feat(rfq-relayer): add MaxBalance param

services/rfq/relayer/quoter/quoter.go

@@ -519,13 +519,17 @@ func (m *Manager) getOriginAmount(parentCtx context.Context, origin, dest int, a
 		quoteAmount = minQuoteAmount
 	}
 
-	// Finally, clip the quoteAmount by the balance
-	if quoteAmount.Cmp(balance) > 0 {
-		span.AddEvent("quote amount greater than balance", trace.WithAttributes(
+	// Finally, clip the quoteAmount by the minimum balance
+	minBalance := m.config.GetMinBalance(dest, address)
+	quotableBalance := new(big.Int).Sub(balance, minBalance)
+	if quoteAmount.Cmp(quotableBalance) > 0 {
+		span.AddEvent("quote amount greater than quotable balance", trace.WithAttributes(
 			attribute.String("quote_amount", quoteAmount.String()),
 			attribute.String("balance", balance.String()),
+			attribute.String("quotable_balance", quotableBalance.String()),
+			attribute.String("min_balance", minBalance.String()),
 		))
-		quoteAmount = balance
+		quoteAmount = quotableBalance
 	}
 
 	// Deduct gas cost from the quote amount, if necessary

services/rfq/relayer/quoter/quoter_test.go

@@ -164,10 +164,11 @@ func (s *QuoterSuite) TestGetOriginAmount() {
 	address := common.HexToAddress("0x0b2c639c533813f4aa9d7837caf62653d097ff85")
 	balance := big.NewInt(1000_000_000) // 1000 USDC
 
-	setQuoteParams := func(quotePct, quoteOffset float64, minQuoteAmount string) {
+	setQuoteParams := func(quotePct, quoteOffset float64, minQuoteAmount string, minBalance string) {
 		s.config.BaseChainConfig.QuotePct = quotePct
 		destTokenCfg := s.config.Chains[dest].Tokens["USDC"]
 		destTokenCfg.MinQuoteAmount = minQuoteAmount
+		destTokenCfg.MinBalance = minBalance
 		originTokenCfg := s.config.Chains[origin].Tokens["USDC"]
 		originTokenCfg.QuoteOffsetBps = quoteOffset
 		s.config.Chains[dest].Tokens["USDC"] = destTokenCfg
@@ -182,40 +183,47 @@ func (s *QuoterSuite) TestGetOriginAmount() {
 	s.Equal(expectedAmount, quoteAmount)
 
 	// Set QuotePct to 50 with MinQuoteAmount of 0; should be 50% of balance.
-	setQuoteParams(50, 0, "0")
+	setQuoteParams(50, 0, "0", "0")
 	quoteAmount, err = s.manager.GetOriginAmount(s.GetTestContext(), origin, dest, address, balance)
 	s.NoError(err)
 	expectedAmount = big.NewInt(500_000_000)
 	s.Equal(expectedAmount, quoteAmount)
 
 	// Set QuotePct to 50 with QuoteOffset of -1%. Should be 1% less than 50% of balance.
-	setQuoteParams(50, -100, "0")
+	setQuoteParams(50, -100, "0", "0")
 	quoteAmount, err = s.manager.GetOriginAmount(s.GetTestContext(), origin, dest, address, balance)
 	s.NoError(err)
 	expectedAmount = big.NewInt(495_000_000)
 	s.Equal(expectedAmount, quoteAmount)
 
 	// Set QuotePct to 25 with MinQuoteAmount of 500; should be 50% of balance.
-	setQuoteParams(25, 0, "500")
+	setQuoteParams(25, 0, "500", "0")
 	quoteAmount, err = s.manager.GetOriginAmount(s.GetTestContext(), origin, dest, address, balance)
 	s.NoError(err)
 	expectedAmount = big.NewInt(500_000_000)
 	s.Equal(expectedAmount, quoteAmount)
 
