feat: 接入预览模式（Next.js Draft Mode）

app/preview/route.ts

@@ -0,0 +1,54 @@
+import { NextRequest, NextResponse } from "next/server";
+import { draftMode, cookies } from "next/headers";
+import {
+  fetchPreviewPage,
+  resolvePreviewPath,
+  PREVIEW_CONTENT_TYPE_COOKIE,
+  PREVIEW_TOKEN_COOKIE,
+} from "@/services/preview.service";
+import type { WagtailPageSummary } from "@/types/wagtail";
+
+/**
+ * Wagtail 编辑器点击"预览"后会重定向到此路由（详见 wagtailcms/settings/base.py
+ * 中 WAGTAIL_HEADLESS_PREVIEW.CLIENT_URLS）。校验 token 有效后开启 Next.js
+ * Draft Mode 并重定向到对应内容的前端路由，由页面组件通过 getPreviewOrFallback
+ * 拉取草稿数据渲染。
+ */
+export async function GET(request: NextRequest) {
+  const contentType = request.nextUrl.searchParams.get("content_type");
+  const token = request.nextUrl.searchParams.get("token");
+
+  if (!contentType || !token) {
+    return NextResponse.json(
+      { error: "缺少 content_type 或 token 参数" },
+      { status: 400 },
+    );
+  }
+
+  // 先校验 token 是否有效并取回 slug，未开启 Draft Mode，避免暴露无效预览。
+  const page = await fetchPreviewPage<WagtailPageSummary>(contentType, token);
+  const path = page ? resolvePreviewPath(contentType, page) : null;
+
+  if (!page || !path) {
+    return NextResponse.json(
+      { error: "预览链接无效或已过期" },
+      { status: 404 },
+    );
+  }
+
+  const draft = await draftMode();
+  draft.enable();
+
+  const isProduction = process.env.NODE_ENV === "production";
+  const cookieStore = await cookies();
+  const cookieOptions = {
+    httpOnly: true,
+    sameSite: "lax" as const,
+    secure: isProduction,
+    path: "/",
+  };
+  cookieStore.set(PREVIEW_CONTENT_TYPE_COOKIE, contentType, cookieOptions);
+  cookieStore.set(PREVIEW_TOKEN_COOKIE, token, cookieOptions);
+
+  return NextResponse.redirect(new URL(path, request.url));
+}