use std::{collections::HashSet, time::Instant};

use glam::{mat4, vec2, vec3, vec4, Mat4, Quat, Vec2, Vec3};
use glium::{
	backend::{glutin::SimpleWindowBuilder, Facade},
	glutin::config::ConfigTemplateBuilder,
	implement_vertex,
	index::PrimitiveType,
	uniform,
	winit::event::{Event, WindowEvent},
	DrawParameters, Program, Surface, VertexBuffer,
};
use winit::{
	event::ElementState,
	event_loop::EventLoop,
	keyboard::{KeyCode, PhysicalKey},
};

mod scene;

// The coordinate system:
// * X: forward
// * Y: left
// * Z: up

#[derive(Copy, Clone)]
struct Vertex {
	position: [f32; 3],
}
implement_vertex!(Vertex, position);

struct DragCtl<S> {
	state: S,
	ctl: Option<(Vec2, S)>,
}

impl<S: Copy> DragCtl<S> {
	pub fn new(state: S) -> Self {
		Self { state, ctl: None }
	}

	pub fn state(&self) -> S {
		self.state
	}

	pub fn on_button(&mut self, pos: Vec2, state: ElementState) {
		match state {
			ElementState::Pressed => {
				if self.ctl.is_none() {
					self.ctl = Some((pos, self.state));
				}
			}
			ElementState::Released => {
				self.ctl = None;
			}
		}
	}

	pub fn on_move(&mut self, pos: Vec2, f: impl FnOnce(S, Vec2) -> S) {
		if let Some((old_pos, old_state)) = self.ctl {
			self.state = f(old_state, pos - old_pos);
		}
	}
}

struct Wireframe {
	color: Vec3,
	mode: PrimitiveType,
	data: VertexBuffer<Vertex>,
}

fn prepare_scene(display: &impl Facade) -> Vec<Wireframe> {
	scene::build()
		.into_iter()
		.map(|line| {
			let color = line.color;
			let mode;
			let data: Vec<Vertex>;
			match line.line {
				scene::Line::Lines(_) => todo!(),
				scene::Line::Strip(pts) => {
					mode = PrimitiveType::LineStrip;
					data = pts
						.into_iter()
						.map(|p| Vertex {
							position: p.to_array(),
						})
						.collect();
				}
				scene::Line::Loop(pts) => {
					mode = PrimitiveType::LineLoop;
					data = pts
						.into_iter()
						.map(|p| Vertex {
							position: p.to_array(),
						})
						.collect();
				}
			};
			let data = VertexBuffer::new(display, &data).unwrap();
			Wireframe { color, mode, data }
		})
		.collect()
}

fn main() {
	let event_loop = EventLoop::builder().build().unwrap();
	let cfg = ConfigTemplateBuilder::new().with_multisampling(8);
	let (window, display) = SimpleWindowBuilder::new()
		.with_config_template_builder(cfg)
		.with_title("Refraction: Wireframe")
		.build(&event_loop);

	let mut keys_pressed = HashSet::<PhysicalKey>::new();

	let vs_src = include_str!("ray.v.glsl");
	let fs_src = include_str!("ray.f.glsl");
	let program = Program::from_source(&display, vs_src, fs_src, None).unwrap();

	let scene = prepare_scene(&display);

	let rot = Quat::from_euler(glam::EulerRot::ZYX, std::f32::consts::FRAC_PI_4, 0., 0.);
	let mut cur_pos = vec2(0., 0.);
	let mut cam_pos = rot * vec3(-200., 0., 50.);
	let mut cam_rot = DragCtl::new(rot);

	let mut t1 = Instant::now();

	#[allow(deprecated)]
	event_loop
		.run(move |ev, window_target| match ev {
			Event::WindowEvent { event, .. } => match event {
				WindowEvent::RedrawRequested => {
					let dt = {
						let t2 = Instant::now();
						let dt = t2 - t1;
						t1 = t2;
						dt.as_secs_f32()
					};
					let v: Vec3 = {
						let ctl_left = keys_pressed.contains(&PhysicalKey::Code(KeyCode::KeyA));
						let ctl_right = keys_pressed.contains(&PhysicalKey::Code(KeyCode::KeyD));
						let ctl_fwd = keys_pressed.contains(&PhysicalKey::Code(KeyCode::KeyW));
						let ctl_bwd = keys_pressed.contains(&PhysicalKey::Code(KeyCode::KeyS));
						let ctl_up = keys_pressed.contains(&PhysicalKey::Code(KeyCode::Space));
						let ctl_down =
							keys_pressed.contains(&PhysicalKey::Code(KeyCode::ShiftLeft));
						[
							(ctl_left, vec3(0., 1., 0.)),
							(ctl_right, vec3(0., -1., 0.)),
							(ctl_fwd, vec3(1., 0., 0.)),
							(ctl_bwd, vec3(-1., 0., 0.)),
							(ctl_up, vec3(0., 0., 1.)),
							(ctl_down, vec3(0., 0., -1.)),
						]
						.into_iter()
						.filter_map(|(ctl, dir)| ctl.then_some(dir))
						.sum()
					};
					cam_pos += 100. * dt * (cam_rot.state() * v);

