fortress-js/src/fToken.ts

A JavaScript SDK for Binance Smart Chain and the Fortress Protocol.

/**
 * @file fToken
 * @desc These methods facilitate interactions with the fToken smart
 *     contracts.
 */

import { ethers } from 'ethers';
import * as eth from './eth';
import { netId } from './helpers';
import {
  constants, address, abi, decimals, underlyings, cTokens
} from './constants';
import { BigNumber } from '@ethersproject/bignumber/lib/bignumber';
import { CallOptions, TrxResponse } from './types';

/**
 * Supplies the user's Binance Smart Chain asset to the Fortress Protocol.
 *
 * @param {string} asset A string of the asset to supply.
 * @param {number | string | BigNumber} amount A string, number, or BigNumber
 *     object of the amount of an asset to supply. Use the `mantissa` boolean in
 *     the `options` parameter to indicate if this value is scaled up (so there 
 *     are no decimals) or in its natural scale.
 * @param {boolean} noApprove Explicitly prevent this method from attempting an 
 *     BEP-20 `approve` transaction prior to sending the `mint` transaction.
 * @param {CallOptions} [options] Call options and Ethers.js overrides for the 
 *     transaction. A passed `gasLimit` will be used in both the `approve` (if 
 *     not supressed) and `mint` transactions.
 *
 * @returns {object} Returns an Ethers.js transaction object of the supply
 *     transaction.
 *
 * @example
 *
 * ```
 * const fortress = new Fortress(window.ethereum);
 *
 * // Ethers.js overrides are an optional 3rd parameter for `supply`
 * // const trxOptions = { gasLimit: 250000, mantissa: false };
 * 
 * (async function() {
 * 
 *   console.log('Supplying DAI to the Fortress Protocol...');
 *   const trx = await fortress.supply(Fortress.DAI, 1);
 *   console.log('Ethers.js transaction object', trx);
 * 
 * })().catch(console.error);
 * ```
 */
export async function supply(
  asset: string,
  amount: string | number | BigNumber,
  noApprove = false,
  options: CallOptions = {}
) : Promise<TrxResponse> {
  await netId(this);
  const errorPrefix = 'Fortress [supply] | ';

  const fTokenName = 'f' + asset;
  const fTokenAddress = address[this._network.name][fTokenName];

  if (!fTokenAddress || !underlyings.includes(asset)) {
    throw Error(errorPrefix + 'Argument `asset` cannot be supplied.');
  }

  if (
    typeof amount !== 'number' &&
    typeof amount !== 'string' &&
    !ethers.BigNumber.isBigNumber(amount)
  ) {
    throw Error(errorPrefix + 'Argument `amount` must be a string, number, or BigNumber.');
  }

  if (!options.mantissa) {
    amount = +amount;
    amount = amount * Math.pow(10, decimals[asset]);
  }

  amount = ethers.BigNumber.from(amount.toString());

  // if (fTokenName === constants.cETH) {
  //   options.abi = abi.cEther;
  // } else {
  //   options.abi = abi.cErc20;
  // }
  if (fTokenName === constants.fBNB) {
    options.abi = abi.fBNB;
  } else {
    options.abi = abi.fBep20;
  }

  options._compoundProvider = this._provider;

  if (fTokenName !== constants.fBNB && noApprove !== true) {
    const underlyingAddress = address[this._network.name][asset];
    const userAddress = this._provider.address;

    // Check allowance
    const allowance = await eth.read(
      underlyingAddress,
      'allowance',
      [ userAddress, fTokenAddress ],
      options
    );

    const notEnough = allowance.lt(amount);

    if (notEnough) {
      // ERC-20 approve transaction
      await eth.trx(
        underlyingAddress,
        'approve',
        [ fTokenAddress, amount ],
        options
      );
    }
  }

  const parameters = [];
  if (fTokenName === constants.fBNB) {
    options.value = amount;
  } else {
    parameters.push(amount);
  }

