package engine

import (
	"math"
	"testing"
	"time"

	"predictor-refactored/internal/weather"
)

// noWind is a WindField that always returns zero wind.
type noWind struct{ epoch time.Time }

func (n noWind) Wind(_ float64, _, _, _ float64) (weather.Sample, error) {
	return weather.Sample{}, nil
}
func (n noWind) Epoch() time.Time { return n.epoch }
func (n noWind) Source() string   { return "test" }

// flatGround returns 0 metres everywhere.
type flatGround struct{}

func (flatGround) Elevation(_, _ float64) float64 { return 0 }

func TestConstantAscentToBurst(t *testing.T) {
	burst := 30000.0
	rate := 5.0

	ascend := &Propagator{
		Name:        "ascent",
		Step:        60,
		Model:       Sum(ConstantRate(rate), WindTransport(noWind{}, nil)),
		Constraints: []Constraint{Altitude{Op: OpGreaterEqual, Limit: burst, On: ActionStop}},
	}

	prof := Profile{Stages: []*Propagator{ascend}, Direction: Forward}
	results := prof.Run(0, State{Lat: 0, Lng: 0, Altitude: 0}, NewEventSink())

	if len(results) != 1 || results[0].Outcome != OutcomeStopped {
		t.Fatalf("expected one stopped stage, got %+v", results)
	}
	if results[0].ConstraintName == "" {
		t.Errorf("ConstraintName not populated")
	}
	if results[0].RefinedState.Altitude == 0 {
		t.Errorf("RefinedState not populated")
	}

	last := results[0].Points[len(results[0].Points)-1]
	if math.Abs(last.Altitude-burst) > 5 {
		t.Errorf("burst altitude = %v, want within 5m of %v", last.Altitude, burst)
	}
	wantTime := burst / rate
	if math.Abs(last.Time-wantTime) > 1 {
		t.Errorf("burst time = %v, want within 1s of %v", last.Time, wantTime)
	}
}

func TestProfileWithFallback(t *testing.T) {
	burst := 1000.0
	rate := 5.0

	descent := &Propagator{
		Name:        "descent",
		Step:        60,
		Model:       ParachuteDescent(rate),
		Constraints: []Constraint{TerrainContact{Provider: flatGround{}, On: ActionStop}},
	}
	ascend := &Propagator{
		Name:        "ascent",
		Step:        60,
		Model:       ConstantRate(rate),
		Constraints: []Constraint{Altitude{Op: OpGreaterEqual, Limit: burst, On: ActionFallback}},
		Fallback:    descent,
	}

	prof := Profile{Stages: []*Propagator{ascend}, Direction: Forward}
	results := prof.Run(0, State{Altitude: 0}, NewEventSink())

	if len(results) != 2 {
		t.Fatalf("expected 2 results (ascent then descent fallback), got %d", len(results))
	}
	if results[0].Outcome != OutcomeFallback {
		t.Errorf("first outcome = %v, want OutcomeFallback", results[0].Outcome)
	}
	if results[1].Outcome != OutcomeStopped {
		t.Errorf("second outcome = %v, want OutcomeStopped", results[1].Outcome)
	}

	last := results[1].Points[len(results[1].Points)-1]
	if math.Abs(last.Altitude) > 5 {
		t.Errorf("final altitude = %v, want within 5m of 0", last.Altitude)
	}
}

func TestReverseDirection(t *testing.T) {
	desc := &Propagator{
		Name:        "rewind",
		Step:        1,
		Model:       ConstantRate(-1),
		Constraints: []Constraint{Altitude{Op: OpGreaterEqual, Limit: 200, On: ActionStop}},
	}
	prof := Profile{Stages: []*Propagator{desc}, Direction: Reverse}
	results := prof.Run(0, State{Altitude: 100}, NewEventSink())

	last := results[0].Points[len(results[0].Points)-1]
	if math.Abs(last.Altitude-200) > 1 {
		t.Errorf("reverse final altitude = %v, want ~200", last.Altitude)
	}
	if last.Time >= 0 {
		t.Errorf("reverse final time = %v, want < 0", last.Time)
	}
}

func TestPiecewiseRate(t *testing.T) {
	m := Piecewise([]RateSegment{
		{Until: 100, Rate: 5},
		{Until: 200, Rate: 3},
		{Until: math.Inf(1), Rate: 0},
	})

	if r := m(50, State{}); r.Altitude != 5 {
		t.Errorf("rate at t=50 = %v, want 5", r.Altitude)
	}
	if r := m(150, State{}); r.Altitude != 3 {
		t.Errorf("rate at t=150 = %v, want 3", r.Altitude)
	}
	if r := m(300, State{}); r.Altitude != 0 {
		t.Errorf("rate at t=300 = %v, want 0", r.Altitude)
	}
}

func TestPiecewiseReferenceResolution(t *testing.T) {
	// Build via the registry with propagator_start segments.
	spec := ModelSpec{
		Type: "piecewise",
		Segments: []PiecewiseSegmentSpec{
			{Until: 100, Rate: 5, Reference: "propagator_start"},
			{Until: 200, Rate: 3, Reference: "propagator_start"},
		},
	}
	built, err := BuildModel(spec, BuildDeps{})
	if err != nil {
		t.Fatalf("BuildModel: %v", err)
	}
	if built.Build == nil {
		t.Fatalf("expected lazy build for propagator_start references")
	}
	ctx := StageContext{ProfileStart: 1000, PropagatorStart: 5000}
	m := built.Build(ctx)
	// Until=100 from propagator_start=5000 → absolute 5100.
	if r := m(5050, State{}); r.Altitude != 5 {
		t.Errorf("rate at t=5050 = %v, want 5", r.Altitude)
	}
	if r := m(5150, State{}); r.Altitude != 3 {
		t.Errorf("rate at t=5150 = %v, want 3", r.Altitude)
	}
}

