astro/eclipse/lunar_local_test.go

package eclipse

import (
	"testing"
	"time"
)

func TestLocalLunarEclipseOnDateByLocalDay(t *testing.T) {
	loc := time.FixedZone("CDT", -5*3600)
	lon, lat, height := -87.65, 41.85, 0.0

	testCases := []struct {
		name string
		date time.Time
		want bool
	}{
		{
			name: "day before no eclipse",
			date: time.Date(2025, 3, 12, 12, 0, 0, 0, loc),
			want: false,
		},
		{
			name: "local start day overlaps",
			date: time.Date(2025, 3, 13, 12, 0, 0, 0, loc),
			want: true,
		},
		{
			name: "local end day overlaps",
			date: time.Date(2025, 3, 14, 12, 0, 0, 0, loc),
			want: true,
		},
		{
			name: "day after no eclipse",
			date: time.Date(2025, 3, 15, 12, 0, 0, 0, loc),
			want: false,
		},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			info, ok := LocalLunarEclipseOnDate(tc.date, lon, lat, height)
			if ok != tc.want {
				t.Fatalf("LocalLunarEclipseOnDate(%v) got %v want %v", tc.date, ok, tc.want)
			}
			if !ok {
				return
			}
			if info.Type != LunarEclipseTotal {
				t.Fatalf("unexpected eclipse type: got %s want %s", info.Type, LunarEclipseTotal)
			}
			if info.Maximum.Location() != loc {
				t.Fatalf("maximum location mismatch: got %q want %q", info.Maximum.Location(), loc)
			}
			if info.PenumbralStart.Day() != 13 || info.PenumbralEnd.Day() != 14 {
				t.Fatalf("unexpected local date span: start=%v end=%v", info.PenumbralStart, info.PenumbralEnd)
			}
		})
	}
}

func TestLocalLunarEclipseVisibilityFilter(t *testing.T) {
	chicagoLoc := time.FixedZone("CDT", -5*3600)
	chicagoDate := time.Date(2023, 10, 28, 12, 0, 0, 0, chicagoLoc)
	chicagoLon, chicagoLat, chicagoHeight := -87.65, 41.85, 0.0

	geometricInfo, geometricOK := GeometricLocalLunarEclipseOnDate(chicagoDate, chicagoLon, chicagoLat, chicagoHeight)
	if !geometricOK {
		t.Fatalf("expected geometric local eclipse on date")
	}
	if geometricInfo.Type != LunarEclipsePartial {
		t.Fatalf("unexpected geometric eclipse type: got %s want %s", geometricInfo.Type, LunarEclipsePartial)
	}
	if geometricInfo.VisibleAtMaximum {
		t.Fatalf("expected geometric eclipse to be below horizon at maximum: %+v", geometricInfo)
	}

	visibleInfo, visibleOK := LocalLunarEclipseOnDate(chicagoDate, chicagoLon, chicagoLat, chicagoHeight)
	if visibleOK {
		t.Fatalf("expected visible filter to reject invisible eclipse, got %+v", visibleInfo)
	}

	londonDate := time.Date(2025, 3, 14, 12, 0, 0, 0, time.UTC)
	londonInfo, londonOK := LocalLunarEclipseOnDate(londonDate, -0.1278, 51.5074, 0)
	if !londonOK {
		t.Fatalf("expected visible local eclipse in London")
	}
	if londonInfo.VisibleAtMaximum {
		t.Fatalf("expected London maximum to be below horizon, got %+v", londonInfo)
	}
}

func TestLocalLunarEclipseSearchSemantics(t *testing.T) {
	loc := time.UTC
	lon, lat, height := -0.1278, 51.5074, 0.0
	current := ClosestLocalLunarEclipseDanjon(time.Date(2025, 3, 14, 12, 0, 0, 0, loc), lon, lat, height)
	if current.Type != LunarEclipseTotal {
		t.Fatalf("unexpected current eclipse type: got %s want %s", current.Type, LunarEclipseTotal)
	}
	assertSameLocalLunarEclipse(t, "ClosestLocalLunarEclipse(default)", ClosestLocalLunarEclipse(current.Maximum, lon, lat, height), current, time.Second)

	last := LastLocalLunarEclipseDanjon(current.Maximum, lon, lat, height)
	assertSameLocalLunarEclipse(t, "LastLocalLunarEclipseDanjon(current.Maximum)", last, current, time.Second)

	closest := ClosestLocalLunarEclipseDanjon(current.Maximum, lon, lat, height)
	assertSameLocalLunarEclipse(t, "ClosestLocalLunarEclipseDanjon(current.Maximum)", closest, current, time.Second)

