package svg
import (
"fmt"
"html"
"math"
"strings"
"time"
"b612.me/astro/basic"
eclipsecore "b612.me/astro/eclipse"
"b612.me/astro/internal/svgmap"
)
const (
lunarEclipseMapDefaultWidth = 960
lunarEclipseMapDefaultHeight = 640
)
// LunarEclipseMapSVGOptions 控制无国界全球可见性地图。
// LunarEclipseMapSVGOptions controls a border-free global visibility map.
type LunarEclipseMapSVGOptions struct {
// Width 和 Height 是 SVG 画布尺寸；宽度小于 640 或高度小于 420 时使用 960x640 默认值。
// Width and Height are SVG canvas dimensions in user units. Width values below 640 and height values below 420 use the 960x640 defaults.
Width int
Height int
// Language 为 "en"（不区分大小写）时使用英文，否则使用中文。
// Language uses English for "en" (case-insensitive) and Chinese otherwise.
Language string
// Location 控制显示的事件时刻；nil 使用 date.Location()。
// Location controls displayed event times. Nil uses date.Location().
Location *time.Location
// Projection 选择地图投影；零值使用等经纬投影，不支持的值使渲染器返回 false。
// Projection selects the map projection. The zero value selects the equirectangular projection; unsupported values make the renderer return false.
Projection EclipseMapProjection
// 空文本字段使用本地化的自动标签。
// Empty text fields use localized automatic labels.
Title string
FooterNote string
}
// LunarEclipseMapSVG 使用默认月食模型绘制全球 P1-P4 可见区域。
// LunarEclipseMapSVG renders the global P1-P4 visibility regions using the default lunar-eclipse model.
func LunarEclipseMapSVG(date time.Time, options LunarEclipseMapSVGOptions) (string, bool) {
return lunarEclipseMapSVG(date, options, eclipsecore.LunarEclipseOnDate)
}
// LunarEclipseMapSVGDanjon 使用 Danjon 模型绘制全球可见区域。
// LunarEclipseMapSVGDanjon renders the global visibility regions with Danjon's model.
func LunarEclipseMapSVGDanjon(date time.Time, options LunarEclipseMapSVGOptions) (string, bool) {
return lunarEclipseMapSVG(date, options, eclipsecore.LunarEclipseOnDateDanjon)
}
// LunarEclipseMapSVGChauvenet 使用 Chauvenet 模型绘制全球可见区域。
// LunarEclipseMapSVGChauvenet renders the global visibility regions with Chauvenet's model.
func LunarEclipseMapSVGChauvenet(date time.Time, options LunarEclipseMapSVGOptions) (string, bool) {
return lunarEclipseMapSVG(date, options, eclipsecore.LunarEclipseOnDateChauvenet)
}
func lunarEclipseMapSVG(
date time.Time,
options LunarEclipseMapSVGOptions,
calculator func(time.Time) (eclipsecore.LunarEclipseInfo, bool),
) (string, bool) {
if !validEclipseMapProjection(options.Projection) {
return "", false
}
info, ok := calculator(date)
if !ok || info.PenumbralStart.IsZero() || info.PenumbralEnd.IsZero() {
return "", false
}
options = normalizeLunarEclipseMapSVGOptions(date, options)
projection := internalEclipseMapProjection(options.Projection)
if projection == "" {
projection = svgmap.ProjectionEquirectangular
}
return renderLunarEclipseMapSVG(info, options, projection), true
}
func normalizeLunarEclipseMapSVGOptions(date time.Time, options LunarEclipseMapSVGOptions) LunarEclipseMapSVGOptions {
if options.Width < 640 {
options.Width = lunarEclipseMapDefaultWidth
}
if options.Height < 420 {
options.Height = lunarEclipseMapDefaultHeight
}
if strings.EqualFold(options.Language, "en") {
options.Language = "en"
} else {
options.Language = "zh"
}
if options.Location == nil {
options.Location = date.Location()