  return eth.trx(fTokenAddress, 'mint', parameters, options);
}

/**
 * Redeems the user's Binance Smart Chain asset from the Fortress Protocol.
 *
 * @param {string} asset A string of the asset to redeem, or its fToken name.
 * @param {number | string | BigNumber} amount A string, number, or BigNumber
 *     object of the amount of an asset to redeem. Use the `mantissa` boolean in
 *     the `options` parameter to indicate if this value is scaled up (so there 
 *     are no decimals) or in its natural scale. This can be an amount of 
 *     fTokens or underlying asset (use the `asset` parameter to specify).
 * @param {CallOptions} [options] Call options and Ethers.js overrides for the 
 *     transaction.
 *
 * @returns {object} Returns an Ethers.js transaction object of the redeem
 *     transaction.
 *
 * @example
 *
 * ```
 * const fortress = new Fortress(window.ethereum);
 * 
 * (async function() {
 * 
 *   console.log('Redeeming DAI...');
 *   const trx = await fortress.redeem(Fortress.DAI, 1); // also accepts fToken args
 *   console.log('Ethers.js transaction object', trx);
 * 
 * })().catch(console.error);
 * ```
 */
export async function redeem(
  asset: string,
  amount: string | number | BigNumber,
  options: CallOptions = {}
): Promise<TrxResponse> {
  await netId(this);
  const errorPrefix = 'Fortress [redeem] | ';

  if (typeof asset !== 'string' || asset.length < 1) {
    throw Error(errorPrefix + 'Argument `asset` must be a non-empty string.');
  }

  const assetIsFToken = asset[0] === 'f';

  const fTokenName = assetIsFToken ? asset : 'f' + asset;
  const fTokenAddress = address[this._network.name][fTokenName];

  const underlyingName = assetIsFToken ? asset.slice(1, asset.length) : asset;

  if (!cTokens.includes(fTokenName) || !underlyings.includes(underlyingName)) {
    throw Error(errorPrefix + 'Argument `asset` is not supported.');
  }

  if (
    typeof amount !== 'number' &&
    typeof amount !== 'string' &&
    !ethers.BigNumber.isBigNumber(amount)
  ) {
    throw Error(errorPrefix + 'Argument `amount` must be a string, number, or BigNumber.');
  }

  if (!options.mantissa) {
    amount = +amount;
    amount = amount * Math.pow(10, decimals[asset]);
  }

  amount = ethers.BigNumber.from(amount.toString());

  const trxOptions: CallOptions = {
    ...options,
    _compoundProvider: this._provider,
    abi: fTokenName === constants.fBNB ? abi.fBNB : abi.fBep20,
  };
  const parameters = [ amount ];
  const method = assetIsFToken ? 'redeem' : 'redeemUnderlying';

  return eth.trx(fTokenAddress, method, parameters, trxOptions);
}

/**
 * Borrows an Binance Smart Chain asset from the Fortress Protocol for the user.
 *     The user's address must first have supplied collateral and entered a 
 *     corresponding market.
 *
 * @param {string} asset A string of the asset to borrow (must be a supported 
 *     underlying asset).
 * @param {number | string | BigNumber} amount A string, number, or BigNumber
 *     object of the amount of an asset to borrow. Use the `mantissa` boolean in
 *     the `options` parameter to indicate if this value is scaled up (so there 
 *     are no decimals) or in its natural scale.
 * @param {CallOptions} [options] Call options and Ethers.js overrides for the 
 *     transaction.
 *
 * @returns {object} Returns an Ethers.js transaction object of the borrow
 *     transaction.
 *
 * @example
 *
 * ```
 * const fortress = new Fortress(window.ethereum);
 * 
 * (async function() {
 * 
 *   const daiScaledUp = '32000000000000000000';
 *   const trxOptions = { mantissa: true };
 * 
 *   console.log('Borrowing 32 DAI...');
 *   const trx = await fortress.borrow(Fortress.DAI, daiScaledUp, trxOptions);
 * 
 *   console.log('Ethers.js transaction object', trx);
 * 
 * })().catch(console.error);
 * ```
 */
export async function borrow(
  asset: string,
  amount: string | number | BigNumber,
  options: CallOptions = {}
) : Promise<TrxResponse> {
  await netId(this);
  const errorPrefix = 'Fortress [borrow] | ';

  const fTokenName = 'f' + asset;
  const fTokenAddress = address[this._network.name][fTokenName];

  if (!fTokenAddress || !underlyings.includes(asset)) {
    throw Error(errorPrefix + 'Argument `asset` cannot be borrowed.');
  }

  if (
    typeof amount !== 'number' &&
    typeof amount !== 'string' &&
    !ethers.BigNumber.isBigNumber(amount)
  ) {
    throw Error(errorPrefix + 'Argument `amount` must be a string, number, or BigNumber.');
  }

  if (!options.mantissa) {
    amount = +amount;
    amount = amount * Math.pow(10, decimals[asset]);
  }

