Get Uniswap prices in a subgraph

uniswap.ts

import { Address, BigInt, BigDecimal, dataSource } from "@graphprotocol/graph-ts"
import { UniswapV2Pair } from '../generated/Pool/UniswapV2Pair'
import { UniswapV2Factory } from '../generated/Pool/UniswapV2Factory'

let UNISWAP_FACTORY = Address.fromString('0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f')
let EIGHTEEN_DECIMALS = BigInt.fromI32(10).pow(18).toBigDecimal()

let wethAddress = new Map<string, Address>()
wethAddress.set('rinkeby', Address.fromString('0xc778417E063141139Fce010982780140Aa0cD5Ab'))
wethAddress.set('mainnet', Address.fromString('0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2'))

let stablecoinAddress = new Map<string, Address>()
stablecoinAddress.set('rinkeby', Address.fromString('0x5592ec0cfb4dbc12d3ab100b257153436a1f0fea'))
stablecoinAddress.set('mainnet', Address.fromString('0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48')) // USDC

function getPair(token0: Address, token1: Address): Address {
  let factory = UniswapV2Factory.bind(UNISWAP_FACTORY)
  return factory.getPair(token0, token1)
}

export function getPairPrice(pairAddress: Address): BigDecimal {
  let pair = UniswapV2Pair.bind(pairAddress)
  let reserves = pair.getReserves()
  let totalSupply = pair.totalSupply();

  if(totalSupply.gt(BigInt.fromI32(0))) {
    let valueOfToken0 = getPrice(pair.token0()) * reserves.value0.divDecimal(EIGHTEEN_DECIMALS)
    let valueOfToken1 = getPrice(pair.token1()) * reserves.value1.divDecimal(EIGHTEEN_DECIMALS)
    let lpTokenPrice = (valueOfToken0 + valueOfToken1) / (pair.totalSupply().divDecimal(EIGHTEEN_DECIMALS))
    return lpTokenPrice;
  }

  return new BigDecimal(BigInt.fromI32(0));
}

export function getPrice(token: Address): BigDecimal {
  let network = dataSource.network()

  let stablecoin = stablecoinAddress.get(network)
  let weth = wethAddress.get(network)

  if (token.toHex() == stablecoin.toHex()) {
    return BigInt.fromI32(1).toBigDecimal()
  }

  if (token == weth) {
    let pair = UniswapV2Pair.bind(getPair(token, stablecoin))
    let reserves = pair.getReserves()

    
    if(reserves.value0 == BigInt.fromI32(0) || reserves.value1 == BigInt.fromI32(0) ) {
      return BigInt.fromI32(1).toBigDecimal()
    }

    let ethPrice = token == pair.token0()
      ? reserves.value1.toBigDecimal() / reserves.value0.toBigDecimal()
      : reserves.value0.toBigDecimal() / reserves.value1.toBigDecimal()
    return ethPrice
  }

  let pair = UniswapV2Pair.bind(getPair(token, weth))
  let reserves = pair.getReserves()
  
  if(reserves.value0 == BigInt.fromI32(0) || reserves.value1 == BigInt.fromI32(0) ) {
    return BigInt.fromI32(1).toBigDecimal()
  }
  
  let priceInETH = token == pair.token0()
    ? reserves.value1.toBigDecimal() / reserves.value0.toBigDecimal()
    : reserves.value0.toBigDecimal() / reserves.value1.toBigDecimal()

  return priceInETH * getPrice(weth)

}