import { BigNumber } from 'ethers'
import { Contract } from 'ethers'
import { ERC20Interface } from '../constants'
import { QueryParams } from '../constants/type/QueryParams'
import { Falsy } from '../model/types'
import { useCall } from './useCall'

/**
 * Returns allowance (tokens left to use by spender) for given token owner - spender relationship.
 * @param tokenAddress address of a token contract
 * @param ownerAddress address of an account to which tokens are linked
 * @param spenderAddress address of an account allowed to spend tokens
 * @param queryParams see {@link QueryParams}.
 * @returns an allowance which is `BigNumber`, or `undefined` if any address or token is `Falsy` or not connected.
 * @public
 * @example
 * const TOKEN_ADDRESS = '0x6b175474e89094c44da98b954eedeac495271d0f'
 * const SPENDER_ADDRESS = '0xA193E42526F1FEA8C99AF609dcEabf30C1c29fAA'
 * const { account, chainId } = useEthers()
 * const allowance = useTokenAllowance(TOKEN_ADDRESS, account, SPENDER_ADDRESS)
 *
 * return (
 *   {allowance && <p>Remaining allowance: {formatUnits(allowance, 18)} tokens</p>}
 * )
 */
export function useTokenAllowance(
  tokenAddress: string | Falsy,
  ownerAddress: string | Falsy,
  spenderAddress: string | Falsy,
  queryParams: QueryParams = {}
): BigNumber | undefined {
  const { value: allowance } =
    useCall(
      ownerAddress &&
        spenderAddress &&
        tokenAddress && {
          contract: new Contract(tokenAddress, ERC20Interface),
          method: 'allowance',
          args: [ownerAddress, spenderAddress],
        },
      queryParams
    ) ?? {}
  return allowance?.[0]
}