Move transform to class syntax and simplify the code a bit (#14)

lib/bind-transform.js

@@ -25,72 +25,77 @@
   ```
 */
 
-function BindTransform() {
-  this.syntax = null;
-}
-
-BindTransform.prototype.transform = function(ast) {
-  var b = this.syntax.builders;
-
-  this.syntax.traverse(ast, {
-    SubExpression(node) {
-      transform(node);
-    },
-    MustacheStatement(node) {
-      transform(node);
-    }
-  });
+module.exports = class BindTransform {
+  constructor() {
+    this.syntax = null;
+  }
+
+  get builders() {
+    return this.syntax.builders;
+  }
 
-  function transform(call) {
-    if (call.path.original === "bind" && call.params.length > 0) {
-      let hasTarget = call.hash.pairs.some(p => p.key === "target");
+  transform(ast) {
+    let transform = node => this.transformNode(node);
+    this.syntax.traverse(ast, {
+      SubExpression: transform,
+      MustacheStatement: transform
+    });
+
+    return ast;
+  }
+
+  transformNode(node) {
+    this.addTarget(node);
+  }
+
+  addTarget(node) {
+    if (node.path.original === "bind" && node.params.length > 0) {
+      let hasTarget = node.hash.pairs.some(p => p.key === "target");
 
       if (!hasTarget) {
-        let target = getDefaultTarget(call.params[0]);
+        let target = this.getDefaultTarget(node.params[0]);
 
-        call.hash.pairs.push(b.pair("target", target));
+        node.hash.pairs.push(this.builders.pair("target", target));
       }
     }
+  }
 
-    function getDefaultTarget(fn) {
-      if (fn.type === "PathExpression") {
-        if (fn.parts.length === 0) {
-          return b.null();
-        } else if (fn.parts.length === 1) {
-          return b.path("this");
-        } else {
-          let parts = fn.parts.slice(0);
-          parts.pop(); // Remove function part
+  getDefaultTarget(fn) {
+    let { builders } = this;
 
-          let lastPart = parts[parts.length - 1];
+    if (fn.type !== "PathExpression") {
+      return builders.null();
+    }
 
-          if (lastPart !== "actions") {
-            return pathFor(parts.join('.'), fn.data);
-          }
+    switch (fn.parts.length) {
+      case 0:
+        return builders.null();
+      case 1:
+        return builders.path("this");
+      default: {
+        let parts = fn.parts.slice(0, -1); // Remove function part
 
-          parts.pop(); // Remove actions part
+        let lastPart = parts[parts.length - 1];
 
-          if (parts.length === 0) {
-            return b.path("this");
-          }
+        // Remove actions part
+        if (lastPart === "actions") {
+          parts.pop();
+        }
 
-          return pathFor(parts.join("."), fn.data);
+        if (parts.length === 0) {
+          return builders.path("this");
         }
-      } else {
-        return b.null();
+
+        return this.pathFor(parts.join("."), fn.data);
       }
     }
   }
 
-  function pathFor(completePath, isData = false /* named argument */) {
-    let path = b.path(completePath);
+  pathFor(completePath, isData = false /* named argument */) {
+    let path = this.builders.path(completePath);
 
     path.data = isData;
 
     return path;
   }
-
-  return ast;
 };
-
-module.exports = BindTransform;