steem-block-db/jsonrpc.go

package main

// thanks to https://github.com/onrik/ethrpc/blob/master/ethrpc.go for
// example

import (
	"bytes"
	"encoding/json"
	"fmt"
	log "github.com/sirupsen/logrus"
	"io"
	"io/ioutil"
	"net/http"
	"time"
)

type httpRPCClient interface {
	Post(url string, contentType string, body io.Reader) (*http.Response, error)
}

type JSONRPCError struct {
	Code    int    `json:"code"`
	Message string `json:"message"`
}

func (err JSONRPCError) Error() string {
	return fmt.Sprintf("Error %d (%s)", err.Code, err.Message)
}

type JSONRPCResponse struct {
	ID      string          `json:"id"`
	JSONRPC string          `json:"jsonrpc"`
	Result  json.RawMessage `json:"result"`
	Error   *JSONRPCError   `json:"error"`
}

type JSONRPCRequest struct {
	ID      string          `json:"id"`
	JSONRPC string          `json:"jsonrpc"`
	Method  string          `json:"method"`
	Params  json.RawMessage `json:"params"`
}

type JSONRPC struct {
	url    string
	client httpRPCClient
}

// New create new rpc client with given url
func NewJSONRPC(url string, options ...func(rpc *JSONRPC)) *JSONRPC {

	netClient := &http.Client{
		Timeout: time.Second * 20,
	}

	rpc := &JSONRPC{
		url:    url,
		client: netClient,
	}
	for _, option := range options {
		option(rpc)
	}

	return rpc
}

// Call returns raw response of method call
func (rpc *JSONRPC) Call(method string, params json.RawMessage) (json.RawMessage, error) {
	request := JSONRPCRequest{
		ID:      "1",
		JSONRPC: "2.0",
		Method:  method,
		Params:  params,
	}

	body, err := json.Marshal(request)
	if err != nil {
		return nil, err
	}

	response, err := rpc.client.Post(rpc.url, "application/json", bytes.NewBuffer(body))
	if response != nil {
		defer response.Body.Close()
	}
	if err != nil {
		log.Infof("jsonrpc error: %v", err)
		return nil, err
	}

	data, err := ioutil.ReadAll(response.Body)
	if err != nil {
		return nil, err
	}

	log.Debugf("%s", method)
	log.Debugf("Request: %s", body)
	log.Debugf("Response: %s", data)

	resp := new(JSONRPCResponse)
	if err := json.Unmarshal(data, resp); err != nil {
		return nil, err
	}

	if resp.Error != nil {
		return nil, *resp.Error
	}

	return resp.Result, nil

}