package calculator

import (
	"math"

	"gonum.org/v1/gonum/mat"
	"gonum.org/v1/gonum/spatial/r3"
)

// OrbitToECMatrix 轨道坐标系到ECI、ECEF坐标系的变换矩阵
func OrbitToECMatrix(pos, vec []float64) *mat.Dense {
	r := r3.Vec{X: pos[0], Y: pos[1], Z: pos[2]}
	rmag := r3.Norm(r) // Magnitude
	v := r3.Vec{X: vec[0], Y: vec[1], Z: vec[2]}
	vmag := r3.Norm(v) // Magnitude of velocity vector
	w := r3.Cross(v, r)
	wmag := r3.Norm(w)

	z0 := r3.Scale(-1/rmag, r) // z方向指向地心
	y0 := r3.Scale(1/wmag, w)
	x0 := r3.Scale(1/vmag, v)

	m := mat.NewDense(3, 3, []float64{
		x0.X, y0.X, z0.X,
		x0.Y, y0.Y, z0.Y,
		x0.Z, y0.Z, z0.Z,
	})

	return m
}

// IntersectionECEF 计算卫星与相机的交点，返回经纬度和高度
// FIXME: 该计算方法有误，待修正
func IntersectionECEF(Qsat2orbit Quaternion, satPos84, vec84 []float64, ucam int) (IntersectionPoint, error) {
	alpha := FOV * math.Pi / 180.0
	alpha = -alpha/2.0 + float64(ucam)*(alpha/float64(PANPixels))
	direction := []float64{0, math.Tan(alpha), -1.3} // 卫星（相机）坐标系下CCD成像方向向量

	// -------- 相机坐标系下CCD成像方向向量转到卫星坐标系 --------
	Rcam := CameraRotMatrix(CameraRoll*math.Pi/180.0, CameraPitch*math.Pi/180.0, 0)
	var dCam mat.VecDense
	dCam.MulVec(Rcam, mat.NewVecDense(3, direction))

	// -------- 转到轨道坐标系 --------
	Rsat2orbit := Qsat2orbit.ToRotationMatrix()
	var r0 mat.VecDense
	r0.MulVec(Rsat2orbit, &dCam)
	dOrbit := r0.RawVector().Data

	// -------- 转到ECEF坐标系 --------
	Rorbit2ecef := OrbitToECMatrix(satPos84, vec84)
	var r1 mat.VecDense
	r1.MulVec(Rorbit2ecef, mat.NewVecDense(3, dOrbit))
	dECEF := r1.RawVector().Data

	// -------- 计算交点 --------}
	intersection, err := intersectWithEllipsoid(satPos84, dECEF)
	if err != nil {
		return IntersectionPoint{}, err
	}

	lat, lon, h := ECEFToGeodetic(intersection[0], intersection[1], intersection[2])

	return IntersectionPoint{Lat: lat, Lon: lon, H: h}, err
}