					let size = window.inner_size();
					let size = vec2(size.width as f32, size.height as f32).normalize()
						* std::f32::consts::SQRT_2;
					let proj = make_proj_matrix(vec3(size.x, size.y, 2.), (1., 4096.));

					let my_to_gl = mat4(
						vec4(0., 0., 1., 0.),
						vec4(-1., 0., 0., 0.),
						vec4(0., 1., 0., 0.),
						vec4(0., 0., 0., 1.),
					);

					let view = my_to_gl
						* Mat4::from_quat(cam_rot.state().inverse())
						* Mat4::from_translation(-cam_pos);

					let mut target = display.draw();
					target.clear_color(0.0, 0.0, 0.0, 0.0);

					let mvp = proj * view;
					let params = DrawParameters {
						blend: glium::Blend {
							color: glium::BlendingFunction::Addition {
								source: glium::LinearBlendingFactor::One,
								destination: glium::LinearBlendingFactor::OneMinusSourceAlpha,
							},
							alpha: glium::BlendingFunction::Addition {
								source: glium::LinearBlendingFactor::One,
								destination: glium::LinearBlendingFactor::OneMinusSourceAlpha,
							},
							constant_value: (0., 0., 0., 0.),
						},
						line_width: Some(3.),
						smooth: Some(glium::Smooth::Nicest),
						..Default::default()
					};
					for mesh in &scene {
						let uniforms = uniform! {
							mvp: mvp.to_cols_array_2d(),
							color: mesh.color.to_array(),
						};
						let indices = glium::index::NoIndices(mesh.mode);
						target
							.draw(&mesh.data, &indices, &program, &uniforms, &params)
							.unwrap();
					}
					target.finish().unwrap();
				}

				WindowEvent::MouseInput {
					device_id: _,
					state,
					button,
				} => match button {
					winit::event::MouseButton::Right => cam_rot.on_button(cur_pos, state),
					_ => {}
				},

				WindowEvent::CursorMoved {
					device_id: _,
					position,
				} => {
					let size = window.inner_size();
					let size = vec2(size.width as f32, size.height as f32);
					cur_pos = vec2(position.x as f32, position.y as f32) / size.length();
					cam_rot.on_move(cur_pos, |init, off| {
						window.request_redraw();
						init * Quat::from_euler(glam::EulerRot::ZYX, 2. * off.x, -2. * off.y, 0.)
					});
				}

				WindowEvent::KeyboardInput {
					device_id: _,
					event,
					is_synthetic: _,
				} => {
					match event.state {
						ElementState::Pressed => keys_pressed.insert(event.physical_key),
						ElementState::Released => keys_pressed.remove(&event.physical_key),
					};
				}

				WindowEvent::Resized(window_size) => {
					display.resize(window_size.into());
				}

				WindowEvent::CloseRequested => {
					window_target.exit();
				}

				_ => (),
			},

			Event::AboutToWait => {
				window.request_redraw();
			}
			_ => (),
		})
		.unwrap();
}

/// Make a projection matrix, assuming input coordinates are (right, up, forward).
///
/// `corner` is a vector that will be mapped to (x=1, y=1) after the perspective division.
/// `zrange` is the Z range that will be mapped to z∈[-1, 1]. It has no other effect. Both ends have to be positive though.
fn make_proj_matrix(corner: Vec3, zrange: (f32, f32)) -> Mat4 {
	let scale = 1.0 / corner;
	let zspan = zrange.1 - zrange.0;
	mat4(
		scale.x * vec4(1., 0., 0., 0.),
		scale.y * vec4(0., 1., 0., 0.),
		scale.z * vec4(0., 0., (zrange.0 + zrange.1) / zspan, 1.),
		scale.z * vec4(0., 0., -2. * zrange.0 * zrange.1 / zspan, 0.),
	)
}

#[cfg(test)]
mod tests {
	use super::*;
	use approx::assert_abs_diff_eq;
	use glam::vec3;

	#[test]
	fn test_proj_matrix() {
		let m = make_proj_matrix(vec3(2., 3., 4.), (0.5, 20.0));

		let v = m * vec4(2., 3., 4., 1.);
		assert_abs_diff_eq!(v.x / v.w, 1.0);
		assert_abs_diff_eq!(v.y / v.w, 1.0);
		assert!(-v.w < v.z && v.z < v.w, "z out of range in {v}");

		let v = m * vec4(2., 3., 0.5, 1.);
		assert_abs_diff_eq!(v.x / v.w, 8.0);
		assert_abs_diff_eq!(v.y / v.w, 8.0);
		assert_abs_diff_eq!(v.z / v.w, -1.0);

		let v = m * vec4(2., 3., 20.0, 1.);
		assert_abs_diff_eq!(v.x / v.w, 0.2);
		assert_abs_diff_eq!(v.y / v.w, 0.2);
		assert_abs_diff_eq!(v.z / v.w, 1.0);
	}
}