Add helpers for txpool

common/types.go

@@ -472,3 +472,5 @@ func (d *Decimal) UnmarshalJSON(input []byte) error {
 		return err
 	}
 }
+
+type ExchangeRates = map[Address]*big.Rat

core/celo_backend.go

@@ -14,14 +14,14 @@ import (
 // CeloBackend provide a partial ContractBackend implementation, so that we can
 // access core contracts during block processing.
 type CeloBackend struct {
-	chainConfig *params.ChainConfig
-	state       *state.StateDB
+	ChainConfig *params.ChainConfig
+	State       *state.StateDB
 }
 
 // ContractCaller implementation
 
 func (b *CeloBackend) CodeAt(ctx context.Context, contract common.Address, blockNumber *big.Int) ([]byte, error) {
-	return b.state.GetCode(contract), nil
+	return b.State.GetCode(contract), nil
 }
 
 func (b *CeloBackend) CallContract(ctx context.Context, call ethereum.CallMsg, blockNumber *big.Int) ([]byte, error) {
@@ -44,7 +44,7 @@ func (b *CeloBackend) CallContract(ctx context.Context, call ethereum.CallMsg, b
 	txCtx := vm.TxContext{}
 	vmConfig := vm.Config{}
 
-	evm := vm.NewEVM(blockCtx, txCtx, b.state, b.chainConfig, vmConfig)
+	evm := vm.NewEVM(blockCtx, txCtx, b.State, b.ChainConfig, vmConfig)
 	ret, _, err := evm.StaticCall(vm.AccountRef(evm.Origin), *call.To, call.Data, call.Gas)
 
 	return ret, err

core/celo_evm.go

@@ -16,7 +16,7 @@ import (
 )
 
 // Returns the exchange rates for all gas currencies from CELO
-func getExchangeRates(caller *CeloBackend) (map[common.Address]*big.Rat, error) {
+func GetExchangeRates(caller bind.ContractCaller) (common.ExchangeRates, error) {
 	exchangeRates := map[common.Address]*big.Rat{}
 	whitelist, err := abigen.NewFeeCurrencyWhitelistCaller(contracts.FeeCurrencyWhitelistAddress, caller)
 	if err != nil {
@@ -57,7 +57,7 @@ func setCeloFieldsInBlockContext(blockContext *vm.BlockContext, header *types.He
 
 	// Add fee currency exchange rates
 	var err error
-	blockContext.ExchangeRates, err = getExchangeRates(caller)
+	blockContext.ExchangeRates, err = GetExchangeRates(caller)
 	if err != nil {
 		log.Error("Error fetching exchange rates!", "err", err)
 	}

core/txpool/legacypool/celo.go

@@ -0,0 +1,92 @@
+package legacypool
+
+import (
+	"errors"
+	"fmt"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/accounts/abi/bind"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/contracts/celo/abigen"
+)
+
+var (
+	unitRate = big.NewRat(1, 1)
+)
+
+// IsWhitelisted checks if a given fee currency is whitelisted
+func IsWhitelisted(exchangeRates common.ExchangeRates, feeCurrency *common.Address) bool {
+	if feeCurrency == nil {
+		return true
+	}
+	_, ok := exchangeRates[*feeCurrency]
+	return ok
+}
+
+// Compares values in different currencies
+// nil currency => native currency
+func CompareValue(exchangeRates common.ExchangeRates, val1 *big.Int, feeCurrency1 *common.Address, val2 *big.Int, feeCurrency2 *common.Address) (int, error) {
+	// Short circuit if the fee currency is the same.
+	if areEqualAddresses(feeCurrency1, feeCurrency2) {
+		return val1.Cmp(val2), nil
+	}
+
+	var exchangeRate1, exchangeRate2 *big.Rat
+	var ok bool
+	if feeCurrency1 == nil {
+		exchangeRate1 = unitRate
+	} else {
+		exchangeRate1, ok = exchangeRates[*feeCurrency1]
+		if !ok {
+			return 0, fmt.Errorf("fee currency not registered: %s", feeCurrency1.Hex())
+		}
+	}
+
+	if feeCurrency2 == nil {
+		exchangeRate2 = unitRate
+	} else {
+		exchangeRate2, ok = exchangeRates[*feeCurrency2]
+		if !ok {
+			return 0, fmt.Errorf("fee currency not registered: %s", feeCurrency1.Hex())
+		}
+	}
+
+	// Below code block is basically evaluating this comparison:
+	// val1 * exchangeRate1.denominator / exchangeRate1.numerator < val2 * exchangeRate2.denominator / exchangeRate2.numerator
+	// It will transform that comparison to this, to remove having to deal with fractional values.
+	// val1 * exchangeRate1.denominator * exchangeRate2.numerator < val2 * exchangeRate2.denominator * exchangeRate1.numerator
+	leftSide := new(big.Int).Mul(
+		val1,
+		new(big.Int).Mul(
+			exchangeRate1.Denom(),
+			exchangeRate2.Num(),
+		),
+	)
+	rightSide := new(big.Int).Mul(
+		val2,
+		new(big.Int).Mul(
+			exchangeRate2.Denom(),
+			exchangeRate1.Num(),
+		),
+	)
+
+	return leftSide.Cmp(rightSide), nil
+}
+
+func areEqualAddresses(addr1, addr2 *common.Address) bool {
+	return (addr1 == nil && addr2 == nil) || (addr1 != nil && addr2 != nil && *addr1 == *addr2)
+}
+
+func GetBalanceOf(backend *bind.ContractCaller, account common.Address, feeCurrency common.Address) (*big.Int, error) {
+	token, err := abigen.NewFeeCurrencyCaller(feeCurrency, *backend)
+	if err != nil {
+		return nil, errors.New("failed to access fee currency token")
+	}
+
+	balance, err := token.BalanceOf(&bind.CallOpts{}, account)
+	if err != nil {
+		return nil, errors.New("failed to access token balance")
+	}
+
+	return balance, nil
+}

