badge

type Store interface {
	// Increment atomically adds delta to a user's badge count and returns the
	// resulting value. A user with no badge yet is treated as zero. delta is
	// typically 1 per unread-eligible message, or a larger amount when several
	// have been coalesced.
	Increment(ctx context.Context, userID *commonpb.UserId, delta uint64) (uint64, error)

	// IncrementBatch applies Increment to each of userIDs and returns the
	// resulting values keyed by string(userID.Value). It exists for a chat's
	// fan-out, where one message bumps many users at once: implementations run
	// the per-user increments concurrently, so a batch costs a few round trips
	// of latency rather than one per user, while each user's increment stays
	// atomic on its own item.
	//
	// Best-effort per user: a failed increment leaves that user out of the
	// result, and the failures are joined into the returned error alongside the
	// partial result. userIDs should be distinct — a duplicate is incremented
	// once per occurrence, and the reported count is that of whichever landed
	// last.
	IncrementBatch(ctx context.Context, userIDs []*commonpb.UserId, delta uint64) (map[string]uint64, error)

	// Get returns a user's current badge count, or zero if the user has none.
	Get(ctx context.Context, userID *commonpb.UserId) (uint64, error)

	// Reset sets a user's badge count back to zero, e.g. when the app is opened.
	Reset(ctx context.Context, userID *commonpb.UserId) error
}