astro/planet/view.go

package planet

import (
	"fmt"
	"sync"
)

type coordSeriesView struct {
	orders [6][]float64
}

type planetView struct {
	scale  float64
	coords [3]coordSeriesView
}

var (
	planetViewsOnce  sync.Once
	planetViewsCache []planetView
	planetViewsErr   error
)

func planetViews() []planetView {
	planetViewsOnce.Do(func() {
		planetViewsCache, planetViewsErr = buildPlanetViews(planetRawData)
	})
	if planetViewsErr != nil {
		panic(planetViewsErr)
	}
	return planetViewsCache
}

func buildPlanetViews(rawData [][]float64) ([]planetView, error) {
	views := make([]planetView, len(rawData))
	for bodyIndex, raw := range rawData {
		if len(raw) < 20 {
			return nil, fmt.Errorf("planet raw data %d too short: %d", bodyIndex, len(raw))
		}
		view := planetView{scale: raw[0]}
		for zn := 0; zn < 3; zn++ {
			pn := zn*6 + 1
			for order := 0; order < 6; order++ {
				start := int(raw[pn+order])
				end := int(raw[pn+order+1])
				if start < 0 || end < start || end > len(raw) {
					return nil, fmt.Errorf("planet raw data %d coord %d order %d invalid cut: %d..%d (len=%d)", bodyIndex, zn, order, start, end, len(raw))
				}
				view.coords[zn].orders[order] = raw[start:end]
			}
		}
		views[bodyIndex] = view
	}
	return views, nil
}