 	// Set QuotePct to 25 with MinQuoteAmount of 500; should be 50% of balance.
-	setQuoteParams(25, 0, "500")
+	setQuoteParams(25, 0, "500", "0")
 	quoteAmount, err = s.manager.GetOriginAmount(s.GetTestContext(), origin, dest, address, balance)
 	s.NoError(err)
 	expectedAmount = big.NewInt(500_000_000)
 	s.Equal(expectedAmount, quoteAmount)
 
 	// Set QuotePct to 25 with MinQuoteAmount of 1500; should be total balance.
-	setQuoteParams(25, 0, "1500")
+	setQuoteParams(25, 0, "1500", "0")
 	quoteAmount, err = s.manager.GetOriginAmount(s.GetTestContext(), origin, dest, address, balance)
 	s.NoError(err)
 	expectedAmount = big.NewInt(1000_000_000)
 	s.Equal(expectedAmount, quoteAmount)
 
+	// Set QuotePct to 25 with MinQuoteAmount of 1500 and MinBalance of 200; should be total balance minus 500.
+	setQuoteParams(25, 0, "1500", "200")
+	quoteAmount, err = s.manager.GetOriginAmount(s.GetTestContext(), origin, dest, address, balance)
+	s.NoError(err)
+	expectedAmount = big.NewInt(800_000_000)
+	s.Equal(expectedAmount, quoteAmount)
+
 	// Toggle insufficient gas; should be 0.
 	s.setGasSufficiency(false)
 	quoteAmount, err = s.manager.GetOriginAmount(s.GetTestContext(), origin, dest, address, balance)

services/rfq/relayer/relconfig/config.go

@@ -128,6 +128,8 @@ type TokenConfig struct {
 	// Note that this value can be positive or negative; if positive it effectively increases the quoted price
 	// of the given token, and vice versa.
 	QuoteOffsetBps float64 `yaml:"quote_offset_bps"`
+	// MinBalance is the minimum balance that should be leftover from quoting, in human-readable units.
+	MinBalance string `yaml:"min_balance"`
 }
 
 // DatabaseConfig represents the configuration for the database.

services/rfq/relayer/relconfig/getters.go

@@ -298,6 +298,41 @@ func (c Config) GetQuoteOffsetBps(chainID int, tokenName string, isOrigin bool)
 	return offset, nil
 }
 
+const defaultMinBalance = 0
+
+// GetMinBalance returns the MinBalance for the given chain and address.
+// Note that this getter returns the value in native token decimals.
+func (c Config) GetMinBalance(chainID int, addr common.Address) *big.Int {
+	chainCfg, ok := c.Chains[chainID]
+	if !ok {
+		return big.NewInt(defaultMinBalance)
+	}
+
+	var tokenCfg *TokenConfig
+	for _, cfg := range chainCfg.Tokens {
+		if common.HexToAddress(cfg.Address).Hex() == addr.Hex() {
+			cfgCopy := cfg
+			tokenCfg = &cfgCopy
+			break
+		}
+	}
+	if tokenCfg == nil {
+		return big.NewInt(defaultMinBalance)
+	}
+	quoteAmountFlt, ok := new(big.Float).SetString(tokenCfg.MinBalance)
+	if !ok {
+		return big.NewInt(defaultMinBalance)
+	}
+	if quoteAmountFlt.Cmp(big.NewFloat(0)) <= 0 {
+		return big.NewInt(defaultMinBalance)
+	}
+
+	// Scale the minBalance by the token decimals.
+	denomDecimalsFactor := new(big.Int).Exp(big.NewInt(10), big.NewInt(int64(tokenCfg.Decimals)), nil)
+	quoteAmountScaled, _ := new(big.Float).Mul(quoteAmountFlt, new(big.Float).SetInt(denomDecimalsFactor)).Int(nil)
+	return quoteAmountScaled
+}
+
 // GetQuoteWidthBps returns the QuoteWidthBps for the given chainID.
 func (c Config) GetQuoteWidthBps(chainID int) (value float64, err error) {
 	rawValue, err := c.getChainConfigValue(chainID, "QuoteWidthBps")