import { listEvents } from "@autoscholar/core";
import { redact } from "@autoscholar/observability";
import { z } from "zod";
import { handler, json, parseQuery } from "@/lib/server/api";
import { db } from "@/lib/server/db";
import { requireAdmin } from "@/lib/server/session";

export const runtime = "nodejs";
export const dynamic = "force-dynamic";

/**
 * Reconnectable event stream. `?after=<seq>` (or `Last-Event-ID`) resumes; `?stream=1` returns Server-Sent Events,
 * otherwise a JSON page. Events are redacted before leaving the server.
 */
export const GET = handler(async (req, { params }) => {
  await requireAdmin(req);
  const { id } = (await params) as { id: string };
  const q = parseQuery(
    req.url,
    z.object({
      after: z.coerce.number().int().min(0).default(0),
      stream: z.string().optional(),
      limit: z.coerce.number().int().min(1).max(1000).default(500),
    }),
  );
  const lastId = Number(req.headers.get("last-event-id") ?? 0);
  let after = Math.max(q.after, Number.isFinite(lastId) ? lastId : 0);
  if (!q.stream) {
    const events = await listEvents(db(), id, after, q.limit);
    return json({ events: redact(events), lastSeq: events.at(-1)?.seq ?? after });
  }
  const encoder = new TextEncoder();
  let closed = false;
  const stream = new ReadableStream<Uint8Array>({
    async start(controller) {
      const send = (data: unknown, seq?: number, event = "run.event") =>
        controller.enqueue(
          encoder.encode(
            `${seq !== undefined ? `id: ${seq}\n` : ""}event: ${event}\ndata: ${JSON.stringify(data)}\n\n`,
          ),
        );
      send({ connected: true, after }, undefined, "hello");
      const started = Date.now();
      while (!closed && Date.now() - started < 10 * 60_000) {
        try {
          const events = await listEvents(db(), id, after, 200);
          for (const ev of events) {
            send(redact(ev), ev.seq);
            after = ev.seq;
          }
          if (events.length === 0) controller.enqueue(encoder.encode(": keepalive\n\n"));
        } catch (e) {
          send({ error: (e as Error).message }, undefined, "error");
        }
        await new Promise((r) => setTimeout(r, 1500));
      }
      controller.close();
    },
    cancel() {
      closed = true;
    },
  });
  return new Response(stream, {
    headers: {
      "content-type": "text/event-stream; charset=utf-8",
      "cache-control": "no-store, no-transform",
      connection: "keep-alive",
      "x-accel-buffering": "no",
    },
  });
});