Creating a Pool Instance

This guide extends the previous Using Ethers.js guide by using the fetched data from the EVM to create a Pool instance using the V3 SDK. A "Pool" as we refer to it here does not mean an actual V3 pool, but a model of one created with the SDK. This model will help us interact with the protocol, or manipulate data relevant to the protocol, in a way that does not require continually fetching pool data from the EVM - which can be time intensive and computationally costly.

Importing the ABI

First we will replace the abi that we previously wrote out manually with a library that contains the total V3 pool abi for us to easily interact with. Note the abi is imported from the v3-core npm package, rather than the v3-sdk npm package, as it is a part of the protocol rather than the SDK.

Depending on your local configuration, you may need to update your tsconfig.json to allow importing of json files with "resolveJsonModule": true,.

import { ethers } from 'ethers'
import { Pool } from '@uniswap/v3-sdk'
import { Token } from '@uniswap/sdk-core'
import { abi as IUniswapV3PoolABI } from '@uniswap/v3-core/artifacts/contracts/interfaces/IUniswapV3Pool.sol/IUniswapV3Pool.json'

Now we'll update the Contract object with our imported ABI - and keep the pool address and provider the same as the previous example.

const provider = new ethers.providers.JsonRpcProvider('https://mainnet.infura.io/v3/<YOUR-ENDPOINT-HERE>')
const poolAddress = '0x8ad599c3A0ff1De082011EFDDc58f1908eb6e6D8'
const poolContract = new ethers.Contract(poolAddress, IUniswapV3PoolABI, provider)

Creating The Interfaces

Create two interfaces with types that are appropriate for the data we need. We won't be using all of this data, but some extra data is fetched for context.

interface Immutables {
  factory: string
  token0: string
  token1: string
  fee: number
  tickSpacing: number
  maxLiquidityPerTick: ethers.BigNumber
}

interface State {
  liquidity: ethers.BigNumber
  sqrtPriceX96: ethers.BigNumber
  tick: number
  observationIndex: number
  observationCardinality: number
  observationCardinalityNext: number
  feeProtocol: number
  unlocked: boolean
}

Fetching Immutable Data

Fetch the immutable data from the deployed V3 pool contract and return it to create a model of the pool.

async function getPoolImmutables() {
  const [factory, token0, token1, fee, tickSpacing, maxLiquidityPerTick] = await Promise.all([
    poolContract.factory(),
    poolContract.token0(),
    poolContract.token1(),
    poolContract.fee(),
    poolContract.tickSpacing(),
    poolContract.maxLiquidityPerTick(),
  ])

  const immutables: Immutables = {
    factory,
    token0,
    token1,
    fee,
    tickSpacing,
    maxLiquidityPerTick,
  }
  return immutables
}

Fetch the state data in with the same Promise.all style. This approach queries state data concurrently, rather than sequentially, to avoid out of sync data that may be returned if sequential queries are executed over the span of two blocks.

sqrtPriceX96 and sqrtRatioX96, despite being named differently, are interchangeable values.

Fetching State Data

async function getPoolState() {
  const [liquidity, slot] = await Promise.all([poolContract.liquidity(), poolContract.slot0()])

  const PoolState: State = {
    liquidity,
    sqrtPriceX96: slot[0],
    tick: slot[1],
    observationIndex: slot[2],
    observationCardinality: slot[3],
    observationCardinalityNext: slot[4],
    feeProtocol: slot[5],
    unlocked: slot[6],
  }

  return PoolState
}

Creating the Pool Instance

Create a function called main, which calls previously written functions, and uses the returned data to construct two Ethers.js Token instances and a V3 SDK Pool instance.

