/*!
Test supports module.

*/

#![allow(dead_code)]

use glium::Display;
use glium::backend::Facade;
use glium::index::PrimitiveType;

use glutin::config::{Config, ConfigTemplateBuilder};
use glutin::context::ContextAttributesBuilder;
use glutin::display::GetGlDisplay;
use glutin::prelude::*;
use glutin::surface::{SurfaceAttributesBuilder, WindowSurface};
use glutin_winit::DisplayBuilder;
use raw_window_handle::{HasWindowHandle, WindowHandle, RawWindowHandle};
use glium::winit::event::Event;
use glium::winit::event_loop::{EventLoop, EventLoopProxy};
use glium::winit::window::Window;

use std::env;
use std::num::NonZeroU32;
use std::sync::{mpsc::Receiver, Mutex, Once, RwLock};
use std::thread;

// The code below here down to `build_display` is a workaround due to a lack of a test initialization hook
// This sort of design is recommended against for applications

// There is a Wayland version of this extension trait but the X11 version also works on Wayland
#[cfg(unix)]
use glium::winit::platform::x11::EventLoopBuilderExtX11;
#[cfg(windows)]
use glium::winit::platform::windows::EventLoopBuilderExtWindows;

// Thread communication
static EVENT_LOOP_PROXY: RwLock<Option<EventLoopProxy<()>>> = RwLock::new(None);
static WINDOW_RECEIVER: Mutex<Option<Receiver<(HandleOrWindow, Config)>>> = Mutex::new(None);

// Initialization
static INIT_EVENT_LOOP: Once = Once::new();
static SEND_PROXY: Once = Once::new();

#[derive(Debug)]
enum HandleOrWindow {
    SendHandle(WindowHandle<'static>),
    RefWindow(&'static Window),
}

impl From<&'static Window> for HandleOrWindow {
    fn from(window: &'static Window) -> Self {
        let window_handle = window.window_handle().unwrap();

        match window_handle.as_raw() {
            RawWindowHandle::Xlib(_) |
            RawWindowHandle::Xcb(_) |
            RawWindowHandle::Drm(_) |
            RawWindowHandle::Win32(_) |
            RawWindowHandle::Web(_)
                => HandleOrWindow::SendHandle(window_handle),
            RawWindowHandle::UiKit(_) |
            RawWindowHandle::AppKit(_) |
            RawWindowHandle::Orbital(_) |
            RawWindowHandle::OhosNdk(_) |
            RawWindowHandle::Wayland(_) |
            RawWindowHandle::Gbm(_) |
            RawWindowHandle::WinRt(_) |
            RawWindowHandle::WebCanvas(_) |
            RawWindowHandle::WebOffscreenCanvas(_) |
            RawWindowHandle::AndroidNdk(_) |
            RawWindowHandle::Haiku(_)
                => HandleOrWindow::RefWindow(window),
            // Intentionally unsupported platforms
            _ => panic!("Unsupported"),
        }
    }
}

impl From<HandleOrWindow> for RawWindowHandle {
    fn from(handle: HandleOrWindow) -> Self {
        let handle = match handle {
            HandleOrWindow::SendHandle(handle) => handle,
            HandleOrWindow::RefWindow(window) => window.window_handle().unwrap(),
        };
        handle.as_raw()
    }
}

// SAFETY
// requires `From` implementation to be kept in sync with `raw_window_handle` and `winit` crates
unsafe impl Send for HandleOrWindow {}

unsafe fn initialize_event_loop() {
    INIT_EVENT_LOOP.call_once(|| {
        // One-time-use channel to get the event loop proxy
        let (ots, otr) = std::sync::mpsc::sync_channel(0);
        // Transfers window and config for creating display
        let (sender, receiver) = std::sync::mpsc::channel();

        let builder = thread::Builder::new().name("event_loop".into());
        builder
            .spawn(|| {
                let event_loop_res = if cfg!(unix) || cfg!(windows) {
                    EventLoop::builder().with_any_thread(true).build()
                } else {
                    EventLoop::builder().build()
                };
                let event_loop = event_loop_res.expect("event loop building");
                let proxy = event_loop.create_proxy();

