Swap Quote

Get a token swap quote based on an input or output value.

Below are the two methods to get a quote for a swap from a given route using JSON-RPC or REST-API:

• Get output quote from exact input amount

• Get input quote from exact output amount

Contract ID: SaucerSwapV1RouterV3

When providing HBAR in the path array, use the wrapped HBAR token ID (WHBAR).

---

Get Output Quote from Input Amount

⛽ No gas cost

Get the output amounts from a given input amount and a swap route.

Function name: getAmountsOut

Parameter Name	Description
uint amountIn	The input token amount in its smallest unit
address[] path	An ordered list of token EVM addresses

Solidity Interface & Function Body

//IUniswapV2Router01.sol

function getAmountsOut(
  uint amountIn,
  address[] calldata path
) external view returns (uint[] memory amounts);

//UniswapV2Router02.sol

function getAmountsOut(uint amountIn, address[] memory path)
  public
  view
  virtual
  override
  returns (uint[] memory amounts)
{
  return UniswapV2Library.getAmountsOut(factory, amountIn, path);
}

Code Overview

JSON RPC

Resources:

• Ethers.js docs (v6)

• Hedera JSON RPC Relay

//Typescript
import * as ethers from 'ethers'; //V6

//Set one of Hedera's JSON RPC Relay as the provider
const provider = new ethers.JsonRpcProvider(hederaJsonRelayUrl, '', {
  batchMaxCount: 1, //workaround for V6
});

//ABI data for the getAmountsOut
const abi = ['function getAmountsOut(uint amountIn, address[] calldata path) external view returns (uint[] memory amounts)'];

//Load the ABI
const abiInterfaces = new ethers.Interface(abi);

//Example route
const tokenIn = '0x' + TokenId.fromString(whbarTokenId).toSolidityAddress();
const tokenOut = '0x' + TokenId.fromString(sauceTokenId).toSolidityAddress();
const route = [tokenIn, tokenOut];

const routerContract = new ethers.Contract(routerEvmAddress, abiInterfaces.fragments, provider);
const result = await routerContract.getAmountsOut(inputAmountInSmallestUnit, route);
const amounts = result; //uint[] amounts
const finalOutputAmount = amounts[amounts.length - 1]; //in token's smallest unit

REST API

Resources:

• Ethers.js docs (v6)

• Hedera REST API

//Typescript
import * as ethers from 'ethers'; //V6

//ABI data for the getAmountsOut
const abi = ['function getAmountsOut(uint amountIn, address[] calldata path) external view returns (uint[] memory amounts)'];

//Load the ABI
const abiInterfaces = new ethers.Interface(abi);

//Example route (WHBAR > SAUCE)
const tokenIn = '0x' + TokenId.fromString(whbarTokenId).toSolidityAddress();
const tokenOut = '0x' + TokenId.fromString(sauceTokenId).toSolidityAddress();
const route = [tokenIn, tokenOut];

const routerContract = ContractId.fromString(config.router);
const params = [inputAmountInSmallestUnit, route];
const encodedData = abiInterfaces.encodeFunctionData(abiInterfaces.getFunction('getAmountsOut')!, params);    

const url = `${mirrorNodeBaseUrl}/api/v1/contracts/call`;
const data = {
  'block': 'latest',
  'data': encodedData,
  'to': routerContract.toSolidityAddress(),
};
 
const response = await axios.post(url, data, { headers: {'content-type': 'application/json'} });
const amounts = abiInterfaces.decodeFunctionResult('getAmountsOut', response.data.result)[0]; //uint[] amounts
const finalOutputAmount = amounts[amounts.length - 1]; //in token's smallest unit

---

Get Input Quote from Output Amount

⛽ No gas cost

Get the input amounts from a given output amount and a swap route.

Function name: getAmountsIn

Parameter Name	Description
uint amountOut	The output token amount in its smallest unit
address[] path	An ordered list of token EVM addresses

Solidity Interface & Function Body

//IUniswapV2Router01.sol

function getAmountsIn(
  uint amountOut,
  address[] calldata path
) external view returns (uint[] memory amounts);

//UniswapV2Router02.sol

function getAmountsIn(uint amountOut, address[] memory path)
  public
  view
  virtual
  override
  returns (uint[] memory amounts)
{
  return UniswapV2Library.getAmountsIn(factory, amountOut, path);
}

Code Overview

JSON RPC

Resources:

• Ethers.js docs (v6)

• Hedera JSON RPC Relay

//Typescript
import * as ethers from 'ethers'; //V6

const networkId = 'testnet';
const provider = new ethers.JsonRpcProvider(`https://${networkId}.hashio.io/api`, '', {
  batchMaxCount: 1,
});

//ABI data for the getAmountsIn
const abi = ['function getAmountsIn(uint amountOut, address[] calldata path) external view returns (uint[] memory amounts)'];

//Load the ABI
const abiInterfaces = new ethers.Interface(abi);

//Example route (WHBAR > SAUCE)
const tokenIn = '0x' + TokenId.fromString(whbarTokenId).toSolidityAddress();
const tokenOut = '0x' + TokenId.fromString(sauceTokenId).toSolidityAddress();
const route = [tokenIn, tokenOut];

const routerContract = new ethers.Contract(routerEvmAddress, abiInterfaces.fragments, provider);
const result = await routerContract.getAmountsIn(outputAmountInSmallestUnit, route);
const amounts = results; //uint[] amounts
const finalInputAmount = amounts[0]; //in token's smallest unit

REST API

Resources:

• Ethers.js docs (v6)

• Hedera REST API

//Typescript
import * as ethers from 'ethers'; //V6

//ABI data for the getAmountsIn
const abi = ['function getAmountsIn(uint amountOut, address[] calldata path) external view returns (uint[] memory amounts)'];

//Load the ABI
const abiInterfaces = new ethers.Interface(abi);

//Example route (WHBAR > SAUCE)
const tokenIn = '0x' + TokenId.fromString(whbarTokenId).toSolidityAddress();
const tokenOut = '0x' + TokenId.fromString(sauceTokenId).toSolidityAddress();
const route = [tokenIn, tokenOut];

const routerContract = ContractId.fromString(config.router);
const params = [outputAmountInSmallestUnit, route];
const encodedData = abiInterfaces.encodeFunctionData(abiInterfaces.getFunction('getAmountsIn')!, params);    

const url = `${mirrorNodeBaseUrl}/api/v1/contracts/call`;
const data = {
  'block': 'latest',
  'data': encodedData,
  'to': routerContract.toSolidityAddress(),
};
 
const response = await axios.post(url, data, { headers: {'content-type': 'application/json'} });
const amounts = abiInterfaces.decodeFunctionResult('getAmountsIn', response.data.result)[0]; //uint[] amounts
const finalInputAmount = amounts[0]; //in token's smallest unit