use Example tests to demonstrate lib capabilities

i couldn't find a good enough solution so decided to remove entirely

README.md

@@ -71,11 +71,16 @@ GubGub offers 2 kinds of topics:
 
 * **AsyncTopic** - Publishing schedules the message to be eventually delivered.
   Subscribing schedules a subscriber to be eventually registered.
-  Only message delivery is guaranteed.
+  Message delivery is guaranteed but not the order.
 
 The type of topic does not relate to how messages are actually delivered.
 Currently we deliver messages sequentially (each subscriber gets the message one after the other).
 
+## TODO
+
+* AsyncTopic guaranteed message order delivery
+* Parallel order delivery
+
 ## Benchmarks
 
 * **SyncTopic** - Subscribers speed and number **will** have a direct impact the publishing performance.

async.go

@@ -23,22 +23,14 @@ type AsyncTopic[T any] struct {
 
 // NewAsyncTopic creates an AsyncTopic.
 func NewAsyncTopic[T any](opts ...TopicOption) *AsyncTopic[T] {
-	options := TopicOptions{
-		onClose:     func() {}, // Called after the Topic is closed and all messages have been delivered.
-		onSubscribe: func() {}, // Called everytime a new subscriber is added
-	}
-
-	for _, opt := range opts {
-		opt(&options)
-	}
-
 	t := AsyncTopic[T]{
-		options:     options,
 		closed:      make(chan struct{}),
 		publishCh:   make(chan T, 1),
 		subscribeCh: make(chan Subscriber[T], 1),
 	}
 
+	t.SetOptions(opts...)
+
 	go t.run()
 
 	return &t
@@ -68,7 +60,7 @@ func (t *AsyncTopic[T]) Close() {
 
 func (t *AsyncTopic[T]) run() {
 	defer close(t.closed)
-	defer t.options.onClose()
+	defer t.options.TriggerClose()
 
 	var subscribers []Subscriber[T]
 
@@ -91,7 +83,7 @@ func (t *AsyncTopic[T]) run() {
 			}
 
 			subscribers = append(subscribers, newCallback)
-			t.options.onSubscribe()
+			t.options.TriggerSubscribe()
 
 		case msg, more := <-t.publishCh:
 			if !more {
@@ -138,3 +130,7 @@ func (t *AsyncTopic[T]) Subscribe(fn Subscriber[T]) error {
 
 	return nil
 }
+
+func (t *AsyncTopic[T]) SetOptions(opts ...TopicOption) {
+	t.options.Apply(opts...)
+}

common.go

@@ -7,6 +7,8 @@ type Subscriber[T any] func(T) bool
 type Topic[T any] interface {
 	Publishable[T]
 	Subscribable[T]
+	OptionsSetter
+	Closer
 }
 
 type Publishable[T any] interface {
@@ -16,3 +18,11 @@ type Publishable[T any] interface {
 type Subscribable[T any] interface {
 	Subscribe(Subscriber[T]) error
 }
+
+type OptionsSetter interface {
+	SetOptions(...TopicOption)
+}
+
+type Closer interface {
+	Close()
+}

example/main.go

@@ -1,77 +0,0 @@
-package main
-
-import (
-	"bufio"
-	"fmt"
-	"log"
-	"os"
-	"strings"
-	"time"
-
-	"github.com/nmoniz/gubgub"
-)
-
-func main() {
-	topic := gubgub.NewAsyncTopic[string]()
-	defer topic.Close()
-
-	err := topic.Subscribe(gubgub.Forever(UpperCaser))
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	err = topic.Subscribe(Countdown(3))
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	err = topic.Subscribe(gubgub.Buffered(gubgub.Forever(Slow)))
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	go func() {
-		feed, err := gubgub.Feed(topic, false)
-		if err != nil {
-			log.Fatal(err)
-		}
-
-		for s := range feed {
-			log.Printf("ForRange: %s", s)
-		}
-	}()
-
-	fmt.Printf("Use 'Ctrl+C' to exit! Type a message followed by 'Enter' to publish it:\n")
-	scanner := bufio.NewScanner(os.Stdin)
-	for {
-		scanner.Scan()
-		err := scanner.Err()
-		if err != nil {
-			log.Fatal(err)
-		}
-
-		topic.Publish(scanner.Text())
-	}
-}
-
-func UpperCaser(input string) {
-	log.Printf("UpperCaser: %s", strings.ToUpper(input))
-}
-
-func Countdown(count int) gubgub.Subscriber[string] {
-	return func(_ string) bool {
-		count--
-		if count > 0 {
-			log.Printf("Countdown: %d...", count)
-			return true
-		} else {
-			log.Print("Countdown: I'm out!")
-			return false
-		}
-	}
-}
-
-func Slow(input string) {
-	time.Sleep(time.Second * 3)
-	log.Printf("Slow: %s", input)
-}

