export const CRYSTAL_ROM = {
  name: "Pokémon Crystal · English US/Europe 1.1",
  sha1: "f2f52230b536214ef7c9924f483392993e226cfb",
  size: 2 * 1024 * 1024,
} as const;

export interface ValidatedRom {
  bytes: Uint8Array;
  sha1: string;
  name: string;
}

export async function validateRom(file: File): Promise<ValidatedRom> {
  if (file.size !== CRYSTAL_ROM.size) {
    throw new Error(
      "Choose an uncompressed Pokémon Crystal English US/Europe 1.1 ROM (.gbc, 2 MiB).",
    );
  }
  if (!globalThis.crypto?.subtle) {
    throw new Error(
      "ROM verification needs HTTPS or localhost. Open this player over a secure connection.",
    );
  }
  const buffer = await file.arrayBuffer();
  const digest = await crypto.subtle.digest("SHA-1", buffer);
  const sha1 = Array.from(new Uint8Array(digest), (byte) =>
    byte.toString(16).padStart(2, "0"),
  ).join("");
  if (sha1 !== CRYSTAL_ROM.sha1) {
    throw new Error(
      "This ROM is not the supported English US/Europe revision 1.1. Other languages, revisions, and modified ROMs are not supported yet.",
    );
  }
  return { bytes: new Uint8Array(buffer), sha1, name: CRYSTAL_ROM.name };
}