}
return options
}
func renderLunarEclipseMapSVG(
info eclipsecore.LunarEclipseInfo,
options LunarEclipseMapSVGOptions,
projection svgmap.Projection,
) string {
frame := eclipseMapFrame(options.Width, options.Height, projection, 142, 92)
startPath, startBoundary := lunarEclipseVisibilityPath(info.PenumbralStart, frame)
endPath, endBoundary := lunarEclipseVisibilityPath(info.PenumbralEnd, frame)
title := options.Title
if title == "" {
date := info.Maximum.In(options.Location).Format("2006-01-02")
if options.Language == "en" {
title = fmt.Sprintf("%s %s Global Visibility", date, lunarEclipseSVGTypeName(info.Type, "en"))
} else {
title = fmt.Sprintf("%s %s全球可见图", date, lunarEclipseSVGTypeName(info.Type, "zh"))
}
}
var builder strings.Builder
fmt.Fprintf(&builder, ``)
return builder.String()
}
func writeLunarEclipseVisibilityMasks(builder *strings.Builder, frame svgmap.Frame) {
writeLunarEclipseVisibilityMask(builder, "lunar-not-visible-mask", frame,
"lunar-visible-p1-shape", "lunar-visible-p4-shape")
writeLunarEclipseVisibilityMask(builder, "lunar-not-p4-mask", frame, "lunar-visible-p4-shape")
writeLunarEclipseVisibilityMask(builder, "lunar-not-p1-mask", frame, "lunar-visible-p1-shape")
}
func writeLunarEclipseVisibilityMask(
builder *strings.Builder,
id string,
frame svgmap.Frame,
excludedShapeIDs ...string,
) {
fmt.Fprintf(builder, ``,
id, frame.X, frame.Y, frame.Width, frame.Height)
fmt.Fprintf(builder, ``,
frame.X, frame.Y, frame.Width, frame.Height)
for _, shapeID := range excludedShapeIDs {
fmt.Fprintf(builder, ``, shapeID)
}
builder.WriteString(``)
}
func eclipseMapFrame(width, height int, projection svgmap.Projection, top, bottom float64) svgmap.Frame {
availableWidth := float64(width) - 90
availableHeight := float64(height) - top - bottom
mapWidth := math.Min(availableWidth, availableHeight*2)
mapHeight := mapWidth / 2
if projection != svgmap.ProjectionEquirectangular {
mapWidth = math.Min(availableWidth, availableHeight)
mapHeight = mapWidth
}
return svgmap.Frame{
X: (float64(width) - mapWidth) / 2,
Y: top,
Width: mapWidth,
Height: mapHeight,
Projection: projection,
}
}
func lunarEclipseVisibilityPath(value time.Time, frame svgmap.Frame) (string, []svgmap.GeoPoint) {
center := lunarEclipseSubpoint(value)
boundary := svgmap.SphericalCircle(center, 90, 360)
path := lunarEclipseVisibilityPathForCenter(center, frame)
closedBoundary := append(append([]svgmap.GeoPoint(nil), boundary...), boundary[0])
return path, closedBoundary
}
func lunarEclipseVisibilityPathForCenter(center svgmap.GeoPoint, frame svgmap.Frame) string {
var builder strings.Builder
for _, polygon := range svgmap.VisibleHemispherePolygons(center, frame.Projection, 360) {
appendEclipseMapPolygonPath(&builder, frame, polygon)
}
return builder.String()
}
func lunarEclipseVisibilityPolygons(
center svgmap.GeoPoint,
projection svgmap.Projection,
samples int,
) [][]svgmap.GeoPoint {
return svgmap.VisibleHemispherePolygons(center, projection, samples)
}
func lunarEclipseSubpoint(value time.Time) svgmap.GeoPoint {
ttJDE := timeToTTJDE(value)
ra, dec := basic.HMoonTrueRaDec(ttJDE)
utJDE := basic.TD2UT(ttJDE, false)
longitude := normalizeDegree180(ra - basic.ApparentSiderealTime(utJDE)*15)