examples_test.go

@@ -0,0 +1,76 @@
+package gubgub_test
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/nmoniz/gubgub"
+)
+
+func ExampleAsyncTopic() {
+	latch := make(chan struct{})
+	topic := gubgub.NewAsyncTopic[string](gubgub.WithOnSubscribe(func() { close(latch) }))
+	defer topic.Close() // It's ok to close a topic multiple times
+
+	receiver := make(chan string, 3) // closed later
+
+	_ = topic.Subscribe(gubgub.Forever(func(msg string) {
+		receiver <- strings.ToUpper(msg)
+	}))
+
+	<-latch // Wait for the subscribe to register
+
+	_ = topic.Publish("aaa")
+	_ = topic.Publish("bbb")
+	_ = topic.Publish("ccc")
+
+	topic.Close() // Close topic in order to wait for all messages to be delivered
+
+	close(receiver) // Now it's safe to close the receiver channel since no more messages will be delivered
+
+	msgLst := make([]string, 0, 3)
+	for msg := range receiver {
+		msgLst = append(msgLst, msg)
+	}
+
+	sort.Strings(msgLst) // Because publish order is not guaranteed with the AsyncTopic (yet) we need to sort results for consistent output
+
+	for _, msg := range msgLst {
+		fmt.Println(msg)
+	}
+
+	// Output: AAA
+	// BBB
+	// CCC
+}
+
+func ExampleSyncTopic() {
+	topic := gubgub.NewSyncTopic[string]()
+	defer topic.Close()
+
+	receiver := make(chan string)
+	defer close(receiver)
+
+	_ = topic.Subscribe(gubgub.Buffered(gubgub.Forever(func(msg string) {
+		receiver <- msg
+	})))
+
+	_ = topic.Publish("aaa")
+	_ = topic.Publish("bbb")
+	_ = topic.Publish("ccc")
+
+	topic.Close()
+
+	// Notice how despite the subscriber is blocked trying to push to an unbuffered channel it doesn't
+	// block publishing to a SyncTopic thanks to the Buffered subscriber. Messages are considered
+	// delivered even if they are in the buffer which is why Close returns.
+
+	for range 3 {
+		fmt.Println(<-receiver)
+	}
+
+	// Output: aaa
+	// bbb
+	// ccc
+}

feed.go

@@ -1,42 +0,0 @@
-package gubgub
-
-import (
-	"iter"
-)
-
-// Feed allows the usage of for/range loop to consume future published messages.
-// The supporting subscriber will eventually be discarded after you exit the for loop.
-func Feed[T any](t Subscribable[T], buffered bool) (iter.Seq[T], error) {
-	feed := make(chan T)               // closed by the subscriber
-	unsubscribe := make(chan struct{}) // closed by the iterator
-
-	subscriber := func(msg T) bool {
-		select {
-		case feed <- msg:
-			return true
-		case <-unsubscribe:
-			close(feed)
-			return false
-		}
-	}
-
-	if buffered {
-		subscriber = Buffered(subscriber)
-	}
-
-	err := t.Subscribe(subscriber)
-	if err != nil {
-		return nil, err
-	}
-
-	// Iterator
-	return func(yield func(T) bool) {
-		defer close(unsubscribe)
-
-		for msg := range feed {
-			if !yield(msg) {
-				return
-			}
-		}
-	}, nil
-}

feed_test.go

@@ -1,64 +0,0 @@
-package gubgub
-
-import (
-	"testing"
-	"time"
-
-	"github.com/stretchr/testify/require"
-)
-
-func TestFeed_Topics(t *testing.T) {
-	const msgCount = 10
-
-	subscriberReady := make(chan struct{}, 1)
-	defer close(subscriberReady)
-
-	onSubscribe := WithOnSubscribe(func() {
-		subscriberReady <- struct{}{}
-	})
-
-	testCases := []struct {
-		name  string
-		topic Topic[int]
-	}{
-		{
-			name:  "sync topic",
-			topic: NewSyncTopic[int](onSubscribe),
-		},
-		{
-			name:  "async topic",
-			topic: NewAsyncTopic[int](onSubscribe),
-		},
-	}
-	for _, tc := range testCases {
-		t.Run(tc.name, func(t *testing.T) {
-			feed, err := Feed(tc.topic, false)
-			require.NoError(t, err)
-
-			feedback := make(chan int)
-			go func() {
-				for i := range feed {
-					feedback <- i
-				}
-			}()
-
-			go func() {
-				<-subscriberReady
-				for i := range msgCount {
-					require.NoError(t, tc.topic.Publish(i))
-				}
-			}()
-
-			var counter int
-			timeout := testTimer(t, time.Second)
-			for counter < msgCount {
-				select {
-				case <-feedback:
-					counter++
-				case <-timeout.C:
-					t.Fatalf("expected %d feedback values by now but only got %d", msgCount, counter)
-				}
-			}
-		})
-	}
-}

options.go

@@ -1,11 +1,11 @@
 package gubgub
 
-import (
-	"sync"
-)
+import "sync"
 
