import { Contract } from '@ethersproject/contracts'
import { Provider } from '@ethersproject/abstract-provider'
import { namehash } from 'ethers/lib/utils'

const REGISTRAR_ABI = [
  {
    constant: true,
    inputs: [
      {
        name: 'node',
        type: 'bytes32'
      }
    ],
    name: 'resolver',
    outputs: [
      {
        name: 'resolverAddress',
        type: 'address'
      }
    ],
    payable: false,
    stateMutability: 'view',
    type: 'function'
  }
]
const REGISTRAR_ADDRESS = '0x00000000000C2E074eC69A0dFb2997BA6C7d2e1e'

const RESOLVER_ABI = [
  {
    constant: true,
    inputs: [
      {
        internalType: 'bytes32',
        name: 'node',
        type: 'bytes32'
      }
    ],
    name: 'contenthash',
    outputs: [
      {
        internalType: 'bytes',
        name: '',
        type: 'bytes'
      }
    ],
    payable: false,
    stateMutability: 'view',
    type: 'function'
  }
]

// cache the resolver contracts since most of them are the public resolver
function resolverContract(resolverAddress: string, provider: Provider): Contract {
  return new Contract(resolverAddress, RESOLVER_ABI, provider)
}

/**
 * Fetches and decodes the result of an ENS contenthash lookup on mainnet to a URI
 * @param ensName to resolve
 * @param provider provider to use to fetch the data
 */
export default async function resolveENSContentHash(ensName: string, provider: Provider): Promise<string> {
  const ensRegistrarContract = new Contract(REGISTRAR_ADDRESS, REGISTRAR_ABI, provider)
  const hash = namehash(ensName)
  const resolverAddress = await ensRegistrarContract.resolver(hash)
  return resolverContract(resolverAddress, provider).contenthash(hash)
}