package main

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

const (
	Width      = 512
	Height     = 512
	ObjectFile = "head.obj"
	Repeat     = 60
)

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

// However flag works... idk
var cpuprofile = flag.String("cpuprofile", "", "write cpu profile to file")
var dozbuf = flag.Bool("zbuffer", false, "Write zbuffer instead of image")
var zcuthigh = flag.Float64("zcuthigh", math.MaxFloat32, "High cutoff for z (values above this will be removed)")
var zcutlow = flag.Float64("zcutlow", -math.MaxFloat32, "Low cutoff for z (values below are removed)")
var p6file = flag.String("p6file", "", "Output binary ppm to given file instead")

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]Vec3f
	var hi = float32(fb.Height - 1)
	minz := float32(math.MaxFloat32)
	maxz := float32(-math.MaxFloat32)
	for range Repeat {
		fb.ResetZBuffer()
		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 = (f[i].X + 1) * halfwidth
				sc[i].Y = hi - (f[i].Y+1)*halfheight
				// NOTE: WE USE NEGATIVE Z BECAUSE IT'S SUPPOSED TO BE DISTANCE! AS-IS, CLOSER
				// POINTS HAVE HIGHER Z VLAUES
				sc[i].Z = -f[i].Z // Pull Z value directly. This is fine, our z-buffer is currently float32
				minz = min(minz, sc[i].Z)
				maxz = max(maxz, sc[i].Z)
			}
			// TESTING
			zch := float32(*zcuthigh)
			zcl := float32(*zcutlow)
			if -sc[0].Z > zch || -sc[1].Z > zch || -sc[2].Z > zch ||
				-sc[0].Z < zcl || -sc[1].Z < zcl || -sc[2].Z < zcl {
				continue
			}
			// To test something, we swap vertex 2 and 3
			//sc[1], sc[2] = sc[2], sc[1]

			l1 := f[2].Sub(f[0])
			n := l1.CrossProduct(f[1].Sub(f[0]))
			n = n.Normalize()
			intensity := n.MultSimp(&light)
			if intensity > 0 {
				Triangle3(&fb, Col2Uint(byte(255*intensity), byte(255*intensity), byte(255*intensity)), sc[0], sc[1], sc[2])
				//Triangle3(&fb, uint(rand.Int()), sc[0], sc[1], sc[2])
				//Triangle1(&fb, uint(rand.Int()), sc[0].ToVec2i(), sc[1].ToVec2i(), sc[2].ToVec2i())
				//Triangle2(&fb, 0xFFFFFF, sc[0], sc[1], sc[2])
			}
		}
	}

	log.Print("Min/max z: ", minz, maxz)

	//log.Print(fb.ZBuffer)

	if *dozbuf {
		log.Printf("Exporting zbuffer ppm to stdout")
		fmt.Print(fb.ZBuffer_ExportPPM())
	} else {
		if *p6file != "" {
			err := os.WriteFile(*p6file, fb.ExportPPMP6(), 0660)
			must(err)
		} else {
			log.Printf("Exporting ppm to stdout")
			fmt.Print(fb.ExportPPM())
		}
	}

	log.Printf("Program end")
}