mv pkg/omni pkg/contract_watcher

pkg/contract_watcher/shared/fetcher/fetcher.go

@@ -0,0 +1,124 @@
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package fetcher
+
+import (
+	"fmt"
+	"log"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+
+	"github.com/vulcanize/vulcanizedb/pkg/core"
+)
+
+// Fetcher serves as the lower level data fetcher that calls the underlying
+// blockchain's FetchConctractData method for a given return type
+
+// Interface definition for a Fetcher
+type FetcherInterface interface {
+	FetchBigInt(method, contractAbi, contractAddress string, blockNumber int64, methodArgs []interface{}) (big.Int, error)
+	FetchBool(method, contractAbi, contractAddress string, blockNumber int64, methodArgs []interface{}) (bool, error)
+	FetchAddress(method, contractAbi, contractAddress string, blockNumber int64, methodArgs []interface{}) (common.Address, error)
+	FetchString(method, contractAbi, contractAddress string, blockNumber int64, methodArgs []interface{}) (string, error)
+	FetchHash(method, contractAbi, contractAddress string, blockNumber int64, methodArgs []interface{}) (common.Hash, error)
+}
+
+// Used to create a new Fetcher error for a given error and fetch method
+func newFetcherError(err error, fetchMethod string) *fetcherError {
+	e := fetcherError{err.Error(), fetchMethod}
+	log.Println(e.Error())
+	return &e
+}
+
+// Fetcher struct
+type Fetcher struct {
+	BlockChain core.BlockChain // Underyling Blockchain
+}
+
+// Fetcher error
+type fetcherError struct {
+	err         string
+	fetchMethod string
+}
+
+// Fetcher error method
+func (fe *fetcherError) Error() string {
+	return fmt.Sprintf("Error fetching %s: %s", fe.fetchMethod, fe.err)
+}
+
+//  Generic Fetcher methods used by Getters to call contract methods
+
+// Method used to fetch big.Int value from contract
+func (f Fetcher) FetchBigInt(method, contractAbi, contractAddress string, blockNumber int64, methodArgs []interface{}) (big.Int, error) {
+	var result = new(big.Int)
+	err := f.BlockChain.FetchContractData(contractAbi, contractAddress, method, methodArgs, &result, blockNumber)
+
+	if err != nil {
+		return *result, newFetcherError(err, method)
+	}
+
+	return *result, nil
+}
+
+// Method used to fetch bool value from contract
+func (f Fetcher) FetchBool(method, contractAbi, contractAddress string, blockNumber int64, methodArgs []interface{}) (bool, error) {
+	var result = new(bool)
+	err := f.BlockChain.FetchContractData(contractAbi, contractAddress, method, methodArgs, &result, blockNumber)
+
+	if err != nil {
+		return *result, newFetcherError(err, method)
+	}
+
+	return *result, nil
+}
+
+// Method used to fetch address value from contract
+func (f Fetcher) FetchAddress(method, contractAbi, contractAddress string, blockNumber int64, methodArgs []interface{}) (common.Address, error) {
+	var result = new(common.Address)
+	err := f.BlockChain.FetchContractData(contractAbi, contractAddress, method, methodArgs, &result, blockNumber)
+
+	if err != nil {
+		return *result, newFetcherError(err, method)
+	}
+
+	return *result, nil
+}
+
+// Method used to fetch string value from contract
+func (f Fetcher) FetchString(method, contractAbi, contractAddress string, blockNumber int64, methodArgs []interface{}) (string, error) {
+	var result = new(string)
+	err := f.BlockChain.FetchContractData(contractAbi, contractAddress, method, methodArgs, &result, blockNumber)
+
+	if err != nil {
+		return *result, newFetcherError(err, method)
+	}
+
+	return *result, nil
+}
+
+// Method used to fetch hash value from contract
+func (f Fetcher) FetchHash(method, contractAbi, contractAddress string, blockNumber int64, methodArgs []interface{}) (common.Hash, error) {
+	var result = new(common.Hash)
+	err := f.BlockChain.FetchContractData(contractAbi, contractAddress, method, methodArgs, &result, blockNumber)
+
+	if err != nil {
+		return *result, newFetcherError(err, method)
+	}
+
+	return *result, nil
+}