	next := NextLocalLunarEclipseDanjon(current.Maximum, lon, lat, height)
	if !next.Maximum.After(current.Maximum) {
		t.Fatalf("NextLocalLunarEclipseDanjon should be strictly future: current=%v next=%v", current.Maximum, next.Maximum)
	}
	if next.Type != LunarEclipseTotal {
		t.Fatalf("unexpected next eclipse type: got %s want %s", next.Type, LunarEclipseTotal)
	}

	wantNextMax := time.Date(2025, 9, 7, 18, 11, 49, 0, loc)
	assertTimeClose(t, "next.Maximum", next.Maximum, wantNextMax, 2*time.Minute)
}

func TestLocalLunarEclipseSearchBeyondFiveYears(t *testing.T) {
	loc := time.FixedZone("CDT", -5*3600)
	lon, lat, height := -87.65, 41.85, 0.0
	current := ClosestLocalLunarEclipseDanjon(time.Date(2025, 3, 14, 12, 0, 0, 0, loc), lon, lat, height)
	if current.Type != LunarEclipseTotal {
		t.Fatalf("unexpected current eclipse type: got %s want %s", current.Type, LunarEclipseTotal)
	}

	next := NextLocalLunarEclipseDanjon(current.Maximum, lon, lat, height)
	if next.Type == LunarEclipseNone || next.Maximum.IsZero() {
		t.Fatalf("expected a future visible local lunar eclipse beyond the old 60-lunation window")
	}
	if !next.Maximum.After(current.Maximum) {
		t.Fatalf("expected strictly future local lunar eclipse: current=%v next=%v", current.Maximum, next.Maximum)
	}
}

func TestLocalTotalLunarEclipseSearch(t *testing.T) {
	loc := time.FixedZone("CDT", -5*3600)
	lon, lat, height := -87.65, 41.85, 0.0
	date := time.Date(2025, 3, 13, 0, 0, 0, 0, loc)

	next, ok := NextLocalTotalLunarEclipse(date, lon, lat, height)
	if !ok {
		t.Fatal("expected to find next local total lunar eclipse")
	}
	if next.Type != LunarEclipseTotal || !next.HasTotal {
		t.Fatalf("unexpected next total lunar eclipse: %+v", next)
	}
	assertTimeClose(t, "NextLocalTotalLunarEclipse", next.Maximum, time.Date(2025, 3, 14, 1, 58, 47, 0, loc), 2*time.Minute)

	last, ok := LastLocalTotalLunarEclipse(next.Maximum, lon, lat, height)
	if !ok {
		t.Fatal("expected to find previous local total lunar eclipse")
	}
	if last.Type != LunarEclipseTotal || !last.HasTotal {
		t.Fatalf("unexpected last total lunar eclipse: %+v", last)
	}
	assertTimeClose(t, "LastLocalTotalLunarEclipse", last.Maximum, next.Maximum, time.Second)
}

func TestLocalTotalLunarEclipseClosest(t *testing.T) {
	loc := time.FixedZone("CDT", -5*3600)
	lon, lat, height := -87.65, 41.85, 0.0
	date := time.Date(2025, 3, 14, 0, 0, 0, 0, loc)

	info, ok := ClosestLocalTotalLunarEclipse(date, lon, lat, height)
	if !ok {
		t.Fatal("expected to find closest local total lunar eclipse")
	}
	if info.Type != LunarEclipseTotal || !info.HasTotal {
		t.Fatalf("unexpected closest total lunar eclipse: %+v", info)
	}
	assertTimeClose(t, "ClosestLocalTotalLunarEclipse", info.Maximum, time.Date(2025, 3, 14, 1, 58, 47, 0, loc), 2*time.Minute)
}

func TestLocalTotalLunarEclipseVisibleRequiresTotalPhaseVisibility(t *testing.T) {
	info, ok := LocalLunarEclipseOnDate(time.Date(2025, 3, 14, 12, 0, 0, 0, time.UTC), -0.1278, 51.5074, 0)
	if !ok {
		t.Fatalf("expected visible local eclipse in London")
	}
	if info.Type != LunarEclipseTotal || !info.HasTotal {
		t.Fatalf("unexpected eclipse type: %+v", info)
	}
	if !localLunarEclipseVisible(info) {
		t.Fatalf("expected some phase to be visible")
	}
	if localTotalLunarEclipseVisible(info) {
		t.Fatalf("expected total phase below horizon to be rejected")
	}
}