  amount = ethers.BigNumber.from(amount.toString());

  const trxOptions: CallOptions = {
    ...options,
    _compoundProvider: this._provider,
  };
  const parameters = [ amount ];
  trxOptions.abi = fTokenName === constants.fBNB ? abi.fBNB : abi.fBep20;

  return eth.trx(fTokenAddress, 'borrow', parameters, trxOptions);
}

/**
 * Repays a borrowed Binance Smart Chain asset for the user or on behalf of 
 *     another Binance Smart Chain address.
 *
 * @param {string} asset A string of the asset that was borrowed (must be a 
 *     supported underlying asset).
 * @param {number | string | BigNumber} amount A string, number, or BigNumber
 *     object of the amount of an asset to borrow. Use the `mantissa` boolean in
 *     the `options` parameter to indicate if this value is scaled up (so there 
 *     are no decimals) or in its natural scale.
 * @param {string | null} [borrower] The Binance Smart Chain address of the borrower 
 *     to repay an open borrow for. Set this to `null` if the user is repaying
 *     their own borrow.
 * @param {boolean} noApprove Explicitly prevent this method from attempting an 
 *     ERC-20 `approve` transaction prior to sending the subsequent repayment 
 *     transaction.
 * @param {CallOptions} [options] Call options and Ethers.js overrides for the 
 *     transaction. A passed `gasLimit` will be used in both the `approve` (if 
 *     not supressed) and `repayBorrow` or `repayBorrowBehalf` transactions.
 *
 * @returns {object} Returns an Ethers.js transaction object of the repayBorrow
 *     or repayBorrowBehalf transaction.
 *
 * @example
 *
 * ```
 * const fortress = new Fortress(window.ethereum);
 * 
 * (async function() {
 * 
 *   console.log('Repaying DAI borrow...');
 *   const address = null; // set this to any address to repayBorrowBehalf
 *   const trx = await fortress.repayBorrow(Fortress.DAI, 32, address);
 * 
 *   console.log('Ethers.js transaction object', trx);
 * 
 * })().catch(console.error);
 * ```
 */
export async function repayBorrow(
  asset: string,
  amount: string | number | BigNumber,
  borrower: string,
  noApprove = false,
  options: CallOptions = {}
) : Promise<TrxResponse> {
  await netId(this);
  const errorPrefix = 'Fortress [repayBorrow] | ';

  const fTokenName = 'f' + asset;
  const fTokenAddress = address[this._network.name][fTokenName];

  if (!fTokenAddress || !underlyings.includes(asset)) {
    throw Error(errorPrefix + 'Argument `asset` is not supported.');
  }

  if (
    typeof amount !== 'number' &&
    typeof amount !== 'string' &&
    !ethers.BigNumber.isBigNumber(amount)
  ) {
    throw Error(errorPrefix + 'Argument `amount` must be a string, number, or BigNumber.');
  }

  const method = ethers.utils.isAddress(borrower) ? 'repayBorrowBehalf' : 'repayBorrow';
  if (borrower && method === 'repayBorrow') {
    throw Error(errorPrefix + 'Invalid `borrower` address.');
  }

  if (!options.mantissa) {
    amount = +amount;
    amount = amount * Math.pow(10, decimals[asset]);
  }

  amount = ethers.BigNumber.from(amount.toString());

  const trxOptions: CallOptions = {
    ...options,
    _compoundProvider: this._provider,
  };

  // eslint-disable-next-line @typescript-eslint/no-explicit-any
  const parameters: any[] = method === 'repayBorrowBehalf' ? [ borrower ] : [];
  if (fTokenName === constants.fBNB) {
    trxOptions.value = amount;
    trxOptions.abi = abi.fBNB;
  } else {
    parameters.push(amount);
    trxOptions.abi = abi.fBep20;
  }

  if (fTokenName !== constants.fBNB && noApprove !== true) {
    const underlyingAddress = address[this._network.name][asset];
    const userAddress = this._provider.address;

    // Check allowance
    const allowance = await eth.read(
      underlyingAddress,
      'allowance',
      [ userAddress, fTokenAddress ],
      trxOptions
    );

    const notEnough = allowance.lt(amount);

    if (notEnough) {
      // ERC-20 approve transaction
      await eth.trx(
        underlyingAddress,
        'approve',
        [ fTokenAddress, amount ],
        trxOptions
      );
    }
  }

  return eth.trx(fTokenAddress, method, parameters, trxOptions);
}