Removing Liquidity

Remove liquidity from an existing token/token liquidity pool.

Outlined below are three methods to remove liquidity from an existing pool:

• Removing HBAR/token liquidity

• Removing token/token liquidity

• Removing HBAR/token liquidity for tokens with custom fees

Contract ID: SaucerSwapV1RouterV3

A spender allowance for the router is required for the LP token.

removeLiquidity supports HTS tokens with custom fees.

---

Removing HBAR/Token Liquidity

Remove liquidity from an existing HBAR/token liquidity pool.

Function name: removeLiquidityETH

⛽ Recommended gas: 2,800,000 gwei (~ $0.24 USD)

Parameter Name	Description
address token	EVM address of the token paired with HBAR
uint liquidity	LP liquidity amount to remove
uint amountTokenMin	The minimum token amount to receive in its smallest unit
uint amountETHMin	The minimum HBAR amount to receive in its smallest unit
address to	EVM address to receive the tokens
uint deadline	Deadline in Unix seconds

Solidity Interface & Function Body

//IUniswapV2Router01.sol

function removeLiquidityETH(
  address token,
  uint liquidity,
  uint amountTokenMin,
  uint amountETHMin,
  address to,
  uint deadline
) external returns (uint amountToken, uint amountETH);

//UniswapV2Router02.sol

function removeLiquidityETH(
  address token,
  uint liquidity,
  uint amountTokenMin,
  uint amountETHMin,
  address to,
  uint deadline
) public virtual override ensure(deadline) returns (uint amountToken, uint amountETH) {
  safeAssociateToken(address(this), token);
  (amountToken, amountETH) = removeLiquidity( 
    token,
    whbar, 
    liquidity,
    amountTokenMin,
    amountETHMin,
    address(this), // used to be msg.sender
    deadline
  );
  safeTransferToken(token, address(this), to, amountToken);
  safeApproveToken(whbar, WHBAR, amountETH);
  IWHBAR(WHBAR).withdraw(address(this), to, amountETH);
  safeDissociateToken(address(this), token);
}

The removeLiquidityETH function operates in HBAR but derives its name from Uniswap on Ethereum. This name was kept to simplify integration for developers versed in Uniswap tools.

Code Overview

Typescript

Resources:

• Hedera JavaScript SDK

• Token approve allowance

• Hedera REST API

• Calling a smart contract function

import { 
  ContractFunctionParameters, 
  ContractExecuteTransaction, 
  AccountAllowanceApproveTransaction,
  .. 
} from '@hashgraph/sdk';

//Client pre-checks:
// - Router contract has spender allowance the LP token

const params = new ContractFunctionParameters();
params.addAddress(tokenAddress); //address token  
params.addUint256(lpTokenAmountToRemove); //uint liquidity
params.addUint256(amountTokenMin); //uint amountTokenMin
params.addUint256(amountETHMin); //uint amountETHMin
params.addAddress(toSoli); //address to
params.addUint256(deadline); //uint deadline
    
const response = await new ContractExecuteTransaction()
 .setContractId(routerContractId)
 .setGas(gasLim)
 .setFunction('removeLiquidityETH', params)
 .execute(client);
 
const record = await response.getRecord(client);
const result = record.contractFunctionResult!;
const values = result.getResult(['uint','uint']);
const amountToken = values[0]; //uint amountToken
const amountHBAR = values[1]; //uint amountETH

---

Removing Token/Token Liquidity

Remove liquidity from an existing token/token liquidity pool.

Function name: removeLiquidity

⛽ Recommended gas: 1,600,000 gwei (~ $0.14 USD)

Parameter Name	Description
address tokenA	EVM address of the first HTS token
address tokenB	EVM address of the second HTS token
uint liquidity	LP liquidity amount to remove in its smallest unit
uint amountAMin	The minimum amount for the first token in its smallest unit
uint amountBMin	The minimum amount for the second token in its smallest unit
address to	EVM address to receive the tokens
uint deadline	Deadline in Unix seconds

Solidity Interface & Function Body

//IUniswapV2Router01.sol

function addLiquidity(
  address tokenA,
  address tokenB,
  uint amountADesired,
  uint amountBDesired,
  uint amountAMin,
  uint amountBMin,
  address to,
  uint deadline
) external returns (uint amountA, uint amountB, uint liquidity);

//UniswapV2Router02.sol

function addLiquidityNewPool(
  address tokenA,
  address tokenB,
  uint amountADesired,
  uint amountBDesired,
  uint amountAMin,
  uint amountBMin,
  address to,
  uint deadline
) external virtual payable override ensure(deadline) returns (uint amountA, uint amountB, uint liquidity) {
  
  require (IUniswapV2Factory(factory).getPair(tokenA, tokenB) == address(0), "UniswapV2Router: POOL ALREADY EXISTS");
  address pair = IUniswapV2Factory(factory).createPair{value: msg.value}(tokenA, tokenB);
  
