From db8bbf0102165afd2038c71f8a6760b765c1873c Mon Sep 17 00:00:00 2001
From: Jordan Eldredge <jordan@jordaneldredge.com>
Date: Sat, 24 Aug 2019 23:49:21 -0700
Subject: [PATCH] Add some generic methods for dealing with selectors (#888)

---
 modern/src/MakiSelectors.ts     | 14 +++++++++-----
 modern/src/runtime/GuiObject.js | 31 +++++++++++++++++++++++--------
 2 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/modern/src/MakiSelectors.ts b/modern/src/MakiSelectors.ts
index 60ee3e75..ae5eed4c 100644
--- a/modern/src/MakiSelectors.ts
+++ b/modern/src/MakiSelectors.ts
@@ -1,14 +1,18 @@
 import * as Utils from "./utils";
 
-function findNodeByUid(state, uid) {
-  return Utils.findInTree(state.xmlTree, node => {
-    return node.uid === uid;
-  });
+function findNodeByUid(uid) {
+  // TODO: Do some clever caching here.
+  return state => {
+    return Utils.findInTree(state.xmlTree, node => {
+      return node.uid === uid;
+    });
+  };
 }
 
 export function getTop(uid) {
+  const findNodeInState = findNodeByUid(uid);
   return state => {
-    const node = findNodeByUid(state, uid);
+    const node = findNodeInState(state);
     return Number(node.attributes.y) || 0;
   };
 }
diff --git a/modern/src/runtime/GuiObject.js b/modern/src/runtime/GuiObject.js
index a8cff28e..289900dd 100644
--- a/modern/src/runtime/GuiObject.js
+++ b/modern/src/runtime/GuiObject.js
@@ -11,6 +11,25 @@ class GuiObject extends MakiObject {
     super(node, parent, annotations, store);
 
     this.visible = true;
+    this._selectorCache = new Map();
+  }
+
+  _useUidSelector(selector) {
+    // TODO: use memoize for this
+    if (!this._selectorCache.has(selector)) {
+      this._selectorCache.set(selector, selector(this._uid));
+    }
+    return this._selectorCache.get(selector)(this._store.getState());
+  }
+
+  _compareToUidSelector(value, selector) {
+    const selectorValue = this._useUidSelector(selector);
+    if (selectorValue !== value) {
+      console.error(
+        `Maki state ${value} is out of sync with tree state ${selectorValue}`
+      );
+    }
+    return value;
   }
 
   /**
@@ -62,14 +81,10 @@ class GuiObject extends MakiObject {
   }
 
   gettop() {
-    const stateTop = MakiSelectors.getTop(this._uid)(this._store.getState());
-    const makiTop = Number(this.attributes.y) || 0;
-    if (stateTop !== makiTop) {
-      console.error(
-        `Maki state ${makiTop} is out of sync with tree state ${stateTop}`
-      );
-    }
-    return makiTop;
+    return this._compareToUidSelector(
+      Number(this.attributes.y) || 0,
+      MakiSelectors.getTop
+    );
   }
 
   getleft() {