initial

README.md

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+# JSON-RPC 2.0
+
+Golang implementation of JSON-RPC 2.0 server with generics.
+
+Go 1.18+ required
+
+## Features:
+
+- [x] Batch request and responses
+- [ ] WebSockets 
+
+## Usage
+
+1. Create JSON-RPC 2.0 server:
+    ```go
+    s := jsonrpc2.New()
+    ```
+2. Write handler:
+    ```go
+    func Multiply(ctx context.Context, args *Args) (int, error) {
+        return args.A * args.B, nil
+    }
+    ```
+   Handler must have exact two arguments (context and input of any json serializable type) and exact two return values (output of any json serializable type and error)
+3. Wrap handler with `jsonrpc2.Wrap` method and register it in server:
+    ```go
+    s.Register("multiply", jsonrpc2.Wrap(Multiply))
+    ```
+4. Use server as common http handler:
+    ```go
+    http.ListenAndServe(":8000", s)
+    ```
+
+## Complete example
+
+[Full code](/examples/http)
+
+```go
+package main
+
+import (
+	"context"
+	"net/http"
+
+	"github.com/neonxp/rpc"
+)
+
+func main() {
+	s := jsonrpc2.New()
+	s.Register("multiply", jsonrpc2.Wrap(Multiply)) // Register handlers
+	s.Register("divide", jsonrpc2.Wrap(Divide))
+
+	http.ListenAndServe(":8000", s)
+}
+
+func Multiply(ctx context.Context, args *Args) (int, error) {
+    //...
+}
+
+func Divide(ctx context.Context, args *Args) (*Quotient, error) {
+    //...
+}
+
+type Args struct {
+	A int `json:"a"`
+	B int `json:"b"`
+}
+
+type Quotient struct {
+	Quo int `json:"quo"`
+	Rem int `json:"rem"`
+}
+
+```

errors.go

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+package jsonrpc2
+
+import "fmt"
+
+const (
+	ErrCodeParseError     = -32700
+	ErrCodeInvalidRequest = -32600
+	ErrCodeMethodNotFound = -32601
+	ErrCodeInvalidParams  = -32602
+	ErrCodeInternalError  = -32603
+	ErrUser               = -32000
+)
+
+var errorMap = map[int]string{
+	-32700: "Parse error",      // Invalid JSON was received by the server. An error occurred on the server while parsing the JSON text.
+	-32600: "Invalid Request",  // The JSON sent is not a valid Request object.
+	-32601: "Method not found", // The method does not exist / is not available.
+	-32602: "Invalid params",   // Invalid method parameter(s).
+	-32603: "Internal error",   // Internal JSON-RPC error.
+	-32000: "Other error",
+}
+
+//-32000 to -32099 	Server error 	Reserved for implementation-defined server-errors.
+
+type Error struct {
+	Code    int    `json:"code"`
+	Message string `json:"message"`
+}
+
+func (e Error) Error() string {
+	return fmt.Sprintf("jsonrpc2 error: code: %d message: %s", e.Code, e.Message)
+}
+
+func NewError(code int) Error {
+	if _, ok := errorMap[code]; ok {
+		return Error{
+			Code:    code,
+			Message: errorMap[code],
+		}
+	}
+	return Error{Code: code}
+}

examples/http/main.go

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+package main
+
+import (
+	"context"
+	"errors"
+	"net/http"
+
+	"github.com/neonxp/rpc"
+)
+
+func main() {
+	s := jsonrpc2.New()
+	s.Register("multiply", jsonrpc2.Wrap(Multiply))
+	s.Register("divide", jsonrpc2.Wrap(Divide))
+
+	http.ListenAndServe(":8000", s)
+}
+
+func Multiply(ctx context.Context, args *Args) (int, error) {
+	return args.A * args.B, nil
+}
+
+func Divide(ctx context.Context, args *Args) (*Quotient, error) {
+	if args.B == 0 {
+		return nil, errors.New("divide by zero")
+	}
+	quo := new(Quotient)
+	quo.Quo = args.A / args.B
+	quo.Rem = args.A % args.B
+	return quo, nil
+}
+
+type Args struct {
+	A int `json:"a"`
+	B int `json:"b"`
+}
+
+type Quotient struct {
+	Quo int `json:"quo"`
+	Rem int `json:"rem"`
+}

examples/http/test.http

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+POST http://localhost:8000/
+Content-Type: application/json
+
+{
+  "jsonrpc": "2.0",
+  "method": "multiply",
+  "params": {
+    "a": 2,
+    "b": 3
+  },
+  "id": 1
+}
+
+###
+
+POST http://localhost:8000/
+Content-Type: application/json
+
+{
+  "jsonrpc": "2.0",
+  "method": "divide",
+  "params": {
+    "a": 10,
+    "b": 3
+  },
+  "id": 2
+}
+
+###
+
+POST http://localhost:8000/
+Content-Type: application/json
+
+[
+  { "jsonrpc": "2.0", "method": "multiply", "params": { "a": 2, "b": 3 }, "id": 10 },
+  {"jsonrpc": "2.0", "method": "sum", "params": [1,2,4], "id": "1"},
+  {"jsonrpc": "2.0", "method": "notify_hello", "params": [7]},
+  {"jsonrpc": "2.0", "method": "subtract", "params": [42,23], "id": "2"},
+  {"foo": "boo"},
+  {"jsonrpc": "2.0", "method": "foo.get", "params": {"name": "myself"}, "id": "5"},
+  {"jsonrpc": "2.0", "method": "get_data", "id": "9"}
+]

go.mod

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+module github.com/neonxp/rpc
+
+go 1.18

