/**
 * Backfill `width` and `height` on Page rows by range-fetching the first
 * 16 KB of each image from R2 and parsing its header with `image-size`.
 *
 * Idempotent: only targets rows where width=0 or height=0.
 *
 * Usage: npx tsx scripts/backfill-page-dims.ts
 */
import { PrismaClient } from "@prisma/client";
import { S3Client, GetObjectCommand } from "@aws-sdk/client-s3";
import { imageSize } from "image-size";
import { keyFromPublicUrl } from "@/lib/r2";

const prisma = new PrismaClient();

const BUCKET = process.env.R2_BUCKET;
if (!BUCKET) throw new Error("R2_BUCKET must be set");

const s3 = new S3Client({
  region: "auto",
  endpoint: `https://${process.env.R2_ACCOUNT_ID}.r2.cloudflarestorage.com`,
  credentials: {
    accessKeyId: process.env.R2_ACCESS_KEY!,
    secretAccessKey: process.env.R2_SECRET_KEY!,
  },
});

const CONCURRENCY = 10;
const HEADER_BYTES = 16_384;

async function fetchHeader(key: string): Promise<Uint8Array> {
  const res = await s3.send(
    new GetObjectCommand({
      Bucket: BUCKET,
      Key: key,
      Range: `bytes=0-${HEADER_BYTES - 1}`,
    })
  );
  if (!res.Body) throw new Error(`No body for ${key}`);
  return res.Body.transformToByteArray();
}

async function main() {
  const pages = await prisma.page.findMany({
    where: { OR: [{ width: 0 }, { height: 0 }] },
    orderBy: { id: "asc" },
  });
  console.log(`Probing ${pages.length} pages with dims unset`);

  let done = 0;
  let failed = 0;

  for (let i = 0; i < pages.length; i += CONCURRENCY) {
    const batch = pages.slice(i, i + CONCURRENCY);
    await Promise.all(
      batch.map(async (page) => {
        try {
          const key = keyFromPublicUrl(page.imageUrl);
          if (!key) throw new Error(`URL outside R2 prefix: ${page.imageUrl}`);
          const header = await fetchHeader(key);
          const { width, height } = imageSize(header);
          if (!width || !height) {
            throw new Error("image-size returned no dimensions");
          }
          await prisma.page.update({
            where: { id: page.id },
            data: { width, height },
          });
          done++;
        } catch (err) {
          failed++;
          console.error(
            `✗ page ${page.id} (${page.imageUrl}):`,
            err instanceof Error ? err.message : err
          );
        }
      })
    );
    console.log(`${Math.min(i + CONCURRENCY, pages.length)}/${pages.length}`);
  }

  console.log(`\nDone. Probed: ${done}, failed: ${failed}`);
  await prisma.$disconnect();
}

main().catch((e) => {
  console.error(e);
  process.exit(1);
});