This repository is related to the core library of the arbitrage bot.

Learning resource

Fetching the XTZ and token balance of the DEX

Our goal it to retrieve the XTZ and token balance from the DEX. With this information we can calculate:

• Spot price by dividing one another
• Trade amounts for a swap that takes into account the depth of liquidity (calculateAmountOutExactIn)

Challenge

The storage structure differs for every DEX and their implementation, therefore this needs to be done case by case.

We can't follow the naive approach of fetching XTZ balance for a given contract address, because some of the XTZ might be reserved for future stake reward payouts!

Solution

We analyze the storage structure of the DEX smart contract and implement methods to retrieve the respective fields tez_pool and token_pool.

// Quipuswap v1 storage
export type Storage = {
    storage: {
        tez_pool: nat;
        token_address: address;
        token_pool: nat;
        ...
    };
    dex_lambdas: BigMap<string, string>;
    ...
};

Implementation

// src/exchangeQuipuswapPlugin.ts

async getContractInstance(exchangeAddress: string) {
  return await this.tezos.contract.at<QuipuswapDexTezTokenContractType>(
    exchangeAddress
  );
}

async getStorage(exchangeAddress: string) {
  const contractInstance = await this.getContractInstance(exchangeAddress);
  return contractInstance.storage();
}

// fetch XTZ balance
await getStorage().storage.tez_pool.toFixed();
// fetch Token balance
await getStorage().storage.storage.token_pool.toFixed()

Fetching the fee

The fee is hardcoded in lambdas and can't be read easily from storage. That's why we have it in src/constants.ts.