package main

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

// --- STL Types and Helpers ---

type Point struct {
	X, Y, Z float64
}

func WriteSTL(filename string, triangles [][3]Point) error {
	f, err := os.Create(filename)
	if err != nil {
		return err
	}
	defer f.Close()

	header := make([]byte, 80)
	copy(header, "Generated by pcb-to-stencil")
	if _, err := f.Write(header); err != nil {
		return err
	}

	count := uint32(len(triangles))
	if err := binary.Write(f, binary.LittleEndian, count); err != nil {
		return err
	}

	buf := make([]byte, 50)
	for _, t := range triangles {
		binary.LittleEndian.PutUint32(buf[0:4], math.Float32bits(0))
		binary.LittleEndian.PutUint32(buf[4:8], math.Float32bits(0))
		binary.LittleEndian.PutUint32(buf[8:12], math.Float32bits(0))

		binary.LittleEndian.PutUint32(buf[12:16], math.Float32bits(float32(t[0].X)))
		binary.LittleEndian.PutUint32(buf[16:20], math.Float32bits(float32(t[0].Y)))
		binary.LittleEndian.PutUint32(buf[20:24], math.Float32bits(float32(t[0].Z)))

		binary.LittleEndian.PutUint32(buf[24:28], math.Float32bits(float32(t[1].X)))
		binary.LittleEndian.PutUint32(buf[28:32], math.Float32bits(float32(t[1].Y)))
		binary.LittleEndian.PutUint32(buf[32:36], math.Float32bits(float32(t[1].Z)))

		binary.LittleEndian.PutUint32(buf[36:40], math.Float32bits(float32(t[2].X)))
		binary.LittleEndian.PutUint32(buf[40:44], math.Float32bits(float32(t[2].Y)))
		binary.LittleEndian.PutUint32(buf[44:48], math.Float32bits(float32(t[2].Z)))

		binary.LittleEndian.PutUint16(buf[48:50], 0)

		if _, err := f.Write(buf); err != nil {
			return err
		}
	}
	return nil
}

func AddBox(triangles *[][3]Point, x, y, w, h, zHeight float64) {
	x0, y0 := x, y
	x1, y1 := x+w, y+h
	z0, z1 := 0.0, zHeight

	p000 := Point{x0, y0, z0}
	p100 := Point{x1, y0, z0}
	p110 := Point{x1, y1, z0}
	p010 := Point{x0, y1, z0}
	p001 := Point{x0, y0, z1}
	p101 := Point{x1, y0, z1}
	p111 := Point{x1, y1, z1}
	p011 := Point{x0, y1, z1}

	addQuad := func(a, b, c, d Point) {
		*triangles = append(*triangles, [3]Point{a, b, c})
		*triangles = append(*triangles, [3]Point{c, d, a})
	}

	addQuad(p000, p010, p110, p100) // Bottom
	addQuad(p101, p111, p011, p001) // Top
	addQuad(p000, p100, p101, p001) // Front
	addQuad(p100, p110, p111, p101) // Right
	addQuad(p110, p010, p011, p111) // Back
	addQuad(p010, p000, p001, p011) // Left
}