import { BigNumberish, Signer } from 'ethers'
import { JsonRpcProvider, Provider } from '@ethersproject/providers'
import { Erc20, Erc20__factory } from './abi/types'
import { BigNumber } from '@ethersproject/bignumber'
import { formatUnits, parseUnits } from 'ethers/lib/utils'

class ERC20Contract {

  private erc20: Erc20

  constructor(address: string, signerOrProvider: string | Signer | Provider) {
    if (typeof signerOrProvider !== 'string') {
      this.erc20 = Erc20__factory.connect(address, signerOrProvider)
    } else {
      const provider = new JsonRpcProvider(signerOrProvider)
      this.erc20 = Erc20__factory.connect(address, provider)
    }
  }

  async details(): Promise<{ name: string, symbol: string, decimals: number }> {
    const name = await this.erc20.callStatic.name()
    const symbol = await this.erc20.callStatic.symbol()
    const decimals = await this.decimals()
    return { name, symbol, decimals }
  }

  async balance(address: string): Promise<BigNumber> {
    return await this.erc20.callStatic.balanceOf(address)
  }

  async balanceFormat(address: string): Promise<string> {
    const decimals = await this.erc20.callStatic.decimals()
    const balance = await this.erc20.callStatic.balanceOf(address)
    return formatUnits(balance, decimals)
  }

  async transfer(to: string, amount: number): Promise<string> {
    if (this.erc20.address === null) {
      throw new Error('invalid signer or provider')
    }

    const decimals = await this.decimals()
    const val = parseUnits(`${amount}`, decimals)
    const tx = await this.erc20.transfer(to, val)
    return tx.hash
  }

  async approve(spender: string, amount: BigNumberish): Promise<string> {
    if (this.erc20.address === null) {
      throw new Error('invalid signer or provider')
    }
    const tx = await this.erc20.approve(spender, amount)
    return tx.hash
  }

  async allowance(owner: string, spender: string): Promise<BigNumber> {
    return this.erc20.callStatic.allowance(owner, spender)
  }

  private async decimals(): Promise<number> {
    let decimals: number
    try {
      decimals = await this.erc20.callStatic.decimals()
    } catch {
      decimals = 0
    }
    return decimals
  }
}

export default ERC20Contract