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

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

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

  // Guard against path traversal (UUIDs are safe, but be explicit)
  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 || !dump.fileName) {
    throw new APIException(
      APIErrorCode.NOT_FOUND,
      404,
      "No file for this dump",
    );
  }

  const path = `${DUMPS_DIR}/${dumpId}`;

  let data: Uint8Array;
  try {
    data = await Deno.readFile(path);
  } catch {
    throw new APIException(APIErrorCode.NOT_FOUND, 404, "File not found");
  }

  const total = data.byteLength;
  ctx.response.headers.set("Content-Type", dump.fileMime);
  ctx.response.headers.set(
    "Content-Disposition",
    `inline; filename="${dump.fileName}"`,
  );
  ctx.response.headers.set("Accept-Ranges", "bytes");

  const rangeHeader = ctx.request.headers.get("Range");

  if (rangeHeader) {
    const match = rangeHeader.match(/^bytes=(\d*)-(\d*)$/);
    if (!match) {
      ctx.response.status = 416;
      ctx.response.headers.set("Content-Range", `bytes */${total}`);
      return;
    }

    const start = match[1]
      ? parseInt(match[1], 10)
      : total - parseInt(match[2], 10);
    const end = match[2]
      ? Math.min(parseInt(match[2], 10), total - 1)
      : total - 1;

    if (start > end || start >= total) {
      ctx.response.status = 416;
      ctx.response.headers.set("Content-Range", `bytes */${total}`);
      return;
    }

    const chunk = data.subarray(start, end + 1);
    ctx.response.status = 206;
    ctx.response.headers.set("Content-Range", `bytes ${start}-${end}/${total}`);
    ctx.response.headers.set("Content-Length", String(chunk.byteLength));
    ctx.response.body = chunk;
  } else {
    ctx.response.headers.set("Content-Length", String(total));
    ctx.response.body = data;
  }
});

export default router;