Added mutexes to writes

bus.go

@@ -1,5 +1,7 @@
 package events
 
+import "sync"
+
 type Bus struct {
 	topics map[string]*topic
 }
@@ -8,11 +10,11 @@ func New() *Bus {
 	return &Bus{topics: make(map[string]*topic)}
 }
 
-func (d *Bus) On(event string, receiver interface{}) {
+func (d *Bus) On(event string, receiver interface{}) *Subscription {
 	// TODO: make thread safe
 	t, hasTopic := d.topics[event]
 	if !hasTopic {
-		t = &topic{}
+		t = &topic{mutex: sync.Mutex{}, head: nil, tail: nil}
 		d.topics[event] = t
 	}
 
@@ -22,6 +24,7 @@ func (d *Bus) On(event string, receiver interface{}) {
 	}
 
 	t.addSubscriber(sub)
+	return sub
 }
 
 func (d *Bus) Fire(event string, args ...interface{}) {
@@ -37,9 +40,30 @@ func (d *Bus) TryFire(event string, args ...interface{}) error {
 
 	preparedArgs := prepareArgs(args)
 
+	topic.mutex.Lock()
+	var head = topic.head
+	topic.mutex.Unlock()
+
 	var errs []error
 
-	for sub := topic.head; sub != nil; sub = sub.next {
+	var lastSub *Subscription = nil
+	for sub := head; sub != nil; sub = sub.next {
+		// Remove unsubscribers
+		if sub.remove {
+			topic.mutex.Lock()
+			if lastSub == nil {
+				topic.head = sub.next
+			} else {
+				lastSub.next = sub.next
+			}
+			if topic.tail == sub {
+				topic.tail = lastSub
+			}
+			topic.mutex.Unlock()
+			continue
+		}
+		lastSub = sub
+
 		err := sub.handler.invoke(preparedArgs)
 		if err != nil {
 			errs = append(errs, err)
@@ -56,11 +80,16 @@ func (d *Bus) TryFire(event string, args ...interface{}) error {
 }
 
 type topic struct {
-	head *subscription
-	tail *subscription
+	// mutex protects writes to the head and tail
+	mutex sync.Mutex
+	head  *Subscription
+	tail  *Subscription
 }
 
-func (t *topic) addSubscriber(sub *subscription) {
+func (t *topic) addSubscriber(sub *Subscription) {
+	t.mutex.Lock()
+	defer t.mutex.Unlock()
+
 	if t.head == nil {
 		t.head = sub
 	}
@@ -70,15 +99,20 @@ func (t *topic) addSubscriber(sub *subscription) {
 	t.tail = sub
 }
 
-type subscription struct {
+type Subscription struct {
+	remove  bool
 	handler receiptHandler
-	next    *subscription
+	next    *Subscription
 }
 
-func newSubscriptionFromFunc(fn interface{}) (*subscription, error) {
+func newSubscriptionFromFunc(fn interface{}) (*Subscription, error) {
 	handler, err := newReceiptHandler(fn)
 	if err != nil {
 		return nil, err
 	}
-	return &subscription{handler: handler, next: nil}, nil
+	return &Subscription{handler: handler, next: nil}, nil
+}
+
+func (s *Subscription) Unsubscribe() {
+	s.remove = true
 }

bus_test.go

@@ -52,6 +52,116 @@ func TestFire(t *testing.T) {
 	})
 }
 
+func TestUnsubscribe(t *testing.T) {
+	t.Run("should remove subscription 1", func(t *testing.T) {
+		fired := make([]int, 3)
+
+		d := New()
+		s1 := d.On("event", func() { fired[0]++ })
+		s2 := d.On("event", func() { fired[1]++ })
+		s3 := d.On("event", func() { fired[2]++ })
+
+		d.Fire("event")
+		assert.Equal(t, []int{1, 1, 1}, fired)
+
+		s1.Unsubscribe()
+		d.Fire("event")
+		assert.Equal(t, []int{1, 2, 2}, fired)
+
+		s2.Unsubscribe()
+		d.Fire("event")
+		assert.Equal(t, []int{1, 2, 3}, fired)
+
+		s3.Unsubscribe()
+		d.Fire("event")
+		assert.Equal(t, []int{1, 2, 3}, fired)
+	})
+
+	t.Run("should remove subscription 2", func(t *testing.T) {
+		fired := make([]int, 3)
+
+		d := New()
+		s1 := d.On("event", func() { fired[0]++ })
+		s2 := d.On("event", func() { fired[1]++ })
+		s3 := d.On("event", func() { fired[2]++ })
+
+		d.Fire("event")
+		assert.Equal(t, []int{1, 1, 1}, fired)
+
+		s3.Unsubscribe()
+		d.Fire("event")
+		assert.Equal(t, []int{2, 2, 1}, fired)
+
+		s2.Unsubscribe()
+		d.Fire("event")
+		assert.Equal(t, []int{3, 2, 1}, fired)
+
+		s1.Unsubscribe()
+		d.Fire("event")
+		assert.Equal(t, []int{3, 2, 1}, fired)
+	})
+
+	t.Run("should remove subscription 3", func(t *testing.T) {
+		fired := make([]int, 3)
+
+		d := New()
+		s1 := d.On("event", func() { fired[0]++ })
+		s2 := d.On("event", func() { fired[1]++ })
+		s3 := d.On("event", func() { fired[2]++ })
+
+		d.Fire("event")
+		assert.Equal(t, []int{1, 1, 1}, fired)
+
+		s2.Unsubscribe()
+		d.Fire("event")
+		assert.Equal(t, []int{2, 1, 2}, fired)
+
+		s1.Unsubscribe()
+		d.Fire("event")
+		assert.Equal(t, []int{2, 1, 3}, fired)
+
+		s3.Unsubscribe()
+		d.Fire("event")
+		assert.Equal(t, []int{2, 1, 3}, fired)
+	})
+
+	t.Run("should support new subscribers subscription", func(t *testing.T) {
+		fired := make([]int, 3)
+
+		d := New()
+		d.On("event", func() { fired[0]++ })
+		s2 := d.On("event", func() { fired[1]++ })
+
+		d.Fire("event")
+		assert.Equal(t, []int{1, 1, 0}, fired)
+
+		s2.Unsubscribe()
+		d.Fire("event")
+		assert.Equal(t, []int{2, 1, 0}, fired)
+
+		s3 := d.On("event", func() { fired[2]++ })
+		s2.Unsubscribe()
+		d.Fire("event")
+		assert.Equal(t, []int{3, 1, 1}, fired)
+
+		s3.Unsubscribe()
+		d.Fire("event")
+		assert.Equal(t, []int{4, 1, 1}, fired)
+	})
+
+	t.Run("should nop if no events", func(t *testing.T) {
+		fired := false
+
+		d := New()
+		s1 := d.On("event", func() { fired = true })
+		s1.Unsubscribe()
+		s1.Unsubscribe()
+
+		d.Fire("event")
+		assert.False(t, fired)
+	})
+}
+
 func TestTryFire(t *testing.T) {
 	errVal := errors.New("bang")
 

go.mod

@@ -1,5 +1,11 @@
-module github.com/lmika/events
+module lmika.dev/pkg/events
 
-go 1.14
+go 1.24
 
-require github.com/stretchr/testify v1.9.0 // indirect
+require github.com/stretchr/testify v1.9.0
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -1,22 +1,10 @@
-github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
-github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
-github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
-github.com/stretchr/objx v0.5.2/go.mod h1:FRsXN1f5AsAjCGJKqEizvkpNtU+EGNCLh3NxZ/8L+MA=
-github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd0=
-github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
-github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=