From 8d43386417d93c4dbbbe1196fb2555e9f9cf47db Mon Sep 17 00:00:00 2001
From: Anant Prakash <anantprakashjsr@gmail.com>
Date: Tue, 24 Jul 2018 17:49:36 +0530
Subject: [PATCH] Add typing cache

---
 .../dendrite/typingserver/cache/cache.go      | 94 +++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 src/github.com/matrix-org/dendrite/typingserver/cache/cache.go

diff --git a/src/github.com/matrix-org/dendrite/typingserver/cache/cache.go b/src/github.com/matrix-org/dendrite/typingserver/cache/cache.go
new file mode 100644
index 000000000..fcf32211a
--- /dev/null
+++ b/src/github.com/matrix-org/dendrite/typingserver/cache/cache.go
@@ -0,0 +1,94 @@
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cache
+
+import (
+	"sync"
+	"time"
+)
+
+var (
+	userExists           = struct{}{} // Value denoting user is present in a userSet
+	defaultTypingTimeout = 10 * time.Second
+)
+
+// userSet is a map of user IDs
+type userSet map[string]struct{}
+
+// TypingCache maintains a list of users typing in each room.
+type TypingCache struct {
+	sync.RWMutex
+	data map[string]userSet
+}
+
+// NewTypingCache returns a new TypingCache initialized for use.
+func NewTypingCache() *TypingCache {
+	return &TypingCache{data: make(map[string]userSet)}
+}
+
+// GetTypingUsers returns the list of users typing in a room.
+func (t *TypingCache) GetTypingUsers(roomID string) (users []string) {
+	t.RLock()
+	usersMap, ok := t.data[roomID]
+	t.RUnlock()
+	if ok {
+		users = make([]string, 0, len(usersMap))
+		for key := range usersMap {
+			users = append(users, key)
+		}
+	}
+
+	return
+}
+
+// AddTypingUser sets an user as typing in a room.
+// expire is the time when the user typing should time out.
+// if expire is nil, defaultTypingTimeout is assumed.
+func (t *TypingCache) AddTypingUser(userID, roomID string, expire *time.Time) {
+	expireTime := getExpireTime(expire)
+	if until := time.Until(expireTime); until > 0 {
+		t.addUser(userID, roomID)
+		t.removeUserAfterDuration(userID, roomID, until)
+	}
+}
+
+func (t *TypingCache) addUser(userID, roomID string) {
+	t.Lock()
+	if t.data[roomID] == nil {
+		t.data[roomID] = make(userSet)
+	}
+
+	t.data[roomID][userID] = userExists
+	t.Unlock()
+}
+
+// Creates a go routine which removes the user after d duration has elapsed.
+func (t *TypingCache) removeUserAfterDuration(userID, roomID string, d time.Duration) {
+	go func() {
+		time.Sleep(d)
+		t.removeUser(userID, roomID)
+	}()
+}
+
+func (t *TypingCache) removeUser(userID, roomID string) {
+	t.Lock()
+	delete(t.data[roomID], userID)
+	t.Unlock()
+}
+
+func getExpireTime(expire *time.Time) time.Time {
+	if expire != nil {
+		return *expire
+	}
+	return time.Now().Add(defaultTypingTimeout)
+}