use bytemuck;
use std::collections::HashMap;
use wgpu::util::DeviceExt;
use winit::{
    event::*,
    event_loop::{ControlFlow, EventLoop},
    window::Window,
    window::WindowBuilder,
};

mod script;
use script::graphics::GraphicsCommand;
mod texture;

#[repr(C)]
#[derive(Copy, Clone, Debug, bytemuck::Pod, bytemuck::Zeroable)]
struct Vertex {
    position: [f32; 3], // TODO: Why do I pass in a Z here?
    tex_coords: [f32; 2],
}

impl Vertex {
    fn desc() -> wgpu::VertexBufferLayout<'static> {
        wgpu::VertexBufferLayout {
            array_stride: std::mem::size_of::<Vertex>() as wgpu::BufferAddress,
            step_mode: wgpu::VertexStepMode::Vertex,
            attributes: &[
                wgpu::VertexAttribute {
                    offset: 0,
                    shader_location: 0,
                    format: wgpu::VertexFormat::Float32x3,
                },
                wgpu::VertexAttribute {
                    offset: std::mem::size_of::<[f32; 3]>() as wgpu::BufferAddress,
                    shader_location: 1,
                    format: wgpu::VertexFormat::Float32x2,
                },
            ],
        }
    }
}

#[repr(C)]
#[derive(Copy, Clone, Debug, bytemuck::Pod, bytemuck::Zeroable)]
struct ScreenUniforms {
    resolution: [f32; 2],
}

impl ScreenUniforms {
    fn new(width: u32, height: u32) -> ScreenUniforms {
        ScreenUniforms {
            resolution: [width as f32, height as f32],
        }
    }
}

struct State {
    surface: wgpu::Surface,
    device: wgpu::Device,
    queue: wgpu::Queue,
    config: wgpu::SurfaceConfiguration,
    size: winit::dpi::PhysicalSize<u32>,
    window: Window,
    render_pipeline: wgpu::RenderPipeline,

    vertex_buffer: wgpu::Buffer,
    max_vertices: usize,

    sprite_bind_group_layout: wgpu::BindGroupLayout,
    sprite_textures: HashMap<u32, wgpu::BindGroup>,

    screen_uniform: ScreenUniforms,
    screen_uniform_buffer: wgpu::Buffer,
    screen_uniform_bind_group: wgpu::BindGroup,

    // Garbage
    mouse_x: f64,
    mouse_y: f64,
}

// TUTORIAL FOR BABIES LIKE ME: https://sotrh.github.io/learn-wgpu/beginner/tutorial2-surface/

impl State {
    // Creating some of the wgpu types requires async code
    async fn new(window: Window) -> Self {
        let size = window.inner_size();

        // The instance is a handle to our GPU
        // Backends::all => Vulkan + Metal + DX12 + Browser WebGPU
        let instance = wgpu::Instance::new(wgpu::InstanceDescriptor {
            backends: wgpu::Backends::all(),
            dx12_shader_compiler: Default::default(),
        });

        // # Safety
        //
        // The surface needs to live as long as the window that created it.
        // State owns the window so this should be safe.
        let surface = unsafe { instance.create_surface(&window) }.unwrap();

        let adapter = instance
            .request_adapter(&wgpu::RequestAdapterOptions {
                power_preference: wgpu::PowerPreference::default(),
                compatible_surface: Some(&surface),
                force_fallback_adapter: false,
            })
            .await
            .unwrap();

        let (device, queue) = adapter
            .request_device(
                &wgpu::DeviceDescriptor {
                    features: wgpu::Features::empty(),
                    // WebGL doesn't support all of wgpu's features, so if
                    // we're building for the web we'll have to disable some.
                    limits: if cfg!(target_arch = "wasm32") {
                        wgpu::Limits::downlevel_webgl2_defaults()
                    } else {
                        wgpu::Limits::default()
                    },
                    label: None,
                },
                None, // Trace path
            )
            .await
            .unwrap();

        let surface_caps = surface.get_capabilities(&adapter);

        // Shader code in this tutorial assumes an sRGB surface
        // texture. Using a different one will result all the colors coming
        // out darker. If you want to support non sRGB surfaces, you'll need
        // to account for that when drawing to the frame.
        let surface_format = surface_caps
            .formats
            .iter()
            .copied()
            .find(|f| f.is_srgb())
            .unwrap_or(surface_caps.formats[0]);
        let config = wgpu::SurfaceConfiguration {
            usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
            format: surface_format,
            width: size.width,
            height: size.height,
            present_mode: surface_caps.present_modes[0],
            alpha_mode: surface_caps.alpha_modes[0],
            view_formats: vec![],
        };
        surface.configure(&device, &config);

