major refactor to accommodate feed

feed.go

@@ -0,0 +1,37 @@
+package gubgub
+
+import "iter"
+
+// Feed allows the usage of for/range to consume future published messages.
+// The supporting subscriber will eventually be discarded after you exit the for loop.
+func Feed[T any](t Subscribable[T], buffered bool) iter.Seq[T] {
+	feed := make(chan T)               // closed by the subscriber
+	unsubscribe := make(chan struct{}) // closed by the iterator
+
+	subscriber := func(msg T) bool {
+		select {
+		case feed <- msg:
+			return true
+		case <-unsubscribe:
+			close(feed)
+			return false
+		}
+	}
+
+	if buffered {
+		subscriber = Buffered(subscriber)
+	}
+
+	t.Subscribe(subscriber)
+
+	// Iterator
+	return func(yield func(T) bool) {
+		defer close(unsubscribe)
+
+		for msg := range feed {
+			if !yield(msg) {
+				return
+			}
+		}
+	}
+}