  (amountA, amountB) = _addLiquidity(tokenA, tokenB, amountADesired, amountBDesired, amountAMin, amountBMin);

  safeTransferToken(
    tokenA, msg.sender, pair, amountA
  );
  safeTransferToken(
    tokenB, msg.sender, pair, amountB
  );
  liquidity = IUniswapV2Pair(pair).mint(to);
}

Code Overview

Typescript

Resources:

• Hedera JavaScript SDK

• Token approve allowance

• Hedera REST API

• Calling a smart contract function

import { 
  ContractFunctionParameters, 
  ContractExecuteTransaction,
  AccountAllowanceApproveTransaction,
  .. 
} from '@hashgraph/sdk';

//Client pre-checks:
// - Router contract has spender allowance for the LP token

const params = new ContractFunctionParameters();
params.addAddress(tokenAAddress); //address tokenA
params.addAddress(tokenBAddress); //address tokenB
params.addUint256(amountADesired); //uint amountADesired
params.addUint256(amountBDesired); //uint amountBDesired
params.addUint256(amountAMin); //uint amountAMin
params.addUint256(amountBMin); //uint amountBMin
params.addAddress(toAddress); //address to
params.addUint256(deadline); //uint deadline
    
const response = await new ContractExecuteTransaction()
 .setContractId(routerContractId)
 .setGas(gasLim)
 .setFunction('addLiquidityNewPool', params)
 .execute(client);
 
const record = await response.getRecord(client);
const result = record.contractFunctionResult!;
const values = result.getResult(['uint','uint']);
const amountA = values[0]; //uint amountA
const amountB = values[1]; //uint amountB

---

Removing HBAR/Token Liquidity Supporting Tokens with Custom Fees

Remove liquidity from an existing HBAR/token liquidity pool supporting HTS tokens with custom fees on transfer.

Function name: removeLiquidityETHSupportingFeeOnTransferTokens

⛽ Recommended gas: 3,000,000 gwei (~ $0.26 USD)

Parameter Name	Description
address token	EVM address of the token paired with HBAR
uint liquidity	LP liquidity amount to remove in its smallest unit
uint amountTokenMin	The minimum token amount to receive in its smallest unit
uint amountETHMin	The minimum HBAR amount to receive in its smallest unit
address to	EVM address to receive the tokens
uint deadline	Deadline in Unix seconds

Solidity Interface & Function Body

//IUniswapV2Router01.sol

function removeLiquidityETHSupportingFeeOnTransferTokens(
  address token,
  uint liquidity,
  uint amountTokenMin,
  uint amountETHMin,
  address to,
  uint deadline
) external returns (uint amountETH);

//UniswapV2Router02.sol

function removeLiquidityETHSupportingFeeOnTransferTokens(
  address token,
  uint liquidity,
  uint amountTokenMin,
  uint amountETHMin,
  address to,
  uint deadline
) public virtual override ensure(deadline) returns (uint amountETH) {
    safeAssociateToken(address(this), token);
    (, amountETH) = removeLiquidity(
      token,
      whbar, 
      liquidity,
      amountTokenMin,
      amountETHMin,
      address(this),
      deadline
    );
    uint256 amountToSend = IERC20(token).balanceOf(address(this));
    require(amountToSend >= amountTokenMin, 'UniswapV2Router: INSUFFICIENT_A_AMOUNT_FOT'); // second slippage check
    safeTransferToken(token, address(this), to, amountToSend);
    safeApproveToken(whbar, WHBAR, amountETH);
    IWHBAR(WHBAR).withdraw(address(this), to, amountETH);
    safeDissociateToken(address(this), token);
}

The removeLiquidityETHSupportingFeeOnTransferTokens function operates in HBAR but derives its name from Uniswap on Ethereum. This name was kept to simplify integration for developers versed in Uniswap tools.

Code Overview

Typescript SDK

Resources:

• Hedera JavaScript SDK

• Token approve allowance

• Hedera REST API

• Calling a smart contract function

import { 
  ContractFunctionParameters, 
  ContractExecuteTransaction,
  AccountAllowanceApproveTransaction,
  .. 
} from '@hashgraph/sdk';

//Client pre-checks:
// - Router contract has spender allowance for the LP token

const params = new ContractFunctionParameters();
params.addAddress(tokenAddress); //address token  
params.addUint256(lpTokenAmountToRemove); //uint liquidity
params.addUint256(amountTokenMin); //uint amountTokenMin
params.addUint256(amountETHMin); //uint amountETHMin
params.addAddress(toAddress); //address to
params.addUint256(deadline); //uint deadline
    
const response = await new ContractExecuteTransaction()
 .setContractId(routerContractId)
 .setGas(gasLim)
 .setFunction('removeLiquidityETHSupportingFeeOnTransferTokens', params)
 .execute(client);
 
const record = await response.getRecord(client);
const result = record.contractFunctionResult!;
const values = result.getResult(['uint']);
const amountHBAR = values[1]; //uint amountETH