use gtk::glib;
use gtk::subclass::prelude::*;
use smithay::utils::{Logical, Size};

use crate::cases::TestCase;

mod imp {
    use std::cell::{Cell, OnceCell, RefCell};
    use std::ptr::null;

    use anyhow::{ensure, Context};
    use gtk::gdk;
    use gtk::prelude::*;
    use niri::render_helpers::{resources, shaders};
    use niri::utils::get_monotonic_time;
    use smithay::backend::egl::ffi::egl;
    use smithay::backend::egl::EGLContext;
    use smithay::backend::renderer::gles::GlesRenderer;
    use smithay::backend::renderer::{Color32F, Frame, Renderer, Unbind};
    use smithay::utils::{Physical, Rectangle, Scale, Transform};

    use super::*;

    type DynMakeTestCase = Box<dyn Fn(Size<i32, Logical>) -> Box<dyn TestCase>>;

    #[derive(Default)]
    pub struct SmithayView {
        gl_area: gtk::GLArea,
        size: Cell<(i32, i32)>,
        renderer: RefCell<Option<Result<GlesRenderer, ()>>>,
        pub make_test_case: OnceCell<DynMakeTestCase>,
        test_case: RefCell<Option<Box<dyn TestCase>>>,
    }

    #[glib::object_subclass]
    impl ObjectSubclass for SmithayView {
        const NAME: &'static str = "NiriSmithayView";
        type Type = super::SmithayView;
        type ParentType = gtk::Widget;

        fn class_init(klass: &mut Self::Class) {
            klass.set_layout_manager_type::<gtk::BinLayout>();
        }
    }

    impl ObjectImpl for SmithayView {
        fn constructed(&self) {
            let obj = self.obj();

            self.parent_constructed();

            self.gl_area.set_allowed_apis(gdk::GLAPI::GLES);
            self.gl_area.set_parent(&*obj);

            self.gl_area.connect_resize({
                let imp = self.downgrade();
                move |_, width, height| {
                    if let Some(imp) = imp.upgrade() {
                        imp.resize(width, height);
                    }
                }
            });

            self.gl_area.connect_render({
                let imp = self.downgrade();
                move |_, gl_context| {
                    if let Some(imp) = imp.upgrade() {
                        if let Err(err) = imp.render(gl_context) {
                            warn!("error rendering: {err:?}");
                        }
                    }
                    glib::Propagation::Stop
                }
            });

            obj.add_tick_callback(|obj, _frame_clock| {
                let imp = obj.imp();

                if let Some(case) = &mut *imp.test_case.borrow_mut() {
                    if case.are_animations_ongoing() {
                        imp.gl_area.queue_draw();
                    }
                }

                glib::ControlFlow::Continue
            });
        }

        fn dispose(&self) {
            self.gl_area.unparent();
        }
    }

    impl WidgetImpl for SmithayView {
        fn unmap(&self) {
            self.test_case.replace(None);
            self.parent_unmap();
        }

        fn unrealize(&self) {
            self.renderer.replace(None);
            self.parent_unrealize();
        }
    }

    impl SmithayView {
        fn resize(&self, width: i32, height: i32) {
            self.size.set((width, height));

            if let Some(case) = &mut *self.test_case.borrow_mut() {
                case.resize(width, height);
            }
        }

        fn render(&self, _gl_context: &gdk::GLContext) -> anyhow::Result<()> {
            // Set up the Smithay renderer.
            let mut renderer = self.renderer.borrow_mut();
            let renderer = renderer.get_or_insert_with(|| {
                unsafe { create_renderer() }
                    .map_err(|err| warn!("error creating a Smithay renderer: {err:?}"))
            });
            let Ok(renderer) = renderer else {
                return Ok(());
            };

            let size = self.size.get();

            // Create the test case if missing.
            let mut case = self.test_case.borrow_mut();
            let case = case.get_or_insert_with(|| {
                let make = self.make_test_case.get().unwrap();
                make(Size::from(size))
            });

            case.advance_animations(get_monotonic_time());

            let rect: Rectangle<i32, Physical> = Rectangle::from_loc_and_size((0, 0), size);

            let elements = unsafe {
                with_framebuffer_save_restore(renderer, |renderer| {
                    case.render(renderer, Size::from(size))
                })
            }?;

            let mut frame = renderer
                .render(rect.size, Transform::Normal)
                .context("error creating frame")?;

            frame
                .clear(Color32F::from([0.3, 0.3, 0.3, 1.]), &[rect])
                .context("error clearing")?;

            for element in elements.iter().rev() {
                let src = element.src();
                let dst = element.geometry(Scale::from(1.));

                if let Some(mut damage) = rect.intersection(dst) {
                    damage.loc -= dst.loc;
                    element
                        .draw(&mut frame, src, dst, &[damage], &[])
                        .context("error drawing element")?;
                }
            }

            Ok(())
        }
    }

    unsafe fn create_renderer() -> anyhow::Result<GlesRenderer> {
        smithay::backend::egl::ffi::make_sure_egl_is_loaded()
            .context("error loading EGL symbols in Smithay")?;

        let egl_display = egl::GetCurrentDisplay();
        ensure!(egl_display != egl::NO_DISPLAY, "no current EGL display");

        let egl_context = egl::GetCurrentContext();
        ensure!(egl_context != egl::NO_CONTEXT, "no current EGL context");

        // There's no config ID on the EGL context and there's no current EGL surface, but we don't
        // really use it anyway so just get some random one.
        let mut egl_config_id = null();
        let mut num_configs = 0;
        let res = egl::GetConfigs(egl_display, &mut egl_config_id, 1, &mut num_configs);
        ensure!(res == egl::TRUE, "error choosing EGL config");
        ensure!(num_configs != 0, "no EGL config");

        let egl_context = EGLContext::from_raw(egl_display, egl_config_id as *const _, egl_context)
            .context("error creating EGL context")?;

        let mut renderer = GlesRenderer::new(egl_context).context("error creating GlesRenderer")?;

        resources::init(&mut renderer);
        shaders::init(&mut renderer);

        Ok(renderer)
    }

    unsafe fn with_framebuffer_save_restore<T>(
        renderer: &mut GlesRenderer,
        f: impl FnOnce(&mut GlesRenderer) -> T,
    ) -> anyhow::Result<T> {
        let mut framebuffer = 0;
        renderer
            .with_context(|gl| unsafe {
                gl.GetIntegerv(
                    smithay::backend::renderer::gles::ffi::FRAMEBUFFER_BINDING,
                    &mut framebuffer,
                );
            })
            .context("error running closure in GL context")?;
        ensure!(framebuffer != 0, "error getting the framebuffer");

        let rv = f(renderer);

        renderer.unbind().context("error unbinding")?;
        renderer
            .with_context(|gl| unsafe {
                gl.BindFramebuffer(
                    smithay::backend::renderer::gles::ffi::FRAMEBUFFER,
                    framebuffer as u32,
                );
            })
            .context("error running closure in GL context")?;

        Ok(rv)
    }
}

glib::wrapper! {
    pub struct SmithayView(ObjectSubclass<imp::SmithayView>)
        @extends gtk::Widget;
}

impl SmithayView {
    pub fn new<T: TestCase + 'static>(
        make_test_case: impl Fn(Size<i32, Logical>) -> T + 'static,
    ) -> Self {
        let obj: Self = glib::Object::builder().build();

        let make = move |size| Box::new(make_test_case(size)) as Box<dyn TestCase>;
        let make_test_case = Box::new(make) as _;
        let _ = obj.imp().make_test_case.set(make_test_case);

        obj
    }
}