use std::{
    num::NonZeroU32,
    time::{Duration, Instant},
};

use game::GameState;
use winit::{
    dpi::PhysicalSize,
    event::{Event, KeyEvent, WindowEvent},
    event_loop::{ControlFlow, EventLoop},
    keyboard::{Key, NamedKey},
    raw_window_handle::{HasDisplayHandle, HasWindowHandle},
    window::WindowBuilder,
};

fn main() {
    let event_loop = EventLoop::new().unwrap();
    let window = WindowBuilder::new()
        .with_inner_size(winit::dpi::Size::Physical(PhysicalSize::new(1200, 700)))
        .build(&event_loop)
        .unwrap();

    // ControlFlow::Poll continuously runs the event loop, even if the OS hasn't
    // dispatched any events. This is ideal for games and similar applications.
    event_loop.set_control_flow(ControlFlow::Poll);

    // ControlFlow::Wait pauses the event loop if no events are available to process.
    // This is ideal for non-game applications that only update in response to user
    // input, and uses significantly less power/CPU time than ControlFlow::Poll.
    event_loop.set_control_flow(ControlFlow::Wait);

    let context = softbuffer::Context::new(window.display_handle().unwrap()).unwrap();
    let mut surface = softbuffer::Surface::new(&context, window.window_handle().unwrap()).unwrap();

    let mut game = GameState::init();

    event_loop
        .run(|event, elwt| {
            elwt.set_control_flow(ControlFlow::WaitUntil(
                Instant::now() + Duration::from_millis(1000 / 60),
            ));

            match event {
                Event::WindowEvent {
                    window_id,
                    event: WindowEvent::RedrawRequested,
                } if window_id == window.id() => {
                    if let (Some(width), Some(height)) = {
                        let size = window.inner_size();
                        (NonZeroU32::new(size.width), NonZeroU32::new(size.height))
                    } {
                        surface.resize(width, height).unwrap();

                        let mut buffer = surface.buffer_mut().unwrap();
                        // for y in 0..height.get() {
                        //     for x in 0..width.get() {
                        //         let red = x % 255;
                        //         let green = y % 255;
                        //         let blue = (x * y) % 255;
                        //         let index = y as usize * width.get() as usize + x as usize;
                        //         buffer[index] = blue | (green << 8) | (red << 16);
                        //     }
                        // }

                        buffer.fill(0);
                        game.update();
                        game.render(&mut buffer, (width, height));

                        buffer.present().unwrap();
                    }
                }
                Event::WindowEvent {
                    event:
                        WindowEvent::CloseRequested
                        | WindowEvent::KeyboardInput {
                            event:
                                KeyEvent {
                                    logical_key: Key::Named(NamedKey::Escape),
                                    ..
                                },
                            ..
                        },
                    window_id,
                } if window_id == window.id() => {
                    elwt.exit();
                }
                _ => {}
            }
        })
        .unwrap();
}

mod game {
    use std::{convert::identity, num::NonZeroU32, time::Instant};

    use softbuffer::Buffer;
    use winit::raw_window_handle::{DisplayHandle, WindowHandle};

    const PADDLE_SIZE: (u32, u32) = (5, 50);
    const BALL_RADIUS: u32 = 10;
    const BALL_VEC_RIGHT_DOWN: (i16, i16) = (8, 12);
    const FIELD_SIZE: (u32, u32) = (1200, 700);
    const FIELD_BORDER_WIDTH: u32 = 5;
    const TICK_LEN: f32 = 1000. / 60.;

    #[derive(Debug, Clone, Copy, PartialEq, Eq)]
    enum BallDirection {
        RightUp,
        RightDown,
        LeftUp,
        LeftDown,
    }

    #[derive(Debug, Clone, Copy, PartialEq, Eq)]
    enum HorizontalCollisionCheck {
        None,
        Left,
        Right,
    }

    #[derive(Debug, Clone, Copy, PartialEq, Eq)]
    enum VerticalCollisionCheck {
        None,
        Top,
        Bottom,
    }

    #[derive(Debug, Clone, Copy, PartialEq, Eq)]
    struct CollisionCheck(HorizontalCollisionCheck, VerticalCollisionCheck);

    impl CollisionCheck {
        fn check_field(obj_pos: (u32, u32), obj_size: (u32, u32)) -> Self {
            let horizontal = if obj_pos.0 == 0 {
                HorizontalCollisionCheck::Left
            } else if (obj_pos.0 + obj_size.0) >= FIELD_SIZE.0 {
                HorizontalCollisionCheck::Right
            } else {
                HorizontalCollisionCheck::None
            };
            let vertical = if obj_pos.1 == 0 {
                VerticalCollisionCheck::Top
            } else if (obj_pos.1 + obj_size.1) >= FIELD_SIZE.1 {
                VerticalCollisionCheck::Bottom
            } else {
                VerticalCollisionCheck::None
            };
            Self(horizontal, vertical)
        }

