From f81e52a51e676a0e66be78ca4cef6dc9c80a8c1a Mon Sep 17 00:00:00 2001
From: Ian Storm Taylor <ian@ianstormtaylor.com>
Date: Sun, 2 Apr 2017 15:45:48 -0700
Subject: [PATCH] change normalize logic to use mutable objects for performance

---
 src/transforms/normalize.js | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/src/transforms/normalize.js b/src/transforms/normalize.js
index 11bf74c59..adaed0f5d 100644
--- a/src/transforms/normalize.js
+++ b/src/transforms/normalize.js
@@ -118,22 +118,28 @@ function normalizeNodeAndChildren(transform, node, schema) {
   // We can't just loop the children and normalize them, because in the process
   // of normalizing one child, we might end up creating another. Instead, we
   // have to normalize one at a time, and check for new children along the way.
-  let stack = node.nodes.map(n => n.key).toStack()
-  let set = new Set()
+  // PERF: use a mutable array here instead of an immutable stack.
+  const keys = node.nodes.toArray().map(n => n.key)
 
   // While there is still a child key that hasn't been normalized yet...
-  while (stack.size) {
+  while (keys.length) {
     const ops = transform.operations.length
     let key
 
+    // PERF: use a mutable set here since we'll be add to it a lot.
+    let set = new Set().asMutable()
+
     // Unwind the stack, normalizing every child and adding it to the set.
-    while (key = stack.peek()) {
+    while (key = keys[0]) {
       const child = node.getChild(key)
       normalizeNodeAndChildren(transform, child, schema)
-      set = set.add(key)
-      stack = stack.pop()
+      set.add(key)
+      keys.shift()
     }
 
+    // Turn the set immutable to be able to compare against it.
+    set = set.asImmutable()
+
     // PERF: Only re-find the node and re-normalize any new children if
     // operations occured that might have changed it.
     if (transform.operations.length != ops) {
@@ -142,7 +148,7 @@ function normalizeNodeAndChildren(transform, node, schema) {
       // Add any new children back onto the stack.
       node.nodes.forEach((n) => {
         if (set.has(n.key)) return
-        stack = stack.push(n.key)
+        keys.unshift(n.key)
       })
     }
   }