func TestLocalLunarEclipseInfoKeepsLocation(t *testing.T) {
	loc := time.FixedZone("JST", 9*3600)
	lon, lat, height := 139.6917, 35.6895, 1234.0
	testCases := []struct {
		name string
		calc func(time.Time, float64, float64, float64) LocalLunarEclipseInfo
	}{
		{name: "danjon", calc: ClosestLocalLunarEclipseDanjon},
		{name: "chauvenet", calc: ClosestLocalLunarEclipseChauvenet},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			info := tc.calc(time.Date(2023, 10, 29, 12, 0, 0, 0, loc), lon, lat, height)

			if info.Type != LunarEclipsePartial {
				t.Fatalf("unexpected eclipse type: got %s want %s", info.Type, LunarEclipsePartial)
			}
			if info.Longitude != lon || info.Latitude != lat || info.Height != height {
				t.Fatalf("observer metadata mismatch: got (%f,%f,%f)", info.Longitude, info.Latitude, info.Height)
			}

			for _, item := range []struct {
				name string
				tm   time.Time
			}{
				{name: "PenumbralStart", tm: info.PenumbralStart},
				{name: "PartialStart", tm: info.PartialStart},
				{name: "Maximum", tm: info.Maximum},
				{name: "PartialEnd", tm: info.PartialEnd},
				{name: "PenumbralEnd", tm: info.PenumbralEnd},
			} {
				if item.tm.Location() != loc {
					t.Fatalf("%s location mismatch: got %q want %q", item.name, item.tm.Location(), loc)
				}
			}
		})
	}
}

func TestLocalLunarEclipseChauvenetRemainsAvailable(t *testing.T) {
	date := time.Date(2025, 3, 14, 12, 0, 0, 0, time.FixedZone("CDT", -5*3600))
	lon, lat, height := -87.65, 41.85, 0.0
	defaultInfo := ClosestLocalLunarEclipse(date, lon, lat, height)
	chauvenetInfo := ClosestLocalLunarEclipseChauvenet(date, lon, lat, height)

	assertFloatClose(t, "Chauvenet.PenumbralMagnitude", chauvenetInfo.PenumbralMagnitude, 2.285431290, 1e-6)
	assertFloatClose(t, "Chauvenet.UmbralMagnitude", chauvenetInfo.UmbralMagnitude, 1.182811712, 1e-6)

	if !(chauvenetInfo.PenumbralMagnitude > defaultInfo.PenumbralMagnitude) {
		t.Fatalf("expected Chauvenet penumbral magnitude > Danjon: chauvenet=%.6f danjon=%.6f", chauvenetInfo.PenumbralMagnitude, defaultInfo.PenumbralMagnitude)
	}
	if !(chauvenetInfo.PenumbralStart.Before(defaultInfo.PenumbralStart) && chauvenetInfo.PenumbralEnd.After(defaultInfo.PenumbralEnd)) {
		t.Fatalf("expected Chauvenet penumbral span to be wider: chauvenet=(%v,%v) danjon=(%v,%v)", chauvenetInfo.PenumbralStart, chauvenetInfo.PenumbralEnd, defaultInfo.PenumbralStart, defaultInfo.PenumbralEnd)
	}
}

