generic-utils: cache the get

Author: purpshell

src/WABinary/generic-utils.ts

@@ -4,12 +4,32 @@ import { type BinaryNode } from './types'
 
 // some extra useful utilities
 
+const indexCache = new WeakMap<BinaryNode, Map<string, BinaryNode[]>>()
+
 export const getBinaryNodeChildren = (node: BinaryNode | undefined, childTag: string) => {
-	if (Array.isArray(node?.content)) {
-		return node.content.filter(item => item.tag === childTag)
-	}
+    if (!node || !Array.isArray(node.content)) return []
 
-	return []
+    let index = indexCache.get(node)
+
+    // Build the index once per node
+    if (!index) {
+        index = new Map<string, BinaryNode[]>()
+
+        for (const child of node.content) {
+            let arr = index.get(child.tag)
+            if (!arr) index.set(child.tag, (arr = []))
+            arr.push(child)
+        }
+
+        indexCache.set(node, index)
+    }
+
+    // Return first matching child
+    return index.get(childTag)
+}
+
+export const getBinaryNodeChild = (node: BinaryNode | undefined, childTag: string) => {
+  return getBinaryNodeChildren(node, childTag)?.[0]
 }
 
 export const getAllBinaryNodeChildren = ({ content }: BinaryNode) => {
@@ -20,12 +40,6 @@ export const getAllBinaryNodeChildren = ({ content }: BinaryNode) => {
 	return []
 }
 
-export const getBinaryNodeChild = (node: BinaryNode | undefined, childTag: string) => {
-	if (Array.isArray(node?.content)) {
-		return node?.content.find(item => item.tag === childTag)
-	}
-}
-
 export const getBinaryNodeChildBuffer = (node: BinaryNode | undefined, childTag: string) => {
 	const child = getBinaryNodeChild(node, childTag)?.content
 	if (Buffer.isBuffer(child) || child instanceof Uint8Array) {