109 lines
3.1 KiB
Go
109 lines
3.1 KiB
Go
// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package cache
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import (
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"sync"
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"time"
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)
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const defaultTypingTimeout = 10 * time.Second
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// userSet is a map of user IDs to a timer, timer fires at expiry.
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type userSet map[string]*time.Timer
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// TypingCache maintains a list of users typing in each room.
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type TypingCache struct {
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sync.RWMutex
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data map[string]userSet
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}
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// NewTypingCache returns a new TypingCache initialized for use.
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func NewTypingCache() *TypingCache {
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return &TypingCache{data: make(map[string]userSet)}
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}
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// GetTypingUsers returns the list of users typing in a room.
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func (t *TypingCache) GetTypingUsers(roomID string) (users []string) {
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t.RLock()
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usersMap, ok := t.data[roomID]
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t.RUnlock()
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if ok {
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users = make([]string, 0, len(usersMap))
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for userID := range usersMap {
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users = append(users, userID)
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}
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}
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return
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}
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// AddTypingUser sets an user as typing in a room.
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// expire is the time when the user typing should time out.
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// if expire is nil, defaultTypingTimeout is assumed.
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func (t *TypingCache) AddTypingUser(userID, roomID string, expire *time.Time) {
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expireTime := getExpireTime(expire)
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if until := time.Until(expireTime); until > 0 {
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timer := time.AfterFunc(until, t.timeoutCallback(userID, roomID))
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t.addUser(userID, roomID, timer)
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}
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}
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// addUser with mutex lock & replace the previous timer.
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func (t *TypingCache) addUser(userID, roomID string, expiryTimer *time.Timer) {
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t.Lock()
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defer t.Unlock()
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if t.data[roomID] == nil {
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t.data[roomID] = make(userSet)
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}
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// Stop the timer to cancel the call to timeoutCallback
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if timer, ok := t.data[roomID][userID]; ok {
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// It may happen that at this stage timer fires but now we have a lock on t.
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// Hence the execution of timeoutCallback will happen after we unlock.
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// So we may lose a typing state, though this event is highly unlikely.
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// This can be mitigated by keeping another time.Time in the map and check against it
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// before removing. This however is not required in most practical scenario.
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timer.Stop()
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}
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t.data[roomID][userID] = expiryTimer
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}
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// Returns a function which is called after timeout happens.
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// This removes the user.
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func (t *TypingCache) timeoutCallback(userID, roomID string) func() {
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return func() {
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t.RemoveUser(userID, roomID)
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}
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}
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// RemoveUser with mutex lock & stop the timer.
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func (t *TypingCache) RemoveUser(userID, roomID string) {
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t.Lock()
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defer t.Unlock()
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if timer, ok := t.data[roomID][userID]; ok {
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timer.Stop()
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delete(t.data[roomID], userID)
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}
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}
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func getExpireTime(expire *time.Time) time.Time {
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if expire != nil {
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return *expire
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}
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return time.Now().Add(defaultTypingTimeout)
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}
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