use bytemuck::{Pod, Zeroable};
use wgpu::{include_wgsl, util::DeviceExt, BindGroup, Buffer, Device, Queue, RenderPipeline, Surface, SurfaceConfiguration, VertexBufferLayout};
use winit::{
    event::{ElementState, Event, MouseButton, WindowEvent}, event_loop::EventLoop, window::Window
};

use crate::state::State;

#[repr(C)]
#[derive(Clone, Copy, Zeroable, Pod, Debug)]
pub struct Vertex {
    pub pos: [f32; 3],
    pub color: [f32; 4]
}
impl Vertex {
    const DESC: VertexBufferLayout<'static> = VertexBufferLayout {
        array_stride: std::mem::size_of::<Vertex>() as wgpu::BufferAddress,
        step_mode: wgpu::VertexStepMode::Vertex,
        attributes: &wgpu::vertex_attr_array![0 => Float32x3, 1 => Float32x4],
    };
}

#[repr(C)]
#[derive(Clone, Copy, Zeroable, Pod, Debug)]
pub struct Uniforms {
    // [x, y, zoom]
    pub camera: [f32; 3],
    pub darkness: f32
}
impl Default for Uniforms {
    fn default() -> Self {
        Self {
            camera: [0., 0., 1.],
            darkness: 0.
        }
    }
}
impl Uniforms {
    const DESC: VertexBufferLayout<'static> = VertexBufferLayout {
        array_stride: std::mem::size_of::<Vertex>() as wgpu::BufferAddress,
        step_mode: wgpu::VertexStepMode::Vertex,
        attributes: &wgpu::vertex_attr_array![0 => Float32x3, 1 => Float32],
    };
}

pub struct Graphics<'a> {
    state: State,
    window: &'a Window,
    surface_config: SurfaceConfiguration,
    surface: Surface<'a>,
    device: Device,
    render_pipeline: RenderPipeline,
    queue: Queue,
    vertex_buf: Buffer,
    index_buf: Buffer,
    uniforms_buf: Buffer,
    uniforms_bind_group: BindGroup
}
impl<'a> Graphics<'a> {
    pub async fn init(window: &'a Window, state: State) -> Self {
        let mut size = window.inner_size();
        size.width = size.width.max(1);
        size.height = size.height.max(1);

        let instance = wgpu::Instance::default();

        let surface = instance.create_surface(window).unwrap();
        let adapter = instance
            .request_adapter(&wgpu::RequestAdapterOptions {
                power_preference: wgpu::PowerPreference::default(),
                force_fallback_adapter: false,
                // Request an adapter which can render to our surface
                compatible_surface: Some(&surface),
            })
            .await
            .expect("Failed to find an appropriate adapter");

        // Create the logical device and command queue
        let (device, queue) = adapter
            .request_device(
                &wgpu::DeviceDescriptor {
                    label: None,
                    required_features: wgpu::Features::empty(),
                    // Make sure we use the texture resolution limits from the adapter, so we can support images the size of the swapchain.
                    required_limits: wgpu::Limits::default()
                        .using_resolution(adapter.limits()),
                    memory_hints: wgpu::MemoryHints::MemoryUsage,
                },
                None,
            )
            .await
            .expect("Failed to create device");

        let vertex_buf = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("Vertex Buffer"),
            contents: &[bytemuck::cast_slice::<Vertex, _>(&state.vertices), &[0; 1024]].concat(),
            usage: wgpu::BufferUsages::VERTEX | wgpu::BufferUsages::COPY_DST,
        });

        let index_buf = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("Index Buffer"),
            contents: &[bytemuck::cast_slice::<u32, _>(&state.indices), &[0; 1024]].concat(),
            usage: wgpu::BufferUsages::INDEX | wgpu::BufferUsages::COPY_DST,
        });

        let uniforms_buf = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("Uniforms Buffer"),
            contents: bytemuck::cast_slice(&[state.uniforms]),
            usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
        });
        let uniforms_bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
            entries: &[
                wgpu::BindGroupLayoutEntry {
                    binding: 0,
                    visibility: wgpu::ShaderStages::VERTEX,
                    ty: wgpu::BindingType::Buffer {
                        ty: wgpu::BufferBindingType::Uniform,
                        has_dynamic_offset: false,
                        min_binding_size: None,
                    },
                    count: None,
                }
            ],
            label: Some("Uniforms Bind Group Layout"),
        });
        let uniforms_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            layout: &uniforms_bind_group_layout,
            entries: &[
                wgpu::BindGroupEntry {
                    binding: 0,
                    resource: uniforms_buf.as_entire_binding(),
                }
            ],
            label: Some("Uniforms Bind Group"),
        });
        

