Enable transactions look-up by signatures (#117)

### TL;DR

Implemented signature lookup for transactions and improved query filtering.

### What changed?

- Activated signature lookup in `GetTransactionsByContractAndSignature` function
- Exported `ExtractFunctionSelector` function
- Updated ClickHouse queries to include function selector for transactions
- Generalised signature clause handling for both logs and transactions in ClickHouse queries

### How to test?

1. Make a GET request to `/{chainId}/transactions/{to}/{signature}` endpoint with a valid contract address and function signature
```
curl --location 'http://localhost:3000/660279/transactions/0x6e55472109e6abe4054a8e8b8d9edffcb31032c5/setMinDstGas(uint16,uint16,uint256)?limit=1' \
--header 'Authorization: Basic ...'
```
2. Verify that the returned transactions are filtered correctly based on the provided signature
```json
{
    "meta": {
        "chain_id": 660279,
        "address": "0x6e55472109e6abe4054a8e8b8d9edffcb31032c5",
        "signature": "0xdf2a5b3b87f900bae4c01587a04a2d9f5990f0066e443e87fe88cf2ce9974ff0",
        "page": 0,
        "limit": 5,
        "total_items": 5,
        "total_pages": 0
    },
    "data": [
        {
            ...
            "to_address": "0x6e55472109e6abe4054a8e8b8d9edffcb31032c5",
            "value": 0,
            "gas": 52119,
            "gas_price": 1600000000,
            "data": "0xdf2a5b3b00000000000000000000000000000000000000000000000000000000000000af00000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000030d40",
            "function_selector": "0xdf2a5b3b",
            ...
        }
    ]
}
```

### Why make this change?

This change enables more precise filtering of transactions based on function signatures, improving the ability to query specific contract interactions. It also aligns the transaction querying capabilities with those already available for logs, providing a more consistent and powerful API for data retrieval.

Author: catalyst17

internal/handlers/transactions_handlers.go

@@ -3,9 +3,11 @@ package handlers
 import (
 	"net/http"
 
+	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/gin-gonic/gin"
 	"github.com/rs/zerolog/log"
 	"github.com/thirdweb-dev/indexer/api"
+	"github.com/thirdweb-dev/indexer/internal/rpc"
 	"github.com/thirdweb-dev/indexer/internal/storage"
 )
 
@@ -104,8 +106,8 @@ func GetTransactionsByContract(c *gin.Context) {
 // @Router /{chainId}/transactions/{to}/{signature} [get]
 func GetTransactionsByContractAndSignature(c *gin.Context) {
 	to := c.Param("to")
-	// TODO: Implement signature lookup before activating this
-	handleTransactionsRequest(c, to, "")
+	signature := c.Param("signature")
+	handleTransactionsRequest(c, to, signature)
 }
 
 func handleTransactionsRequest(c *gin.Context, contractAddress, signature string) {
@@ -122,10 +124,9 @@ func handleTransactionsRequest(c *gin.Context, contractAddress, signature string
 	}
 
 	signatureHash := ""
-	// TODO: implement signature lookup
-	// if signature != "" {
-	// 	signatureHash = crypto.Keccak256Hash([]byte(signature)).Hex()
-	// }
+	if signature != "" {
+		signatureHash = rpc.ExtractFunctionSelector(crypto.Keccak256Hash([]byte(signature)).Hex())
+	}
 
 	mainStorage, err := getMainStorage()
 	if err != nil {

internal/rpc/serializer.go

@@ -185,7 +185,7 @@ func serializeTransaction(chainId *big.Int, tx map[string]interface{}, blockTime
 		Gas:                  hexToUint64(tx["gas"]),
 		GasPrice:             hexToBigInt(tx["gasPrice"]),
 		Data:                 interfaceToString(tx["input"]),
-		FunctionSelector:     extractFunctionSelector(interfaceToString(tx["input"])),
+		FunctionSelector:     ExtractFunctionSelector(interfaceToString(tx["input"])),
 		MaxFeePerGas:         hexToBigInt(tx["maxFeePerGas"]),
 		MaxPriorityFeePerGas: hexToBigInt(tx["maxPriorityFeePerGas"]),
 		TransactionType:      uint8(hexToUint64(tx["type"])),
@@ -270,7 +270,7 @@ func serializeTransaction(chainId *big.Int, tx map[string]interface{}, blockTime
 /**
  * Extracts the function selector (first 4 bytes) from a transaction input.
  */
-func extractFunctionSelector(s string) string {
+func ExtractFunctionSelector(s string) string {
 	if len(s) < 10 {
 		return ""
 	}

internal/storage/clickhouse.go

@@ -339,7 +339,7 @@ func (c *ClickHouseConnector) GetBlocks(qf QueryFilter) (blocks []common.Block,
 }
 
 func (c *ClickHouseConnector) GetTransactions(qf QueryFilter) (QueryResult[common.Transaction], error) {
-	columns := "chain_id, hash, nonce, block_hash, block_number, block_timestamp, transaction_index, from_address, to_address, value, gas, gas_price, data, max_fee_per_gas, max_priority_fee_per_gas, transaction_type, r, s, v, access_list"
+	columns := "chain_id, hash, nonce, block_hash, block_number, block_timestamp, transaction_index, from_address, to_address, value, gas, gas_price, data, function_selector, max_fee_per_gas, max_priority_fee_per_gas, transaction_type, r, s, v, access_list"
 	return executeQuery[common.Transaction](c, "transactions", columns, qf, scanTransaction)
 }
 
@@ -359,7 +359,7 @@ func (c *ClickHouseConnector) GetAggregations(table string, qf QueryFilter) (Que
 	}
 	query = addContractAddress(table, query, qf.ContractAddress)
 	if qf.Signature != "" {
-		query += fmt.Sprintf(" AND topic_0 = '%s'", qf.Signature)
+		query = addSignatureClause(table, query, qf.Signature)
 	}
 	for key, value := range qf.FilterParams {
 		query = addFilterParams(key, strings.ToLower(value), query)
@@ -452,7 +452,7 @@ func (c *ClickHouseConnector) buildQuery(table, columns string, qf QueryFilter)
 
 	// Add signature clause
 	if qf.Signature != "" {
-		query += fmt.Sprintf(" AND topic_0 = '%s'", qf.Signature)
+		query = addSignatureClause(table, query, qf.Signature)
 	}
 	// Add filter params
 	for key, value := range qf.FilterParams {
@@ -516,6 +516,15 @@ func addContractAddress(table, query string, contractAddress string) string {
 	return query
 }
 
+func addSignatureClause(table, query, signature string) string {
+	if table == "logs" {
+		query += fmt.Sprintf(" AND topic_0 = '%s'", signature)
+	} else if table == "transactions" {
+		query += fmt.Sprintf(" AND function_selector = '%s'", signature)
+	}
+	return query
+}
+
 func getTopicValueFormat(topic string) string {
 	if topic == "" {
 		// if there is no indexed topic, indexer stores an empty string
@@ -545,6 +554,7 @@ func scanTransaction(rows driver.Rows) (common.Transaction, error) {
 		&tx.Gas,
 		&tx.GasPrice,
 		&tx.Data,
+		&tx.FunctionSelector,
 		&tx.MaxFeePerGas,
 		&tx.MaxPriorityFeePerGas,
 		&tx.TransactionType,