import { NextRequest } from "next/server";
import { Job } from "bullmq";
import { getPipelineQueue, getValhallaQueue } from "@/lib/queue";
import type { PipelineJobData, JobProgress } from "@/lib/queue";
import type { SSEEvent } from "@transportationer/shared";

export const runtime = "nodejs";

function fmt(event: SSEEvent): string {
  return `data: ${JSON.stringify(event)}\n\n`;
}

export async function GET(
  req: NextRequest,
  { params }: { params: Promise<{ id: string }> },
): Promise<Response> {
  const { id } = await params;
  const queue = getPipelineQueue();
  const encoder = new TextEncoder();
  let timer: ReturnType<typeof setInterval> | null = null;

  // Resolve citySlug from the refresh-city job that was returned to the UI.
  // We track progress by citySlug across all pipeline stages because
  // refresh-city itself completes almost immediately after enqueueing children.
  let citySlug: string;
  try {
    const job = await Job.fromId<PipelineJobData>(queue, id);
    if (!job) {
      return new Response(fmt({ type: "failed", jobId: id, error: "Job not found" }), {
        headers: { "Content-Type": "text/event-stream" },
      });
    }
    citySlug = job.data.citySlug ?? "";
  } catch {
    return new Response(fmt({ type: "failed", jobId: id, error: "Queue unavailable" }), {
      headers: { "Content-Type": "text/event-stream" },
    });
  }

  const valhallaQueue = getValhallaQueue();

  const stream = new ReadableStream({
    start(ctrl) {
      const enqueue = (e: SSEEvent) => {
        try {
          ctrl.enqueue(encoder.encode(fmt(e)));
        } catch {
          /* controller already closed */
        }
      };

      const cleanup = () => {
        if (timer) { clearInterval(timer); timer = null; }
        try { ctrl.close(); } catch { /* already closed */ }
      };

      const poll = async () => {
        try {
          // 1. Find the currently active stage across both queues.
          const [pipelineActive, valhallaActive] = await Promise.all([
            queue.getActive(0, 100),
            valhallaQueue.getActive(0, 100),
          ]);
          const activeJob = [...pipelineActive, ...valhallaActive].find(
            (j) => j.data.citySlug === citySlug && j.data.type !== "refresh-city",
          );

          if (activeJob) {
            const p = activeJob.progress as JobProgress | undefined;
            if (p?.stage) {
              enqueue({
                type: "progress",
                stage: p.stage,
                pct: p.pct,
                message: p.message,
                bytesDownloaded: p.bytesDownloaded,
                totalBytes: p.totalBytes,
              });
            } else {
              enqueue({ type: "heartbeat" });
            }
            return;
          }

          // 2. No active stage — check for a recent failure in either queue.
          const [pipelineFailed, valhallaFailed] = await Promise.all([
            queue.getFailed(0, 50),
            valhallaQueue.getFailed(0, 50),
          ]);
          const recentFail = [...pipelineFailed, ...valhallaFailed].find(
            (j) =>
              j.data.citySlug === citySlug &&
              j.data.type !== "refresh-city" &&
              Date.now() - (j.finishedOn ?? 0) < 600_000,
          );
          if (recentFail) {
            enqueue({
              type: "failed",
              jobId: recentFail.id ?? "",
              error: recentFail.failedReason ?? "Pipeline stage failed",
            });
            cleanup();
            return;
          }

          // 3. Check if compute-scores completed recently → full pipeline done.
          const completed = await queue.getCompleted(0, 100);
          const finalDone = completed.find(
            (j) =>
              j.data.citySlug === citySlug &&
              j.data.type === "compute-scores" &&
              Date.now() - (j.finishedOn ?? 0) < 3_600_000,
          );
          if (finalDone) {
            enqueue({ type: "completed", jobId: finalDone.id ?? "" });
            cleanup();
            return;
          }

          // 4. Still pending — heartbeat.
          enqueue({ type: "heartbeat" });
        } catch {
          enqueue({ type: "heartbeat" });
        }
      };

      poll();
      timer = setInterval(poll, 1000);

      req.signal.addEventListener("abort", cleanup);
    },

    cancel() {
      if (timer) clearInterval(timer);
    },
  });

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