use std::path::{Path, PathBuf};
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::LazyLock;

use dear_imgui_rs::{
    DrawCmd as ImguiDrawCmd,
    Key as ImguiKey,
    MouseButton as ImguiMouseButton,
};
use ecs::component::local::Local;
use ecs::component::Component;
use ecs::event::component::{Changed, EventMatchExt};
use ecs::pair::Pair;
use ecs::query::term::With;
use ecs::sole::Single;
use ecs::system::initializable::Initializable;
use ecs::system::observer::Observe;
use ecs::system::Into;
use ecs::{Component, Query, Sole};

use crate::asset::{Assets, Handle as AssetHandle, Label as AssetLabel};
use crate::data_types::color::Rgba;
use crate::data_types::dimens::Dimens;
use crate::delta_time::DeltaTime;
use crate::image::{
    Image,
    PixelBuffer as ImagePixelBuffer,
    PixelBufferLenIncorrectForSize as ImagePixelBufferLenIncorrectForSize,
};
use crate::input::keyboard::{Key, Keyboard};
use crate::input::mouse::{Button as MouseButton, Buttons as MouseButtons, Mouse};
use crate::mesh::vertex_buffer::{
    NamedVertexAttr as MeshNamedVertexAttr,
    VertexAttrInfo as MeshVertexAttrInfo,
    VertexBuffer as MeshVertexBuffer,
};
use crate::mesh::{
    Mesh,
    VertexAttrType as MeshVertexAttrType,
    POSITION_VERTEX_ATTRIB_NAME,
};
use crate::projection::{
    ClipVolume as ProjectionClipVolume,
    Orthographic as OrthographicProjection,
};
use crate::rendering::blending::{
    Config as RenderingBlendingConfiguration,
    Equation as RenderingBlendingEquation,
    Factor as RenderingBlendingFactor,
};
use crate::rendering::object::Id as RenderingObjectId;
use crate::rendering::shader::cursor::{
    BindingValue as ShaderBindingValue,
    Cursor as ShaderCursor,
};
use crate::rendering::shader::{
    Context as ShaderContext,
    EntrypointFlags as ShaderEntrypointFlags,
    ModuleSource as ShaderModuleSource,
};
use crate::rendering::{
    AssetOrValue,
    Command as RenderingCommand,
    DrawMeshOptions,
    DrawProperties,
    DrawPropertiesUpdateFlags,
    MeshUsage,
    RenderPass,
    RenderPasses,
    ScissorBox,
    SurfaceId,
    SurfaceSpec,
    PRE_RENDER_PHASE,
};
use crate::texture::{Properties as TextureProperties, Texture};
use crate::util::MapVec;
use crate::vector::Vec2;
use crate::windowing::dpi::PhysicalSize;
use crate::windowing::window::Window;

mod reexports
{
    pub use dear_imgui_rs as dear_imgui;
}

pub use reexports::*;

pub static SHADER_ASSET_LABEL: LazyLock<AssetLabel> = LazyLock::new(|| AssetLabel {
    path: Path::new("").into(),
    name: Some("imgui_shader".into()),
});

/// Dear Imgui context
#[derive(Sole)]
pub struct Context
{
    pub enabled: bool,
    ctx: inner_context_wrapper::InnerContextWrapper,
    texture_lookup: MapVec<TextureLookupId, RenderingObjectId>,
}

impl Context
{
    pub fn frame(&mut self) -> Option<&mut dear_imgui_rs::Ui>
    {
        if !self.enabled {
            return None;
        }

        self.ctx.get_frame()
    }

    pub fn register_texture(&mut self, texture_data: &mut dear_imgui_rs::OwnedTextureData)
    {
        self.ctx.register_texture(texture_data);
    }
}

#[derive(Debug, Default)]
#[non_exhaustive]
pub struct Extension
{
    start_enabled: bool,
    settings_ini_file_path: Option<PathBuf>,
}

impl Extension
{
    pub fn with_start_enabled(mut self, start_enabled: bool) -> Self
    {
        self.start_enabled = start_enabled;
        self
    }

    pub fn with_settings_ini_file(
        mut self,
        settings_ini_file_path: Option<PathBuf>,
    ) -> Self
    {
        self.settings_ini_file_path = settings_ini_file_path;
        self
    }
}

impl ecs::extension::Extension for Extension
{
    fn collect(self, mut collector: ecs::extension::Collector<'_>)
    {
        let mut context = Context {
            enabled: self.start_enabled,
            ctx: inner_context_wrapper::InnerContextWrapper::new(),
            texture_lookup: MapVec::with_capacity(8),
        };

        if let Err(err) = context
            .ctx
            .set_settings_ini_file_path(self.settings_ini_file_path)
        {
            tracing::error!("Failed to set path of imgui settings ini file: {err}");
        }

        collector.add_sole(context).ok();

        collector.add_system(
            *PRE_RENDER_PHASE,
            update.into_system().initialize((State::default(),)),
        );

        collector.add_observer(handle_window_changed);
    }
}

#[tracing::instrument(skip_all)]
fn handle_window_changed(
    observe: Observe<Pair<Changed, Window>>,
    mut context: Single<Context>,
)
{
    let Ok(context) = context.get_mut() else {
        unreachable!();
    };

    let Some(event_match) = observe
        .iter()
        .find(|event_match| event_match.get_entity().has_component(TargetWindow::id()))
    else {
        return;
    };

    let window = event_match.get_ent_target_comp();

    let hidpi_factor = window.scale_factor().round();

    context
        .ctx
        .get_io_mut()
        .set_display_framebuffer_scale([hidpi_factor as f32, hidpi_factor as f32]);

