import type { Provider } from "ethers";
import { getAddress, isAddress } from "ethers";

export const ERC1967_IMPLEMENTATION_SLOT =
  "0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc";

export const ERC1967_ADMIN_SLOT =
  "0xb53127684a568b3173ae13b9f8a6016e243e63b6e8ee1178d6a717850b5d6103";

const getERC1967Address = async (
  provider: Pick<Provider, "getStorage">,
  proxyAddress: string,
  slot: string,
  label: string,
): Promise<string | undefined> => {
  if (!isAddress(proxyAddress)) {
    throw new Error("Invalid proxy candidate address: " + proxyAddress);
  }
  const storage = await provider.getStorage(proxyAddress, slot);
  if (!/^0x[0-9a-fA-F]{64}$/.test(storage)) {
    throw new Error(`Invalid ERC1967 ${label} slot value for ${proxyAddress}`);
  }
  const storedAddress = "0x" + storage.slice(-40);
  if (storedAddress.toLowerCase() === "0x" + "00".repeat(20)) {
    return undefined;
  }
  return getAddress(storedAddress);
};

export const getERC1967Implementation = async (
  provider: Pick<Provider, "getStorage">,
  proxyAddress: string,
): Promise<string | undefined> => {
  return getERC1967Address(
    provider,
    proxyAddress,
    ERC1967_IMPLEMENTATION_SLOT,
    "implementation",
  );
};

export const getERC1967Admin = async (
  provider: Pick<Provider, "getStorage">,
  proxyAddress: string,
): Promise<string | undefined> => {
  return getERC1967Address(provider, proxyAddress, ERC1967_ADMIN_SLOT, "admin");
};