refactor: elegance

packages/state/synchronizer.js

@@ -20,46 +20,39 @@ export class StateSynchronizer {
   }
 
   diff(previousState) {
-    const state = this._state;
-    const diff = {};
-    for (const key in this._statefuls) {
-      if (previousState.get(key) !== state.get(key)) {
-        diff[key] = this.diffStateful(
-          previousState.get(key),
-          state.get(key)
-        );
-      }
-    }
-    return diff;
+    // Take a pure JS diff.
+    const steps = immutablediff(previousState, this._state).toJS();
+    const updateSteps = steps.filter(StateSynchronizer.isStepUpdate);
+    return StateSynchronizer.hydratePathValues(updateSteps);
   }
 
-  diffStateful(previous, current) {
-    // Take a pure JS diff.
-    const steps = immutablediff(previous, current).toJS();
-    let diff = {};
-    for (const {op, path, value} of steps) {
-      if ('replace' === op || 'add' === op) {
-        if ('/' === path) {
-          diff = value;
-        }
-        else {
-          const parts = path.split('/');
-          parts.shift();
-          let walk = diff;
-          for (let i = 0; i < parts.length; ++i) {
-            const part = parts[i];
-            walk[part] = walk[part] || {};
-            if (i === parts.length - 1) {
-              walk[part] = value;
-            }
-            else {
-              walk = walk[part];
-            }
+  static hydratePathValues(pathValues) {
+    let accumulated = {};
+    for (const {path, value} of pathValues) {
+      if ('/' === path) {
+        accumulated = value;
+      }
+      else {
+        const parts = path.split('/');
+        parts.shift();
+        let walk = accumulated;
+        for (let i = 0; i < parts.length; ++i) {
+          const part = parts[i];
+          walk[part] = walk[part] || {};
+          if (i === parts.length - 1) {
+            walk[part] = value;
+          }
+          else {
+            walk = walk[part];
           }
         }
       }
     }
-    return diff;
+    return accumulated;
+  }
+
+  static isStepUpdate(step) {
+    return -1 !== ['add', 'replace'].indexOf(step.op);
   }
 
   get state() {