        fn no_collisions(&self) -> bool {
            matches!(
                self,
                CollisionCheck(HorizontalCollisionCheck::None, VerticalCollisionCheck::None)
            )
        }
    }

    struct MovingObject {
        prev_pos: (u32, u32),
    }

    impl BallDirection {
        fn get_vec(&self) -> (i16, i16) {
            match self {
                BallDirection::RightDown => BALL_VEC_RIGHT_DOWN,
                BallDirection::RightUp => (BALL_VEC_RIGHT_DOWN.0, -BALL_VEC_RIGHT_DOWN.1),
                BallDirection::LeftUp => (-BALL_VEC_RIGHT_DOWN.0, BALL_VEC_RIGHT_DOWN.1),
                BallDirection::LeftDown => (-BALL_VEC_RIGHT_DOWN.0, -BALL_VEC_RIGHT_DOWN.1),
            }
        }
    }

    pub struct GameState {
        ball_pos: (u32, u32),
        ball_direction: BallDirection,
        paddle_r_pos: u32,
        paddle_y_pos: u32,
        scores: (u32, u32),
        last_frame_time: Instant,
    }

    impl GameState {
        pub fn init() -> Self {
            Self {
                ball_pos: (FIELD_SIZE.0 / 2, FIELD_SIZE.1 / 2),
                paddle_r_pos: FIELD_SIZE.0 / 2,
                paddle_y_pos: FIELD_SIZE.0 / 2,
                ball_direction: BallDirection::RightDown,
                scores: (0, 0),
                last_frame_time: Instant::now(),
            }
        }

        pub fn render(
            &self,
            buf: &mut Buffer<'_, DisplayHandle<'_>, WindowHandle<'_>>,
            win_size: (NonZeroU32, NonZeroU32),
        ) {
            let win_size = (win_size.0.get(), win_size.1.get());
            self.render_field(buf, win_size);
            self.render_ball(buf, win_size);
        }

        pub fn update(&mut self) {
            let delta_t = self.delta_time();

            self.last_frame_time = Instant::now();
            self.move_ball();
        }

        fn move_ball(&mut self) {
            let vec = self.ball_direction.get_vec();
            let delta_t = self.delta_time();

            let new_pos = (
                self.ball_pos
                    .0
                    .saturating_add_signed((vec.0 as f32 * delta_t) as i32)
                    .clamp(0, FIELD_SIZE.0 - BALL_RADIUS),
                self.ball_pos
                    .1
                    .saturating_add_signed((vec.1 as f32 * delta_t) as i32)
                    .clamp(0, FIELD_SIZE.1 - BALL_RADIUS),
            );
            // println!("{:?} -> {:?}", self.ball_pos, new_pos);
            self.ball_pos = new_pos;

            let check_res = CollisionCheck::check_field(
                (
                    new_pos.0.saturating_sub(BALL_RADIUS),
                    new_pos.1.saturating_sub(BALL_RADIUS),
                ),
                (BALL_RADIUS * 2, BALL_RADIUS * 2),
            );

            let CollisionCheck(horizontal, vertical) = check_res;

            self.ball_direction = match (self.ball_direction, (horizontal, vertical)) {
                (
                    BallDirection::RightUp,
                    (HorizontalCollisionCheck::None, VerticalCollisionCheck::Bottom),
                )
                | (
                    BallDirection::RightDown,
                    (HorizontalCollisionCheck::None, VerticalCollisionCheck::None),
                )
                | (
                    BallDirection::LeftUp,
                    (HorizontalCollisionCheck::Left, VerticalCollisionCheck::None),
                )
                | (
                    BallDirection::LeftDown,
                    (HorizontalCollisionCheck::Left, VerticalCollisionCheck::Top),
                ) => BallDirection::RightDown,

                (
                    BallDirection::RightUp,
                    (HorizontalCollisionCheck::None, VerticalCollisionCheck::None),
                )
                | (
                    BallDirection::RightDown,
                    (HorizontalCollisionCheck::None, VerticalCollisionCheck::Top),
                )
                | (
                    BallDirection::LeftUp,
                    (HorizontalCollisionCheck::Left, VerticalCollisionCheck::Top),
                )
                | (
                    BallDirection::LeftDown,
                    (HorizontalCollisionCheck::Left, VerticalCollisionCheck::None),
                ) => BallDirection::RightUp,

                (
                    BallDirection::RightUp,
                    (HorizontalCollisionCheck::Right, VerticalCollisionCheck::Bottom),
                )
                | (
                    BallDirection::RightDown,
                    (HorizontalCollisionCheck::Right, VerticalCollisionCheck::None),
                )
                | (
                    BallDirection::LeftUp,
                    (HorizontalCollisionCheck::None, VerticalCollisionCheck::None),
                )
                | (
                    BallDirection::LeftDown,
                    (HorizontalCollisionCheck::None, VerticalCollisionCheck::Bottom),
                ) => BallDirection::LeftUp,

