json rpc 2.0

main.go

package main

import (
	"log"
	"encoding/json"
	"errors"
	"net/http"
)

const JSONRPCVersion = "2.0"

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

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

type Method string

type JSONRPCServer struct {
	Endpoints map[Method]JSONRPCEndpoint
}

func NewJSONRPCServer() *JSONRPCServer {
	return &JSONRPCServer{
		Endpoints: make(map[Method]JSONRPCEndpoint),
	}
}

type JSONRPCEndpoint func(req JSONRPCRequest) JSONRPCResponse

func (s *JSONRPCServer) addEndpoint(method Method, endpoint JSONRPCEndpoint) {
	s.Endpoints[method] = endpoint
}

func (s *JSONRPCServer) getEndpoint(method Method) (JSONRPCEndpoint, error) {
	e, ok := s.Endpoints[method]
	if !ok {
		return nil, errors.New("method not allowed")
	}
	return e, nil
}

func main() {
	server := NewJSONRPCServer()
	server.addEndpoint("ping", func(req JSONRPCRequest) JSONRPCResponse {
		return JSONRPCResponse{
			JSONRPC:JSONRPCVersion,
			Result:"pong",
			ID:req.ID,
		}
	})

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			w.WriteHeader(http.StatusMethodNotAllowed)
			return
		}
		var j JSONRPCRequest
		if r.Body == nil {
			http.Error(w, "please send a JSON RPC 2.0 request", http.StatusBadRequest)
			return
		}
		err := json.NewDecoder(r.Body).Decode(&j)
		if err != nil {
			http.Error(w, err.Error(), 400)
			return
		}
		if j.JSONRPC != JSONRPCVersion {
			http.Error(w, "please send a JSON RPC 2.0 request", http.StatusBadRequest)
			return
		}

		e, err := server.getEndpoint(j.Method)
		if err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
		}
		res := e(j)
		json.NewEncoder(w).Encode(res)
	})
	log.Fatal(http.ListenAndServe(":8001", nil))
}