// fixedWind returns a constant wind sample.
type fixedWind struct{ u, v float64 }

func (w fixedWind) Wind(_ float64, _, _, _ float64) (weather.Sample, error) {
	return weather.Sample{U: w.u, V: w.v}, nil
}
func (fixedWind) Epoch() time.Time { return time.Unix(0, 0) }
func (fixedWind) Source() string   { return "test-fixed" }

func TestWindTransportUnitConversion(t *testing.T) {
	wind := WindTransport(fixedWind{u: 10, v: 0}, nil)
	d := wind(0, State{Lat: 0, Lng: 0, Altitude: 0})
	wantLng := (180.0 / math.Pi) * 10.0 / 6371009.0
	if math.Abs(d.Lng-wantLng) > 1e-12 {
		t.Errorf("dlng = %v, want %v", d.Lng, wantLng)
	}
	if math.Abs(d.Lat) > 1e-12 {
		t.Errorf("dlat = %v, want 0 for u=10 v=0", d.Lat)
	}

	wind2 := WindTransport(fixedWind{u: 0, v: 5}, nil)
	d = wind2(0, State{Lat: 60, Lng: 0, Altitude: 0})
	wantLat := (180.0 / math.Pi) * 5.0 / 6371009.0
	if math.Abs(d.Lat-wantLat) > 1e-12 {
		t.Errorf("dlat at lat=60 = %v, want %v", d.Lat, wantLat)
	}
}

// aboveModelWind reports AboveModel on every sample. Used to verify event emission.
type aboveModelWind struct{}

func (aboveModelWind) Wind(_ float64, _, _, _ float64) (weather.Sample, error) {
	return weather.Sample{AboveModel: true}, nil
}
func (aboveModelWind) Epoch() time.Time { return time.Unix(0, 0) }
func (aboveModelWind) Source() string   { return "above" }

func TestWindTransportEmitsAboveModel(t *testing.T) {
	sink := NewEventSink()
	wind := WindTransport(aboveModelWind{}, sink)
	for range 3 {
		_ = wind(0, State{})
	}
	events := sink.Snapshot()
	if len(events) != 1 || events[0].Type != "above_model" || events[0].Count != 3 {
		t.Errorf("expected one above_model event with count=3, got %+v", events)
	}
}

func TestStateAddWrapsLongitude(t *testing.T) {
	s := stateAdd(State{Lat: 0, Lng: 350, Altitude: 0}, 1, State{Lng: 20})
	if math.Abs(s.Lng-10) > 1e-9 {
		t.Errorf("addState wrap: lng = %v, want 10", s.Lng)
	}

	mid := stateLerp(State{Lng: 350}, State{Lng: 10}, 0.5)
	if math.Abs(mid.Lng-0) > 1e-9 && math.Abs(mid.Lng-360) > 1e-9 {
		t.Errorf("lerpState lng wrap: %v, want 0 or 360", mid.Lng)
	}
}

func TestPolygonInside(t *testing.T) {
	// Unit square at the equator.
	square := []PolygonVertex{
		{Lat: -1, Lng: -1},
		{Lat: -1, Lng: 1},
		{Lat: 1, Lng: 1},
		{Lat: 1, Lng: -1},
	}
	c := Polygon{Vertices: square, Mode: PolygonInside, On: ActionStop}
	if !c.Violated(0, State{Lat: 0, Lng: 0}) {
		t.Errorf("origin should be inside the square")
	}
	if c.Violated(0, State{Lat: 5, Lng: 0}) {
		t.Errorf("(5, 0) should be outside the square")
	}
}

func TestPolygonOutsideAntimeridian(t *testing.T) {
	// A polygon centred near the antimeridian, spanning lng 170..-170
	// (i.e. lng 170..190 in [0, 360) form).
	poly := []PolygonVertex{
		{Lat: -10, Lng: 170},
		{Lat: -10, Lng: 190},
		{Lat: 10, Lng: 190},
		{Lat: 10, Lng: 170},
	}
	c := Polygon{Vertices: poly, Mode: PolygonInside, On: ActionStop}
	// A point at the antimeridian.
	if !c.Violated(0, State{Lat: 0, Lng: 180}) {
		t.Errorf("(0, 180) should be inside the antimeridian polygon")
	}
	if c.Violated(0, State{Lat: 0, Lng: 0}) {
		t.Errorf("(0, 0) should be outside")
	}
}