Caption support (#2462)

Co-authored-by: WithoutPants <53250216+WithoutPants@users.noreply.github.com>

vendor/github.com/asticode/go-astikit/limiter.go

@@ -0,0 +1,101 @@
+package astikit
+
+import (
+	"context"
+	"sync"
+	"time"
+)
+
+// Limiter represents a limiter
+type Limiter struct {
+	buckets map[string]*LimiterBucket
+	m       *sync.Mutex // Locks buckets
+}
+
+// NewLimiter creates a new limiter
+func NewLimiter() *Limiter {
+	return &Limiter{
+		buckets: make(map[string]*LimiterBucket),
+		m:       &sync.Mutex{},
+	}
+}
+
+// Add adds a new bucket
+func (l *Limiter) Add(name string, cap int, period time.Duration) *LimiterBucket {
+	l.m.Lock()
+	defer l.m.Unlock()
+	if _, ok := l.buckets[name]; !ok {
+		l.buckets[name] = newLimiterBucket(cap, period)
+	}
+	return l.buckets[name]
+}
+
+// Bucket retrieves a bucket from the limiter
+func (l *Limiter) Bucket(name string) (b *LimiterBucket, ok bool) {
+	l.m.Lock()
+	defer l.m.Unlock()
+	b, ok = l.buckets[name]
+	return
+}
+
+// Close closes the limiter properly
+func (l *Limiter) Close() {
+	l.m.Lock()
+	defer l.m.Unlock()
+	for _, b := range l.buckets {
+		b.Close()
+	}
+}
+
+// LimiterBucket represents a limiter bucket
+type LimiterBucket struct {
+	cancel context.CancelFunc
+	cap    int
+	ctx    context.Context
+	count  int
+	period time.Duration
+	o      *sync.Once
+}
+
+// newLimiterBucket creates a new bucket
+func newLimiterBucket(cap int, period time.Duration) (b *LimiterBucket) {
+	b = &LimiterBucket{
+		cap:    cap,
+		count:  0,
+		period: period,
+		o:      &sync.Once{},
+	}
+	b.ctx, b.cancel = context.WithCancel(context.Background())
+	go b.tick()
+	return
+}
+
+// Inc increments the bucket count
+func (b *LimiterBucket) Inc() bool {
+	if b.count >= b.cap {
+		return false
+	}
+	b.count++
+	return true
+}
+
+// tick runs a ticker to purge the bucket
+func (b *LimiterBucket) tick() {
+	var t = time.NewTicker(b.period)
+	defer t.Stop()
+	for {
+		select {
+		case <-t.C:
+			b.count = 0
+		case <-b.ctx.Done():
+			return
+		}
+	}
+}
+
+// close closes the bucket properly
+func (b *LimiterBucket) Close() {
+	b.o.Do(func() {
+		b.cancel()
+	})
+}