package jsonrpc

import (
	"encoding/json"
	"io"
	"net/http"

	"github.com/gorilla/websocket"
)

const (
	rpcParseError     = -32700
	rpcMethodNotFound = -32601
	rpcInvalidParams  = -32602
)

// RPCServer provides a jsonrpc 2.0 http server handler
type RPCServer struct {
	methods handlers
}

// NewServer creates new RPCServer instance
func NewServer() *RPCServer {
	return &RPCServer{
		methods: map[string]rpcHandler{},
	}
}

var upgrader = websocket.Upgrader{}

func (s *RPCServer) handleWS(w http.ResponseWriter, r *http.Request) {
	c, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Error(err)
		w.WriteHeader(500)
		return
	}
	defer c.Close()

	handleWsConn(r.Context(), c, s.methods, nil, nil)
}

// TODO: return errors to clients per spec
func (s *RPCServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if r.Header.Get("Connection") == "Upgrade" {
		s.handleWS(w, r)
		return
	}

	s.methods.handleReader(r.Context(), r.Body, w, s.rpcError)
}

func (s *RPCServer) rpcError(w io.Writer, req *request, code int, err error) {
	w.(http.ResponseWriter).WriteHeader(500)
	if req.ID == nil { // notification
		return
	}

	resp := response{
		Jsonrpc: "2.0",
		ID:      *req.ID,
		Error: &respError{
			Code:    code,
			Message: err.Error(),
		},
	}

	_ = json.NewEncoder(w).Encode(resp)
}

// Register registers new RPC handler
//
// Handler is any value with methods defined
func (s *RPCServer) Register(namespace string, handler interface{}) {
	s.methods.register(namespace, handler)
}

var _ error = &respError{}