use bytemuck::{Pod, Zeroable};
use winit::event::*;

#[rustfmt::skip]
pub const OPENGL_TO_WGPU_MATRIX: cgmath::Matrix4<f32> = cgmath::Matrix4::new(
    1.0, 0.0, 0.0, 0.0,
    0.0, 1.0, 0.0, 0.0,
    0.0, 0.0, 0.5, 0.0,
    0.0, 0.0, 0.5, 1.0,
);

pub struct Camera {
    pub eye: cgmath::Point3<f32>,
    pub target: cgmath::Point3<f32>,
    pub up: cgmath::Vector3<f32>,
    pub aspect: f32,
    pub fovy: f32,
    pub znear: f32,
    pub zfar: f32,
}

impl Camera {
    pub fn build_view_projection_matrix(&self) -> cgmath::Matrix4<f32> {
        let view = cgmath::Matrix4::look_at_rh(self.eye, self.target, self.up);
        let proj = cgmath::perspective(cgmath::Deg(self.fovy), self.aspect, self.znear, self.zfar);

        OPENGL_TO_WGPU_MATRIX * proj * view
    }
}

// This is so we can store this in a buffer
#[repr(C)]
#[derive(Debug, Copy, Clone, Pod, Zeroable)]
pub struct CameraUniform {
    // We can't use cgmath with bytemuck directly so we'll have
    // to convert the Matrix4 into a 4x4 f32 array
    pub view_proj: [[f32; 4]; 4],
}

impl CameraUniform {
    pub fn new() -> Self {
        use cgmath::SquareMatrix;
        Self {
            view_proj: cgmath::Matrix4::identity().into(),
        }
    }

    pub fn update_view_proj(&mut self, camera: &Camera) {
        self.view_proj = camera.build_view_projection_matrix().into();
    }
}

pub struct CameraController {
    pub speed: f32,
    pub is_up_pressed: bool,
    pub is_down_pressed: bool,
    pub is_forward_pressed: bool,
    pub is_backward_pressed: bool,
    pub is_left_pressed: bool,
    pub is_right_pressed: bool,
}

impl CameraController {
    pub fn new(speed: f32) -> Self {
        Self {
            speed,
            is_up_pressed: false,
            is_down_pressed: false,
            is_forward_pressed: false,
            is_backward_pressed: false,
            is_left_pressed: false,
            is_right_pressed: false,
        }
    }

    pub fn process_events(&mut self, event: &WindowEvent) -> bool {
        match event {
            WindowEvent::KeyboardInput {
                input:
                    KeyboardInput {
                        state,
                        virtual_keycode: Some(keycode),
                        ..
                    },
                ..
            } => {
                let is_pressed = *state == ElementState::Pressed;
                match keycode {
                    VirtualKeyCode::Space => {
                        self.is_up_pressed = is_pressed;
                        true
                    }
                    VirtualKeyCode::LShift => {
                        self.is_down_pressed = is_pressed;
                        true
                    }
                    VirtualKeyCode::W | VirtualKeyCode::Up => {
                        self.is_forward_pressed = is_pressed;
                        true
                    }
                    VirtualKeyCode::A | VirtualKeyCode::Left => {
                        self.is_left_pressed = is_pressed;
                        true
                    }
                    VirtualKeyCode::S | VirtualKeyCode::Down => {
                        self.is_backward_pressed = is_pressed;
                        true
                    }
                    VirtualKeyCode::D | VirtualKeyCode::Right => {
                        self.is_right_pressed = is_pressed;
                        true
                    }
                    _ => false,
                }
            }
            _ => false,
        }
    }

    pub fn update_camera(&self, camera: &mut Camera) {
        use cgmath::InnerSpace;

        let forward = camera.target - camera.eye;
        let forward_norm = forward.normalize();
        let forward_mag = forward.magnitude();

        // Prevents glitching when camera gets too close to the
        // center of the scene.
        if self.is_forward_pressed && forward_mag > self.speed {
            camera.eye += forward_norm * self.speed;
        }

        if self.is_backward_pressed {
            camera.eye -= forward_norm * self.speed;
        }

        let right = forward_norm.cross(camera.up);

        // Redo radius calc in case the up/ down is pressed.
        let forward = camera.target - camera.eye;
        let forward_mag = forward.magnitude();

        if self.is_right_pressed {
            // Rescale the distance between the target and eye so
            // that it doesn't change. The eye therefore still
            // lies on the circle made by the target and eye.
            camera.eye = camera.target - (forward + right * self.speed).normalize() * forward_mag;
        }

        if self.is_left_pressed {
            camera.eye = camera.target - (forward - right * self.speed).normalize() * forward_mag;
        }
    }
}