 // TopicOptions holds common options for topics.
 type TopicOptions struct {
+	mu sync.Mutex
+
 	// onClose is called after the Topic is closed and all messages have been delivered. Even
 	// though you might call Close multiple times, topics are effectively closed only once thus
 	// this should be called only once.
@@ -15,16 +15,63 @@ type TopicOptions struct {
 	onSubscribe func()
 }
 
+func (to *TopicOptions) TriggerClose() {
+	to.mu.Lock()
+	defer to.mu.Unlock()
+
+	if to.onClose == nil {
+		return
+	}
+
+	to.onClose()
+}
+
+func (to *TopicOptions) TriggerSubscribe() {
+	to.mu.Lock()
+	defer to.mu.Unlock()
+
+	if to.onSubscribe == nil {
+		return
+	}
+
+	to.onSubscribe()
+}
+
+func (to *TopicOptions) Apply(opts ...TopicOption) {
+	to.mu.Lock()
+	defer to.mu.Unlock()
+
+	for _, opt := range opts {
+		opt(to)
+	}
+}
+
 type TopicOption func(*TopicOptions)
 
 func WithOnClose(fn func()) TopicOption {
 	return func(opts *TopicOptions) {
-		opts.onClose = sync.OnceFunc(fn)
+		if opts.onClose == nil {
+			opts.onClose = fn
+		} else {
+			oldFn := opts.onClose // preserve previous onClose handler
+			opts.onClose = func() {
+				fn()
+				oldFn()
+			}
+		}
 	}
 }
 
 func WithOnSubscribe(fn func()) TopicOption {
 	return func(opts *TopicOptions) {
+		if opts.onSubscribe == nil {
 			opts.onSubscribe = fn
+		} else {
+			oldFn := opts.onSubscribe // preserve previous onSubscribe handler
+			opts.onSubscribe = func() {
+				fn()
+				oldFn()
+			}
+		}
 	}
 }

options_test.go

@@ -7,6 +7,38 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+func TestTriggerClose(t *testing.T) {
+	to := TopicOptions{}
+
+	var calls int
+	to.Apply(
+		WithOnClose(func() { calls++ }),
+		WithOnClose(func() { calls++ }),
+		WithOnClose(func() { calls++ }))
+
+	to.TriggerClose()
+
+	if calls != 3 {
+		t.Fatalf("wants 3 calls but got %d", calls)
+	}
+}
+
+func TestTriggerSubscribe(t *testing.T) {
+	to := TopicOptions{}
+
+	var calls int
+	to.Apply(
+		WithOnSubscribe(func() { calls++ }),
+		WithOnSubscribe(func() { calls++ }),
+		WithOnSubscribe(func() { calls++ }))
+
+	to.TriggerSubscribe()
+
+	if calls != 3 {
+		t.Fatalf("wants 3 calls but got %d", calls)
+	}
+}
+
 func TestWithOnClose(t *testing.T) {
 	type closable interface {
 		Close()

sync.go

@@ -19,24 +19,17 @@ type SyncTopic[T any] struct {
 
 // NewSyncTopic creates a SyncTopic with the specified options.
 func NewSyncTopic[T any](opts ...TopicOption) *SyncTopic[T] {
-	options := TopicOptions{
-		onClose:     func() {},
-		onSubscribe: func() {},
-	}
+	t := &SyncTopic[T]{}
 
-	for _, opt := range opts {
-		opt(&options)
-	}
+	t.SetOptions(opts...)
 
-	return &SyncTopic[T]{
-		options: options,
-	}
+	return t
 }
 
 // Close will prevent further publishing and subscribing.
 func (t *SyncTopic[T]) Close() {
 	t.closed.Store(true)
-	t.options.onClose()
+	t.options.TriggerClose()
 }
 
 // Publish broadcasts a message to all subscribers.
@@ -63,7 +56,11 @@ func (t *SyncTopic[T]) Subscribe(fn Subscriber[T]) error {
 	defer t.mu.Unlock()
 
 	t.subscribers = append(t.subscribers, fn)
-	t.options.onSubscribe()
+	t.options.TriggerSubscribe()
 
 	return nil
 }
+
+func (t *SyncTopic[T]) SetOptions(opts ...TopicOption) {
+	t.options.Apply(opts...)
+}