mod mesh_loader;

use std::fs::File;
use std::{env, io};
use std::f32::consts::PI;
use std::io::{BufRead, BufReader, BufWriter};
use std::io::Write;
use rand::Rng;
use glm::*;
use crate::mesh_loader::load_mesh;

const W: i32 = 320;
const H: i32 = 240;
const SCALE: f32 = 30.0;

#[derive(Copy, Clone)]
struct Color(u8, u8, u8);

#[derive(Copy, Clone)]
struct Comparer {
	coef: Vec2,
	thr: f32,
}

impl Comparer {
	fn new(a: Vec2, b: Vec2) -> Comparer {
		let d = b - a;
		let ortho = vec2(-d.y, d.x);
		Comparer {
			coef: ortho,
			thr: dot(a, ortho),
		}
	}

	fn dist(&self, p: Vec2) -> f32 {
		dot(p, self.coef) - self.thr
	}

	fn test(&self, p: Vec2) -> bool {
		self.dist(p) > 0.0
	}
}

struct Image {
	w: i32,
	h: i32,
	data: Vec<u8>,
}

impl Image {
	fn data(&self) -> &[u8] {
		self.data.as_slice()
	}

	fn put_pixel(&mut self, x: i32, y: i32, color: Color) {
		if x < 0 || x >= self.w || y < 0 || y > self.h {
			return;
		}
		let index = 3 * (x + self.w * y) as usize;
		self.data[index] = color.0;
		self.data[index + 1] = color.1;
		self.data[index + 2] = color.2;
	}

	fn draw_line(&mut self, a: IVec2, b: IVec2, color: Color) {}
	fn draw_tri(&mut self, a: Vec2, b: Vec2, c: Vec2, color: Color) {
		let u = Comparer::new(a, b);
		let v = Comparer::new(b, c);
		let w = Comparer::new(c, a);
		for y in 0..self.h {
			for x in 0..self.w {
				let p = vec2(x as f32, y as f32);
				if u.test(p) && v.test(p) && w.test(p) || !u.test(p) && !v.test(p) && !w.test(p) {
					self.put_pixel(x, y, color);
				}
			}
		}
	}
}

fn main() -> io::Result<()> {
	let args: Vec<String> = env::args().collect();
	let mesh = {
		let f = File::open(&args[1])?;
		let mut f = BufReader::new(f);
		load_mesh(&mut f)?
	};
	let mut img = Image {
		w: W,
		h: H,
		data: vec![0; (3 * W * H) as usize],
	};
	let yaw = PI / 4.0;
	let pitch = PI / 6.0;
	let roll = 0.0f32;
	let m_roll = mat3(
		roll.cos(), roll.sin(), 0.0,
		-roll.sin(), roll.cos(), 0.0,
		0.0, 0.0, 1.0);
	let m_yaw = mat3(
		-yaw.cos(), 0.0, yaw.sin(),
		0.0, 1.0, 0.0,
		-yaw.sin(), 0.0, -yaw.cos());
	let m_pitch = mat3(
		1.0, 0.0, 0.0,
		0.0, pitch.cos(), pitch.sin(),
		0.0, -pitch.sin(), pitch.cos());
	let m_view = m_roll * m_pitch * m_yaw;
	let m_camera = transpose(&m_view);
	let img_size = vec2(W as f32, H as f32);
	for y in 0..H {
		for x in 0..W {
			let img_coords: Vec2 = vec2(x as f32, y as f32);

			// perspective projection
			let off = (img_coords - img_size * 0.5) / img_size.y;
			let base = vec3(0.0, 0.0, -20.0);
			let ray = vec3(off.x, off.y, 1.0);

			// orthographic projection
			// let off = (img_coords - img_size * 0.5) / SCALE;
			// let base = vec3(off.x, off.y, -10.0);
			// let ray = vec3(0.0, 0.0, 1.0);

			let base = m_camera * base;
			let ray = m_camera * normalize(ray);
			let mut dist = f32::INFINITY;

			for f in &mesh {
				let color = clamp(to_ivec3(f.normal * 120.0 + 128.0), ivec3(0, 0, 0), ivec3(255, 255, 255));
				let fs = (0..3).map(|k| edge_dist(f.vertices[k], f.vertices[(k + 1) % 3], base, ray));
				if fs.into_iter().all(|f| f > 0.0) {
					let m = Mat3 { c0: f.vertices[1] - f.vertices[0], c1: f.vertices[2] - f.vertices[0], c2: -ray };
					if let Some(m) = m.inverse() {
						let rel = m * (base - f.vertices[0]);
						if rel.z > dist {
							continue;
						}
						dist = rel.z;
					} else {
						continue;
					}
					img.put_pixel(x, y, Color(color.x as u8, color.y as u8, color.z as u8));
				}
			}
		}
	}
	let f = File::create("1.ppm")?;
	let mut f = BufWriter::new(f);
	write!(f, "P6\n")?;
	write!(f, "{W} {H} 255\n")?;
	f.write(img.data())?;
	Ok(())
}

fn edge_dist(a: Vec3, b: Vec3, base: Vec3, dir: Vec3) -> f32 {
	Mat3 { c0: b - a, c1: base - a, c2: dir }.determinant()
	Mat3 { c0: b - a, c1: base - a, c2: -dir }.determinant()
}