Add a way to bypass Reddit API restrictions

internal/glance/singleflight.go

@@ -0,0 +1,44 @@
+package glance
+
+import "sync"
+
+type SingleflightCall[T any] struct {
+	done chan struct{}
+	val  T
+	err  error
+}
+
+type Singleflight[T any] struct {
+	fn      func() (T, error)
+	mu      sync.Mutex
+	current *SingleflightCall[T]
+}
+
+func (s *Singleflight[T]) Do() (T, error) {
+	s.mu.Lock()
+	if s.current != nil {
+		// Wait for the current call to finish and return its result
+		c := s.current
+		s.mu.Unlock()
+		<-c.done
+		return c.val, c.err
+	}
+
+	// Initiate a new call
+	c := &SingleflightCall[T]{done: make(chan struct{})}
+	s.current = c
+	s.mu.Unlock()
+
+	c.val, c.err = s.fn()
+
+	s.mu.Lock()
+	s.current = nil
+	s.mu.Unlock()
+	close(c.done)
+	return c.val, c.err
+}
+
+func NewSingleflight[T any](fn func() (T, error)) func() (T, error) {
+	sf := &Singleflight[T]{fn: fn}
+	return sf.Do
+}