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Using the Berancer SDK, you can remove liquidity using two primary methods (see RemoveLiquidityKind):
  1. Proportional - remove liquidity proportionally across all tokens
  2. SingleTokenExactIn - remove liquidity and receive a single token
For more comprehensive remove liquidity examples, see the remove liquidity examples in the BEX SDK repository.

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Example: single token exit

In this example, we’ll demonstrate how to remove liquidity and receive a single token (BERA) while calculating the price impact of the transaction. 
import { ethers } from "ethers";
import {
  BalancerApi,
  RemoveLiquidity,
  RemoveLiquidityKind,
  Slippage,
  PriceImpact,
} from "@berachain-foundation/berancer-sdk";

// Initialize provider and wallet
const RPC_URL = "https://rpc.berachain.com/";
const provider = new ethers.JsonRpcProvider(RPC_URL);
const wallet = new ethers.Wallet(process.env.PRIVATE_KEY, provider);
const balancerApi = new BalancerApi("https://chgbtcc9ffu7rbdw2kmu4urwy.stellate.sh/", 80094);

// Get pool data
const poolId = "POOL_ID";
const poolState = await balancerApi.pools.fetchPoolState(poolId);

// Prepare remove liquidity input for single token exit
const removeLiquidityInput = {
  chainId: CHAIN_ID,
  kind: RemoveLiquidityKind.SingleTokenExactIn,
  rpcUrl: RPC_URL,
  bptIn: {
    address: poolState.address,
    decimals: 18,
    rawAmount: ethers.parseUnits("0.1", 18), // 0.1 BPT
  },
  tokenOut: WBERA_TOKEN
};

const removeLiquidity = new RemoveLiquidity();

// Query expected outputs and calculate price impact in parallel
const [queryOutput, priceImpact] = await Promise.all([
  removeLiquidity.query(removeLiquidityInput, poolState),
  PriceImpact.removeLiquidity(removeLiquidityInput, poolState)
]);

console.log(
  "Expected Token Out:",
  ethers.formatUnits(queryOutput.amountsOut[0].amount, queryOutput.amountsOut[0].token.decimals),
  queryOutput.amountsOut[0].token.symbol
);
console.log("Price Impact:", priceImpact.percentage, "%");

// Build transaction with 1% slippage
const slippage = Slippage.fromPercentage("1");
const deadline = BigInt(Math.floor(Date.now() / 1000) + 60);

const callData = removeLiquidity.buildCall({
  ...queryOutput,
  sender: wallet.address,
  recipient: wallet.address,
  wethIsEth: true,
  slippage,
  deadline,
});

// Send transaction
const tx = await wallet.sendTransaction({
  to: callData.to,
  data: callData.callData,
  value: callData.value,
});

console.log("Transaction sent:", tx.hash);

const receipt = await tx.wait();
Below we breakdown the code example above.

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Helper classes

The main helper classes we use from the SDK are:
  • BalancerApi - to simplify retrieving pool data from the Pools API
  • RemoveLiquidity - to build removeLiquidity queries and transactions
  • Slippage - to simplify creating limits with user defined slippage
  • PriceImpact - to calculate the price impact of single token exits

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Fetching pool data

After initializing the BalancerApi class, we can fetch current pool data using fetchPoolState. 
const balancerApi = new BalancerApi("https://chgbtcc9ffu7rbdw2kmu4urwy.stellate.sh/", 80094);

// Get pool data
const poolId =
  "POOL_ID";
const poolState = await balancerApi.pools.fetchPoolState(poolId);

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Simulation and slippage setting

The PriceImpact class calculates the price impact of unbalanced liquidity operations. A PriceImpactAmount is returned, with the price impact expressed in a number of different units. Its use in the above example is informational, but can be used to provide detailed slippage information. 
const [queryOutput, priceImpact] = await Promise.all([
  removeLiquidity.query(removeLiquidityInput, poolState),
  PriceImpact.removeLiquidity(removeLiquidityInput, poolState)
]);

const slippage = Slippage.fromPercentage("1");

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Building the transaction

The RemoveLiquidity class has a buildCall method that allows us to build the transaction. This method takes in the queryOutput and address parameters. 
const slippage = Slippage.fromPercentage("1");
const callData = removeLiquidity.buildCall({
  ...queryOutput,
  sender: wallet.address,
  recipient: wallet.address,
  wethIsEth: true,
  slippage,
  deadline
});