logger.go

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+package jsonrpc2
+
+import "log"
+
+type Logger interface {
+	Logf(format string, args ...interface{})
+}
+
+type nopLogger struct{}
+
+func (n nopLogger) Logf(format string, args ...interface{}) {
+}
+
+type stdLogger struct{}
+
+func (n stdLogger) Logf(format string, args ...interface{}) {
+	log.Printf(format, args...)
+}
+
+var StdLogger = stdLogger{}

server.go

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+package jsonrpc2
+
+import (
+	"bufio"
+	"context"
+	"encoding/json"
+	"io"
+	"net/http"
+	"sync"
+)
+
+const version = "2.0"
+
+type Server struct {
+	Logger              Logger
+	IgnoreNotifications bool
+	handlers            map[string]Handler
+	mu                  sync.RWMutex
+}
+
+func (r *Server) ServeHTTP(writer http.ResponseWriter, request *http.Request) {
+	writer.Header().Set("Content-Type", "application/json")
+	buf := bufio.NewReader(request.Body)
+	defer request.Body.Close()
+	firstByte, err := buf.Peek(1)
+	if err != nil {
+		r.Logger.Logf("Can't read body: %v", err)
+		writeError(ErrCodeParseError, writer)
+		return
+	}
+	if string(firstByte) == "[" {
+		r.batchRequest(writer, request, buf)
+		return
+	}
+	r.singleRequest(writer, request, buf)
+}
+
+func New() *Server {
+	return &Server{
+		Logger:              nopLogger{},
+		IgnoreNotifications: true,
+		handlers:            map[string]Handler{},
+		mu:                  sync.RWMutex{},
+	}
+}
+
+func (r *Server) Register(method string, handler Handler) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.handlers[method] = handler
+}
+
+func (r *Server) singleRequest(writer http.ResponseWriter, request *http.Request, buf *bufio.Reader) {
+	req := new(rpcRequest)
+	if err := json.NewDecoder(buf).Decode(req); err != nil {
+		r.Logger.Logf("Can't read body: %v", err)
+		writeError(ErrCodeParseError, writer)
+		return
+	}
+	resp := r.callMethod(request.Context(), req)
+	if req.Id == nil && r.IgnoreNotifications {
+		// notification request
+		return
+	}
+	if err := json.NewEncoder(writer).Encode(resp); err != nil {
+		r.Logger.Logf("Can't write response: %v", err)
+		writeError(ErrCodeInternalError, writer)
+		return
+	}
+}
+
+func (r *Server) batchRequest(writer http.ResponseWriter, request *http.Request, buf *bufio.Reader) {
+	var req []rpcRequest
+	if err := json.NewDecoder(buf).Decode(&req); err != nil {
+		r.Logger.Logf("Can't read body: %v", err)
+		writeError(ErrCodeParseError, writer)
+		return
+	}
+	var responses []*rpcResponse
+	wg := sync.WaitGroup{}
+	wg.Add(len(req))
+	for _, j := range req {
+		go func(req rpcRequest) {
+			defer wg.Done()
+			resp := r.callMethod(request.Context(), &req)
+			if req.Id == nil && r.IgnoreNotifications {
+				// notification request
+				return
+			}
+			responses = append(responses, resp)
+		}(j)
+	}
+	wg.Wait()
+	if err := json.NewEncoder(writer).Encode(responses); err != nil {
+		r.Logger.Logf("Can't write response: %v", err)
+		writeError(ErrCodeInternalError, writer)
+	}
+}
+
+func (r *Server) callMethod(ctx context.Context, req *rpcRequest) *rpcResponse {
+	r.mu.RLock()
+	h, ok := r.handlers[req.Method]
+	r.mu.RUnlock()
+	if !ok {
+		return &rpcResponse{
+			Jsonrpc: version,
+			Error:   NewError(ErrCodeMethodNotFound),
+			Id:      req.Id,
+		}
+	}
+	resp, err := h(ctx, req.Params)
+	if err != nil {
+		r.Logger.Logf("User error %v", err)
+		return &rpcResponse{
+			Jsonrpc: version,
+			Error:   err,
+			Id:      req.Id,
+		}
+	}
+	return &rpcResponse{
+		Jsonrpc: version,
+		Result:  resp,
+		Id:      req.Id,
+	}
+}
+
+func writeError(code int, w io.Writer) {
+	_ = json.NewEncoder(w).Encode(rpcResponse{
+		Jsonrpc: version,
+		Error:   NewError(code),
+	})
+}
+
+type rpcRequest struct {
+	Jsonrpc string          `json:"jsonrpc"`
+	Method  string          `json:"method"`
+	Params  json.RawMessage `json:"params"`
+	Id      any             `json:"id"`
+}
+
+type rpcResponse struct {
+	Jsonrpc string          `json:"jsonrpc"`
+	Result  json.RawMessage `json:"result,omitempty"`
+	Error   error           `json:"error,omitempty"`
+	Id      any             `json:"id,omitempty"`
+}

wrapper.go

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+package jsonrpc2
+
+import (
+	"context"
+	"encoding/json"
+)
+
+func Wrap[RQ any, RS any](handler func(context.Context, *RQ) (RS, error)) Handler {
+	return func(ctx context.Context, in json.RawMessage) (json.RawMessage, error) {
+		req := new(RQ)
+		if err := json.Unmarshal(in, req); err != nil {
+			return nil, NewError(ErrCodeParseError)
+		}
+		resp, err := handler(ctx, req)
+		if err != nil {
+			return nil, Error{
+				Code:    ErrUser,
+				Message: err.Error(),
+			}
+		}
+		return json.Marshal(resp)
+	}
+}
+
+type Handler func(context.Context, json.RawMessage) (json.RawMessage, error)