server: add long-polling support

server/longpolling.go

@@ -0,0 +1,76 @@
+package main
+
+import (
+	"asink"
+	"sync"
+	"time"
+)
+
+type LongPollGroup struct {
+	channels []*chan *asink.Event
+	lock     sync.Mutex
+}
+
+type PollingManager struct {
+	lock   sync.RWMutex
+	groups map[string]*LongPollGroup
+}
+
+var pm *PollingManager
+
+func init() {
+	pm = new(PollingManager)
+	pm.groups = make(map[string]*LongPollGroup)
+}
+
+func addPoller(uid string, channel *chan *asink.Event) {
+	pm.lock.RLock()
+
+	group := pm.groups[uid]
+	if group != nil {
+		group.lock.Lock()
+		pm.lock.RUnlock()
+		group.channels = append(group.channels, channel)
+		group.lock.Unlock()
+	} else {
+		pm.lock.RUnlock()
+		pm.lock.Lock()
+		group = new(LongPollGroup)
+		group.channels = append(group.channels, channel)
+		pm.groups[uid] = group
+		pm.lock.Unlock()
+	}
+
+	//set timer to call function after one minute
+	timeout := time.Duration(1)*time.Minute
+	time.AfterFunc(timeout, func() {
+		group.lock.Lock()
+		for i, c := range group.channels {
+			if c == channel {
+				copy(group.channels[i:], group.channels[i+1:])
+				group.channels = group.channels[:len(group.channels)-1]
+				break
+			}
+		}
+		group.lock.Unlock()
+		close(*channel)
+	})
+}
+
+func broadcastToPollers(uid string, event *asink.Event) {
+	//store off the long polling group we're trying to send to and remove
+	//it from PollingManager.groups
+	pm.lock.Lock()
+	group := pm.groups[uid]
+	pm.groups[uid] = nil
+	pm.lock.Unlock()
+
+	//send event down each of group's channels
+	if group != nil {
+		group.lock.Lock()
+		for _, c := range group.channels {
+			*c <- event
+		}
+		group.lock.Unlock()
+	}
+}