package engine

// Profile is an ordered chain of propagators executed sequentially. Each
// propagator picks up where the previous one finished.
type Profile struct {
	// Stages are run in order. For Direction=Reverse they are still iterated
	// from index 0 onwards, but each propagator integrates with negative dt.
	Stages []*Propagator

	// Direction controls the sign of dt across the whole profile.
	Direction Direction

	// Globals are constraints evaluated alongside each stage's local Constraints.
	// Useful for profile-wide bounds like "stop after N hours total".
	Globals []Constraint
}

// Run executes the profile from the given launch point. Returns one Result
// per executed stage, including any Fallback chains that were activated.
func (p *Profile) Run(t0 float64, launch State) []Result {
	if p.Direction == 0 {
		p.Direction = Forward
	}

	results := make([]Result, 0, len(p.Stages))
	t, s := t0, launch

	for i := 0; i < len(p.Stages); i++ {
		stage := p.Stages[i]
		res := stage.run(t, s, p.Direction, p.Globals)
		results = append(results, res)

		last := res.Points[len(res.Points)-1]
		t = last.Time
		s = State{Lat: last.Lat, Lng: last.Lng, Altitude: last.Altitude}

		// Follow Fallback chains until none remains. Each fallback consumes
		// from the same point the previous stage stopped at.
		for res.Outcome == OutcomeFallback && stage.Fallback != nil {
			stage = stage.Fallback
			res = stage.run(t, s, p.Direction, p.Globals)
			results = append(results, res)
			last = res.Points[len(res.Points)-1]
			t = last.Time
			s = State{Lat: last.Lat, Lng: last.Lng, Altitude: last.Altitude}
		}

		// If a propagator's stop fired (not a fallback), end the profile.
		if res.Outcome == OutcomeStopped {
			continue
		}
	}

	return results
}