ethcoder: helper EventTopicHash function

ethcoder/events.go

@@ -0,0 +1,47 @@
+package ethcoder
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/0xsequence/ethkit"
+)
+
+// EventTopicHash returns the keccak256 hash of the event signature
+//
+// e.g. "Transfer(address indexed from, address indexed to, uint256 value)"
+// will return 0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef
+func EventTopicHash(event string) (ethkit.Hash, error) {
+	eventSig := parseEventSignature(event)
+	if eventSig == "" {
+		return ethkit.Hash{}, fmt.Errorf("ethcoder: event format is invalid, expecting Method(arg1,arg2,..)")
+	}
+	return Keccak256Hash([]byte(eventSig)), nil
+}
+
+func parseEventSignature(event string) string {
+	if !strings.Contains(event, "(") || !strings.Contains(event, ")") {
+		return ""
+	}
+	p := strings.Split(event, "(")
+	if len(p) != 2 {
+		return ""
+	}
+	method := p[0]
+
+	args := strings.TrimSuffix(p[1], ")")
+	if args == "" {
+		return fmt.Sprintf("%s()", method)
+	}
+
+	typs := []string{}
+	p = strings.Split(args, ",")
+	for _, a := range p {
+		typ := strings.Split(strings.TrimSpace(a), " ")[0]
+		typs = append(typs, typ)
+	}
+
+	x := fmt.Sprintf("%s(%s)", method, strings.Join(typs, ","))
+	fmt.Println(x)
+	return x
+}

ethcoder/events_test.go

@@ -0,0 +1,24 @@
+package ethcoder_test
+
+import (
+	"testing"
+
+	"github.com/0xsequence/ethkit/ethcoder"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEventTopicHash(t *testing.T) {
+	in := []struct {
+		event string
+	}{
+		{"Transfer(address indexed from, address indexed to, uint256 value)"},
+		{"Transfer(address from, address indexed to, uint256 value)"},
+		{"Transfer(address, address , uint256 )"},
+	}
+
+	for _, x := range in {
+		topicHash, err := ethcoder.EventTopicHash(x.event)
+		require.NoError(t, err)
+		require.Equal(t, "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef", topicHash.String())
+	}
+}