                (
                    BallDirection::RightUp,
                    (HorizontalCollisionCheck::Right, VerticalCollisionCheck::None),
                )
                | (
                    BallDirection::RightDown,
                    (HorizontalCollisionCheck::Right, VerticalCollisionCheck::Top),
                )
                | (
                    BallDirection::LeftUp,
                    (HorizontalCollisionCheck::None, VerticalCollisionCheck::Top),
                )
                | (
                    BallDirection::LeftDown,
                    (HorizontalCollisionCheck::None, VerticalCollisionCheck::None),
                ) => BallDirection::LeftDown,

                other => panic!("Invalid collision: {other:#?}"),
            };
        }

        fn delta_time(&self) -> f32 {
            Instant::now()
                .duration_since(self.last_frame_time)
                .as_millis() as f32
                / TICK_LEN
        }

        fn render_field(
            &self,
            buf: &mut Buffer<'_, DisplayHandle<'_>, WindowHandle<'_>>,
            win_size: (u32, u32),
        ) {
            let field_pos = (
                (win_size.0 / 2).saturating_sub(FIELD_SIZE.0 / 2),
                (win_size.1 / 2).saturating_sub(FIELD_SIZE.1 / 2),
            );

            // top border
            draw_rect(
                buf,
                win_size,
                (
                    field_pos.0.saturating_sub(FIELD_BORDER_WIDTH),
                    field_pos.1.saturating_sub(FIELD_BORDER_WIDTH),
                ),
                (
                    FIELD_SIZE.0.saturating_add(FIELD_BORDER_WIDTH * 2),
                    FIELD_BORDER_WIDTH,
                ),
                0xff0000,
            );
            // right border
            draw_rect(
                buf,
                win_size,
                (field_pos.0.saturating_add(FIELD_SIZE.0), field_pos.1),
                (FIELD_BORDER_WIDTH, FIELD_SIZE.1),
                0x00ff00,
            );
            // bottom border
            draw_rect(
                buf,
                win_size,
                (
                    field_pos.0.saturating_sub(FIELD_BORDER_WIDTH),
                    field_pos.1.saturating_add(FIELD_SIZE.1),
                ),
                (
                    FIELD_SIZE.0.saturating_add(FIELD_BORDER_WIDTH * 2),
                    FIELD_BORDER_WIDTH,
                ),
                0xff00ff,
            );
            // left border
            draw_rect(
                buf,
                win_size,
                (field_pos.0.saturating_sub(FIELD_BORDER_WIDTH), field_pos.1),
                (FIELD_BORDER_WIDTH, FIELD_SIZE.1),
                0x00ffff,
            );
            // draw midline
            draw_rect(
                buf,
                win_size,
                ((win_size.0 / 2) - (FIELD_BORDER_WIDTH / 2), field_pos.1),
                (FIELD_BORDER_WIDTH, FIELD_SIZE.1),
                0x7f7f7f,
            )
        }
        fn render_ball(
            &self,
            buf: &mut Buffer<'_, DisplayHandle<'_>, WindowHandle<'_>>,
            win_size: (u32, u32),
        ) {
            let field_pos = (
                (win_size.0 / 2).saturating_sub(FIELD_SIZE.0 / 2),
                (win_size.1 / 2).saturating_sub(FIELD_SIZE.1 / 2),
            );
            // let field_pos = identity((
            //     (win_size.0 / 2).saturating_sub(FIELD_SIZE.0 / 2),
            //     (win_size.1 / 2).saturating_sub(FIELD_SIZE.1 / 2),
            // ));
            // println!("{}, {}", field_pos.0, field_pos.1);

            let ball_render_pos = (
                (self.ball_pos.0 + field_pos.0).saturating_sub(BALL_RADIUS),
                (self.ball_pos.1 + field_pos.1).saturating_sub(BALL_RADIUS),
            );

            draw_rect(
                buf,
                win_size,
                ball_render_pos,
                (BALL_RADIUS * 2, BALL_RADIUS * 2),
                0xffffff,
            );
        }
        fn render_paddles(
            &self,
            buf: &mut Buffer<'_, DisplayHandle<'_>, WindowHandle<'_>>,
            win_size: (u32, u32),
        ) {
            todo!()
        }
        fn render_paddle(
            &self,
            buf: &mut Buffer<'_, DisplayHandle<'_>, WindowHandle<'_>>,
            win_size: (u32, u32),
        ) {
            todo!()
        }
        fn render_scores(
            &self,
            buf: &mut Buffer<'_, DisplayHandle<'_>, WindowHandle<'_>>,
            win_size: (u32, u32),
        ) {
            todo!()
        }
    }

    fn draw_rect(
        buf: &mut Buffer<'_, DisplayHandle<'_>, WindowHandle<'_>>,
        buf_size: (u32, u32),
        pos: (u32, u32),
        size: (u32, u32),
        color: u32,
    ) {
        for y in pos.1..(pos.1 + size.1) {
            for x in pos.0..(pos.0 + size.0) {
                let index = y as usize * buf_size.0 as usize + x as usize;
                if let Some(px) = buf.get_mut(index) {
                    *px = color
                }
            }
        }
    }
}