core/txpool/legacypool/celo_test.go

@@ -0,0 +1,175 @@
+package legacypool
+
+import (
+	"math/big"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+var (
+	currA         = common.HexToAddress("0xA")
+	currB         = common.HexToAddress("0xB")
+	currX         = common.HexToAddress("0xF")
+	exchangeRates = common.ExchangeRates{
+		currA: big.NewRat(47, 100),
+		currB: big.NewRat(45, 100),
+	}
+)
+
+func TestCompareFees(t *testing.T) {
+	type args struct {
+		val1         *big.Int
+		feeCurrency1 *common.Address
+		val2         *big.Int
+		feeCurrency2 *common.Address
+	}
+	tests := []struct {
+		name       string
+		args       args
+		wantResult int
+		wantErr    bool
+	}{
+		// Native currency
+		{
+			name: "Same amount of native currency",
+			args: args{
+				val1:         big.NewInt(1),
+				feeCurrency1: nil,
+				val2:         big.NewInt(1),
+				feeCurrency2: nil,
+			},
+			wantResult: 0,
+		}, {
+			name: "Different amounts of native currency 1",
+			args: args{
+				val1:         big.NewInt(2),
+				feeCurrency1: nil,
+				val2:         big.NewInt(1),
+				feeCurrency2: nil,
+			},
+			wantResult: 1,
+		}, {
+			name: "Different amounts of native currency 2",
+			args: args{
+				val1:         big.NewInt(1),
+				feeCurrency1: nil,
+				val2:         big.NewInt(5),
+				feeCurrency2: nil,
+			},
+			wantResult: -1,
+		},
+		// Mixed currency
+		{
+			name: "Same amount of mixed currency",
+			args: args{
+				val1:         big.NewInt(1),
+				feeCurrency1: nil,
+				val2:         big.NewInt(1),
+				feeCurrency2: &currA,
+			},
+			wantResult: -1,
+		}, {
+			name: "Different amounts of mixed currency 1",
+			args: args{
+				val1:         big.NewInt(100),
+				feeCurrency1: nil,
+				val2:         big.NewInt(47),
+				feeCurrency2: &currA,
+			},
+			wantResult: 0,
+		}, {
+			name: "Different amounts of mixed currency 2",
+			args: args{
+				val1:         big.NewInt(100),
+				feeCurrency1: nil,
+				val2:         big.NewInt(45),
+				feeCurrency2: &currB,
+			},
+			wantResult: 0,
+		},
+		// Two fee currencies
+		{
+			name: "Same amount of same currency",
+			args: args{
+				val1:         big.NewInt(1),
+				feeCurrency1: &currA,
+				val2:         big.NewInt(1),
+				feeCurrency2: &currA,
+			},
+			wantResult: 0,
+		}, {
+			name: "Different amounts of same currency 1",
+			args: args{
+				val1:         big.NewInt(3),
+				feeCurrency1: &currA,
+				val2:         big.NewInt(1),
+				feeCurrency2: &currA,
+			},
+			wantResult: 1,
+		}, {
+			name: "Different amounts of same currency 2",
+			args: args{
+				val1:         big.NewInt(1),
+				feeCurrency1: &currA,
+				val2:         big.NewInt(7),
+				feeCurrency2: &currA,
+			},
+			wantResult: -1,
+		},
+		// Unregistered fee currency
+		{
+			name: "Different amounts of different currencies",
+			args: args{
+				val1:         big.NewInt(1),
+				feeCurrency1: &currA,
+				val2:         big.NewInt(1),
+				feeCurrency2: &currX,
+			},
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := CompareValue(exchangeRates, tt.args.val1, tt.args.feeCurrency1, tt.args.val2, tt.args.feeCurrency2)
+
+			if tt.wantErr && err == nil {
+				t.Error("Expected error in celoContextImpl.CompareFees")
+			}
+			if got != tt.wantResult {
+				t.Errorf("celoContextImpl.CompareFees() = %v, want %v", got, tt.wantResult)
+			}
+		})
+	}
+}
+
+func TestIsWhitelisted(t *testing.T) {
+	tests := []struct {
+		name        string
+		feeCurrency *common.Address
+		want        bool
+	}{
+		{
+			name:        "no fee currency",
+			feeCurrency: nil,
+			want:        true,
+		},
+		{
+			name:        "valid fee currency",
+			feeCurrency: &currA,
+			want:        true,
+		},
+		{
+			name:        "invalid fee currency",
+			feeCurrency: &currX,
+			want:        false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := IsWhitelisted(exchangeRates, tt.feeCurrency); got != tt.want {
+				t.Errorf("IsWhitelisted() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

core/vm/evm.go

@@ -93,7 +93,7 @@ type BlockContext struct {
 	ExcessBlobGas *uint64        // ExcessBlobGas field in the header, needed to compute the data
 
 	// Celo specific information
-	ExchangeRates map[common.Address]*big.Rat
+	ExchangeRates common.ExchangeRates
 }
 
 // TxContext provides the EVM with information about a transaction.