feat: add progress indication for long downloads

app/api/progress/[progressId]/route.ts

@@ -0,0 +1,64 @@
+import { getSession } from "@/lib/auth"
+import { getOrCreateProgress, getProgressById } from "@/models/progress"
+import { NextRequest, NextResponse } from "next/server"
+
+const POLL_INTERVAL_MS = 2000 // 2 seconds
+
+export async function GET(req: NextRequest, { params }: { params: Promise<{ progressId: string }> }) {
+  const session = await getSession()
+  if (!session || !session.user) {
+    return NextResponse.json({ error: "Unauthorized" }, { status: 401 })
+  }
+
+  const userId = session.user.id
+  const { progressId } = await params
+  const url = new URL(req.url)
+  const type = url.searchParams.get("type") || "unknown"
+
+  await getOrCreateProgress(userId, progressId, type)
+
+  const encoder = new TextEncoder()
+  const stream = new ReadableStream({
+    async start(controller) {
+      let lastSent: any = null
+      let stopped = false
+
+      req.signal.addEventListener("abort", () => {
+        stopped = true
+        controller.close()
+      })
+
+      while (!stopped) {
+        const progress = await getProgressById(userId, progressId)
+        if (!progress) {
+          controller.enqueue(encoder.encode(`event: error\ndata: {"error":"Not found"}\n\n`))
+          controller.close()
+          break
+        }
+
+        // Only send if progress has changed
+        if (JSON.stringify(progress) !== JSON.stringify(lastSent)) {
+          controller.enqueue(encoder.encode(`data: ${JSON.stringify(progress)}\n\n`))
+          lastSent = progress
+
+          // If progress is complete, close the connection
+          if (progress.current === progress.total && progress.total > 0) {
+            controller.close()
+            break
+          }
+        }
+
+        await new Promise((res) => setTimeout(res, POLL_INTERVAL_MS))
+      }
+    },
+  })
+
+  return new Response(stream, {
+    headers: {
+      "Content-Type": "text/event-stream",
+      "Cache-Control": "no-cache, no-transform",
+      Connection: "keep-alive",
+      "Access-Control-Allow-Origin": "*",
+    },
+  })
+}