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

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

/**
 * Builds an RFC 6266 `Content-Disposition` value that is always a valid
 * ByteString. `headers.set` throws a TypeError if the value contains any
 * character > U+00FF, so a filename with an emoji / accent / CJK character
 * (e.g. an uploaded file) would otherwise crash the response. We provide an
 * ASCII-only `filename="…"` fallback plus an RFC 5987 `filename*` with the
 * full UTF-8 name for modern browsers.
 */
function contentDisposition(name: string): string {
  const asciiFallback = name
    .replace(/["\\]/g, "_")
    .replace(/[^\x20-\x7e]/g, "_");
  return `inline; filename="${asciiFallback}"; filename*=UTF-8''${
    encodeURIComponent(name)
  }`;
}

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",
    contentDisposition(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;