use std::time::Duration;

use futures::executor::block_on;
use glutin::event_loop::ControlFlow;
use glutin::{
    dpi,
    event::{DeviceEvent, ElementState, Event, MouseButton, MouseScrollDelta, WindowEvent},
    event_loop::EventLoop,
    window::{Window, WindowBuilder},
    ContextWrapper, GlProfile, GlRequest, NotCurrent, PossiblyCurrent, WindowedContext,
};
use hedgewars_engine::instance::EngineInstance;
use integral_geometry::Point;
use std::error::Error;
use wgpu::{
    Adapter, BackendBit, Color, CommandEncoderDescriptor, Device, DeviceDescriptor, Features,
    LoadOp, Operations, PowerPreference, PresentMode, Queue, RenderPassColorAttachmentDescriptor,
    RenderPassDescriptor, RequestAdapterOptions, Surface, SwapChain, SwapChainDescriptor,
    TextureFormat, TextureUsage,
};

type HwGlRendererContext = ContextWrapper<PossiblyCurrent, Window>;

struct HwWgpuRenderingContext {
    window: Window,
    surface: Surface,
    adapter: Adapter,
    device: Device,
    queue: Queue,
    swap_chain: SwapChain,
}

enum HwRendererContext {
    Gl(HwGlRendererContext),
    Wgpu(HwWgpuRenderingContext),
}

struct ErrorStub;

impl<T: Error> From<T> for ErrorStub {
    fn from(_: T) -> Self {
        ErrorStub
    }
}

impl HwRendererContext {
    fn get_framebuffer_size(window: &Window) -> (u32, u32) {
        window.inner_size().into()
    }

    fn create_wpgu_swap_chain(window: &Window, surface: &Surface, device: &Device) -> SwapChain {
        let (width, height) = Self::get_framebuffer_size(window);
        device.create_swap_chain(
            &surface,
            &SwapChainDescriptor {
                usage: TextureUsage::OUTPUT_ATTACHMENT,
                format: TextureFormat::Bgra8Unorm,
                width,
                height,
                present_mode: PresentMode::Fifo,
            },
        )
    }

    fn init_wgpu(
        event_loop: &EventLoop<()>,
        size: dpi::LogicalSize<f64>,
    ) -> HwWgpuRenderingContext {
        let builder = WindowBuilder::new()
            .with_title("hwengine")
            .with_inner_size(size);
        let window = builder.build(event_loop).unwrap();

        let instance = wgpu::Instance::new(BackendBit::PRIMARY);

        let surface = unsafe { instance.create_surface(&window) };

        let adapter = block_on(instance.request_adapter(&RequestAdapterOptions {
            power_preference: PowerPreference::HighPerformance,
            compatible_surface: Some(&surface),
        }))
        .unwrap();

        let (device, queue) = block_on(adapter.request_device(&Default::default(), None)).unwrap();

        let swap_chain = Self::create_wpgu_swap_chain(&window, &surface, &device);

        HwWgpuRenderingContext {
            window,
            surface,
            adapter,
            device,
            queue,
            swap_chain,
        }
    }

    fn init_gl(event_loop: &EventLoop<()>, size: dpi::LogicalSize<f64>) -> HwGlRendererContext {
        use glutin::ContextBuilder;

        let builder = WindowBuilder::new()
            .with_title("hwengine")
            .with_inner_size(size);

        let context = ContextBuilder::new()
            .with_gl(GlRequest::Latest)
            .with_gl_profile(GlProfile::Core)
            .build_windowed(builder, &event_loop)
            .ok()
            .unwrap();

        unsafe {
            let wrapper = context.make_current().unwrap();
            gl::load_with(|ptr| wrapper.get_proc_address(ptr) as *const _);

            let (width, height) = Self::get_framebuffer_size(wrapper.window());
            gl::Viewport(0, 0, width as i32, height as i32);
            wrapper
        }
    }

    fn new(event_loop: &EventLoop<()>, size: dpi::LogicalSize<f64>, use_wgpu: bool) -> Self {
        if use_wgpu {
            Self::Wgpu(Self::init_wgpu(event_loop, size))
        } else {
            Self::Gl(Self::init_gl(event_loop, size))
        }
    }

