streamdeck-obs-replay/slobs/client.go

package slobs

import (
	"encoding/json"
	"errors"
	"github.com/dchest/uniuri"
	"github.com/gorilla/websocket"
	"log"
	"math/rand"
	"net/http"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"
)

type SubscriptionHandler func(*ResourceEvent)
type ResponseHandler func(*RPCResponse)

const (
	Event        = "EVENT"
	Subscription = "SUBSCRIPTION"
)

var (
	ErrNoRequest = errors.New("request not found")
	ErrNoHandler = errors.New("handler not found")
)

type Client struct {
	conn      *websocket.Conn
	connected bool

	Address string

	requestId   int32
	requests    map[int]ResponseHandler
	requestLock sync.RWMutex

	subscriptions    map[string]SubscriptionHandler
	subscriptionLock sync.RWMutex
}

func NewClient(address string) *Client {
	return &Client{
		Address:       address,
		requests:      make(map[int]ResponseHandler),
		subscriptions: make(map[string]SubscriptionHandler),
	}
}

func (c *Client) Connected() bool {
	return c.connected
}

func (c *Client) Connect() error {
	if c.connected {
		return errors.New("already connected")
	}

	endpoint := "ws://" + c.Address + "/api/" + paddedRandomIntn(999) + "/" + uniuri.New() + "/websocket"

	var err error

	c.conn, _, err = websocket.DefaultDialer.Dial(endpoint, http.Header{})

	if err != nil {
		return err
	}

	_, data, err := c.conn.ReadMessage()

	if err != nil {
		return err
	}

	if data[0] != 'o' {
		return errors.New("invalid initial message")
	}

	c.connected = true

	go c.loop()

	return nil
}

func (c *Client) Disconnect() error {
	return c.conn.Close()
}

func (c *Client) Subscribe(resource, method string, handler SubscriptionHandler) {
	c.SendRPC(resource, method, func(response *RPCResponse) {
		res := &ResourceEvent{}

		json.Unmarshal(*response.Result, &res)

		c.subscriptionLock.Lock()
		c.subscriptions[res.ResourceId] = handler
		c.subscriptionLock.Unlock()
	})
}

func (c *Client) SendRPC(resource, method string, handler ResponseHandler) error {
	m := make(map[string]interface{})

	m["resource"] = resource
	m["args"] = []string{}

	atomic.AddInt32(&c.requestId, 1)

	newRequestId := int(atomic.LoadInt32(&c.requestId))

	request := &RPCRequest{
		ID:      newRequestId,
		Method:  method,
		Params:  m,
		JSONRPC: "2.0",
	}

	b, err := json.Marshal(request)

	if err != nil {
		return err
	}

	if handler != nil {
		c.requestLock.Lock()
		c.requests[newRequestId] = handler
		c.requestLock.Unlock()
	}

	return c.conn.WriteJSON([]string{string(b) + "\n"})
}

func (c *Client) loop() error {
	for {
		_, data, err := c.conn.ReadMessage()

		if err != nil {
			c.connected = false
			return err
		}

		if len(data) < 1 {
			continue
		}

		switch data[0] {
		case 'h':
			// Heartbeat
			continue
		case 'a':
			// Normal message
			arr := make([]string, 0)
			err := json.Unmarshal(data[1:], &arr)

			if err != nil {
				continue
			}

			for _, message := range arr {
				resp := &RPCResponse{}

				message = strings.TrimSpace(message)

				log.Println("Handling", message)

				err = json.Unmarshal([]byte(message), &resp)

				if err != nil {
					continue
				}

				go c.handle(resp)
			}
		case 'c':
			// Session closed
			var v []interface{}
			if err := json.Unmarshal(data[1:], &v); err != nil {
				log.Printf("Closing session: %s", err)
				return nil
			}
			break
		default:
			log.Println("Unknown:", data[0])
		}
	}
}

func (c *Client) handle(resp *RPCResponse) error {
	if resp.ID != nil {
		c.requestLock.RLock()
		h, ok := c.requests[*resp.ID]
		c.requestLock.RUnlock()

		if !ok {
			return ErrNoRequest
		}

		h(resp)

		c.requestLock.Lock()
		delete(c.requests, *resp.ID)
		c.requestLock.Unlock()
		return nil
	}

	res := &ResourceEvent{}

	err := json.Unmarshal(*resp.Result, &res)

	if err != nil {
		return err
	}

	switch res.Type {
	case Event:
		c.subscriptionLock.RLock()
		h, exists := c.subscriptions[res.ResourceId]
		c.subscriptionLock.RUnlock()

		if !exists {
			return ErrNoHandler
		}

		h(res)
	}

	return nil
}

func paddedRandomIntn(max int) string {
	var (
		ml = len(strconv.Itoa(max))
		ri = rand.Intn(max)
		is = strconv.Itoa(ri)
	)

	if len(is) < ml {
		is = strings.Repeat("0", ml-len(is)) + is
	}

	return is
}