Get ABI via etherscan API (#96)

- Added ABI request
- Add unique constraint on contract hash for watched contracts

cmd/subscribe_contract/main.go

@@ -12,10 +12,12 @@ func main() {
 	contractHash := flag.String("contract-hash", "", "contract-hash=x1234")
 	abiFilepath := flag.String("abi-filepath", "", "path/to/abifile.json")
 	flag.Parse()
+
+	contractAbiString := cmd.GetAbi(*abiFilepath, *contractHash)
 	config := cmd.LoadConfig(*environment)
 	repository := cmd.LoadPostgres(config.Database)
 	watchedContract := core.Contract{
-		Abi:  cmd.ReadAbiFile(*abiFilepath),
+		Abi:  contractAbiString,
 		Hash: *contractHash,
 	}
 	repository.CreateContract(watchedContract)

cmd/utils.go

@@ -5,6 +5,8 @@ import (
 
 	"path/filepath"
 
+	"fmt"
+
 	"github.com/8thlight/vulcanizedb/pkg/config"
 	"github.com/8thlight/vulcanizedb/pkg/geth"
 	"github.com/8thlight/vulcanizedb/pkg/repositories"
@@ -36,3 +38,19 @@ func ReadAbiFile(abiFilepath string) string {
 	}
 	return abi
 }
+
+func GetAbi(abiFilepath string, contractHash string) string {
+	var contractAbiString string
+	if abiFilepath != "" {
+		contractAbiString = ReadAbiFile(abiFilepath)
+	} else {
+		etherscan := geth.NewEtherScanClient("https://api.etherscan.io")
+		fmt.Println("No ABI supplied. Retrieving ABI from Etherscan")
+		contractAbiString, _ = etherscan.GetAbi(contractHash)
+	}
+	_, err := geth.ParseAbi(contractAbiString)
+	if err != nil {
+		log.Fatalln("Invalid ABI")
+	}
+	return contractAbiString
+}