some type stubs

queue.go

@@ -0,0 +1,62 @@
+package main
+
+import (
+	"context"
+	"time"
+
+	"github.com/go-errors/errors"
+)
+
+type Queue struct {
+	driver Driver
+}
+
+func NewTestQueue() Queue {
+	return Queue{driver: NewTestDB()}
+}
+
+func NewQueue(driver Driver) Queue {
+	return Queue{driver: driver}
+}
+
+func (q Queue) Push(ctx context.Context, m Message) error {
+	return q.driver.Set(ctx, "q", m.ID, m.Serialize())
+}
+
+func (q Queue) PeekFirst(ctx context.Context) (Message, error) {
+	for {
+		m, err := q.peekFirst(ctx)
+		if err != nil {
+			return m, err
+		}
+
+		if !m.Empty() {
+			return m, nil
+		}
+
+		select {
+		case <-ctx.Done():
+			return Message{}, ctx.Err()
+		case <-time.After(time.Second):
+		}
+	}
+}
+
+func (q Queue) Ack(ctx context.Context, id string) error {
+	return q.driver.Set(ctx, "q", id, nil)
+}
+
+func (q Queue) peekFirst(ctx context.Context) (Message, error) {
+	var m Message
+	subctx, subcan := context.WithCancel(ctx)
+	defer subcan()
+	err := q.driver.ForEach(subctx, "q", func(_ string, value []byte) error {
+		m = MustDeserialize(value)
+		subcan()
+		return nil
+	})
+	if errors.Is(err, subctx.Err()) {
+		err = nil
+	}
+	return m, err
+}