package main

import (
	"flag"
	"fmt"
	"log"
	// "math/rand"
	"os"
	"runtime/pprof" // For performance profiling (unnecessary)
)

const (
	Width      = 512
	Height     = 512
	ObjectFile = "head.obj"
	Repeat     = 600
)

func must(err error) {
	if err != nil {
		panic(err)
	}
}

// However flag works... idk
var cpuprofile = flag.String("cpuprofile", "", "write cpu profile to file")

func main() {
	log.Printf("Program start")

	// Little section for doing cpu profiling. I guess that's all you have to do?
	flag.Parse()
	if *cpuprofile != "" {
		log.Printf("CPU profiling requested, write to %s", *cpuprofile)
		f, err := os.Create(*cpuprofile)
		must(err)
		defer f.Close()
		err = pprof.StartCPUProfile(f)
		must(err)
		defer pprof.StopCPUProfile()
	}

	fb := NewFramebuffer(Width, Height)

	log.Printf("Loading obj %s", ObjectFile)

	of, err := os.Open(ObjectFile)
	must(err)
	defer of.Close()
	o, err := ParseObj(of)
	must(err)

	log.Printf("Running render")

	light := Vec3f{0, 0, -1}

	// for range Repeat  {
	// 	Triangle2(&fb, 0xFF0000, Vec2i{10, 70}, Vec2i{50, 160}, Vec2i{70, 80})
	// 	Triangle2(&fb, 0xFFFFFF, Vec2i{180, 50}, Vec2i{150, 1}, Vec2i{70, 180})
	// 	Triangle2(&fb, 0x00FF00, Vec2i{180, 150}, Vec2i{120, 160}, Vec2i{130, 180})
	// }

	halfwidth := float32(fb.Width / 2)
	halfheight := float32(fb.Height / 2)
	var sc [3]Vec2i
	var hi = int(fb.Height - 1)
	for range Repeat {
		for _, f := range o.Faces {
			// Precompute perspective for vertices to save time. Notice Z
			// is not considered: is this orthographic projection? Yeah probably...
			for i := range 3 { // Triangles, bro
				sc[i].X = int((f[i].X + 1) * halfwidth)
				sc[i].Y = hi - int((f[i].Y+1)*halfheight)
			}
			l1 := f[2].Sub(f[0])
			n := l1.CrossProduct(f[1].Sub(f[0]))
			n = n.Normalize()
			intensity := n.MultSimp(&light)
			if intensity > 0 {
				Triangle2(&fb, Col2Uint(byte(255*intensity), byte(255*intensity), byte(255*intensity)), sc[0], sc[1], sc[2])
				//Triangle2(&fb, 0xFFFFFF, sc[0], sc[1], sc[2])
			}
			// Vec2i{10, 70}, Vec2i{50, 160}, Vec2i{70, 80})
			// Bresenham2(&fb, 0xFFFFFF, x[0], y[0], x[1], y[1])
			// Bresenham2(&fb, 0xFFFFFF, x[1], y[1], x[2], y[2])
			// Bresenham2(&fb, 0xFFFFFF, x[2], y[2], x[0], y[0])
		}
	}

	log.Printf("Exporting ppm to stdout")
	fmt.Print(fb.ExportPPM())

	log.Printf("Program end")
}