use strict'
 
-module.exports = function () {
+module.exports = function (options) {
+  if (!options) {
+    options = {}
+  }
+
+  if (options.replaceExtension === undefined) {
+    options.replaceExtension = false
+  }
+
   return function posthtmlWebp (tree) {
     tree.match({ tag: 'img' }, function (imgNode) {
       if (imgNode.skip) return imgNode
-      return getPicture(imgNode)
+      return getPicture(imgNode, options)
     })
 
     return tree
   }
 }
 
-function getPicture (imgNode) {
+function removeExtension (filename) {
+  var extIndex = filename.lastIndexOf('.')
+  if (extIndex === -1) {
+    // Filename has no extension
+    return filename
+  } else {
+    return filename.substring(0, extIndex)
+  }
+}
+
+function getPicture (imgNode, options) {
   imgNode.skip = true
+
+  var src = imgNode.attrs.src
+  if (options.replaceExtension) {
+    src = removeExtension(src)
+  }
+  src += '.webp'
+
   return {
     tag: 'picture',
     content: [
       {
         tag: 'source',
         attrs: {
           type: 'image/webp',
-          srcset: imgNode.attrs.src + '.webp'
+          srcset: src
         }
       },
       imgNode