package stl2gltf

import (
	"encoding/binary"
	"log"
	"math"
	"os"
)

func Load(filePath string) (stl STL) {
	file, err := os.OpenFile(filePath, os.O_RDONLY, os.ModePerm)
	if err != nil {
		log.Panic("open file " + filePath + " error: " + err.Error())
	}

	// load 80 header
	headerBuf := make([]byte, 80)
	file.Read(headerBuf)
	// int32
	triangleNumBuf := make([]byte, 4)
	file.Read(triangleNumBuf)

	stl.Header = string(headerBuf)
	stl.TriangleNum = int(binary.LittleEndian.Uint32(triangleNumBuf))

	stl.Triangles = make([]Triangle, 0)

	max := []float32{0, 0, 0}
	min := []float32{0, 0, 0}
	for range stl.TriangleNum {
		normalBuf := make([]byte, 4*3)
		file.Read(normalBuf)

		positionBuf := make([]byte, 4*3*3)
		file.Read(positionBuf)
		// find max/min xyz
		for r := range 3 {
			x := math.Float32frombits(binary.LittleEndian.Uint32(positionBuf[:4+(r*4)]))
			y := math.Float32frombits(binary.LittleEndian.Uint32(positionBuf[(r * 4) : (r*4)+4]))
			z := math.Float32frombits(binary.LittleEndian.Uint32(positionBuf[(r*4)+4 : (r*4)+8]))
			if max[0] < x {
				max[0] = x
			}
			if max[1] < y {
				max[1] = y
			}
			if max[2] < z {
				max[2] = z
			}
			if min[0] > x {
				min[0] = x
			}
			if min[1] > y {
				min[1] = y
			}
			if min[2] > z {
				min[2] = z
			}
		}

		attributeBuf := make([]byte, 2)
		file.Read(attributeBuf)

		stl.Triangles = append(stl.Triangles, Triangle{
			Normal:    normalBuf,
			Position:  positionBuf,
			Attribute: attributeBuf,
		})
	}

	stl.Max = max
	stl.Min = min

	return stl
}