contact

type Server struct {
	contactpb.UnimplementedContactListServer
	// contains filtered or unexported fields
}

type Store interface {
	// GetChecksum returns the user's stored checksum. Returns ErrNotFound when
	// the user has no stored contact list row.
	GetChecksum(ctx context.Context, userID *commonpb.UserId) (*commonpb.Hash, error)

	// GetHashes returns the HMAC-SHA256 hashes of every phone number in the
	// user's stored contact list. Returns ErrNotFound when the user has no
	// stored contact list row. Returns an empty slice (no error) when the
	// row exists but the contact list is empty.
	GetHashes(ctx context.Context, userID *commonpb.UserId) ([]*commonpb.Hash, error)

	// ApplyDelta applies adds and removes to the user's contact set under
	// compare-and-swap on the checksum:
	//
	//   - If the stored checksum equals oldChecksum, the delta is applied and
	//     the stored checksum becomes newChecksum.
	//   - If the stored checksum equals newChecksum, the call is treated as a
	//     no-op retry and nil is returned.
	//   - Otherwise ErrChecksumDrift is returned.
	//
	// addHashes and removeHashes are HMAC-SHA256 hashes of the phone numbers
	// being added/removed. Adds use INSERT-IF-NOT-EXISTS semantics; removes use
	// DELETE-IF-EXISTS semantics.
	//
	// If applying the delta would leave the user with more than
	// MaxContactsPerUser contacts, ErrTooManyContacts is returned and the delta
	// is not applied.
	ApplyDelta(
		ctx context.Context,
		userID *commonpb.UserId,
		addHashes []*commonpb.Hash,
		removeHashes []*commonpb.Hash,
		oldChecksum *commonpb.Hash,
		newChecksum *commonpb.Hash,
	) error

	// Replace replaces the user's contact set entirely with the provided
	// HMAC-SHA256 hashes and stores expectedChecksum as the new checksum.
	//
	// If len(hashes) > MaxContactsPerUser, ErrTooManyContacts is returned and
	// no changes are made.
	Replace(
		ctx context.Context,
		userID *commonpb.UserId,
		hashes []*commonpb.Hash,
		expectedChecksum *commonpb.Hash,
	) error
}