func TestLocalLunarEclipseAgainstNASABaseline(t *testing.T) {
	testCases := []struct {
		name               string
		date               time.Time
		lon                float64
		lat                float64
		height             float64
		wantType           LunarEclipseType
		wantPenumbralMag   float64
		wantUmbralMag      float64
		wantPenumbralStart time.Time
		wantPartialStart   time.Time
		wantTotalStart     time.Time
		wantMaximum        time.Time
		wantTotalEnd       time.Time
		wantPartialEnd     time.Time
		wantPenumbralEnd   time.Time
		wantMoonAltitude   float64
	}{
		{
			name:               "2023-10-29 tokyo partial",
			date:               time.Date(2023, 10, 29, 12, 0, 0, 0, time.FixedZone("JST", 9*3600)),
			lon:                139.6917,
			lat:                35.6895,
			height:             0,
			wantType:           LunarEclipsePartial,
			wantPenumbralMag:   1.1181,
			wantUmbralMag:      0.122,
			wantPenumbralStart: time.Date(2023, 10, 29, 03, 01, 43, 0, time.FixedZone("JST", 9*3600)),
			wantPartialStart:   time.Date(2023, 10, 29, 04, 35, 18, 0, time.FixedZone("JST", 9*3600)),
			wantMaximum:        time.Date(2023, 10, 29, 05, 14, 06, 0, time.FixedZone("JST", 9*3600)),
			wantPartialEnd:     time.Date(2023, 10, 29, 05, 52, 53, 0, time.FixedZone("JST", 9*3600)),
			wantPenumbralEnd:   time.Date(2023, 10, 29, 07, 26, 19, 0, time.FixedZone("JST", 9*3600)),
			wantMoonAltitude:   9.1,
		},
		{
			name:               "2025-03-14 chicago total",
			date:               time.Date(2025, 3, 14, 12, 0, 0, 0, time.FixedZone("CDT", -5*3600)),
			lon:                -87.65,
			lat:                41.85,
			height:             0,
			wantType:           LunarEclipseTotal,
			wantPenumbralMag:   2.2595,
			wantUmbralMag:      1.1784,
			wantPenumbralStart: time.Date(2025, 3, 13, 22, 57, 28, 0, time.FixedZone("CDT", -5*3600)),
			wantPartialStart:   time.Date(2025, 3, 14, 0, 9, 40, 0, time.FixedZone("CDT", -5*3600)),
			wantTotalStart:     time.Date(2025, 3, 14, 1, 26, 6, 0, time.FixedZone("CDT", -5*3600)),
			wantMaximum:        time.Date(2025, 3, 14, 1, 58, 41, 0, time.FixedZone("CDT", -5*3600)),
			wantTotalEnd:       time.Date(2025, 3, 14, 2, 31, 26, 0, time.FixedZone("CDT", -5*3600)),
			wantPartialEnd:     time.Date(2025, 3, 14, 3, 47, 56, 0, time.FixedZone("CDT", -5*3600)),
			wantPenumbralEnd:   time.Date(2025, 3, 14, 5, 0, 9, 0, time.FixedZone("CDT", -5*3600)),
			wantMoonAltitude:   48.2,
		},
	}

	const timeTolerance = 2 * time.Minute
	const umbralMagnitudeTolerance = 0.02
	const penumbralMagnitudeTolerance = 0.1
	const altitudeTolerance = 1.5

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			info := ClosestLocalLunarEclipse(tc.date, tc.lon, tc.lat, tc.height)
			if info.Type != tc.wantType {
				t.Fatalf("type mismatch: got %s want %s", info.Type, tc.wantType)
			}

			assertFloatClose(t, "PenumbralMagnitude", info.PenumbralMagnitude, tc.wantPenumbralMag, penumbralMagnitudeTolerance)
			assertFloatClose(t, "UmbralMagnitude", info.UmbralMagnitude, tc.wantUmbralMag, umbralMagnitudeTolerance)

			assertTimeClose(t, "PenumbralStart", info.PenumbralStart, tc.wantPenumbralStart, timeTolerance)
			assertTimeClose(t, "PartialStart", info.PartialStart, tc.wantPartialStart, timeTolerance)
			assertTimeClose(t, "TotalStart", info.TotalStart, tc.wantTotalStart, timeTolerance)
			assertTimeClose(t, "Maximum", info.Maximum, tc.wantMaximum, timeTolerance)
			assertTimeClose(t, "TotalEnd", info.TotalEnd, tc.wantTotalEnd, timeTolerance)
			assertTimeClose(t, "PartialEnd", info.PartialEnd, tc.wantPartialEnd, timeTolerance)
			assertTimeClose(t, "PenumbralEnd", info.PenumbralEnd, tc.wantPenumbralEnd, timeTolerance)
			assertFloatClose(t, "MoonAltitude", info.MoonAltitude, tc.wantMoonAltitude, altitudeTolerance)
		})
	}
}

func TestLocalPenumbralLunarEclipseKeepsNegativeUmbralMagnitude(t *testing.T) {
	cdt := time.FixedZone("CDT", -5*3600)
	info := ClosestLocalLunarEclipse(time.Date(2024, 3, 25, 2, 0, 0, 0, cdt), -87.65, 41.85, 0)
	if info.Type != LunarEclipsePenumbral {
		t.Fatalf("type mismatch: got %s want %s", info.Type, LunarEclipsePenumbral)
	}
	if !(info.UmbralMagnitude < 0) {
		t.Fatalf("expected negative umbral magnitude for penumbral eclipse, got %.12f", info.UmbralMagnitude)
	}
	if !(info.PenumbralMagnitude > 0) {
		t.Fatalf("expected positive penumbral magnitude, got %.12f", info.PenumbralMagnitude)
	}
}

func assertSameLocalLunarEclipse(t *testing.T, name string, got, want LocalLunarEclipseInfo, tolerance time.Duration) {
	t.Helper()
	if got.Type != want.Type {
		t.Fatalf("%s type mismatch: got %s want %s", name, got.Type, want.Type)
	}
	assertTimeClose(t, name+".Maximum", got.Maximum, want.Maximum, tolerance)
}