import { Router } from "@oak/oak";
import { APIErrorCode, APIException } from "../model/interfaces.ts";
import { getDump } from "../services/dump-service.ts";
import { DUMPS_DIR, THUMBNAILS_DIR } from "../config.ts";

const router = new Router({ prefix: "/api/thumbnails" });

async function ffmpegAvailable(): Promise<boolean> {
  try {
    const cmd = new Deno.Command("ffmpeg", {
      args: ["-version"],
      stderr: "null",
      stdout: "null",
    });
    const { success } = await cmd.output();
    return success;
  } catch {
    return false;
  }
}

async function generateThumbnail(
  srcPath: string,
  outPath: string,
): Promise<void> {
  await Deno.mkdir(THUMBNAILS_DIR, { recursive: true });
  const cmd = new Deno.Command("ffmpeg", {
    args: [
      "-ss",
      "00:00:01",
      "-i",
      srcPath,
      "-frames:v",
      "1",
      "-vf",
      "scale=320:-1",
      "-f",
      "image2",
      "-y",
      outPath,
    ],
    stdout: "null",
    stderr: "null",
  });
  const { success } = await cmd.output();
  if (!success) throw new Error("ffmpeg failed");
}

router.get("/:dumpId", async (ctx) => {
  const { dumpId } = ctx.params;

  if (!/^[0-9a-f-]{36}$/.test(dumpId)) {
    throw new APIException(APIErrorCode.BAD_REQUEST, 400, "Invalid dump ID");
  }

  const dump = getDump(dumpId);

  if (dump.kind !== "file" || !dump.fileMime?.startsWith("video/")) {
    throw new APIException(
      APIErrorCode.NOT_FOUND,
      404,
      "No video for this dump",
    );
  }

  const thumbPath = `${THUMBNAILS_DIR}/${dumpId}.jpg`;

  // Serve cached thumbnail if it exists
  try {
    const data = await Deno.readFile(thumbPath);
    ctx.response.headers.set("Content-Type", "image/jpeg");
    ctx.response.headers.set(
      "Cache-Control",
      "public, max-age=31536000, immutable",
    );
    ctx.response.body = data;
    return;
  } catch {
    // Not cached yet — generate it
  }

  if (!await ffmpegAvailable()) {
    throw new APIException(
      APIErrorCode.NOT_FOUND,
      404,
      "Thumbnail generation unavailable",
    );
  }

  const srcPath = `${DUMPS_DIR}/${dumpId}`;
  try {
    await generateThumbnail(srcPath, thumbPath);
  } catch {
    throw new APIException(
      APIErrorCode.NOT_FOUND,
      404,
      "Could not generate thumbnail",
    );
  }

  const data = await Deno.readFile(thumbPath);
  ctx.response.headers.set("Content-Type", "image/jpeg");
  ctx.response.headers.set(
    "Cache-Control",
    "public, max-age=31536000, immutable",
  );
  ctx.response.body = data;
});

export default router;