From 5697c689d9835147dc06061c7c1b350d55548e4c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Zugmeyer?= <bzugmeyer@gmail.com>
Date: Tue, 21 May 2019 11:55:43 +0200
Subject: [PATCH] reuse serialized nodes ids (#12)

* reuse serialized nodes ids

With this patch, each DOM node keeps its id during its existence. This
allows to apply RRWeb events to previous snapshots if needed.

`resetId` has been removed because it loses its meaning: calling it
would not reset the existing nodes ids anymore, only the new ones.

Since we don't reset the id anymore, we may exhaust the available ids
quicker, but Number.MAX_SAFE_INTEGER (2 ** 53 - 1) is pretty large, so I
doubt this'll cause any problem.

* improv TS typing

The `nAsINode` variable was not very elegant.  Simplify this by removing
the cast, and make the INode interface compatible with Node.

* update typings
---
 src/index.ts          |  4 ++--
 src/snapshot.ts       | 20 ++++++++++----------
 typings/index.d.ts    |  4 ++--
 typings/snapshot.d.ts |  5 ++---
 4 files changed, 16 insertions(+), 17 deletions(-)

diff --git a/src/index.ts b/src/index.ts
index f3238ea2..5b2b0b9f 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,5 +1,5 @@
-import snapshot, { serializeNodeWithId, resetId } from './snapshot';
+import snapshot, { serializeNodeWithId } from './snapshot';
 import rebuild, { buildNodeWithSN } from './rebuild';
 export * from './types';
 
-export { snapshot, serializeNodeWithId, resetId, rebuild, buildNodeWithSN };
+export { snapshot, serializeNodeWithId, rebuild, buildNodeWithSN };
diff --git a/src/snapshot.ts b/src/snapshot.ts
index dd2a5447..2c0e170e 100644
--- a/src/snapshot.ts
+++ b/src/snapshot.ts
@@ -13,10 +13,6 @@ function genId(): number {
   return _id++;
 }
 
-export function resetId() {
-  _id = 1;
-}
-
 function getCssRulesString(s: CSSStyleSheet): string | null {
   try {
     const rules = s.rules || s.cssRules;
@@ -239,7 +235,7 @@ function serializeNode(
 }
 
 export function serializeNodeWithId(
-  n: Node,
+  n: Node | INode,
   doc: Document,
   map: idNodeMap,
   blockClass: string | RegExp,
@@ -252,11 +248,16 @@ export function serializeNodeWithId(
     console.warn(n, 'not serialized');
     return null;
   }
-  const serializedNode = Object.assign(_serializedNode, {
-    id: genId(),
-  });
+  let id
+  // Try to reuse the previous id
+  if ('__sn' in n) {
+    id = n.__sn.id
+  } else {
+    id = genId()
+  }
+  const serializedNode = Object.assign(_serializedNode, { id });
   (n as INode).__sn = serializedNode;
-  map[serializedNode.id] = n as INode;
+  map[id] = (n as INode);
   let recordChild = !skipChild;
   if (serializedNode.type === NodeType.Element) {
     recordChild = recordChild && !serializedNode.needBlock;
@@ -290,7 +291,6 @@ function snapshot(
   blockClass: string | RegExp = 'rr-block',
   inlineStylesheet = true,
 ): [serializedNodeWithId | null, idNodeMap] {
-  resetId();
   const idNodeMap: idNodeMap = {};
   return [
     serializeNodeWithId(n, n, idNodeMap, blockClass, false, inlineStylesheet),
diff --git a/typings/index.d.ts b/typings/index.d.ts
index 60e49702..87f610a3 100644
--- a/typings/index.d.ts
+++ b/typings/index.d.ts
@@ -1,4 +1,4 @@
-import snapshot, { serializeNodeWithId, resetId } from './snapshot';
+import snapshot, { serializeNodeWithId } from './snapshot';
 import rebuild, { buildNodeWithSN } from './rebuild';
 export * from './types';
-export { snapshot, serializeNodeWithId, resetId, rebuild, buildNodeWithSN };
+export { snapshot, serializeNodeWithId, rebuild, buildNodeWithSN };
diff --git a/typings/snapshot.d.ts b/typings/snapshot.d.ts
index 61ed5163..e8605417 100644
--- a/typings/snapshot.d.ts
+++ b/typings/snapshot.d.ts
@@ -1,6 +1,5 @@
-import { serializedNodeWithId, idNodeMap } from './types';
-export declare function resetId(): void;
+import { serializedNodeWithId, INode, idNodeMap } from './types';
 export declare function absoluteToStylesheet(cssText: string, href: string): string;
-export declare function serializeNodeWithId(n: Node, doc: Document, map: idNodeMap, blockClass: string | RegExp, skipChild?: boolean, inlineStylesheet?: boolean): serializedNodeWithId | null;
+export declare function serializeNodeWithId(n: Node | INode, doc: Document, map: idNodeMap, blockClass: string | RegExp, skipChild?: boolean, inlineStylesheet?: boolean): serializedNodeWithId | null;
 declare function snapshot(n: Document, blockClass?: string | RegExp, inlineStylesheet?: boolean): [serializedNodeWithId | null, idNodeMap];
 export default snapshot;