feat: add token approve handler

internal/handler/token_approve.go

@@ -0,0 +1,78 @@
+package handler
+
+import (
+	"context"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/grassrootseconomics/eth-tracker/pkg/event"
+	"github.com/grassrootseconomics/eth-tracker/pkg/router"
+	"github.com/lmittmann/w3"
+)
+
+const approveEventName = "TOKEN_APPROVE"
+
+var (
+	tokenApproveEvent = w3.MustNewEvent("Approval(address indexed _owner, address indexed _spender, uint256 _value)")
+	tokenApproveToSig = w3.MustNewFunc("approve(address, uint256)", "bool")
+)
+
+func HandleTokenApproveLog() router.LogHandlerFunc {
+	return func(ctx context.Context, lp router.LogPayload, c router.Callback) error {
+		var (
+			owner   common.Address
+			spender common.Address
+			value   big.Int
+		)
+
+		if err := tokenApproveEvent.DecodeArgs(lp.Log, &owner, &spender, &value); err != nil {
+			return err
+		}
+
+		tokenApproveEvent := event.Event{
+			Index:           lp.Log.Index,
+			Block:           lp.Log.BlockNumber,
+			ContractAddress: lp.Log.Address.Hex(),
+			Success:         true,
+			Timestamp:       lp.Timestamp,
+			TxHash:          lp.Log.TxHash.Hex(),
+			TxType:          approveEventName,
+			Payload: map[string]any{
+				"owner":   owner.Hex(),
+				"spender": spender.Hex(),
+				"value":   value.String(),
+			},
+		}
+
+		return c(ctx, tokenApproveEvent)
+	}
+}
+
+func HandleTokenApproveInputData() router.InputDataHandlerFunc {
+	return func(ctx context.Context, idp router.InputDataPayload, c router.Callback) error {
+		var (
+			spender common.Address
+			value   big.Int
+		)
+
+		if err := tokenApproveToSig.DecodeArgs(w3.B(idp.InputData), &spender, &value); err != nil {
+			return err
+		}
+
+		tokenApproveEvent := event.Event{
+			Block:           idp.Block,
+			ContractAddress: idp.ContractAddress,
+			Success:         false,
+			Timestamp:       idp.Timestamp,
+			TxHash:          idp.TxHash,
+			TxType:          approveEventName,
+			Payload: map[string]any{
+				"owner":   idp.From,
+				"spender": spender.Hex(),
+				"value":   value.String(),
+			},
+		}
+
+		return c(ctx, tokenApproveEvent)
+	}
+}