        // TODO: DELETE THIS
        // let diffuse_bytes = include_bytes!("happy-tree.png");
        // let diffuse_texture =
        //     texture::Texture::from_bytes(&device, &queue, diffuse_bytes, "happy-tree.png").unwrap();

        let sprite_bind_group_layout =
            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
                entries: &[
                    wgpu::BindGroupLayoutEntry {
                        binding: 0,
                        visibility: wgpu::ShaderStages::FRAGMENT,
                        ty: wgpu::BindingType::Texture {
                            multisampled: false,
                            view_dimension: wgpu::TextureViewDimension::D2,
                            sample_type: wgpu::TextureSampleType::Float { filterable: true },
                        },
                        count: None,
                    },
                    wgpu::BindGroupLayoutEntry {
                        binding: 1,
                        visibility: wgpu::ShaderStages::FRAGMENT,
                        // This should match the filterable field of the
                        // corresponding Texture entry above.
                        ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering),
                        count: None,
                    },
                ],
                label: Some("sprite_bind_group_layout"),
            });

        // TODO: DELETE THIS
        // let sprite_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
        //     layout: &sprite_bind_group_layout,
        //     entries: &[
        //         wgpu::BindGroupEntry {
        //             binding: 0,
        //             resource: wgpu::BindingResource::TextureView(&diffuse_texture.view),
        //         },
        //         wgpu::BindGroupEntry {
        //             binding: 1,
        //             resource: wgpu::BindingResource::Sampler(&diffuse_texture.sampler),
        //         },
        //     ],
        //     label: Some("diffuse_bind_group"),
        // });

        let screen_uniform = ScreenUniforms::new(size.width, size.height);
        let screen_uniform_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("Screen Uniform Buffer"),
            contents: bytemuck::cast_slice(&[screen_uniform]),
            usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
        });

        let screen_uniform_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("screen_bind_group_layout"),
            });

        let screen_uniform_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            layout: &screen_uniform_bind_group_layout,
            entries: &[wgpu::BindGroupEntry {
                binding: 0,
                resource: screen_uniform_buffer.as_entire_binding(),
            }],
            label: Some("camera_bind_group"),
        });

        let shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
            label: Some("Shader"),
            source: wgpu::ShaderSource::Wgsl(include_str!("shader.wgsl").into()),
        });

        let render_pipeline_layout =
            device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
                label: Some("Render Pipeline Layout"),
                bind_group_layouts: &[&sprite_bind_group_layout, &screen_uniform_bind_group_layout],
                push_constant_ranges: &[],
            });

        let render_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: Some("Render Pipeline"),
            layout: Some(&render_pipeline_layout),
            vertex: wgpu::VertexState {
                module: &shader,
                entry_point: "vs_main",
                buffers: &[Vertex::desc()],
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: "fs_main",
                targets: &[Some(wgpu::ColorTargetState {
                    format: config.format,
                    blend: Some(wgpu::BlendState::REPLACE),
                    write_mask: wgpu::ColorWrites::ALL,
                })],
            }),
            primitive: wgpu::PrimitiveState {
                topology: wgpu::PrimitiveTopology::TriangleList,
                strip_index_format: None,
                front_face: wgpu::FrontFace::Ccw,
                cull_mode: Some(wgpu::Face::Back),
                // Setting this to anything other than Fill requires Features::NON_FILL_POLYGON_MODE
                polygon_mode: wgpu::PolygonMode::Fill,
                // Requires Features::DEPTH_CLIP_CONTROL
                unclipped_depth: false,
                // Requires Features::CONSERVATIVE_RASTERIZATION
                conservative: false,
            },
            depth_stencil: None,
            multisample: wgpu::MultisampleState {
                count: 1,
                mask: !0,
                alpha_to_coverage_enabled: false,
            },
            multiview: None,
        });

        let max_vertices: usize = 4096;
        let vertex_buffer = device.create_buffer(&wgpu::BufferDescriptor {
            label: Some("Vertex Buffer"),
            size: (max_vertices * std::mem::size_of::<Vertex>())
                .try_into()
                .unwrap(),
            mapped_at_creation: false,
            usage: wgpu::BufferUsages::VERTEX | wgpu::BufferUsages::COPY_DST,
        });