                #[allow(deprecated)]
                event_loop.run(move |event, window_target| {
                    match event {
                        Event::UserEvent(_) => {
                            let window_attributes = Window::default_attributes().with_visible(false);
                            let config_template_builder = ConfigTemplateBuilder::new();
                            let display_builder =
                                DisplayBuilder::new().with_window_attributes(Some(window_attributes));
                            let (window, gl_config) = display_builder
                                .build(window_target, config_template_builder, |mut configs| {
                                    // Just use the first configuration since we don't have any special preferences here
                                    configs.next().unwrap()
                                })
                                .unwrap();

                            // Leak the window object to obtain a static reference
                            let boxed_window = Box::new(window.unwrap());
                            let window = Box::leak(boxed_window);

                            sender.send(((&*window).into(), gl_config)).unwrap();
                        }
                        _ => {
                            // Send event loop proxy ASAP
                            SEND_PROXY.call_once(|| {
                                ots.send(proxy.clone()).unwrap();
                            });
                        }
                    }
                })
                .unwrap();
            })
            .unwrap();

        // `recv` will block until any non-user event is encountered
        let event_loop_proxy = otr.recv().unwrap();

        // Write to the thread communication variables while still in `call_once`'s closure
        *EVENT_LOOP_PROXY.write().unwrap() = Some(event_loop_proxy);

        *WINDOW_RECEIVER.lock().unwrap() = Some(receiver);
    });
}

/// Builds a display for tests.
pub fn build_display() -> Display<WindowSurface> {
    // SAFETY
    // This is the first function to run when any test thread calls build_display.
    // `Once` spawns a new thread to create the event loop and sets up the communication channels.
    // The static mut variables are only ever read with synchronization after initialization.
    unsafe { initialize_event_loop(); }

    // Tell event loop to create a window and config for creating a display
    EVENT_LOOP_PROXY
        .read().unwrap()
        .as_ref().unwrap()
        .send_event(()).unwrap();

    // Receive said window and config one thread at a time
    let (handle_or_window, gl_config) =
        WINDOW_RECEIVER
            .lock().unwrap()
            .as_ref().unwrap()
            .recv().unwrap();

    // Then the configuration which decides which OpenGL version we'll end up using, here we just use the default which is currently 3.3 core
    // When this fails we'll try and create an ES context, this is mainly used on mobile devices or various ARM SBC's
    // If you depend on features available in modern OpenGL Versions you need to request a specific, modern, version. Otherwise things will very likely fail.
    let version = parse_version();
    let raw_window_handle = handle_or_window.into();
    let context_attributes = ContextAttributesBuilder::new()
        .with_context_api(version)
        .build(Some(raw_window_handle));

    let not_current_gl_context = unsafe {
        gl_config.display().create_context(&gl_config, &context_attributes).unwrap()
    };

    let attrs = SurfaceAttributesBuilder::<WindowSurface>::new().build(
        raw_window_handle,
        NonZeroU32::new(800).unwrap(),
        NonZeroU32::new(600).unwrap(),
    );

    // Now we can create our surface, use it to make our context current and finally create our display
    let surface = unsafe { gl_config.display().create_window_surface(&gl_config, &attrs).unwrap() };
    let current_context = not_current_gl_context.make_current(&surface).unwrap();

    Display::from_context_surface(current_context, surface).unwrap()
}


/// Rebuilds an existing display.
///
/// In real applications this is used for things such as switching to fullscreen. Some things are
/// invalidated during a rebuild, and this has to be handled by glium.
pub fn rebuild_display(_display: &glium::Display<WindowSurface>) {
    todo!();
    /*
    let version = parse_version();
    let event_loop = glium::winit::event_loop::EventLoop::new();
    let wb = glium::winit::window::WindowBuilder::new().with_visible(false);
    let cb = glutin::ContextBuilder::new()
        .with_gl_debug_flag(true)
        .with_gl(version);
    display.rebuild(wb, cb, &event_loop).unwrap();
     */
}

fn parse_version() -> glutin::context::ContextApi {
    match env::var("GLIUM_GL_VERSION") {
        Ok(version) => {
            // expects "OpenGL 3.3" for example

            let mut iter = version.rsplitn(2, ' ');

            let version = iter.next().unwrap();
            let ty = iter.next().unwrap();

