# Hifi Flash Swap ![npm (scoped)](https://img.shields.io/npm/v/@hifi/flash-swap)

Flash swap implementations for liquidating underwater accounts.

The build artifacts can be browsed via [unpkg.com](https://unpkg.com/browse/@hifi/flash-swap@latest/).

## Installation

With yarn:

```bash
$ yarn add @hifi/flash-swap
```

Or npm:

```bash
$ npm install @hifi/flash-swap
```

## Usage

The node package that you just installed contains both Solidity and JavaScript code. The former is the smart contracts
themselves; the latter, the smart contract ABIs and the TypeChain bindings.

### FlashUniswapV2

#### Solidity

You are not supposed to import the smart contracts. Instead, you should interact with the Uniswap pool
directly. For example, with the [UniswapV2Pair](https://github.com/Uniswap/v2-core/blob/v1.0.1/contracts/UniswapV2Pair.sol)
contract you would call the `swap` function, and then Uniswap will forward the call to the `FlashUniswapV2`
contract. You can read more about flash swaps work in Uniswap V2 on
[docs.uniswap.org](https://docs.uniswap.org/protocol/V2/concepts/core-concepts/flash-swaps).

#### JavaScript

Example for Uniswap V2:

```javascript
import { defaultAbiCoder } from "@ethersproject/abi";
import { parseUnits } from "@ethersproject/units";
import { UniswapV2Pair__factory } from "@hifi/flash-swap/dist/types/factories/contracts/UniswapV2Pair__factory";

async function flashSwap() {
  const signer = "..."; // Get hold of an ethers.js Signer
  const pairFactory = new UniswapV2Pair__factory(signer);
  const pair = pairFactory.attach("0x...");

  const token0Amount = parseUnits("100", 18);
  const token1Amount = parseUnits("0", 18);
  const to = "0x..."; // Address of FlashUniswapV2, get it from https://docs.hifi.finance

  const borrower = "0x...";
  const hToken = "0x...";
  const collateral = "0x...";
  const turnout = parseUnits("1", 18);
  const data = defaultAbiCoder.encode(
    ["address", "address", "address", "uint256"],
    [borrower, hToken, collateral, turnout],
  );

  await pair.swap(token0Amount, token1Amount, to, data);
}
```

### FlashUniswapV3

#### Solidity

To interact with the `FlashUniswapV3` contract, you will call the `flashLiquidate` function directly. This function performs the flash swap internally and requires you to pass the necessary liquidation parameters as a `FlashLiquidateParams` object.

#### JavaScript

Example for Uniswap V3:

```javascript
import { parseUnits } from "@ethersproject/units";
import { FlashUniswapV3__factory } from "@hifi/flash-swap/dist/types/factories/FlashUniswapV3__factory";

async function flashLiquidate() {
  const signer = "..."; // Get hold of an ethers.js Signer
  const flashUniswapV3Factory = new FlashUniswapV3__factory(signer);
  const flashUniswapV3 = flashUniswapV3Factory.attach("0x...");

  const borrower = "0x...";
  const hToken = "0x...";
  const collateral = "0x...";
  const poolFee = 3000;
  const turnout = parseUnits("1", 18);
  const underlyingAmount = parseUnits("100", 18);

  await flashUniswapV3.flashLiquidate({
    borrower: borrower,
    bond: hToken,
    collateral: collateral,
    poolFee: poolFee,
    turnout: turnout,
    underlyingAmount: underlyingAmount,
  });
}
```

## Deployment

### Flash Uniswap V2

```bash
$ yarn hardhat deploy:contract:flash-uniswap-v2 \
    --balance-sheet ${BALANCE_SHEET} \
    --uni-v2-factory ${UNI_V2_FACTORY} \
    --uni-v2-pair-init-code-hash ${UNI_V2_PAIR_INIT_CODE_HASH} \
    --confirmations 5 \
    --network ${NETWORK} \
    --print true \
    --verify true
```

### Flash Uniswap V3

```bash
$ yarn hardhat deploy:contract:flash-uniswap-v3 \
    --balance-sheet ${BALANCE_SHEET} \
    --uni-v3-factory ${UNI_V3_FACTORY} \
    --confirmations 5 \
    --network ${NETWORK} \
    --print true \
    --verify true
```

## License

[LGPL v3](./LICENSE.md) © Mainframe Group Inc.