81 lines
2.9 KiB
Go
81 lines
2.9 KiB
Go
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package geojson_test
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import (
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"encoding/json"
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"math"
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"testing"
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"time"
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"b612.me/astro/eclipse"
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"b612.me/astro/geojson"
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)
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// TestLunarGeoJSONDropsAntimeridianSlivers 固定月食可见区的环卫生契约：日界线剪裁会在相邻
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// 世界各输出一次"全部顶点落在同一条子午线、平面面积只剩浮点噪声"的零宽薄片（实测
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// 1.8e-12 deg²，刚好越过共享剪裁器 1e-12 的零面积阈值），导出时必须在月食这一层丢弃，
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// 同时不能连带丢掉有面积的面。
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// TestLunarGeoJSONDropsAntimeridianSlivers pins the ring-hygiene contract of the lunar
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// visibility export: the antimeridian split emits one zero-width sliver per adjacent world whose
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// vertices all sit on one meridian with a planar area of floating-point noise (measured
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// 1.8e-12 deg^2, just past the shared splitter's 1e-12 zero-area floor). The lunar export must
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// drop it without dropping polygons that do have area.
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func TestLunarGeoJSONDropsAntimeridianSlivers(t *testing.T) {
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for _, day := range []string{"2022-11-08", "2026-03-03", "4026-03-16", "1904-09-24", "2025-03-14"} {
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t.Run(day, func(t *testing.T) {
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date, err := time.Parse("2006-01-02", day)
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if err != nil {
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t.Fatal(err)
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}
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info, ok := eclipse.LunarEclipseOnDate(date)
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if !ok {
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t.Fatal("missing lunar eclipse")
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}
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data, err := geojson.MarshalLunarEclipse(info, 360)
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if err != nil {
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t.Fatal(err)
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}
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collection := decodeCollection(t, data)
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for _, role := range []string{"visible-at-p1", "visible-at-p4"} {
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feature := featureWithRole(t, collection, role)
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var polygons [][][][]float64
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if err := json.Unmarshal(feature.Geometry.Coordinates, &polygons); err != nil {
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t.Fatal(err)
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}
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if len(polygons) == 0 {
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t.Fatalf("%s has no polygons", role)
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}
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for index, polygon := range polygons {
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area := 0.0
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for _, ring := range polygon {
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if len(ring) < 4 {
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t.Fatalf("%s polygon %d ring has %d positions", role, index, len(ring))
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}
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distinct := 0
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for position, point := range ring {
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if position == 0 || math.Abs(point[0]-ring[position-1][0]) > 1e-9 ||
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math.Abs(point[1]-ring[position-1][1]) > 1e-9 {
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distinct++
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}
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}
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if distinct > 1 &&
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math.Abs(ring[0][0]-ring[len(ring)-1][0]) <= 1e-9 &&
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math.Abs(ring[0][1]-ring[len(ring)-1][1]) <= 1e-9 {
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// 闭合点不是独立顶点 / The closing position is not a distinct vertex.
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distinct--
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}
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if distinct < 3 {
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t.Fatalf("%s polygon %d is a zero-width sliver: %v", role, index, ring)
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}
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for position := 0; position+1 < len(ring); position++ {
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area += ring[position][0]*ring[position+1][1] - ring[position+1][0]*ring[position][1]
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}
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}
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if math.Abs(area/2) < 1e-12 {
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t.Fatalf("%s polygon %d has no area: %v", role, index, polygon)
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}
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}
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}
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})
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}
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}
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