get the best route in v3 for an exact in swap

src/hooks/useAllV3Routes.ts

@@ -27,7 +27,6 @@ function computeAllRoutes(
 
     const outputToken = pool.token0.equals(tokenIn) ? pool.token1 : pool.token0
     if (outputToken.equals(tokenOut)) {
-      console.log(startCurrencyIn, [...currentPath, pool], currencyOut)
       allPaths.push(new Route([...currentPath, pool], startCurrencyIn, currencyOut))
     } else if (maxHops > 1) {
       computeAllRoutes(

src/hooks/useBestV3Route.ts

+import { Token, ChainId, Currency, CurrencyAmount, TokenAmount } from '@uniswap/sdk-core'
+import { Route } from '@uniswap/v3-sdk'
+import { Pool } from '@uniswap/v3-sdk/dist/'
+import { useMemo } from 'react'
+import { useSingleContractMultipleData } from '../state/multicall/hooks'
+import { wrappedCurrency } from '../utils/wrappedCurrency'
+import { useActiveWeb3React } from './index'
+import { useAllV3Routes } from './useAllV3Routes'
+import { useV3Quoter } from './useContract'
+import { BigNumber, utils } from 'ethers'
+
+/**
+ * Converts a route to a path
+ * @param route the v3 path to convert to an encoded path
+ * @param chainId the current chain ID, used to wrap the route's input currency
+ */
+function routeToPath(route: Route, chainId: ChainId): string {
+  const firstInputToken = wrappedCurrency(route.input, chainId)
+
+  if (!firstInputToken) throw new Error('Could not wrap input currency')
+
+  return route.pools.reduce(
+    (
+      { inputToken, path }: { inputToken: Token; path: string },
+      pool: Pool,
+      index
+    ): { inputToken: Token; path: string } => {
+      const outputToken: Token = pool.token0.equals(inputToken) ? pool.token1 : pool.token0
+      if (index === 0) {
+        return {
+          inputToken: outputToken,
+          path: utils.solidityPack(
+            ['address', 'uint24', 'address'],
+            [inputToken.address, pool.fee, outputToken.address]
+          ),
+        }
+      } else {
+        return {
+          inputToken: outputToken,
+          path: `${path}${utils.solidityPack(['uint24', 'address'], [pool.fee, outputToken.address]).slice(2)}`,
+        }
+      }
+    },
+    { inputToken: firstInputToken, path: '' }
+  ).path
+}
+
+export function useBestV3RouteExactIn(
+  amountIn?: CurrencyAmount,
+  currencyOut?: Currency
+): { route: Route; amountOut: CurrencyAmount } | null {
+  const { chainId } = useActiveWeb3React()
+  const quoter = useV3Quoter()
+  const routes = useAllV3Routes(amountIn?.currency, currencyOut)
+  const paths = useMemo(() => {
+    if (!chainId) return []
+    return routes.map((route) => routeToPath(route, chainId))
+  }, [chainId, routes])
+
+  const quoteInputs = useMemo(() => {
+    return paths.map((path) => [path, amountIn ? `0x${amountIn.raw.toString(16)}` : undefined])
+  }, [amountIn, paths])
+
+  const quotesResults = useSingleContractMultipleData(quoter, 'quoteExactInput', quoteInputs)
+
+  return useMemo(() => {
+    const { bestRoute, amountOut } = quotesResults.reduce(
+      (best: { bestRoute: Route | null; amountOut: BigNumber | null }, { valid, loading, result }, i) => {
+        if (loading || !valid || !result) return best
+
+        if (best.amountOut === null) {
+          return {
+            bestRoute: routes[i],
+            amountOut: result.amountOut,
+          }
+        } else if (best.amountOut.lt(result.amountOut)) {
+          return {
+            bestRoute: routes[i],
+            amountOut: result.amountOut,
+          }
+        }
+
+        return best
+      },
+      {
+        bestRoute: null,
+        amountOut: null,
+      }
+    )
+    if (!bestRoute || !amountOut) return null
+    return {
+      route: bestRoute,
+      amountOut:
+        currencyOut instanceof Token
+          ? new TokenAmount(currencyOut, amountOut.toString())
+          : CurrencyAmount.ether(amountOut.toString()),
+    }
+  }, [currencyOut, quotesResults, routes])
+}

src/state/swap/hooks.ts

+import { useBestV3RouteExactIn } from '../../hooks/useBestV3Route'
 import useENS from '../../hooks/useENS'
 import { parseUnits } from '@ethersproject/units'
 import { Currency, CurrencyAmount, ETHER, Token, TokenAmount } from '@uniswap/sdk-core'
@@ -138,6 +139,10 @@ export function useDerivedSwapInfo(): {
   const bestTradeExactIn = useV2TradeExactIn(isExactIn ? parsedAmount : undefined, outputCurrency ?? undefined)
   const bestTradeExactOut = useV2TradeExactOut(inputCurrency ?? undefined, !isExactIn ? parsedAmount : undefined)
 
+  const bestRouteExactInV3 = useBestV3RouteExactIn(isExactIn ? parsedAmount : undefined, outputCurrency ?? undefined)
+  // todo: do something with this information
+  console.log('best v3 route for the swap', bestRouteExactInV3)
+
   const v2Trade = isExactIn ? bestTradeExactIn : bestTradeExactOut
 
   const currencyBalances = {