server

type Event interface {
	Context() context.Context // Returns the context of the emitted event from the source
	Key() any                 // Returns the key (or "type") of the event. Returns nil if an error event
	Value() any               // Returns the value of the event. Returns an error if an error event
	Error() error             // Returns the error or nil if not an error event

	// Emit an event on a channel. If the channel is buffered, returns false if the
	// event could not be sent (buffered channel is full). Blocks if an unbuferred channel.
	// Returns false if an error occured.
	Emit(chan<- Event) bool
}

type EventReceiver interface {
	Rcv(context.Context, func(Event) error, ...EventSource) error
}

type EventSource interface {
	Sub() <-chan Event
	Unsub(<-chan Event)
}

type Plugin interface {
	Name() string                                // Return the name of the task. This should be unique amongst all registered plugins
	Label() string                               // Return the label for the task. This should be unique amongst all plugins with the same name
	New(context.Context, Provider) (Task, error) // Create a new task with provider of other tasks
}

type Provider interface {
	Task
	plugin.Log

	// Create a new task from a plugin and return it. This should only
	// be called during the initialisation phase of the provider, not once
	// the provider is running.
	New(context.Context, Plugin) (Task, error)

	// Return a task with name and label. Two arguments are required if the first argument is
	// the task name and the second is the task label. Returns nil if there isn't exactly one
	// task to return.
	Get(...string) Task
}

type Task interface {
	EventSource

	// Run the task until the context is cancelled, and return any errors
	Run(context.Context) error
}