        Self {
            window,
            surface,
            device,
            queue,
            config,
            size,
            render_pipeline,
            vertex_buffer,
            max_vertices,
            sprite_bind_group_layout,
            sprite_textures: HashMap::new(),
            screen_uniform,
            screen_uniform_buffer,
            screen_uniform_bind_group,

            mouse_x: 0.0,
            mouse_y: 0.0,
        }
    }

    pub fn window(&self) -> &Window {
        &self.window
    }

    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);
        }
    }

    fn input(&mut self, _event: &WindowEvent) -> bool {
        false
    }

    fn update(&mut self) {
        self.screen_uniform = ScreenUniforms::new(self.size.width, self.size.height);
        self.queue.write_buffer(
            &self.screen_uniform_buffer,
            0,
            bytemuck::cast_slice(&[self.screen_uniform]),
        );
    }

    fn render(&mut self, commands: Vec<GraphicsCommand>) -> Result<(), wgpu::SurfaceError> {
        let output = self.surface.get_current_texture()?;
        let view = output
            .texture
            .create_view(&wgpu::TextureViewDescriptor::default());

        // Group the commands into passes.
        struct Pass {
            color: Option<[f64; 4]>,
            commands: Vec<GraphicsCommand>,
        }
        let mut passes = Vec::new();
        for command in commands {
            match command {
                GraphicsCommand::Clear(cc) => passes.push(Pass {
                    color: Some(cc.color),
                    commands: Vec::new(),
                }),
                GraphicsCommand::CreateTexture(ct) => {
                    let texture = texture::Texture::from_image(
                        &self.device,
                        &self.queue,
                        &ct.image,
                        Some(&ct.label),
                    );
                    let sprite_bind_group =
                        self.device.create_bind_group(&wgpu::BindGroupDescriptor {
                            layout: &self.sprite_bind_group_layout,
                            entries: &[
                                wgpu::BindGroupEntry {
                                    binding: 0,
                                    resource: wgpu::BindingResource::TextureView(&texture.view),
                                },
                                wgpu::BindGroupEntry {
                                    binding: 1,
                                    resource: wgpu::BindingResource::Sampler(&texture.sampler),
                                },
                            ],
                            label: Some(&ct.label),
                        });

                    self.sprite_textures.insert(ct.id, sprite_bind_group);
                }
                GraphicsCommand::EndFrame => (),
                other => match passes.last_mut() {
                    Some(pass) => pass.commands.push(other),
                    None => passes.push(Pass {
                        color: None,
                        commands: vec![other],
                    }),
                },
            }
        }

        let mut vertices = Vec::new();
        for pass in passes {
            // TODO: It would be great if we could use multiple passes in a
            //       single encoder but right now because of the dyanmic
            //       nature of vertices we can't, I think? Because
            //       queue.write_buffer doesn't actually happen until we call
            //       submit...
            let mut encoder = self
                .device
                .create_command_encoder(&wgpu::CommandEncoderDescriptor {
                    label: Some("Render Encoder"),
                });

            {
                let mut render_pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                    label: Some("Render Pass"),
                    color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                        view: &view,
                        resolve_target: None,
                        ops: wgpu::Operations {
                            load: if let Some([r, g, b, a]) = pass.color {
                                wgpu::LoadOp::Clear(wgpu::Color {
                                    r, //0.1,
                                    g, //0.2,
                                    b,
                                    a,
                                })
                            } else {
                                wgpu::LoadOp::Load
                            },
                            store: true,
                        },
                    })],
                    depth_stencil_attachment: None,
                });

                let mut texture_id = None;
                vertices.clear();
                for command in pass.commands {
                    match command {
                        GraphicsCommand::Print(pc) => {
                            println!("{}", pc.text);
                        }
                        GraphicsCommand::Sprite(sc) => {
                            vertices.push(Vertex {
                                position: [sc.x, sc.y, 0.0],
                                tex_coords: [sc.u, sc.v + sc.sh],
                            });
                            vertices.push(Vertex {
                                position: [sc.x + sc.w, sc.y, 0.0],
                                tex_coords: [sc.u + sc.sw, sc.v + sc.sh],
                            });
                            vertices.push(Vertex {
                                position: [sc.x, sc.y + sc.h, 0.0],
                                tex_coords: [sc.u, sc.v],
                            });
                            vertices.push(Vertex {
                                position: [sc.x, sc.y + sc.h, 0.0],
                                tex_coords: [sc.u, sc.v],
                            });
                            vertices.push(Vertex {
                                position: [sc.x + sc.w, sc.y, 0.0],
                                tex_coords: [sc.u + sc.sw, sc.v + sc.sh],
                            });
                            vertices.push(Vertex {
                                position: [sc.x + sc.w, sc.y + sc.h, 0.0],
                                tex_coords: [sc.u + sc.sw, sc.v],
                            });
                        }

