From 97c4b4f6e1519fc2e4b155c0b98cf3bbb5988f69 Mon Sep 17 00:00:00 2001
From: Yanzhen Yu <yanzhen@smartx.com>
Date: Wed, 1 Apr 2026 12:00:00 +0800
Subject: [PATCH] basic snapshot implementation

---
 src/index.ts  | 138 ++++++++++++++++++++++++++++++++++++++++++++++++++
 tsconfig.json |   5 +-
 tslint.json   |   3 +-
 3 files changed, 143 insertions(+), 3 deletions(-)

diff --git a/src/index.ts b/src/index.ts
index e69de29b..4a003d2b 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -0,0 +1,138 @@
+let _id = 1;
+
+function genId(): number {
+  return _id++;
+}
+
+enum NodeType {
+  Document,
+  DocumentType,
+  Element,
+  Text,
+  CDATA,
+  Comment,
+}
+
+type serializedNode =
+  | documentNode
+  | documentTypeNode
+  | elementNode
+  | textNode
+  | cdataNode
+  | commentNode;
+
+type documentNode = {
+  type: NodeType.Document;
+  childNodes: serializedNode[];
+};
+
+type documentTypeNode = {
+  type: NodeType.DocumentType;
+  name: string;
+  publicId: string;
+  systemId: string;
+};
+
+type attributes = {
+  [key: string]: string;
+};
+type elementNode = {
+  type: NodeType.Element;
+  tagName: string;
+  attributes: attributes;
+  childNodes: serializedNode[];
+};
+
+type textNode = {
+  type: NodeType.Text;
+  textContent: string;
+};
+
+type cdataNode = {
+  type: NodeType.CDATA;
+  textContent: '';
+};
+
+type commentNode = {
+  type: NodeType.Comment;
+  textContent: string;
+};
+
+function serializeNode(n: Node): serializedNode | false {
+  switch (n.nodeType) {
+    case n.DOCUMENT_NODE:
+      return {
+        type: NodeType.Document,
+        childNodes: [],
+      };
+    case n.DOCUMENT_TYPE_NODE:
+      return {
+        type: NodeType.DocumentType,
+        name: (n as DocumentType).name,
+        publicId: (n as DocumentType).publicId,
+        systemId: (n as DocumentType).systemId,
+      };
+    case n.ELEMENT_NODE:
+      const tagName = (n as HTMLElement).tagName.toLowerCase();
+      const attributes: attributes = {};
+      for (const { name, value } of Array.from((n as HTMLElement).attributes)) {
+        attributes[name] = value;
+      }
+      return {
+        type: NodeType.Element,
+        tagName,
+        attributes,
+        childNodes: [],
+      };
+    case n.TEXT_NODE:
+      // The parent node may not be a html element which has a tagName attribute.
+      // So just let it be undefined which is ok in this use case.
+      const parentTagName =
+        n.parentNode && (n.parentNode as HTMLElement).tagName;
+      let textContent = (n as Text).textContent;
+      if (parentTagName === 'SCRIPT') {
+        textContent = '';
+      }
+      return {
+        type: NodeType.Text,
+        textContent,
+      };
+    case n.CDATA_SECTION_NODE:
+      return {
+        type: NodeType.CDATA,
+        textContent: '',
+      };
+    case n.COMMENT_NODE:
+      return {
+        type: NodeType.Comment,
+        textContent: (n as Comment).textContent,
+      };
+    default:
+      return false;
+  }
+}
+
+type serializedNodeWithId = serializedNode & { id: number };
+
+function snapshot(n: Node): serializedNodeWithId | null {
+  const _serializedNode = serializeNode(n);
+  if (!_serializedNode) {
+    // TODO: dev only
+    console.warn(n, 'not serialized');
+    return null;
+  }
+  const serializedNode: serializedNodeWithId = Object.assign(_serializedNode, {
+    id: genId(),
+  });
+  if (
+    serializedNode.type === NodeType.Document ||
+    serializedNode.type === NodeType.Element
+  ) {
+    for (const childN of Array.from(n.childNodes)) {
+      serializedNode.childNodes.push(snapshot(childN));
+    }
+  }
+  return serializedNode;
+}
+
+export default snapshot;
diff --git a/tsconfig.json b/tsconfig.json
index 1aec14ff..ce1b7e3c 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -6,7 +6,8 @@
     "preserveConstEnums": true,
     "sourceMap": true,
     "rootDir": "src",
-    "outDir": "build"
+    "outDir": "build",
+    "lib": ["es6", "dom"]
   },
   "compileOnSave": true
-}
\ No newline at end of file
+}
diff --git a/tslint.json b/tslint.json
index c82ebf60..3a0c0801 100644
--- a/tslint.json
+++ b/tslint.json
@@ -8,7 +8,8 @@
     "ordered-imports": false,
     "object-literal-sort-keys": false,
     "no-unused-variable": true,
-    "object-literal-key-quotes": false
+    "object-literal-key-quotes": false,
+    "variable-name": [true, "ban-keywords", "check-format", "allow-leading-underscore"]
   },
   "rulesDirectory": []
 }
\ No newline at end of file