Decreasing liquidity (V2)

import * as ethers from 'ethers'; //V6
import { Pool, Position, nearestUsableTick, priceToClosestTick } from '@uniswap/v3-sdk';
import { Fraction, Percent, Token, Price } from '@uniswap/sdk-core';
import { ContractExecuteTransaction } from '@hashgraph/sdk';

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

//Load the ABI data for UniswapV3Pool
const poolInterfaces = new ethers.Interface(poolAbi);

//Load the ABI data for NonfungiblePositionManager
const nftManagerInterfaces = new ethers.Interface(nftManagerAbi);

//Construct the pool contract
const poolContract = new ethers.Contract(poolEvmAddress,
  poolInterfaces.fragments, provider);

//Construct the NFT Manager contract
const nftManagerContract = new ethers.Contract(nftManagerEvmAddress,
  nftManagerInterfaces.fragments, provider);

//Get current position data for the given NFT token serial number
const lp = await nftManagerContract.positions(tokenSN);
const token0Address = lp.token0;
const token1Address = lp.token1;
const feeTier = Number(lp.fee);
const tickLower = Number(lp.tickLower);
const tickUpper = Number(lp.tickUpper);
const liquidity = lp.liquidity.toString();

//Get current slot0 and liquidity data from the pool
const [slot0, poolLiquidity] = await Promise.all([
  poolContract.slot0(),
  poolContract.liquidity()
]);

//Construct the tokens
//For Hedera chain id, see https://chainlist.org/?testnets=true&search=Hedera
const token0 = new Token(hederaChainId, token0Address, token0Decimals);
const token1 = new Token(hederaChainId, token1Address, token1Decimals);

//Construct the pool using the latest data
const pool = new Pool(
  token0, token1,
  feeTier, slot0.sqrtPriceX96.toString(),
  poolLiquidity.toString(), Number(slot0.tick)
);

//Construct a position from liquidity and range
const position = new Position({
  pool: pool,
  tickUpper: tickUpper,
  tickLower: tickLower,
  liquidity: liquidity
});

//Calculate the maximum amounts factoring in the price slippage % and range
const priceSlippagePercent = new Percent(1, 100); //1% price slippage
const burnAmounts = position.burnAmountsWithSlippage(priceSlippagePercent);
const amount0Min = burnAmounts.amount0.toString();
const amount1Min = burnAmounts.amount1.toString();

//DecreaseLiquidityParams struct
const params = {
  tokenSN: tokenSN,
  liquidity: liquidity, //liquidity amount to remove
  amount0Min: amount0Min, //in smallest unit
  amount1Min: amount1Min, //in smallest unit
  deadline: deadline, //Unix seconds
};

//get max possible value for amount0Max and amount1Max
const MAX_UINT128 = new BigNumber(2).pow(128).minus(1).toFixed(0);

//CollectParams struct
const collectParams = {
  tokenSN: tokenSN,
  recipient: recipientAddress, //0x..
  amount0Max: MAX_UINT128, //collect max fees and amount
  amount1Max: MAX_UINT128, //collect max fees and amount
};

//Construct encoded data for each function
//The unwrapWHBAR is needed when collecting the HBAR swap fees
//Optionally include 'collect' here to collect fees.
//Optionally include 'burn' to burn the NFT if all liquidity is removed.
const decreaseEncoded = nftManagerInterfaces.encodeFunctionData('decreaseLiquidity', [params]);
const collectEncoded = nftManagerInterfaces.encodeFunctionData('collect', [collectParams]);

//The unwrapWHBAR is only needed when removing liquidity that includes HBAR
const unwrapWHBAREncoded = nftManagerInterfaces.encodeFunctionData('unwrapWHBAR', [0, recipientAddress]);

//Build encoded data for the multicall
const encodedData = nftManagerInterfaces.encodeFunctionData('multicall',
  [[decreaseEncoded, collectEncoded, unwrapWHBAREncoded]]);
const encodedDataAsUint8Array = hexToUint8Array(encodedData.substring(2));

//Execute the contract call
const response = await new ContractExecuteTransaction()
  .setContractId(nftManagerContractId)
  .setGas(gasGwei)
  .setFunctionParameters(encodedDataAsUint8Array)
  .execute(client);

//Fetch the result
const record = await response.getRecord(client);
const result = record.contractFunctionResult!;
const results = nftManagerInterfaces.decodeFunctionResult('multicall', result.bytes)[0];
const collectResult = nftManagerInterfaces.decodeFunctionResult('collect', results[1]);

//Retrieve the amounts removed for informative purposes
const removedAmount0 = BigNumber(collectResult.amount0);
const removedAmount1 = BigNumber(collectResult.amount1);

//Updated code to include burning of the NFT token

//Construct encoded data for each function
//The unwrapWHBAR is needed when collecting the HBAR swap fees
//Optionally include 'collect' here to collect fees.
//Optionally include 'burn' to burn the NFT if all liquidity is removed.
const decreaseEncoded = nftManagerInterfaces.encodeFunctionData('decreaseLiquidity', [params]);
const collectEncoded = nftManagerInterfaces.encodeFunctionData('collect', [collectParams]);
const burnEncoded = nftManagerInterfaces.encodeFunctionData('burn', [tokenSN]);

//The unwrapWHBAR is only needed when removing liquidity that includes HBAR
const unwrapWHBAREncoded = nftManagerInterfaces.encodeFunctionData('unwrapWHBAR', [0, recipientAddress]);

//Build encoded data for the multicall
const encodedData = nftManagerInterfaces.encodeFunctionData('multicall',
  [[decreaseEncoded, collectEncoded, unwrapWHBAREncoded, burnEncoded]]);
const encodedDataAsUint8Array = hexToUint8Array(encodedData.substring(2));

//Give NFT spender allowance to NFT Manager contract
const nftId = new NftId(lpTokenId, tokenSN);
const approveResult = await new AccountAllowanceApproveTransaction()
  .approveTokenNftAllowance(nftId, ownerId, nftManagerContractId)
  .execute(client);

const allowanceReceipt = await approveResult.getReceipt(client);
console.log(`NFT allowance status: ${allowanceReceipt.status}`);

//Execute the contract call
const response = await new ContractExecuteTransaction()
  .setContractId(nftManagerContractId)
  .setGas(gasGwei)
  .setFunctionParameters(encodedDataAsUint8Array)
  .execute(client);