127 lines
3.5 KiB
Go
127 lines
3.5 KiB
Go
package event
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import (
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"git.openprivacy.ca/openprivacy/libricochet-go/log"
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"git.openprivacy.ca/openprivacy/libricochet-go/utils"
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"sync"
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)
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// Event is a structure which binds a given set of data to an Type
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type Event struct {
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EventType Type
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EventID string
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Data map[Field]string
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}
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// NewEvent creates a new event object with a unique ID and the given type and data.
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func NewEvent(eventType Type, data map[Field]string) Event {
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return Event{EventType: eventType, EventID: utils.GetRandNumber().String(), Data: data}
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}
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// NewEventList creates a new event object with a unique ID and the given type and data supplied in a list format and composed into a map of Type:string
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func NewEventList(eventType Type, args ...interface{}) Event {
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data := map[Field]string{}
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for i := 0; i < len(args); i += 2 {
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key, kok := args[i].(Field)
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val, vok := args[i+1].(string)
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if kok && vok {
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data[key] = val
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}
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}
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return Event{EventType: eventType, EventID: utils.GetRandNumber().String(), Data: data}
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}
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// Manager is an Event Bus which allows subsystems to subscribe to certain EventTypes and publish others.
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type manager struct {
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subscribers map[Type][]chan Event
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events chan Event
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mapMutex sync.Mutex
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internal chan bool
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closed bool
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}
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// Manager is an interface for an event bus
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type Manager interface {
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Subscribe(Type, chan Event)
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Publish(Event)
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PublishLocal(Event)
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Shutdown()
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}
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// NewEventManager returns an initialized EventManager
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func NewEventManager() Manager {
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em := &manager{}
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em.initialize()
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return em
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}
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// Initialize sets up the Manager.
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func (em *manager) initialize() {
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em.subscribers = make(map[Type][]chan Event)
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em.events = make(chan Event)
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em.internal = make(chan bool)
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em.closed = false
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go em.eventBus()
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}
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// Subscribe takes an eventType and an Channel and associates them in the eventBus. All future events of that type
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// will be sent to the eventChannel.
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func (em *manager) Subscribe(eventType Type, eventChannel chan Event) {
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em.mapMutex.Lock()
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defer em.mapMutex.Unlock()
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em.subscribers[eventType] = append(em.subscribers[eventType], eventChannel)
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}
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// Publish takes an Event and sends it to the internal eventBus where it is distributed to all Subscribers
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func (em *manager) Publish(event Event) {
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if event.EventType != "" && em.closed != true {
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em.events <- event
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}
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}
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// Publish an event only locally, not going over an IPC bridge if there is one
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func (em *manager) PublishLocal(event Event) {
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em.Publish(event)
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}
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// eventBus is an internal function that is used to distribute events to all subscribers
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func (em *manager) eventBus() {
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for {
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event := <-em.events
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// In the case on an empty event. Teardown the Queue
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if event.EventType == "" {
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break
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}
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// maps aren't thread safe
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em.mapMutex.Lock()
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subscribers := em.subscribers[event.EventType]
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em.mapMutex.Unlock()
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// Send the event to any subscribers to that event type
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for _, subscriber := range subscribers {
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select {
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case subscriber <- event:
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log.Debugf("Sending %v to %v", event.EventType, subscriber)
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default:
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log.Errorf("Failed to send %v to %v. The subsystem might be running too slow!", event.EventType, subscriber)
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}
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}
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}
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// We are about to exit the eventbus thread, fire off an event internally
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em.internal <- true
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}
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// Shutdown triggers, and waits for, the internal eventBus goroutine to finish
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func (em *manager) Shutdown() {
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em.events <- Event{}
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em.closed = true
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// wait for eventBus to finish
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<-em.internal
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close(em.events)
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close(em.internal)
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}
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