context

type Context struct {
	RootValue cue.Value
	GoContext gocontext.Context

	FlowStack []string

	Stdin  io.Reader
	Stdout io.Writer
	Stderr io.Writer

	Value cue.Value
	Error error

	// debug / internal
	Verbosity int

	Middlewares  []Middleware
	TaskRegistry *sync.Map

	// BOOKKEEPING
	Tasks *sync.Map

	// experimental
	BaseTask *task.BaseTask

	// Middleware
	Pools *sync.Map

	// Global (for this context, tbd shared) lock around CUE evaluator
	CUELock *sync.Mutex

	// map of cue.Values
	ValStore *sync.Map

	// map of chan?
	Mailbox *sync.Map
}

type Middleware interface {
	Apply(*Context, RunnerFunc) RunnerFunc
}

type Runner interface {
	// Runner runs given the current value and returns a new value which is to
	// be unified with the original result.
	Run(ctx *Context) (results interface{}, err error)
}

type RunnerFunc func(v cue.Value) (Runner, error)