Add firebase support

server/topic.go

@@ -2,7 +2,6 @@ package server
 
 import (
 	"context"
-	"errors"
 	"log"
 	"math/rand"
 	"sync"
@@ -14,7 +13,7 @@ import (
 type topic struct {
 	id          string
 	subscribers map[int]subscriber
-	messages    int
+	messages    []*message
 	last        time.Time
 	ctx         context.Context
 	cancel      context.CancelFunc
@@ -45,21 +44,17 @@ func (t *topic) Subscribe(s subscriber) int {
 	return subscriberID
 }
 
-func (t *topic) Unsubscribe(id int) int {
+func (t *topic) Unsubscribe(id int) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 	delete(t.subscribers, id)
-	return len(t.subscribers)
 }
 
 func (t *topic) Publish(m *message) error {
 	t.mu.Lock()
 	defer t.mu.Unlock()
-	if len(t.subscribers) == 0 {
-		return errors.New("no subscribers")
-	}
 	t.last = time.Now()
-	t.messages++
+	t.messages = append(t.messages, m)
 	for _, s := range t.subscribers {
 		if err := s(m); err != nil {
 			log.Printf("error publishing message to subscriber")
@@ -68,10 +63,36 @@ func (t *topic) Publish(m *message) error {
 	return nil
 }
 
+func (t *topic) Messages(since time.Time) []*message {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	messages := make([]*message, 0) // copy!
+	for _, m := range t.messages {
+		msgTime := time.Unix(m.Time, 0)
+		if msgTime == since || msgTime.After(since) {
+			messages = append(messages, m)
+		}
+	}
+	return messages
+}
+
+func (t *topic) Prune(keep time.Duration) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	for i, m := range t.messages {
+		msgTime := time.Unix(m.Time, 0)
+		if time.Since(msgTime) < keep {
+			t.messages = t.messages[i:]
+			return
+		}
+	}
+	t.messages = make([]*message, 0)
+}
+
 func (t *topic) Stats() (subscribers int, messages int) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
-	return len(t.subscribers), t.messages
+	return len(t.subscribers), len(t.messages)
 }
 
 func (t *topic) Close() {