            let mut iter = version.split('.');
            let major = iter.next().unwrap().parse().unwrap();
            let minor = iter.next().unwrap().parse().unwrap();

            if ty == "OpenGL" {
                glutin::context::ContextApi::OpenGl(Some(glutin::context::Version::new(major, minor)))
            } else if ty == "OpenGL ES" {
                glutin::context::ContextApi::Gles(Some(glutin::context::Version::new(major, minor)))
            } else if ty == "WebGL" {
                glutin::context::ContextApi::Gles(Some(glutin::context::Version::new(major, minor)))
            } else {
                panic!();
            }
        },
        Err(_) => glutin::context::ContextApi::OpenGl(None),
    }
}

/// Builds a 2x2 unicolor texture.
pub fn build_unicolor_texture2d<F: ?Sized>(facade: &F, red: f32, green: f32, blue: f32)
    -> glium::Texture2d where F: Facade
{
    let color = ((red * 255.0) as u8, (green * 255.0) as u8, (blue * 255.0) as u8);

    glium::texture::Texture2d::new(facade, vec![
        vec![color, color],
        vec![color, color],
    ]).unwrap()
}

/// Builds a 2x2 depth texture.
pub fn build_constant_depth_texture<F>(facade: &F, depth: f32) -> glium::texture::DepthTexture2d
where F: Facade + ?Sized
{
    glium::texture::DepthTexture2d::new(facade, vec![
        vec![depth, depth],
        vec![depth, depth],
    ]).unwrap()
}

/// Builds a vertex buffer, index buffer, and program, to draw red `(1.0, 0.0, 0.0, 1.0)` to the whole screen.
pub fn build_fullscreen_red_pipeline<F: ?Sized>(facade: &F) -> (glium::vertex::VertexBufferAny,
    glium::index::IndexBufferAny, glium::Program) where F: Facade
{
    #[derive(Copy, Clone)]
    struct Vertex {
        position: [f32; 2],
    }

    implement_vertex!(Vertex, position);

    (
        glium::VertexBuffer::new(facade, &[
            Vertex { position: [-1.0,  1.0] }, Vertex { position: [1.0,  1.0] },
            Vertex { position: [-1.0, -1.0] }, Vertex { position: [1.0, -1.0] },
        ]).unwrap().into(),

        glium::IndexBuffer::new(facade, PrimitiveType::TriangleStrip, &[0u8, 1, 2, 3]).unwrap().into(),

        program!(facade,
            110 => {
                vertex: "
                    #version 110

                    attribute vec2 position;

                    void main() {
                        gl_Position = vec4(position, 0.0, 1.0);
                    }
                ",
                fragment: "
                    #version 110

                    void main() {
                        gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
                    }
                ",
            },
            100 => {
                vertex: "
                    #version 100

                    attribute lowp vec2 position;

                    void main() {
                        gl_Position = vec4(position, 0.0, 1.0);
                    }
                ",
                fragment: "
                    #version 100

                    void main() {
                        gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
                    }
                ",
            },
        ).unwrap()
    )
}

/// Builds a vertex buffer and an index buffer corresponding to a rectangle.
///
/// The vertex buffer has the "position" attribute of type "vec2".
pub fn build_rectangle_vb_ib<F: ?Sized>(facade: &F)
    -> (glium::vertex::VertexBufferAny, glium::index::IndexBufferAny) where F: Facade
{
    #[derive(Copy, Clone)]
    struct Vertex {
        position: [f32; 2],
    }

    implement_vertex!(Vertex, position);

    (
        glium::VertexBuffer::new(facade, &[
            Vertex { position: [-1.0,  1.0] }, Vertex { position: [1.0,  1.0] },
            Vertex { position: [-1.0, -1.0] }, Vertex { position: [1.0, -1.0] },
        ]).unwrap().into(),

        glium::IndexBuffer::new(facade, PrimitiveType::TriangleStrip, &[0u8, 1, 2, 3]).unwrap().into(),
    )
}

/// Builds a texture suitable for rendering.
pub fn build_renderable_texture<F: ?Sized>(facade: &F) -> glium::Texture2d where F: Facade {
    glium::Texture2d::empty(facade, 1024, 1024).unwrap()
}