    pub fn window(&self) -> &Window {
        match self {
            HwRendererContext::Gl(gl) => &gl.window(),
            HwRendererContext::Wgpu(wgpu) => &wgpu.window,
        }
    }

    pub fn update(&mut self) {
        match self {
            HwRendererContext::Gl(context) => unsafe {
                let (width, height) = Self::get_framebuffer_size(&context.window());
                gl::Viewport(0, 0, width as i32, height as i32);
            },
            HwRendererContext::Wgpu(context) => {
                context.swap_chain = Self::create_wpgu_swap_chain(
                    &context.window,
                    &context.surface,
                    &context.device,
                );
            }
        }
    }

    pub fn present(&mut self) -> Result<(), ErrorStub> {
        match self {
            HwRendererContext::Gl(context) => context.swap_buffers()?,
            HwRendererContext::Wgpu(context) => {
                let frame_view = &context.swap_chain.get_current_frame()?.output.view;

                let mut encoder =
                    context
                        .device
                        .create_command_encoder(&CommandEncoderDescriptor {
                            label: Some("Main encoder"),
                        });
                encoder.begin_render_pass(&RenderPassDescriptor {
                    color_attachments: &[RenderPassColorAttachmentDescriptor {
                        attachment: &frame_view,
                        resolve_target: None,
                        ops: Operations {
                            load: LoadOp::Clear(Color {
                                r: 0.7,
                                g: 0.4,
                                b: 0.2,
                                a: 1.0,
                            }),
                            store: false,
                        },
                    }],
                    depth_stencil_attachment: None,
                });
                let buffer = encoder.finish();
                context.queue.submit(std::iter::once(buffer));
            }
        }
        Ok(())
    }
}

fn main() {
    let use_wgpu = false;
    let mut event_loop = EventLoop::<()>::new();
    let (w, h) = (1024.0, 768.0);

    let mut context = HwRendererContext::new(&event_loop, dpi::LogicalSize::new(w, h), use_wgpu);

    let mut engine = EngineInstance::new();
    if !use_wgpu {
        engine.world.create_renderer(w as u16, h as u16);
    }

    let mut dragging = false;

    use std::time::Instant;

    let mut now = Instant::now();
    let mut update_time = Instant::now();
    let mut render_time = Instant::now();

    let current_time = Instant::now();
    let delta = current_time - now;
    now = current_time;
    let ms = delta.as_secs() as f64 * 1000.0 + delta.subsec_millis() as f64;
    context.window().set_title(&format!("hwengine {:.3}ms", ms));

    event_loop.run(move |event, _, control_flow| {
        *control_flow = ControlFlow::Poll;
        match event {
            Event::WindowEvent { event, .. } => match event {
                WindowEvent::CloseRequested => {
                    *control_flow = ControlFlow::Exit;
                }
                WindowEvent::Resized(_) | WindowEvent::ScaleFactorChanged { .. } => {
                    context.update()
                }

                WindowEvent::MouseInput { button, state, .. } => {
                    if let MouseButton::Right = button {
                        dragging = state == ElementState::Pressed;
                    }
                }

                WindowEvent::MouseWheel { delta, .. } => {
                    let zoom_change = match delta {
                        MouseScrollDelta::LineDelta(x, y) => y as f32 * 0.1f32,
                        MouseScrollDelta::PixelDelta(delta) => delta.y as f32 * 0.1f32,
                    };
                    engine.world.move_camera(Point::ZERO, zoom_change);
                }
                _ => (),
            },
            Event::DeviceEvent { event, .. } => match event {
                DeviceEvent::MouseMotion { delta } => {
                    if dragging {
                        engine
                            .world
                            .move_camera(Point::new(delta.0 as i32, delta.1 as i32), 0.0)
                    }
                }
                _ => {}
            },

            _ => (),
        }

        let current_time = Instant::now();

        if update_time.elapsed() > Duration::from_millis(10) {
            update_time = current_time;
            engine.world.step()
        }

        if render_time.elapsed() > Duration::from_millis(16) {
            render_time = current_time;
            if !use_wgpu {
                engine.render();
            }
            context.present().ok().unwrap();
        }
    });
}