use std::time::Duration;

use futures::executor::block_on;
use glutin::{
    dpi, ContextTrait, DeviceEvent, ElementState, Event, EventsLoop, GlProfile, GlRequest,
    MouseButton, MouseScrollDelta, Window, WindowBuilder, WindowEvent, 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 = WindowedContext;

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

    pub fn update(&mut self, size: dpi::LogicalSize) {
        let phys = size.to_physical(self.window().get_hidpi_factor());
        match self {
            HwRendererContext::Gl(context) => unsafe {
                gl::Viewport(0, 0, phys.width as i32, phys.height as i32);
            },
            HwRendererContext::Wgpu(context) => {
                context.swap_chain = context.device.create_swap_chain(
                    &context.surface,
                    &SwapChainDescriptor {
                        usage: TextureUsage::OUTPUT_ATTACHMENT,
                        format: TextureFormat::Bgra8Unorm,
                        width: phys.width as u32,
                        height: phys.height as u32,
                        present_mode: PresentMode::Fifo,
                    },
                );
            }
        }
    }

    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::BLUE),
                            store: false,
                        },
                    }],
                    depth_stencil_attachment: None,
                });
                let buffer = encoder.finish();
                context.queue.submit(std::iter::once(buffer));
            }
        }
        Ok(())
    }
}

fn init_wgpu(event_loop: &EventsLoop, size: dpi::LogicalSize) -> HwWgpuRenderingContext {
    let builder = WindowBuilder::new()
        .with_title("hwengine")
        .with_dimensions(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 size = window.get_inner_size().unwrap();

    let phys = size.to_physical(window.get_hidpi_factor());

    let mut swap_chain = device.create_swap_chain(
        &surface,
        &SwapChainDescriptor {
            usage: TextureUsage::OUTPUT_ATTACHMENT,
            format: TextureFormat::Bgra8Unorm,
            width: phys.width as u32,
            height: phys.height as u32,
            present_mode: PresentMode::Fifo,
        },
    );

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

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

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

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

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

        if let Some(sz) = context.get_inner_size() {
            let phys = sz.to_physical(context.get_hidpi_factor());

            gl::Viewport(0, 0, phys.width as i32, phys.height as i32);
        }
    }

    context
}

fn init(event_loop: &EventsLoop, size: dpi::LogicalSize, use_wgpu: bool) -> HwRendererContext {
    if use_wgpu {
        HwRendererContext::Wgpu(init_wgpu(event_loop, size))
    } else {
        HwRendererContext::Gl(init_gl(event_loop, size))
    }
}

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

    let mut context = init(&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 mut is_running = true;

    while is_running {
        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));

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

        event_loop.poll_events(|event| match event {
            Event::WindowEvent { event, .. } => match event {
                WindowEvent::CloseRequested => {
                    is_running = false;
                }
                WindowEvent::Resized(size) => context.update(size),

                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) => {
                            let physical = delta.to_physical(context.window().get_hidpi_factor());
                            physical.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)
                    }
                }
                _ => {}
            },
            _ => (),
        });

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