// app/api/transcoder/claim/route.ts
// Atomically claims the next available transcoding job.
// Uses SELECT … FOR UPDATE SKIP LOCKED so multiple workers never race on the
// same video.

import { NextResponse } from "next/server";
import { prisma } from "@/lib/prisma";
import { Prisma } from "@prisma/client";
import { verifyTranscoderToken } from "@/lib/transcoder-auth";

export const dynamic = "force-dynamic";

export async function POST(request: Request) {
  if (!verifyTranscoderToken(request)) {
    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
  }

  try {
    const video = await prisma.$transaction(async (tx) => {
      // Atomically lock the oldest uploaded video, skipping rows already
      // locked by concurrent workers.
      const rows = await tx.$queryRaw<{ id: string }[]>(
        Prisma.sql`
          SELECT id
          FROM   "Video"
          WHERE  "transcodingStatus" = 'uploaded'
          ORDER  BY "createdAt" ASC
          LIMIT  1
          FOR    UPDATE SKIP LOCKED
        `
      );

      if (rows.length === 0) return null;

      return tx.video.update({
        where: { id: rows[0].id },
        data: { transcodingStatus: "processing" },
      });
    });

    if (!video) {
      // No work available – return null body so the worker knows to stop.
      return NextResponse.json(null, { status: 200 });
    }

    // Build the download URL from the public CMS base URL.
    const cmsBase =
      process.env.NEXTAUTH_URL?.replace(/\/$/, "") ??
      process.env.CMS_PUBLIC_URL?.replace(/\/$/, "") ??
      "";

    return NextResponse.json({
      videoId: video.id,
      downloadUrl: `${cmsBase}/api/transcoder/download/${video.id}`,
    });
  } catch (err) {
    console.error("[Transcoder Claim] Error:", err);
    return NextResponse.json({ error: "Internal server error" }, { status: 500 });
  }
}