fix(ampl): do not swap ampl via pairs other than DAI/ETH

src/constants/index.ts

@@ -15,6 +15,7 @@ export const USDC = new Token(ChainId.MAINNET, '0xA0b86991c6218b36c1d19D4a2e9Eb0
 export const USDT = new Token(ChainId.MAINNET, '0xdAC17F958D2ee523a2206206994597C13D831ec7', 6, 'USDT', 'Tether USD')
 export const COMP = new Token(ChainId.MAINNET, '0xc00e94Cb662C3520282E6f5717214004A7f26888', 18, 'COMP', 'Compound')
 export const MKR = new Token(ChainId.MAINNET, '0x9f8F72aA9304c8B593d555F12eF6589cC3A579A2', 18, 'MKR', 'Maker')
+export const AMPL = new Token(ChainId.MAINNET, '0xD46bA6D942050d489DBd938a2C909A5d5039A161', 9, 'AMPL', 'Ampleforth')
 
 const WETH_ONLY: ChainTokenList = {
   [ChainId.MAINNET]: [WETH[ChainId.MAINNET]],
@@ -30,6 +31,16 @@ export const BASES_TO_CHECK_TRADES_AGAINST: ChainTokenList = {
   [ChainId.MAINNET]: [...WETH_ONLY[ChainId.MAINNET], DAI, USDC, USDT, COMP, MKR]
 }
 
+/**
+ * Some tokens can only be swapped via certain pairs, so we override the list of bases that are considered for these
+ * tokens.
+ */
+export const CUSTOM_BASES: { [chainId in ChainId]?: { [tokenAddress: string]: Token[] } } = {
+  [ChainId.MAINNET]: {
+    [AMPL.address]: [DAI, WETH[ChainId.MAINNET]]
+  }
+}
+
 // used for display in the default list when adding liquidity
 export const SUGGESTED_BASES: ChainTokenList = {
   ...WETH_ONLY,

src/hooks/Trades.ts

@@ -2,9 +2,8 @@ import { Currency, CurrencyAmount, Pair, Token, Trade } from '@uniswap/sdk'
 import flatMap from 'lodash.flatmap'
 import { useMemo } from 'react'
 
-import { BASES_TO_CHECK_TRADES_AGAINST } from '../constants'
+import { BASES_TO_CHECK_TRADES_AGAINST, CUSTOM_BASES } from '../constants'
 import { PairState, usePairs } from '../data/Reserves'
-import { maxHopsFor } from '../utils/maxHopsFor'
 import { wrappedCurrency } from '../utils/wrappedCurrency'
 
 import { useActiveWeb3React } from './index'
@@ -18,18 +17,36 @@ function useAllCommonPairs(currencyA?: Currency, currencyB?: Currency): Pair[] {
     ? [wrappedCurrency(currencyA, chainId), wrappedCurrency(currencyB, chainId)]
     : [undefined, undefined]
 
-  const allPairCombinations: [Token | undefined, Token | undefined][] = useMemo(
-    () => [
-      // the direct pair
-      [tokenA, tokenB],
-      // token A against all bases
-      ...bases.map((base): [Token | undefined, Token | undefined] => [tokenA, base]),
-      // token B against all bases
-      ...bases.map((base): [Token | undefined, Token | undefined] => [tokenB, base]),
-      // each base against all bases
-      ...flatMap(bases, (base): [Token, Token][] => bases.map(otherBase => [base, otherBase]))
-    ],
-    [tokenA, tokenB, bases]
+  const allPairCombinations: [Token, Token][] = useMemo(
+    () =>
+      [
+        // the direct pair
+        [tokenA, tokenB],
+        // token A against all bases
+        ...bases.map((base): [Token | undefined, Token | undefined] => [tokenA, base]),
+        // token B against all bases
+        ...bases.map((base): [Token | undefined, Token | undefined] => [tokenB, base]),
+        // each base against all bases
+        ...flatMap(bases, (base): [Token, Token][] => bases.map(otherBase => [base, otherBase]))
+      ]
+        .filter((tokens): tokens is [Token, Token] => Boolean(tokens[0] && tokens[1]))
+        .filter(([tokenA, tokenB]) => {
+          if (!chainId) return true
+          const customBases = CUSTOM_BASES[chainId]
+          if (!customBases) return true
+
+          const customBasesA: Token[] | undefined = customBases[tokenA.address]
+          const customBasesB: Token[] | undefined = customBases[tokenB.address]
+
+          if (!customBasesA && !customBasesB) return true
+
+          if (customBasesA && customBasesA.findIndex(base => tokenB.equals(base)) === -1) return false
+          if (customBasesB && customBasesB.findIndex(base => tokenA.equals(base)) === -1) return false
+          console.log(tokenA, tokenB, customBasesA, customBasesB, 'allowing')
+
+          return true
+        }),
+    [tokenA, tokenB, bases, chainId]
   )
 
   const allPairs = usePairs(allPairCombinations)
@@ -59,9 +76,8 @@ export function useTradeExactIn(currencyAmountIn?: CurrencyAmount, currencyOut?:
 
   return useMemo(() => {
     if (currencyAmountIn && currencyOut && allowedPairs.length > 0) {
-      const maxHops = maxHopsFor(currencyAmountIn.currency, currencyOut)
       return (
-        Trade.bestTradeExactIn(allowedPairs, currencyAmountIn, currencyOut, { maxHops, maxNumResults: 1 })[0] ?? null
+        Trade.bestTradeExactIn(allowedPairs, currencyAmountIn, currencyOut, { maxHops: 3, maxNumResults: 1 })[0] ?? null
       )
     }
     return null
@@ -76,9 +92,9 @@ export function useTradeExactOut(currencyIn?: Currency, currencyAmountOut?: Curr
 
   return useMemo(() => {
     if (currencyIn && currencyAmountOut && allowedPairs.length > 0) {
-      const maxHops = maxHopsFor(currencyIn, currencyAmountOut.currency)
       return (
-        Trade.bestTradeExactOut(allowedPairs, currencyIn, currencyAmountOut, { maxHops, maxNumResults: 1 })[0] ?? null
+        Trade.bestTradeExactOut(allowedPairs, currencyIn, currencyAmountOut, { maxHops: 3, maxNumResults: 1 })[0] ??
+        null
       )
     }
     return null

src/utils/maxHopsFor.ts

-import { ChainId, Currency, ETHER, Token, WETH } from '@uniswap/sdk'
-
-function isEtherish(currency: Currency): boolean {
-  return currency === ETHER || (currency instanceof Token && WETH[currency.chainId].equals(currency))
-}
-
-const AMPL_TOKEN_ADDRESS = '0xD46bA6D942050d489DBd938a2C909A5d5039A161'
-
-/**
- * Band-aid on maxHops because some tokens seems to always fail with multihop swaps
- * @param currencyIn currency in
- * @param currencyOut currency out
- */
-export function maxHopsFor(currencyIn: Currency, currencyOut: Currency): number {
-  if (
-    isEtherish(currencyIn) &&
-    currencyOut instanceof Token &&
-    currencyOut.chainId === ChainId.MAINNET &&
-    currencyOut.address === AMPL_TOKEN_ADDRESS
-  ) {
-    return 1
-  } else if (
-    isEtherish(currencyOut) &&
-    currencyIn instanceof Token &&
-    currencyIn.chainId === ChainId.MAINNET &&
-    currencyIn.address === AMPL_TOKEN_ADDRESS
-  ) {
-    return 1
-  }
-
-  return 3
-}