use wgpu::util::DeviceExt;

use winit::{
    event::*,
    event_loop::{ControlFlow, EventLoop},
    window::WindowBuilder,
};

mod camera;

use camera::*;

struct Renderer {
    pub device: wgpu::Device,
    pub mesh_pool: MeshPool,
    pub size: winit::dpi::PhysicalSize<u32>,
    surface: wgpu::Surface,
    queue: wgpu::Queue,
    config: wgpu::SurfaceConfiguration,
}

impl Renderer {
    pub async fn new(window: &winit::window::Window) -> Self {
        let size = window.inner_size();

        let instance = wgpu::Instance::new(wgpu::Backends::all());
        let surface = unsafe { instance.create_surface(window) };
        let adapter = instance
            .request_adapter(&wgpu::RequestAdapterOptions {
                power_preference: wgpu::PowerPreference::HighPerformance,
                compatible_surface: Some(&surface),
                force_fallback_adapter: false,
            })
            .await
            .unwrap();

        let (device, queue) = adapter
            .request_device(
                &wgpu::DeviceDescriptor {
                    features: wgpu::Features::empty(),
                    limits: wgpu::Limits::default(),
                    label: None,
                },
                None,
            )
            .await
            .unwrap();

        let config = wgpu::SurfaceConfiguration {
            usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
            format: surface.get_preferred_format(&adapter).unwrap(),
            width: size.width,
            height: size.height,
            present_mode: wgpu::PresentMode::Fifo,
        };
        surface.configure(&device, &config);

        let mesh_pool = MeshPool::default();

        Self {
            size,
            surface,
            device,
            queue,
            config,
            mesh_pool,
        }
    }

    pub fn resize(&mut self, new_size: winit::dpi::PhysicalSize<u32>) {
        if new_size.width > 0 && new_size.height > 0 {
            self.size = new_size;
            self.config.width = new_size.width;
            self.config.height = new_size.height;
            self.surface.configure(&self.device, &self.config);
        }
    }

    pub fn render(
        &mut self,
        camera: &impl Camera,
        meshes: &MeshCommands,
    ) -> Result<(), wgpu::SurfaceError> {
        Ok(())
    }
}

struct MeshGroup {
    vertices: wgpu::Buffer,
    vertex_capacity: usize,
    indices: wgpu::Buffer,
    index_capacity: usize,
}

impl MeshGroup {
    pub fn new(device: &wgpu::Device, data: &MeshData) -> Self {
        let vertex_capacity = data.vertices.len();
        let vertices = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("Vertex Buffer"),
            contents: bytemuck::cast_slice(&data.vertices),
            usage: wgpu::BufferUsages::VERTEX,
        });

        let index_capacity = data.indices.len();
        let indices = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("Index Buffer"),
            contents: bytemuck::cast_slice(&data.indices),
            usage: wgpu::BufferUsages::VERTEX,
        });

        Self {
            vertex_capacity,
            vertices,
            index_capacity,
            indices,
        }
    }
}

#[derive(Default)]
struct MeshPool {
    groups: slab::Slab<MeshGroup>,
}

impl MeshPool {
    pub fn allocate(&mut self, device: &wgpu::Device, data: &MeshData) -> MeshHandle {
        let group = MeshGroup::new(device, data);
        let group_id = self.groups.insert(group);
        let sub_id = 0;
        MeshHandle { group_id, sub_id }
    }
}

#[repr(C)]
#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
struct CameraUniform {
    vp: [[f32; 4]; 4],
}

#[repr(C)]
#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
struct Vertex {
    position: [f32; 3],
}

type Index = u32;

struct MeshData {
    vertices: Vec<Vertex>,
    indices: Vec<Index>,
}

#[repr(C)]
#[derive(Copy, Clone, Eq, Hash, PartialEq)]
struct MeshHandle {
    group_id: usize,
    // unused for now, since each group contains only one mesh
    sub_id: usize,
}

#[derive(Copy, Clone, PartialEq)]
struct MeshInstance {
    pub handle: MeshHandle,
    pub transform: glam::Mat4,
}

type MeshCommands = Vec<MeshInstance>;

fn main() {
    let event_loop = EventLoop::new();
    let window = WindowBuilder::new().build(&event_loop).unwrap();
    let mut camera = Flycam::new(10.0, 0.002);
    let mut is_grabbed = false;
    let mut ren = pollster::block_on(Renderer::new(&window));
    let commands = MeshCommands::new();

    event_loop.run(move |event, _, control_flow| match event {
        Event::RedrawRequested(_) => match ren.render(&camera, &commands) {
            Ok(_) => {}
            Err(wgpu::SurfaceError::Lost) => ren.resize(ren.size),
            Err(wgpu::SurfaceError::OutOfMemory) => *control_flow = ControlFlow::Exit,
            Err(e) => println!("error: {:?}", e),
        },
        Event::MainEventsCleared => {
            camera.update();
            window.request_redraw();
        }
        Event::DeviceEvent { ref event, .. } => match event {
            DeviceEvent::MouseMotion { delta } => {
                if is_grabbed {
                    camera.process_mouse(delta.0, delta.1);
                }
            }
            _ => {}
        },
        Event::WindowEvent {
            ref event,
            window_id,
        } if window_id == window.id() => match event {
            WindowEvent::KeyboardInput {
                input:
                    KeyboardInput {
                        virtual_keycode: Some(key),
                        state,
                        ..
                    },
                ..
            } => {
                if *state == ElementState::Pressed && *key == VirtualKeyCode::Escape {
                    if is_grabbed {
                        window.set_cursor_grab(false).unwrap();
                        window.set_cursor_visible(true);
                        is_grabbed = false;
                    }
                } else {
                    camera.process_keyboard(*key, *state);
                }
            }
            WindowEvent::MouseInput {
                button: MouseButton::Left,
                state: ElementState::Pressed,
                ..
            } => {
                if !is_grabbed {
                    window.set_cursor_grab(true).unwrap();
                    window.set_cursor_visible(false);
                    is_grabbed = true;
                }
            }
            WindowEvent::CloseRequested => *control_flow = ControlFlow::Exit,
            WindowEvent::Resized(physical_size) => {
                ren.resize(*physical_size);
                camera.resize(physical_size.width, physical_size.height);
            }
            WindowEvent::ScaleFactorChanged { new_inner_size, .. } => {
                ren.resize(**new_inner_size);
                camera.resize(new_inner_size.width, new_inner_size.height);
            }
            _ => {}
        },
        _ => {}
    });
}