The final constructor argument when creating a Pool, ticks, is optional. ticks takes all tick data, including the liquidity within, which can be used to model the result of a swap. Because this can add up to a lot of data fetched from the EVM, it is optional and may be left out when not needed. In this example, we have left it out.

async function main() {
  const [immutables, state] = await Promise.all([getPoolImmutables(), getPoolState()])

  const TokenA = new Token(3, immutables.token0, 6, 'USDC', 'USD Coin')

  const TokenB = new Token(3, immutables.token1, 18, 'WETH', 'Wrapped Ether')

  const poolExample = new Pool(
    TokenA,
    TokenB,
    immutables.fee,
    state.sqrtPriceX96.toString(),
    state.liquidity.toString(),
    state.tick
  )
  console.log(poolExample)
}

main()

If everything is working, the script should return something like this:

Pool {
  token0: Token {
    chainId: 1,
    decimals: 6,
    symbol: 'USDC',
    name: 'USD Coin',
    isNative: false,
    isToken: true,
    address: '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48'
  },
  token1: Token {
    chainId: 1,
    decimals: 18,
    symbol: 'WETH',
    name: 'Wrapped Ether',
    isNative: false,
    isToken: true,
    address: '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2'
  },
  fee: 3000,
  sqrtRatioX96: JSBI(4) [ 1389262056, -1079304777, -1721588872, 19633, sign: false ],
  liquidity: JSBI(3) [ 988036789, -62655684, 1, sign: false ],
  tickCurrent: 197709,
  tickDataProvider: NoTickDataProvider {}
}

The Final Script

import { ethers } from 'ethers'
import { Pool } from '@uniswap/v3-sdk'
import { Token } from '@uniswap/sdk-core'
import { abi as IUniswapV3PoolABI } from '@uniswap/v3-core/artifacts/contracts/interfaces/IUniswapV3Pool.sol/IUniswapV3Pool.json'

const provider = new ethers.providers.JsonRpcProvider('https://mainnet.infura.io/v3/<YOUR-ENDPOINT-HERE>')

const poolAddress = '0x8ad599c3A0ff1De082011EFDDc58f1908eb6e6D8'

const poolContract = new ethers.Contract(poolAddress, IUniswapV3PoolABI, provider)

interface Immutables {
  factory: string
  token0: string
  token1: string
  fee: number
  tickSpacing: number
  maxLiquidityPerTick: ethers.BigNumber
}

interface State {
  liquidity: ethers.BigNumber
  sqrtPriceX96: ethers.BigNumber
  tick: number
  observationIndex: number
  observationCardinality: number
  observationCardinalityNext: number
  feeProtocol: number
  unlocked: boolean
}

async function getPoolImmutables() {
  const [factory, token0, token1, fee, tickSpacing, maxLiquidityPerTick] = await Promise.all([
    poolContract.factory(),
    poolContract.token0(),
    poolContract.token1(),
    poolContract.fee(),
    poolContract.tickSpacing(),
    poolContract.maxLiquidityPerTick(),
  ])

  const immutables: Immutables = {
    factory,
    token0,
    token1,
    fee,
    tickSpacing,
    maxLiquidityPerTick,
  }
  return immutables
}

async function getPoolState() {
  const [liquidity, slot] = await Promise.all([poolContract.liquidity(), poolContract.slot0()])

  const PoolState: State = {
    liquidity,
    sqrtPriceX96: slot[0],
    tick: slot[1],
    observationIndex: slot[2],
    observationCardinality: slot[3],
    observationCardinalityNext: slot[4],
    feeProtocol: slot[5],
    unlocked: slot[6],
  }

  return PoolState
}

async function main() {
  const [immutables, state] = await Promise.all([getPoolImmutables(), getPoolState()])

  const TokenA = new Token(3, immutables.token0, 6, 'USDC', 'USD Coin')

  const TokenB = new Token(3, immutables.token1, 18, 'WETH', 'Wrapped Ether')

  const poolExample = new Pool(
    TokenA,
    TokenB,
    immutables.fee,
    state.sqrtPriceX96.toString(),
    state.liquidity.toString(),
    state.tick
  )
  console.log(poolExample)
}

main()