package calculator

import (
	"math"
	"time"

	"gonum.org/v1/gonum/mat"
)

// 常量
const (
	focal   = 1.3  // 焦距, m
	FOV     = 1.7  // 视场角,degree
	nPixels = 9344 // 像素数
)

func Intersection(q Quaternion, satPos []float64, satTime time.Time, ucam int) (float64, float64) {
	alpha := FOV * math.Pi / 180.0
	alpha = -alpha/2.0 + float64(ucam)*(alpha/float64(nPixels))
	direction := []float64{0, math.Tan(alpha), -1.3}

	Ratt := q.ToRotationMatrix()
	RattT := &mat.Dense{}
	RattT.Inverse(Ratt)

	v := mat.NewVecDense(3, direction)
	var result mat.VecDense
	result.MulVec(Ratt, v)
	eciDirection := result.RawVector().Data

	// intersection := intersectWithEllipsoid(satPos, eciDirection)
	// lat, lon, _ := J2000ToWGS84(intersection[0], intersection[1], intersection[2], satTime)

	x, y, z := ECItoECEF(eciDirection[0], eciDirection[1], eciDirection[2], satTime)
	ecefDirection := []float64{x, y, z}
	intersection := intersectWithEllipsoid(satPos, ecefDirection)
	lat, lon, _ := ECEFToGeodetic(intersection[0], intersection[1], intersection[2])

	return lat, lon

}

// 计算与椭球表面的交点
func intersectWithEllipsoid(p0, d []float64) []float64 {
	a2 := a * a
	b2 := b * b

	A := d[0]*d[0]/a2 + d[1]*d[1]/a2 + d[2]*d[2]/b2
	B := 2 * (p0[0]*d[0]/a2 + p0[1]*d[1]/a2 + p0[2]*d[2]/b2)
	C := p0[0]*p0[0]/a2 + p0[1]*p0[1]/a2 + p0[2]*p0[2]/b2 - 1

	delta := B*B - 4*A*C
	if delta < 0 {
		return nil // No intersection
	}
	t1 := (-B + math.Sqrt(delta)) / (2 * A)
	t2 := (-B - math.Sqrt(delta)) / (2 * A)
	t := math.Max(t1, t2)
	return []float64{
		p0[0] + t*d[0],
		p0[1] + t*d[1],
		p0[2] + t*d[2],
	}
}