Add class no notify named waiters.

notifier.go

@@ -0,0 +1,100 @@
+/**
+ * Standalone signaling server for the Nextcloud Spreed app.
+ * Copyright (C) 2021 struktur AG
+ *
+ * @author Joachim Bauch <bauch@struktur.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package signaling
+
+import (
+	"context"
+	"sync"
+)
+
+type Waiter struct {
+	key string
+	ch  chan bool
+}
+
+func (w *Waiter) Wait(ctx context.Context) error {
+	select {
+	case <-w.ch:
+		return nil
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+}
+
+type Notifier struct {
+	sync.Mutex
+
+	waiters map[string]*Waiter
+}
+
+func (n *Notifier) NewWaiter(key string) *Waiter {
+	n.Lock()
+	defer n.Unlock()
+
+	_, found := n.waiters[key]
+	if found {
+		panic("already waiting")
+	}
+
+	waiter := &Waiter{
+		key: key,
+		ch:  make(chan bool, 1),
+	}
+	if n.waiters == nil {
+		n.waiters = make(map[string]*Waiter)
+	}
+	n.waiters[key] = waiter
+	return waiter
+}
+
+func (n *Notifier) Reset() {
+	n.Lock()
+	defer n.Unlock()
+
+	for _, w := range n.waiters {
+		close(w.ch)
+	}
+	n.waiters = nil
+}
+
+func (n *Notifier) Release(w *Waiter) {
+	n.Lock()
+	defer n.Unlock()
+
+	if _, found := n.waiters[w.key]; found {
+		delete(n.waiters, w.key)
+		close(w.ch)
+	}
+}
+
+func (n *Notifier) Notify(key string) {
+	n.Lock()
+	defer n.Unlock()
+
+	if w, found := n.waiters[key]; found {
+		select {
+		case w.ch <- true:
+		default:
+			// Ignore, already notified
+		}
+	}
+}

notifier_test.go

@@ -0,0 +1,120 @@
+/**
+ * Standalone signaling server for the Nextcloud Spreed app.
+ * Copyright (C) 2021 struktur AG
+ *
+ * @author Joachim Bauch <bauch@struktur.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package signaling
+
+import (
+	"context"
+	"sync"
+	"testing"
+	"time"
+)
+
+func TestNotifierNoWaiter(t *testing.T) {
+	var notifier Notifier
+
+	// Notifications can be sent even if no waiter exists.
+	notifier.Notify("foo")
+}
+
+func TestNotifierSimple(t *testing.T) {
+	var notifier Notifier
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+
+	waiter := notifier.NewWaiter("foo")
+	defer notifier.Release(waiter)
+
+	go func() {
+		defer wg.Done()
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+		defer cancel()
+		if err := waiter.Wait(ctx); err != nil {
+			t.Error(err)
+		}
+	}()
+
+	notifier.Notify("foo")
+	wg.Wait()
+}
+
+func TestNotifierMultiNotify(t *testing.T) {
+	var notifier Notifier
+
+	waiter := notifier.NewWaiter("foo")
+	defer notifier.Release(waiter)
+
+	notifier.Notify("foo")
+	// The second notification will be ignored while the first is still pending.
+	notifier.Notify("foo")
+}
+
+func TestNotifierWaitClosed(t *testing.T) {
+	var notifier Notifier
+
+	waiter := notifier.NewWaiter("foo")
+	notifier.Release(waiter)
+
+	if err := waiter.Wait(context.Background()); err != nil {
+		t.Error(err)
+	}
+}
+
+func TestNotifierResetWillNotify(t *testing.T) {
+	var notifier Notifier
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+
+	waiter := notifier.NewWaiter("foo")
+	defer notifier.Release(waiter)
+
+	go func() {
+		defer wg.Done()
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+		defer cancel()
+		if err := waiter.Wait(ctx); err != nil {
+			t.Error(err)
+		}
+	}()
+
+	notifier.Reset()
+	wg.Wait()
+}
+
+func TestNotifierDuplicate(t *testing.T) {
+	var notifier Notifier
+
+	waiter := notifier.NewWaiter("foo")
+	defer notifier.Release(waiter)
+
+	defer func() {
+		if e := recover(); e != nil {
+			if e.(string) != "already waiting" {
+				t.Errorf("Expected error about already waiting, got %+v", e)
+			}
+		}
+	}()
+
+	// Creating a waiter for an existing key will panic.
+	notifier.NewWaiter("foo")
+}