wsrpc/clientctx.go

// Client handler
package wsrpc

import (
	"errors"
	"log"
	"reflect"
	"strings"
	"sync"

	"github.com/google/uuid"
	"golang.org/x/net/websocket"
)

var (
	ErrNParam            = errors.New("Invalid number of parameters")
	ErrNReturn           = errors.New("Number of outputs mismatch")
	ErrBadImplementation = errors.New("Bad implementation")

	errorInterface = reflect.TypeOf((*error)(nil)).Elem()
)

// Call object
type CallObj struct {
	OP     string `json:"op"`     // operation
	ID     string `json:"id"`     // Id of the call
	Method string `json:"method"` // could be param 0 instead?

	Params   []interface{} `json:"params"`
	Response interface{}   `json:"response"`
}

// DataObj common structure for dymanic json object
//type DataObj map[string]interface{}

// ListenerFunc function type to handle browser events
type ListenerFunc func(...interface{}) (interface{}, error)

// Request request type for handling requests channels

// ClientCtx main client struct
type ClientCtx struct {
	locker sync.Mutex

	WS *websocket.Conn
	// stuff
	listeners map[string]ListenerFunc
	requests  map[string]chan interface{}
}

//NewHandler creates a new WsRPC client handler
func NewHandler(id string, ws *websocket.Conn) *ClientCtx {
	var c = ClientCtx{
		WS:        ws,
		listeners: map[string]ListenerFunc{},
		requests:  map[string]chan interface{}{},
	}
	return &c
}

// Process messages
func (c *ClientCtx) Process(data CallObj) {
	switch data.OP {
	case "call":
		params := data.Params
		var idn = data.Method
		var reqID = data.ID
		var fn, ok = c.listeners[idn]
		if !ok {
			return
		}
		go func() { // async send
			ret, err := fn(params...)
			if err != nil {
				log.Println("Create error response, panic?")
			}
			var responseObj = CallObj{
				OP:       "response",
				ID:       reqID,
				Response: ret,
			}
			//log.Println("Sending response")
			websocket.JSON.Send(c.WS, responseObj)
		}()
	case "response":
		c.locker.Lock()
		mchan, ok := c.requests[data.ID]
		delete(c.requests, data.ID)
		c.locker.Unlock()
		if ok {
			mchan <- data.Response
		}
	}
}

// Call a client method and estabilishes a request id
func (c *ClientCtx) Call(method string, params ...interface{}) interface{} {
	u := uuid.New()
	uuidStr := u.String()

	var callObj = CallObj{
		OP:     "call",
		ID:     uuidStr,
		Method: method,
		Params: params,
	}

	res := make(chan interface{}, 1)
	c.locker.Lock()
	c.requests[uuidStr] = res
	c.locker.Unlock()
	websocket.JSON.Send(c.WS, &callObj)

	return <-res // Block until value
}

//On add a event listener on browser
func (c *ClientCtx) Define(name string, listener ListenerFunc) {
	c.listeners[name] = listener
}

func (c *ClientCtx) Export(obj interface{}) {
	// Reflect here
	typ := reflect.TypeOf(obj)
	val := reflect.ValueOf(obj)

	for i := 0; i < typ.NumField(); i++ {
		fTyp := typ.Field(i)
		if fTyp.Type.Kind() != reflect.Func {
			log.Println("Ignore non func value")
			continue
		}
		tag, ok := fTyp.Tag.Lookup("wsexport")
		if !ok {
			continue
		}
		tagParts := strings.Split(tag, ",")

		exportName := tagParts[0]
		fnVal := val.Field(i)
		// Slow?
		c.listeners[exportName] = func(params ...interface{}) (interface{}, error) {
			if len(params) != fnVal.Type().NumIn() {
				return nil, ErrNParam
			}
			if fnVal.Type().NumOut() != 2 {
				return nil, ErrNReturn
			}
			if !fnVal.Type().Out(1).Implements(errorInterface) {
				return nil, ErrBadImplementation

			}

			vparam := []reflect.Value{}
			for _, p := range params {
				vparam = append(vparam, reflect.ValueOf(p))
			}
			r := fnVal.Call(vparam)
			return r[0].Interface(), r[1].Interface().(error)
		}

		// It is a func, check for tag
	}

}