# README

zenrpc: JSON-RPC 2.0 Server Implementation with SMD support

zenrpc is a JSON-RPC 2.0 server library with Service Mapping Description support. It's built on top of go generate instead of reflection.

How to Use

Service is struct with RPC methods, service represents RPC namespace.

Install zenrpc generator go get github.com/semrush/zenrpc/v2/zenrpc
Import github.com/semrush/zenrpc/v2 into our code with rpc service.
Add trailing comment //zenrpc to your service or embed zenrpc.Service into your service struct.
Write your funcs almost as usual.
Do not forget run go generate or zenrpc for magic

Accepted Method Signatures

func(Service) Method([args]) (<value>, <error>)
func(Service) Method([args]) <value>
func(Service) Method([args]) <error>
func(Service) Method([args])

Value could be a pointer
Error is error or *zenrpc.Error

Example

package main

import (
	"flag"
	"context"
	"errors"
	"math"
	"log"
	"net/http"
	"os"	
	
	"github.com/semrush/zenrpc/v2"
	"github.com/semrush/zenrpc/v2/testdata"
)

type ArithService struct{ zenrpc.Service }

// Sum sums two digits and returns error with error code as result and IP from context.
func (as ArithService) Sum(ctx context.Context, a, b int) (bool, *zenrpc.Error) {
	r, _ := zenrpc.RequestFromContext(ctx)

	return true, zenrpc.NewStringError(a+b, r.Host)
}

// Multiply multiples two digits and returns result.
func (as ArithService) Multiply(a, b int) int {
	return a * b
}

type Quotient struct {
	Quo, Rem int
}

func (as ArithService) Divide(a, b int) (quo *Quotient, err error) {
	if b == 0 {
		return nil, errors.New("divide by zero")
	} else if b == 1 {
		return nil, zenrpc.NewError(401, errors.New("we do not serve 1"))
	}

	return &Quotient{
		Quo: a / b,
		Rem: a % b,
	}, nil
}

// Pow returns x**y, the base-x exponential of y. If Exp is not set then default value is 2.
//zenrpc:exp=2
func (as ArithService) Pow(base float64, exp float64) float64 {
	return math.Pow(base, exp)
}

//go:generate zenrpc

func main() {
	addr := flag.String("addr", "localhost:9999", "listen address")
	flag.Parse()

	rpc := zenrpc.NewServer(zenrpc.Options{ExposeSMD: true})
	rpc.Register("arith", testdata.ArithService{})
	rpc.Register("", testdata.ArithService{}) // public
	rpc.Use(zenrpc.Logger(log.New(os.Stderr, "", log.LstdFlags)))

	http.Handle("/", rpc)

	log.Printf("starting arithsrv on %s", *addr)
	log.Fatal(http.ListenAndServe(*addr, nil))
}

Magic comments

All comments are optional.

Method comments
//zenrpc:<method parameter>[=<default value>][whitespaces<description>]
//zenrpc:<error code>[whitespaces<description>]
//zenrpc:return[whitespaces<description>]
 
Struct comments
type MyService struct {} //zenrpc