package main

import (
    "encoding/json"
    "errors"
    "os"

    "github.com/bitwurx/jrpc2"
)

// This struct is used for unmarshaling the method params
type AddParams struct {
    X *float64 `json:"x"`
    Y *float64 `json:"y"`
}

// Each params struct must implement the FromPositional method.
// This method will be passed an array of interfaces if positional parameters
// are passed in the rpc call
func (ap *AddParams) FromPositional(params []interface{}) error {
    if len(params) != 2 {
        return errors.New("exactly two integers are required")
    }

    x := params[0].(float64)
    y := params[1].(float64)
    ap.X = &x
    ap.Y = &y

    return nil
}

// Each method should match the prototype <fn(json.RawMessage) (inteface{}, *ErrorObject)>
func Add(params json.RawMessage) (interface{}, *jrpc2.ErrorObject) {
    p := new(AddParams)

    // ParseParams is a helper function that automatically invokes the FromPositional
    // method on the params instance if required
    if err := jrpc2.ParseParams(params, p); err != nil {
        return nil, err
    }

    if p.X == nil || p.Y == nil {
        return nil, &jrpc2.ErrorObject{
            Code:    jrpc2.InvalidParamsCode,
            Message: jrpc2.InvalidParamsMsg,
            Data:    "exactly two integers are required",
        }
    }

    return *p.X + *p.Y, nil
}

func main() {
    // create a new server instance
    s := jrpc2.NewServer(":8888", "/api/v1/rpc")

    // register the add method
    s.Register("add", jrpc2.Method{Method: Add})

    // register the subtract method to proxy another rpc server
    // s.Register("add", jrpc2.Method{Url: "http://localhost:9999/api/v1/rpc"})

    // start the server instance
    s.Start()
}