import { discoverBeadsDir } from "@/lib/discover";
import { loadBeadsData } from "@/lib/parse-beads";
import { watchBeadsFiles } from "@/lib/watch-beads";

// Prevent Next.js from statically optimizing this route
export const dynamic = "force-dynamic";

export async function GET(request: Request) {
  let cleanup: (() => void) | null = null;

  const stream = new ReadableStream({
    start(controller) {
      const encoder = new TextEncoder();

      function send(data: unknown) {
        try {
          controller.enqueue(
            encoder.encode(`data: ${JSON.stringify(data)}\n\n`)
          );
        } catch {
          // Stream closed — cleanup will handle
        }
      }

      try {
        const { beadsDir } = discoverBeadsDir();

        // Send initial data
        const initialData = loadBeadsData(beadsDir);
        send(initialData);

        // Watch for changes and push updates
        cleanup = watchBeadsFiles(beadsDir, () => {
          try {
            const newData = loadBeadsData(beadsDir);
            send(newData);
          } catch (err) {
            console.error("Failed to reload beads data:", err);
          }
        });

        // Heartbeat every 30s to keep connection alive through proxies/firewalls
        const heartbeat = setInterval(() => {
          try {
            controller.enqueue(encoder.encode(": heartbeat\n\n"));
          } catch {
            clearInterval(heartbeat);
          }
        }, 30000);

        // Clean up when client disconnects
        request.signal.addEventListener("abort", () => {
          clearInterval(heartbeat);
          if (cleanup) cleanup();
          try {
            controller.close();
          } catch {
            /* already closed */
          }
        });
      } catch (err: unknown) {
        // Discovery failed — send error and close
        const message =
          err instanceof Error ? err.message : "Unknown error";
        send({ error: message });
        controller.close();
      }
    },

    cancel() {
      if (cleanup) cleanup();
    },
  });

  return new Response(stream, {
    headers: {
      "Content-Type": "text/event-stream",
      "Cache-Control": "no-cache, no-transform",
      Connection: "keep-alive",
      "X-Accel-Buffering": "no", // Disable Nginx buffering
    },
  });
}