return svgmap.GeoPoint{Longitude: longitude, Latitude: dec}
}
func appendEclipseMapPolygonPath(builder *strings.Builder, frame svgmap.Frame, points []svgmap.GeoPoint) {
if len(points) < 3 {
return
}
for index, point := range points {
x, y, ok := frame.Project(point.Longitude, point.Latitude)
if !ok {
continue
}
command := "L"
if index == 0 {
command = "M"
}
fmt.Fprintf(builder, `%s %.3f %.3f `, command, x, y)
}
builder.WriteString(`Z `)
}
func writeEclipseMapGeoLine(
builder *strings.Builder,
frame svgmap.Frame,
points []svgmap.GeoPoint,
className, color string,
strokeWidth float64,
dash, clipID string,
) {
for _, segment := range svgmap.PolylineSegments(points, frame.Projection) {
if len(segment) < 2 {
continue
}
fmt.Fprintf(builder, ``,
clipID, color, strokeWidth, dash)
}
}
func writeLunarEclipseUnavailableRegion(builder *strings.Builder, frame svgmap.Frame) {
if frame.IsPolar() {
fmt.Fprintf(builder, ``,
frame.X+frame.Width/2, frame.Y+frame.Height/2, frame.Width/2)
return
}
fmt.Fprintf(builder, ``,
frame.X, frame.Y, frame.Width, frame.Height)
}
func writeLunarEclipseMapSummary(builder *strings.Builder, info eclipsecore.LunarEclipseInfo, options LunarEclipseMapSVGOptions) {
start := info.PenumbralStart.In(options.Location)
maximum := info.Maximum.In(options.Location)
end := info.PenumbralEnd.In(options.Location)
zone, _ := maximum.Zone()
if zone == "" {
zone = "UTC"
}
text := fmt.Sprintf("P1 %s | 食甚 %s | P4 %s (%s) | 半影食分 %.3f | 本影食分 %.3f",
start.Format("15:04:05"), maximum.Format("15:04:05"), end.Format("15:04:05"), zone,
info.PenumbralMagnitude, info.UmbralMagnitude)
if options.Language == "en" {
text = fmt.Sprintf("P1 %s | Greatest %s | P4 %s (%s) | penumbral magnitude %.3f | umbral magnitude %.3f",
start.Format("15:04:05"), maximum.Format("15:04:05"), end.Format("15:04:05"), zone,
info.PenumbralMagnitude, info.UmbralMagnitude)
}
fmt.Fprintf(builder, `%s`,
float64(options.Width)/2, html.EscapeString(text))
}
func writeLunarEclipseMapLegend(builder *strings.Builder, frame svgmap.Frame, language string) {
labels := []string{"全程可见", "带食月出", "带食月落", "不可见"}
colors := []string{"#5e846d", "#4e9da0", "#e2aa4b", "#747b7d"}
if language == "en" {
labels = []string{"Entire eclipse", "Moonrise during eclipse", "Moonset during eclipse", "Not visible"}
}
y := frame.Y + frame.Height + 31
itemWidth := frame.Width / 4
for index, label := range labels {
x := frame.X + float64(index)*itemWidth
fmt.Fprintf(builder, ``, x, y-8, colors[index])
fmt.Fprintf(builder, `%s`,
x+24, y, html.EscapeString(label))
}
}
func writeLunarEclipseMapFooter(
builder *strings.Builder,
frame svgmap.Frame,
options LunarEclipseMapSVGOptions,
projection svgmap.Projection,
) {
text := options.FooterNote
if text == "" {
if options.Language == "en" {
text = eclipseMapProjectionLabel(projection, "en") + "; P1/P4 Moon-visible hemispheres; Natural Earth 1:50m physical land, no administrative boundaries."
} else {
text = eclipseMapProjectionLabel(projection, "zh") + "；按 P1/P4 月球可见半球分区；Natural Earth 1:50m 物理陆地底图，不含行政边界。"
}
}
fmt.Fprintf(builder, `%s`,
frame.X, float64(options.Height)-38, html.EscapeString(text))
}
func normalizeDegree180(value float64) float64 {
value = math.Mod(value+180, 360)
if value < 0 {
value += 360
}
return value - 180
}