type Config struct {
	Context   Context              // Context is required
	Framework *mesos.FrameworkInfo // FrameworkInfo is required
	Caller    calls.Caller         // Caller  is required

	// Handler (optional) processes scheduler events. The controller's internal event processing
	// loop is aborted if a Handler returns a non-nil error, after which the controller may attempt
	// to re-register (subscribe) with Mesos.
	Handler events.Handler

	// RegistrationTokens (optional) limits the rate at which a framework (re)registers with Mesos.
	// The returned chan should either be non-blocking (nil/closed), or should yield a struct{} in
	// order to allow the framework registration process to continue. May be nil.
	RegistrationTokens <-chan struct{}
}

type Context interface {
	// Done returns true when the controller should exit
	Done() bool

	// FrameworkID returns the current Mesos-assigned framework ID. Frameworks are expected to
	// track this ID (that comes from Mesos, in a SUBSCRIBED event).
	FrameworkID() string

	// Error is an error handler that is invoked at the end of every subscription cycle; the given
	// error may be nil (if no errors occurred).
	Error(error)
}

type ContextAdapter struct {
	// FrameworkIDFunc is optional; nil tells the controller to always register as a new framework
	// for each subscription attempt.
	FrameworkIDFunc func() string

	// Done is optional; nil equates to a func that always returns false
	DoneFunc func() bool

	// ErrorFunc is optional; if nil then errors are swallowed
	ErrorFunc func(error)
}

type Controller interface {
	// Run executes the controller using the given Config
	Run(Config) error
}

type ControllerFunc func(Config) error

type ErrEvent string