Init etherscan client

op-bindings/etherscan/client.go

+package etherscan
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"time"
+
+	"github.com/ethereum-optimism/optimism/op-service/retry"
+)
+
+type client struct {
+	baseUrl string
+	httpClient *http.Client
+}
+
+type apiResponse struct {
+	Status  string          `json:"status"`
+	Message string          `json:"message"`
+	Result  json.RawMessage `json:"result"`
+}
+
+type rpcResponse struct {
+	JsonRpc string          `json:"jsonrpc"`
+	Id      int             `json:"id"`
+	Result  json.RawMessage `json:"result"`
+}
+
+type TxInfo struct {
+	TxHash string `json:"txHash"`
+	To     string `json:"to"`
+	Input  string `json:"input"`
+}
+
+const apiMaxRetries = 3
+const apiRetryDelay = time.Duration(2) * time.Second
+const errRateLimited = "Max rate limit reached"
+
+func NewClient(baseUrl, apiKey string) *client {
+	return &client{
+		baseUrl: baseUrl + "/api?apikey=" + apiKey + "&",
+		httpClient: &http.Client{
+			Timeout: time.Second * 10,
+		},
+	}
+}
+
+func NewEthereumClient(apiKey string) *client {
+	return NewClient("https://api.etherscan.io", apiKey)
+}
+
+func NewOptimismClient(apiKey string) *client {
+	return NewClient("https://api-optimistic.etherscan.io", apiKey)
+}
+
+func (c *client) fetch(ctx context.Context, url string) ([]byte, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+	return body, nil
+}
+
+func (c *client) fetchEtherscanApi(ctx context.Context, url string) (apiResponse, error) {
+	return retry.Do[apiResponse](ctx, apiMaxRetries, retry.Fixed(apiRetryDelay), func() (apiResponse, error) {
+		body, err := c.fetch(ctx, url)
+		if err != nil {
+			return apiResponse{}, err
+		}
+
+		var response apiResponse
+		err = json.Unmarshal(body, &response)
+		if err != nil {
+			return apiResponse{}, fmt.Errorf("failed to unmarshal as apiResponse: %w", err)
+		}
+
+		if response.Message != "OK" {
+			var resultString string
+			err = json.Unmarshal(response.Result, &resultString)
+			if err != nil {
+				return apiResponse{}, fmt.Errorf("response for %s not OK, returned message: %s", url, response.Message)
+			}
+
+			if resultString == errRateLimited {
+				return apiResponse{}, errors.New(errRateLimited)
+			}
+
+			return apiResponse{}, fmt.Errorf("there was an issue with the Etherscan request to %s, received response: %v", url, response)
+		}
+
+		return response, nil
+	})
+}
+
+func (c *client) fetchEtherscanRpc(ctx context.Context, url string) (rpcResponse, error) {
+	return retry.Do[rpcResponse](ctx, apiMaxRetries, retry.Fixed(apiRetryDelay), func() (rpcResponse, error) {
+		body, err := c.fetch(ctx, url)
+		if err != nil {
+			return rpcResponse{}, err
+		}
+
+		var response rpcResponse
+		err = json.Unmarshal(body, &response)
+		if err != nil {
+			return rpcResponse{}, fmt.Errorf("failed to unmarshal as rpcResponse: %w", err)
+		}
+
+		var resultString string
+		_ = json.Unmarshal(response.Result, &resultString)
+		if err != nil {
+			return rpcResponse{}, fmt.Errorf("failed to unmarshal response.Result as a string: %w", err)
+		}
+		if resultString == errRateLimited {
+			return rpcResponse{}, errors.New(errRateLimited)
+		}
+
+		return response, nil
+	})
+}
+
+func (c *client) FetchAbi(ctx context.Context, address string) (string, error) {
+	params := url.Values{}
+	params.Set("address", address)
+	url := constructUrl(c.baseUrl, "getabi", "contract", params)
+	response, err := c.fetchEtherscanApi(ctx, url)
+	if err != nil {
+		return "", err
+	}
+
+	var abi string
+	err = json.Unmarshal(response.Result, &abi)
+	if err != nil {
+		return "", fmt.Errorf("API response result is not expected ABI string: %w", err)
+	}
+
+	return abi, nil
+}
+
+func (c *client) FetchDeployedBytecode(ctx context.Context, address string) (string, error) {
+	params := url.Values{}
+	params.Set("address", address)
+	url := constructUrl(c.baseUrl, "eth_getCode", "proxy", params)
+	response, err := c.fetchEtherscanRpc(ctx, url)
+	if err != nil {
+		return "", fmt.Errorf("error fetching deployed bytecode: %w", err)
+	}
+
+	var bytecode string
+	err = json.Unmarshal(response.Result, &bytecode)
+	if err != nil {
+		return "", errors.New("API response result is not expected bytecode string")
+	}
+
+	return bytecode, nil
+}
+
+func (c *client) FetchDeploymentTxHash(ctx context.Context, address string) (string, error) {
+	params := url.Values{}
+	params.Set("contractaddresses", address)
+	url := constructUrl(c.baseUrl, "getcontractcreation", "contract", params)
+	response, err := c.fetchEtherscanApi(ctx, url)
+	if err != nil {
+		return "", err
+	}
+
+	var results []TxInfo
+	err = json.Unmarshal(response.Result, &results)
+	if err != nil {
+		return "", fmt.Errorf("failed to unmarshal API response as []txInfo: %w", err)
+	}
+
+	if len(results) == 0 {
+		return "", fmt.Errorf("API response result is an empty array")
+	}
+
+	return results[0].TxHash, nil
+}
+
+func (c *client) FetchDeploymentTx(ctx context.Context, txHash string) (TxInfo, error) {
+	params := url.Values{}
+	params.Set("txHash", txHash)
+	params.Set("tag", "latest")
+	url := constructUrl(c.baseUrl, "eth_getTransactionByHash", "proxy", params)
+	response, err := c.fetchEtherscanRpc(ctx, url)
+	if err != nil {
+		return TxInfo{}, err
+	}
+
+	resultBytes, err := json.Marshal(response.Result)
+	if err != nil {
+		return TxInfo{}, fmt.Errorf("failed to marshal Result into JSON: %w", err)
+	}
+
+	var tx TxInfo
+	err = json.Unmarshal(resultBytes, &tx)
+	if err != nil {
+		return TxInfo{}, fmt.Errorf("API response result is not expected txInfo struct: %w", err)
+	}
+
+	return tx, nil
+}
+
+func constructUrl(baseUrl, action, module string, params url.Values) string {
+	params.Set("action", action)
+	params.Set("module", module)
+	queryFragment := params.Encode()
+	return baseUrl + queryFragment
+}