use log::info;

#[allow(dead_code)]
pub fn cast_slice<T>(data: &[T]) -> &[u8] {
    use std::mem::size_of;
    use std::slice::from_raw_parts;

    unsafe { from_raw_parts(data.as_ptr() as *const u8, data.len() * size_of::<T>()) }
}

#[allow(dead_code)]
pub enum ShaderStage {
    Vertex,
    Fragment,
    Compute,
}

pub fn load_glsl(code: &str, stage: ShaderStage) -> Vec<u8> {
    use std::io::Read;

    let ty = match stage {
        ShaderStage::Vertex => glsl_to_spirv::ShaderType::Vertex,
        ShaderStage::Fragment => glsl_to_spirv::ShaderType::Fragment,
        ShaderStage::Compute => glsl_to_spirv::ShaderType::Compute,
    };

    let mut output = glsl_to_spirv::compile(&code, ty).unwrap();
    let mut spv = Vec::new();
    output.read_to_end(&mut spv).unwrap();
    spv
}

pub trait Example {
    fn init(sc_desc: &wgpu::SwapChainDescriptor, device: &mut wgpu::Device) -> Self;
    fn resize(&mut self, sc_desc: &wgpu::SwapChainDescriptor, device: &mut wgpu::Device);
    fn update(&mut self, event: wgpu::winit::WindowEvent);
    fn render(&mut self, frame: &wgpu::SwapChainOutput, device: &mut wgpu::Device);
}

pub fn run<E: Example>(title: &str) {
    use wgpu::winit::{
        ElementState,
        Event,
        EventsLoop,
        KeyboardInput,
        VirtualKeyCode,
        WindowEvent,
    };

    env_logger::init();

    let mut events_loop = EventsLoop::new();

    info!("Initializing the window...");

    #[cfg(not(feature = "gl"))]
    let (_window, instance, hidpi_factor, size, surface) = {
        use wgpu::winit::Window;

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

        let window = Window::new(&events_loop).unwrap();
        window.set_title(title);
        let hidpi_factor = window.get_hidpi_factor();
        let size = window.get_inner_size().unwrap().to_physical(hidpi_factor);

        let surface = instance.create_surface(&window);

        (window, instance, hidpi_factor, size, surface)
    };

    #[cfg(feature = "gl")]
    let (instance, hidpi_factor, size, surface) = {
        let wb = wgpu::winit::WindowBuilder::new();
        let cb = wgpu::glutin::ContextBuilder::new().with_vsync(true);
        let context = wgpu::glutin::WindowedContext::new_windowed(wb, cb, &events_loop).unwrap();
        context.window().set_title(title);

        let hidpi_factor = context.window().get_hidpi_factor();
        let size = context
            .window()
            .get_inner_size()
            .unwrap()
            .to_physical(hidpi_factor);

        let instance = wgpu::Instance::new(context);
        let surface = instance.get_surface();

        (instance, hidpi_factor, size, surface)
    };

    let adapter = instance.get_adapter(&wgpu::AdapterDescriptor {
        power_preference: wgpu::PowerPreference::LowPower,
    });

    let mut device = adapter.request_device(&wgpu::DeviceDescriptor {
        extensions: wgpu::Extensions {
            anisotropic_filtering: false,
        },
        limits: wgpu::Limits::default(),
    });

    let mut sc_desc = wgpu::SwapChainDescriptor {
        usage: wgpu::TextureUsage::OUTPUT_ATTACHMENT,
        format: wgpu::TextureFormat::Bgra8Unorm,
        width: size.width.round() as u32,
        height: size.height.round() as u32,
    };
    let mut swap_chain = device.create_swap_chain(&surface, &sc_desc);

    info!("Initializing the example...");
    let mut example = E::init(&sc_desc, &mut device);

    info!("Entering render loop...");
    let mut running = true;
    while running {
        events_loop.poll_events(|event| match event {
            Event::WindowEvent {
                event: WindowEvent::Resized(size),
                ..
            } => {
                let physical = size.to_physical(hidpi_factor);
                info!("Resizing to {:?}", physical);
                sc_desc.width = physical.width.round() as u32;
                sc_desc.height = physical.height.round() as u32;
                swap_chain = device.create_swap_chain(&surface, &sc_desc);
                example.resize(&sc_desc, &mut device);
            }
            Event::WindowEvent { event, .. } => match event {
                WindowEvent::KeyboardInput {
                    input:
                        KeyboardInput {
                            virtual_keycode: Some(VirtualKeyCode::Escape),
                            state: ElementState::Pressed,
                            ..
                        },
                    ..
                }
                | WindowEvent::CloseRequested => {
                    running = false;
                }
                _ => {
                    example.update(event);
                }
            },
            _ => (),
        });

        let frame = swap_chain.get_next_texture();
        example.render(&frame, &mut device);
        running &= !cfg!(feature = "metal-auto-capture");
    }
}

// This allows treating the framework as a standalone example,
// thus avoiding listing the example names in `Cargo.toml`.
#[allow(dead_code)]
fn main() {}