package delivery

import "time"

// **Whether a module is being delivered on a node, read from its want and its have** (novox/hq ADR 0564 clause 13 and
// Limits 12, ADR 0540 §7; issue 1952 S7): one derivation, used by the delivery view, which says a module `moving`,
// `settled` or `stuck` (the messenger's hold hears those), and by the condition keeper, which holds a module's own
// findings while it is delivered there and raises what still stands when the delivery ends. Before, it lived in the view
// alone (mesh-delivery-view internal/view motionOf), and a second reader would have judged a delivery its own way.

// The motion of a module on a node, as the view says it.
const (
	MotionMoving  = "moving"
	MotionSettled = "settled"
	MotionStuck   = "stuck"
)

// The outcomes of a motion that settled or stuck.
const (
	// OutcomeRunning is a settled module: the have reached the want, running and healthy.
	OutcomeRunning = "running"
	// OutcomeFailed is a have at the wanted fingerprint whose apply or health check failed.
	OutcomeFailed = "failed"
	// OutcomeStopped is a module held, or a want the watchman says stopped moving past its bound.
	OutcomeStopped = "stopped"
)

// DefaultDeliveryBound is how long a module's delivery holds its own findings when its manifest names no bound (ADR 0564
// clause 13 (d)): past it, what is held is raised, saying the delivery did not end.
const DefaultDeliveryBound = 15 * time.Minute

// Motion is where one module's want stands on one node.
type Motion struct {
	// State is MotionMoving, MotionSettled or MotionStuck; empty when there is no want to move to (none, removed, or
	// naming no fingerprint).
	State string
	// Outcome and Words are a settled or stuck motion's: running; failed with the have's words; stopped with the have's
	// words (held) or the watchman's (stopped moving).
	Outcome string
	Words   string
	// Delivering says the module is being delivered there (clause 13 (a)): its want names a fingerprint other than its
	// have's, or its have's phase is applying.
	Delivering bool
	// Failed says the delivery ended failed (Limits 12): the node refused or failed its apply (the have's phase failed,
	// at whichever fingerprint it kept), or the have at the wanted fingerprint is unhealthy. What a hold kept is raised
	// at once. Apart from State, which says failed only at the wanted fingerprint, as the view always has.
	Failed bool
}

// Ended says the delivery ended, failed or settled healthy at the want: what a hold kept is judged now.
func (m Motion) Ended() bool { return m.Failed || (m.State == MotionSettled && !m.Delivering) }

// MotionOf is the motion of a module on a node from its want (wanted: one was read), its have (has: one was read) and
// the watchman's words when it says the want stopped moving (stuck: it says so and the want has not moved since).
func MotionOf(w Want, wanted bool, h Have, has bool, stuckWords string, stuck bool) Motion {
	if !wanted || w.Removed || w.FP == "" {
		return Motion{}
	}
	m := Motion{Delivering: !has || h.FP != w.FP || h.Phase == PhaseApplying,
		Failed: has && (h.Phase == PhaseFailed || (h.FP == w.FP && h.Health == HealthFailed))}
	applied := has && h.FP == w.FP && (h.Composed == "" || h.Composed == w.Composed)
	switch {
	case applied && h.Phase == PhaseRunning && h.Health == HealthOK:
		m.State, m.Outcome = MotionSettled, OutcomeRunning
	case has && h.Phase == PhaseHeld:
		m.State, m.Outcome, m.Words = MotionStuck, OutcomeStopped, h.Detail
	case has && h.FP == w.FP && (h.Health == HealthFailed || h.Phase == PhaseFailed):
		m.State, m.Outcome, m.Words = MotionStuck, OutcomeFailed, h.Detail
	case stuck:
		m.State, m.Outcome, m.Words = MotionStuck, OutcomeStopped, stuckWords
	default:
		m.State = MotionMoving
	}
	return m
}