        // Load the shaders from disk
        let shader = device.create_shader_module(include_wgsl!("shader.wgsl"));

        let pipeline_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
            label: None,
            bind_group_layouts: &[
                &uniforms_bind_group_layout
            ],
            push_constant_ranges: &[],
        });

        let swapchain_capabilities = surface.get_capabilities(&adapter);
        let swapchain_format = swapchain_capabilities.formats[0];

        let render_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: None,
            layout: Some(&pipeline_layout),
            vertex: wgpu::VertexState {
                module: &shader,
                entry_point: "vs_main",
                buffers: &[
                    Vertex::DESC
                ],
                compilation_options: Default::default(),
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: "fs_main",
                compilation_options: Default::default(),
                targets: &[Some(swapchain_format.into())],
            }),
            primitive: wgpu::PrimitiveState::default(),
            depth_stencil: None,
            multisample: wgpu::MultisampleState::default(),
            multiview: None,
            cache: None,
        });

        let surface_config = surface
            .get_default_config(&adapter, size.width, size.height)
            .unwrap();
        surface.configure(&device, &surface_config);

        Self {
            state,
            window,
            surface_config,
            surface,
            device,
            render_pipeline,
            queue,
            vertex_buf,
            index_buf,
            uniforms_buf,
            uniforms_bind_group
        }
    }
    pub fn run(&mut self, event_loop: EventLoop<()>) {
        event_loop.run(move |event, target| {
            // Have the closure take ownership of the resources.
            // `event_loop.run` never returns, therefore we must do this to ensure
            // the resources are properly cleaned up.
            let _ = &self;

            match event {
                Event::WindowEvent {
                    event: WindowEvent::Resized(new_size),
                    ..
                } => {
                    // Reconfigure the surface with the new size
                    self.surface_config.width = new_size.width.max(1);
                    self.surface_config.height = new_size.height.max(1);
                    self.surface.configure(&self.device, &self.surface_config);
                    // On macos the window needs to be redrawn manually after resizing
                    self.window.request_redraw();
                },
                Event::WindowEvent {
                    event: WindowEvent::RedrawRequested,
                    ..
                } => {
                    self.update();
                    self.render();
                },
                Event::WindowEvent {
                    event: WindowEvent::CloseRequested,
                    ..
                } => target.exit(),
                Event::AboutToWait => {
                    // RedrawRequested will only trigger once unless we manually
                    // request it.
                    self.window.request_redraw();
                },
                e => self.state.input(e)
            }
            
        })
        .unwrap();
    }
    fn render(&self) {
        let frame = self.surface
            .get_current_texture()
            .expect("Failed to acquire next swap chain texture");
        let view = frame
            .texture
            .create_view(&wgpu::TextureViewDescriptor::default());
        let mut encoder =
            self.device.create_command_encoder(&wgpu::CommandEncoderDescriptor {
                label: None,
            });
        {
            let mut rpass =
                encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                    label: None,
                    color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                        view: &view,
                        resolve_target: None,
                        ops: wgpu::Operations {
                            load: wgpu::LoadOp::Clear(wgpu::Color::BLACK),
                            store: wgpu::StoreOp::Store,
                        },
                    })],
                    depth_stencil_attachment: None,
                    timestamp_writes: None,
                    occlusion_query_set: None,
                });
            rpass.set_pipeline(&self.render_pipeline);
            rpass.set_bind_group(0, &self.uniforms_bind_group, &[]);
            rpass.set_vertex_buffer(0, self.vertex_buf.slice(..));
            rpass.set_index_buffer(self.index_buf.slice(..), wgpu::IndexFormat::Uint32);
            rpass.draw_indexed(0..self.state.indices.len() as u32, 0, 0..1);
            // rpass.draw(0..self.state.vertices.len() as u32, 0..1);
        }

        self.queue.submit(Some(encoder.finish()));
        frame.present();
    }
    fn update(&mut self) {
        self.state.update();
        self.queue.write_buffer(&self.vertex_buf, 0, bytemuck::cast_slice(&self.state.vertices));
        self.queue.write_buffer(&self.index_buf, 0, bytemuck::cast_slice(&self.state.indices));
        self.queue.write_buffer(&self.uniforms_buf, 0, bytemuck::cast_slice(&[self.state.uniforms]));
    }
}