                        GraphicsCommand::UseTexture(id) => texture_id = Some(id),
                        GraphicsCommand::CreateTexture(_) => (), // Already handled
                        GraphicsCommand::Clear(_) => (),         // Already handled
                        GraphicsCommand::EndFrame => (),         // Should never appear
                    }
                }

                if let Some(id) = texture_id {
                    assert!(vertices.len() < self.max_vertices); // !
                    self.queue.write_buffer(
                        &self.vertex_buffer,
                        0,
                        bytemuck::cast_slice(&vertices),
                    );
                    render_pass.set_pipeline(&self.render_pipeline);

                    let bind_group = self.sprite_textures.get(&id).unwrap();
                    render_pass.set_bind_group(0, bind_group, &[]);

                    render_pass.set_bind_group(1, &self.screen_uniform_bind_group, &[]);
                    render_pass.set_vertex_buffer(0, self.vertex_buffer.slice(..));
                    render_pass.draw(0..(vertices.len() as u32), 0..1);
                }
            }

            // Submit will accept anything that implements IntoIter
            self.queue.submit(std::iter::once(encoder.finish()));
        }

        // {
        //     // BEGIN GARBAGE
        //     let r: f64 = (self.mouse_x / f64::from(self.size.width)).clamp(0.0, 1.0) * 0.1;
        //     let g: f64 = (self.mouse_y / f64::from(self.size.height)).clamp(0.0, 1.0) * 0.2;
        //     // END GARBAGE

        //     let mut render_pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
        //         label: Some("Render Pass"),
        //         color_attachments: &[Some(wgpu::RenderPassColorAttachment {
        //             view: &view,
        //             resolve_target: None,
        //             ops: wgpu::Operations {
        //                 load: wgpu::LoadOp::Clear(wgpu::Color {
        //                     r, //0.1,
        //                     g, //0.2,
        //                     b: 0.3,
        //                     a: 1.0,
        //                 }),
        //                 store: true,
        //             },
        //         })],
        //         depth_stencil_attachment: None,
        //     });

        //     render_pass.set_pipeline(&self.render_pipeline);
        //     render_pass.set_bind_group(0, &self.diffuse_bind_group, &[]);
        //     render_pass.set_vertex_buffer(0, self.vertex_buffer.slice(..));
        //     render_pass.set_index_buffer(self.index_buffer.slice(..), wgpu::IndexFormat::Uint16);
        //     render_pass.draw_indexed(0..self.num_indices, 0, 0..1);
        // }

        output.present();

        Ok(())
    }
}

pub async fn run() {
    env_logger::init();
    let event_loop = EventLoop::new();
    let window = WindowBuilder::new().build(&event_loop).unwrap();

    let mut state = State::new(window).await;

    let context = script::ScriptContext::new();
    context.init();

    event_loop.run(move |event, _, control_flow| {
        control_flow.set_poll();

        match event {
            Event::WindowEvent {
                ref event,
                window_id,
            } if window_id == state.window().id() => {
                if !state.input(event) {
                    match event {
                        WindowEvent::CloseRequested
                        | WindowEvent::KeyboardInput {
                            input:
                                KeyboardInput {
                                    state: ElementState::Pressed,
                                    virtual_keycode: Some(VirtualKeyCode::Escape),
                                    ..
                                },
                            ..
                        } => *control_flow = ControlFlow::Exit,

                        WindowEvent::CursorMoved { position, .. } => {
                            state.mouse_x = position.x;
                            state.mouse_y = position.y;
                            state.window().request_redraw();
                        }

                        WindowEvent::Resized(physical_size) => {
                            state.resize(*physical_size);
                        }

                        WindowEvent::ScaleFactorChanged { new_inner_size, .. } => {
                            // new_inner_size is &&mut so we have to dereference it twice
                            state.resize(**new_inner_size);
                        }

                        _ => {}
                    }
                }
            }

            Event::RedrawRequested(window_id) if window_id == state.window().id() => {
                context.update();
                state.update();

                match state.render(context.render()) {
                    Ok(_) => {}
                    // Reconfigure the surface if lost
                    Err(wgpu::SurfaceError::Lost) => state.resize(state.size),
                    // The system is out of memory, we should probably quit
                    Err(wgpu::SurfaceError::OutOfMemory) => *control_flow = ControlFlow::Exit,
                    // All other errors (Outdated, Timeout) should be resolved by the next frame
                    Err(e) => eprintln!("{:?}", e),
                }
            }

            Event::MainEventsCleared => {
                // RedrawRequested will only trigger once, unless we manually
                // request it.
                state.window().request_redraw();
            }

            _ => {}
        }
    });
}