queue

type Capabilities struct {
	NativeDeadLetterQueue bool
	DelayedDelivery       bool
	OrderedDelivery       bool
	LeaseExtension        bool
	NativeFanOut          bool
}

type Claim struct {
	TaskID  string
	Attempt int
	Token   string
}

type EventBus interface {
	Publish(ctx context.Context, topic string, payload []byte) error

	// Subscribe registers one subscriber for topic and returns a channel
	// of payloads for that subscriber plus an unsubscribe function. The
	// returned channel is closed once unsubscribe is called or ctx is
	// done, whichever happens first.
	Subscribe(ctx context.Context, topic string) (payloads <-chan []byte, unsubscribe func(), err error)
}

type NoOpEventBus struct{}

type Task struct {
	ID      string
	Payload []byte
}

type TaskQueue interface {
	Enqueue(ctx context.Context, task Task) error

	// Claim attempts to claim one available task. ok=false means nothing
	// is claimable right now.
	Claim(ctx context.Context) (claim Claim, ok bool, err error)

	// Complete marks a claim's task attempt as durably finished (Watermill
	// Ack). It must fail if the claim's token has been invalidated by a
	// reclaim, so a worker that was killed mid-attempt cannot double-report
	// success after another worker has already reclaimed the task.
	Complete(ctx context.Context, claim Claim) error

	// Nack reports that a claimed attempt failed (Watermill Nack). A
	// retryable failure (permanent=false) makes the task claimable again
	// for another attempt. A permanent failure (permanent=true) routes the
	// task to the backend's poison-task destination (ADR-006 rule 5:
	// "permanent error -> Ack plus publication to a poison-task
	// destination"); a permanently-failed task must never be claimable
	// again. Nack must fail under the same stale-token condition as
	// Complete.
	Nack(ctx context.Context, claim Claim, permanent bool) error
}