things

type Channel struct {
	ID       string
	Owner    string
	Name     string
	Metadata map[string]interface{}
}

type ChannelCache interface {
	// Connect channel thing connection.
	Connect(string, string) error

	// HasThing checks if thing is connected to channel.
	HasThing(string, string) bool

	// Disconnects thing from channel.
	Disconnect(string, string) error

	// Removes channel from cache.
	Remove(string) error
}

type ChannelRepository interface {
	// Save persists the channel. Successful operation is indicated by unique
	// identifier accompanied by nil error response. A non-nil error is
	// returned to indicate operation failure.
	Save(Channel) (string, error)

	// Update performs an update to the existing channel. A non-nil error is
	// returned to indicate operation failure.
	Update(Channel) error

	// RetrieveByID retrieves the channel having the provided identifier, that is owned
	// by the specified user.
	RetrieveByID(string, string) (Channel, error)

	// RetrieveAll retrieves the subset of channels owned by the specified user.
	RetrieveAll(string, uint64, uint64) ChannelsPage

	// RetrieveByThing retrieves the subset of channels owned by the specified
	// user and have specified thing connected to them.
	RetrieveByThing(string, string, uint64, uint64) ChannelsPage

	// Remove removes the channel having the provided identifier, that is owned
	// by the specified user.
	Remove(string, string) error

	// Connect adds thing to the channel's list of connected things.
	Connect(string, string, string) error

	// Disconnect removes thing from the channel's list of connected
	// things.
	Disconnect(string, string, string) error

	// HasThing determines whether the thing with the provided access key, is
	// "connected" to the specified channel. If that's the case, it returns
	// thing's ID.
	HasThing(string, string) (string, error)
}

type ChannelsPage struct {
	PageMetadata
	Channels []Channel
}

type IdentityProvider interface {
	// ID generates the unique identifier.
	ID() string
}

type PageMetadata struct {
	Total  uint64
	Offset uint64
	Limit  uint64
}

type Service interface {
	// AddThing adds new thing to the user identified by the provided key.
	AddThing(string, Thing) (Thing, error)

	// UpdateThing updates the thing identified by the provided ID, that
	// belongs to the user identified by the provided key.
	UpdateThing(string, Thing) error

	// ViewThing retrieves data about the thing identified with the provided
	// ID, that belongs to the user identified by the provided key.
	ViewThing(string, string) (Thing, error)

	// ListThings retrieves data about subset of things that belongs to the
	// user identified by the provided key.
	ListThings(string, uint64, uint64) (ThingsPage, error)

	// ListThingsByChannel retrieves data about subset of things that are
	// connected to specified channel and belong to the user identified by
	// the provided key.
	ListThingsByChannel(string, string, uint64, uint64) (ThingsPage, error)

	// RemoveThing removes the thing identified with the provided ID, that
	// belongs to the user identified by the provided key.
	RemoveThing(string, string) error

	// CreateChannel adds new channel to the user identified by the provided key.
	CreateChannel(string, Channel) (Channel, error)

	// UpdateChannel updates the channel identified by the provided ID, that
	// belongs to the user identified by the provided key.
	UpdateChannel(string, Channel) error

	// ViewChannel retrieves data about the channel identified by the provided
	// ID, that belongs to the user identified by the provided key.
	ViewChannel(string, string) (Channel, error)

	// ListChannels retrieves data about subset of channels that belongs to the
	// user identified by the provided key.
	ListChannels(string, uint64, uint64) (ChannelsPage, error)

	// ListChannelsByThing retrieves data about subset of channels that have
	// specified thing connected to them and belong to the user identified by
	// the provided key.
	ListChannelsByThing(string, string, uint64, uint64) (ChannelsPage, error)

	// RemoveChannel removes the thing identified by the provided ID, that
	// belongs to the user identified by the provided key.
	RemoveChannel(string, string) error

	// Connect adds thing to the channel's list of connected things.
	Connect(string, string, string) error

	// Disconnect removes thing from the channel's list of connected
	// things.
	Disconnect(string, string, string) error

	// CanAccess determines whether the channel can be accessed using the
	// provided key and returns thing's id if access is allowed.
	CanAccess(string, string) (string, error)

	// Identify returns thing ID for given thing key.
	Identify(string) (string, error)
}

type Thing struct {
	ID       string
	Owner    string
	Name     string
	Key      string
	Metadata map[string]interface{}
}

type ThingCache interface {
	// Save stores pair thing key, thing id.
	Save(string, string) error

	// ID returns thing ID for given key.
	ID(string) (string, error)

	// Removes thing from cache.
	Remove(string) error
}

type ThingRepository interface {
	// Save persists the thing. Successful operation is indicated by non-nil
	// error response.
	Save(Thing) (string, error)

	// Update performs an update to the existing thing. A non-nil error is
	// returned to indicate operation failure.
	Update(Thing) error

	// RetrieveByID retrieves the thing having the provided identifier, that is owned
	// by the specified user.
	RetrieveByID(string, string) (Thing, error)

	// RetrieveByKey returns thing ID for given thing key.
	RetrieveByKey(string) (string, error)

	// RetrieveAll retrieves the subset of things owned by the specified user.
	RetrieveAll(string, uint64, uint64) ThingsPage

	// RetrieveByChannel retrieves the subset of things owned by the specified
	// user and connected to specified channel.
	RetrieveByChannel(string, string, uint64, uint64) ThingsPage

	// Remove removes the thing having the provided identifier, that is owned
	// by the specified user.
	Remove(string, string) error
}

type ThingsPage struct {
	PageMetadata
	Things []Thing
}