Develop (#250)

lib/event/manager.go

@@ -0,0 +1,152 @@
+package event
+
+import (
+	"fmt"
+	"sync"
+	"github.com/wailsapp/wails/lib/logger"
+	"github.com/wailsapp/wails/lib/messages"
+	"github.com/wailsapp/wails/lib/interfaces"
+)
+
+// Manager handles and processes events
+type Manager struct {
+	incomingEvents chan *messages.EventData
+	listeners      map[string][]*eventListener
+	exit           bool
+	log            *logger.CustomLogger
+	renderer       interfaces.Renderer // Messages will be dispatched to the frontend
+}
+
+// NewManager creates a new event manager with a 100 event buffer
+func NewManager() interfaces.EventManager {
+	return &Manager{
+		incomingEvents: make(chan *messages.EventData, 100),
+		listeners:      make(map[string][]*eventListener),
+		exit:           false,
+		log:            logger.NewCustomLogger("Events"),
+	}
+}
+
+// PushEvent places the given event on to the event queue
+func (e *Manager) PushEvent(eventData *messages.EventData) {
+	e.incomingEvents <- eventData
+}
+
+// eventListener holds a callback function which is invoked when
+// the event listened for is emitted. It has a counter which indicates
+// how the total number of events it is interested in. A value of zero
+// means it does not expire (default).
+type eventListener struct {
+	callback func(...interface{}) // Function to call with emitted event data
+	counter  int                  // Expire after counter callbacks. 0 = infinite
+	expired  bool                 // Indicates if the listener has expired
+}
+
+// Creates a new event listener from the given callback function
+func (e *Manager) addEventListener(eventName string, callback func(...interface{}), counter int) error {
+
+	// Sanity check inputs
+	if callback == nil {
+		return fmt.Errorf("nil callback bassed to addEventListener")
+	}
+
+	// Check event has been registered before
+	if e.listeners[eventName] == nil {
+		e.listeners[eventName] = []*eventListener{}
+	}
+
+	// Create the callback
+	listener := &eventListener{
+		callback: callback,
+		counter:  counter,
+	}
+
+	// Register listener
+	e.listeners[eventName] = append(e.listeners[eventName], listener)
+
+	// All good mate
+	return nil
+}
+
+// On adds a listener for the given event
+func (e *Manager) On(eventName string, callback func(...interface{})) {
+	// Add a persistent eventListener (counter = 0)
+	e.addEventListener(eventName, callback, 0)
+}
+
+// Emit broadcasts the given event to the subscribed listeners
+func (e *Manager) Emit(eventName string, optionalData ...interface{}) {
+	e.incomingEvents <- &messages.EventData{Name: eventName, Data: optionalData}
+}
+
+// Start the event manager's queue processing
+func (e *Manager) Start(renderer interfaces.Renderer) {
+
+	e.log.Info("Starting")
+
+	// Store renderer
+	e.renderer = renderer
+
+	// Set up waitgroup so we can wait for goroutine to start
+	var wg sync.WaitGroup
+	wg.Add(1)
+
+	// Run main loop in separate goroutine
+	go func() {
+		wg.Done()
+		e.log.Info("Listening")
+		for e.exit == false {
+			// TODO: Listen for application exit
+			select {
+			case event := <-e.incomingEvents:
+				e.log.DebugFields("Got Event", logger.Fields{
+					"data": event.Data,
+					"name": event.Name,
+				})
+
+				// Notify renderer
+				e.renderer.NotifyEvent(event)
+
+				// Notify Go listeners
+				var listenersToRemove []*eventListener
+
+				// Iterate listeners
+				for _, listener := range e.listeners[event.Name] {
+
+					// Call listener, perhaps with data
+					if event.Data == nil {
+						go listener.callback()
+					} else {
+						unpacked := event.Data.([]interface{})
+						go listener.callback(unpacked...)
+					}
+
+					// Update listen counter
+					if listener.counter > 0 {
+						listener.counter = listener.counter - 1
+						if listener.counter == 0 {
+							listener.expired = true
+						}
+					}
+				}
+
+				// Remove expired listeners in place
+				if len(listenersToRemove) > 0 {
+					listeners := e.listeners[event.Name][:0]
+					for _, listener := range listeners {
+						if !listener.expired {
+							listeners = append(listeners, listener)
+						}
+					}
+				}
+			}
+		}
+	}()
+
+	// Wait for goroutine to start
+	wg.Wait()
+}
+
+func (e *Manager) stop() {
+	e.exit = true
+}