Reject oversized pastes before the browser can truncate the document

README.md

@@ -10,7 +10,7 @@
 
 ## 快速开始
 
-使用 Node.js 24 和 npm，在示例目录上做一次只读检查。
+CLI 支持 Node.js 20 及以上版本。下面使用 Node.js 24 和 npm，在示例目录做一次只读检查。桌面打包所需的运行时见[构建说明](docs/build.md)。
 
 ```sh
 git clone https://github.com/Chumaniac/skillsync.git

browser/main.ts

@@ -4,15 +4,37 @@ const status = document.querySelector<HTMLElement>("#status")!;
 const message = document.querySelector<HTMLElement>("#message")!;
 const fields = document.querySelector<HTMLElement>("#fields")!;
 const example = "---\nname: inventory-check\ndescription: 对照清单核对库存。\n---\n\n先读取清单，再逐项核对应有与实收数量。";
+const byteLimit = 24 * 1024;
+const encoder = new TextEncoder();
+function tooLarge(value: string) {
+  return value.length > byteLimit || encoder.encode(value).length > byteLimit;
+}
+function oversized() {
+  fields.replaceChildren();
+  status.textContent = "文档过大";
+  message.textContent = "最多可检查 24 KiB。请缩短文档后重试。";
+}
+function checkInsertion(event: Event, text: string | null) {
+  if (!text) return;
+  if (text.length > byteLimit || tooLarge(input.value.slice(0, input.selectionStart) + text + input.value.slice(input.selectionEnd))) {
+    event.preventDefault();
+    oversized();
+    message.textContent = "本次输入超过 24 KiB，原文已保留。";
+  }
+}
+input.addEventListener("paste", event => checkInsertion(event, event.clipboardData?.getData("text/plain") ?? null));
+input.addEventListener("beforeinput", event => {
+  if (event.cancelable && event.inputType.startsWith("insert")) checkInsertion(event, event.data);
+});
 function clear() {
   status.textContent = "等待检查";
   message.textContent = "文档已更新，请重新检查。";
   fields.replaceChildren();
 }
 function check() {
   fields.replaceChildren();
-  if (new TextEncoder().encode(input.value).length > 24576) {
-    status.textContent = "文档过大"; message.textContent = "请缩短至 24 KiB 后重试。"; return;
+  if (tooLarge(input.value)) {
+    oversized(); return;
   }
   const parsed = parseSkillDocument(input.value);
   if (!parsed.ok) {