first commit

app/api/testcase-generator/download/[taskId]/route.ts

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+import { NextRequest } from "next/server";
+import { getTask, getZipPathForTask } from "@/lib/testcase-backend";
+import fs from "fs/promises";
+
+export async function GET(
+  _req: NextRequest,
+  { params }: { params: Promise<{ taskId: string }> }
+) {
+  const { taskId } = await params;
+  if (!taskId) {
+    return Response.json({ error: "缺少 taskId" }, { status: 400 });
+  }
+
+  const task = getTask(taskId);
+  if (!task) {
+    return Response.json({ error: "任务未找到" }, { status: 404 });
+  }
+
+  if (task.status !== "completed") {
+    return Response.json({ error: "任务尚未完成" }, { status: 400 });
+  }
+
+  const zipPath = getZipPathForTask(taskId);
+  if (!zipPath) {
+    return Response.json({ error: "文件未找到" }, { status: 404 });
+  }
+
+  try {
+    const buffer = await fs.readFile(zipPath);
+    const filename = `${task.englishName}_testcases.zip`;
+    return new Response(buffer, {
+      status: 200,
+      headers: {
+        "Content-Type": "application/zip",
+        "Content-Disposition": `attachment; filename="${encodeURIComponent(filename)}"`,
+      },
+    });
+  } catch (e) {
+    console.error("[testcase] download read error:", e);
+    return Response.json({ error: "文件读取失败" }, { status: 500 });
+  }
+}