    let window_size_logical = PhysicalSize {
        width: window.inner_size.width as f64,
        height: window.inner_size.height as f64,
    }
    .to_logical::<f64>(hidpi_factor);

    context.ctx.get_io_mut().set_display_size([
        window_size_logical.width as f32,
        window_size_logical.height as f32,
    ]);
}

fn update(
    target_window_query: Query<(&Window, &SurfaceSpec), (With<TargetWindow>,)>,
    mut context: Single<Context>,
    delta_time: Single<DeltaTime>,
    mut assets: Single<Assets>,
    mut render_passes: Single<RenderPasses>,
    shader_context: Single<ShaderContext>,
    keyboard: Single<Keyboard>,
    mouse: Single<Mouse>,
    mouse_buttons: Single<MouseButtons>,
    mut state: Local<State>,
) -> Result<(), crate::Error>
{
    let Ok(context) = context.get_mut() else {
        unreachable!();
    };

    let delta_time = delta_time.get()?;
    let assets = assets.get_mut()?;
    let render_passes = render_passes.get_mut()?;
    let shader_context = shader_context.get()?;
    let keyboard = keyboard.get()?;
    let mouse = mouse.get()?;
    let mouse_buttons = mouse_buttons.get()?;

    let Some((window, window_surface_spec)) = target_window_query.iter().next() else {
        return Ok(());
    };

    let curr_state = std::mem::replace(&mut *state, State::Unreachable);

    match curr_state {
        State::NotInitialized => {
            let Some((shader_asset, mesh_obj_id, mesh)) = initialize_context(
                context,
                &window,
                window_surface_spec.id,
                assets,
                render_passes,
                &shader_context,
            ) else {
                *state = State::NotInitialized;
                return Ok(());
            };

            context.ctx.new_frame();

            *state = State::Ready { shader_asset, mesh_obj_id, mesh };
        }
        State::Ready { shader_asset, mesh_obj_id, mut mesh } => {
            if !context.enabled {
                *state = State::Ready { shader_asset, mesh_obj_id, mesh };
                return Ok(());
            }

            context
                .ctx
                .get_io_mut()
                .set_delta_time(delta_time.duration.as_secs_f32());

            update_inputs(context, &window, keyboard, mouse, mouse_buttons);

            add_drawing_render_pass(
                context,
                render_passes,
                shader_context,
                window_surface_spec.id,
                shader_asset.clone(),
                mesh_obj_id,
                &mut mesh,
            );

            context.ctx.new_frame();

            *state = State::Ready { shader_asset, mesh_obj_id, mesh };
        }
        State::Unreachable => unreachable!(),
    }

    Ok(())
}

#[derive(Debug, Component)]
pub struct TargetWindow;

#[derive(Debug, Default, Component)]
enum State
{
    #[default]
    NotInitialized,
    Ready
    {
        shader_asset: AssetHandle<ShaderModuleSource>,
        mesh_obj_id: RenderingObjectId,
        mesh: Mesh,
    },
    Unreachable,
}

fn initialize_context(
    context: &mut Context,
    window: &Window,
    window_surface_id: SurfaceId,
    assets: &mut Assets,
    render_passes: &mut RenderPasses,
    shader_context: &ShaderContext,
) -> Option<(AssetHandle<ShaderModuleSource>, RenderingObjectId, Mesh)>
{
    let shader_asset = if let Some(shader_asset) =
        assets.get_handle_to_loaded::<ShaderModuleSource>(SHADER_ASSET_LABEL.clone())
    {
        shader_asset
    } else {
        assets.store_with_label(
            SHADER_ASSET_LABEL.clone(),
            ShaderModuleSource {
                name: "imgui_shader.slang".into(),
                file_path: Path::new("@engine/imgui_shader").into(),
                source: include_str!("../../res/imgui_shader.slang").into(),
                link_entrypoints: ShaderEntrypointFlags::VERTEX
                    | ShaderEntrypointFlags::FRAGMENT,
            },
        );

        // We want to wait with initializing until the shader have been processed by the
        // shader context
        return None;
    };

    let hidpi_factor = window.scale_factor().round();

    context
        .ctx
        .get_io_mut()
        .set_display_framebuffer_scale([hidpi_factor as f32, hidpi_factor as f32]);

    let window_size = Dimens {
        width: window.inner_size.width as f32,
        height: window.inner_size.height as f32,
    };

    let window_logical_size = window_size / (hidpi_factor as f32);

    context
        .ctx
        .get_io_mut()
        .set_display_size([window_logical_size.width, window_logical_size.height]);

    let mesh_obj_id = RenderingObjectId::new_sequential();

    let mesh = Mesh::builder()
        .vertices(MeshVertexBuffer::with_capacity(
            &[
                MeshVertexAttrInfo {
                    name: POSITION_VERTEX_ATTRIB_NAME.into(),
                    ty: MeshVertexAttrType::Float32Array { length: 3 },
                },
                MeshVertexAttrInfo {
                    name: "color".into(),
                    ty: MeshVertexAttrType::Float32Array { length: 4 },
                },
                MeshVertexAttrInfo {
                    name: "texture_coords".into(),
                    ty: MeshVertexAttrType::Float32Array { length: 2 },
                },
            ],
            128,
        ))
        .indices([])
        .build();

    render_passes.passes.push_back(RenderPass {
        commands: vec![
            RenderingCommand::MakeCurrent(window_surface_id),
            RenderingCommand::CreateShaderProgram(
                RenderingObjectId::Asset(shader_asset.id()),
                shader_context
                    .get_program(&shader_asset.id())
                    .expect("Not possible")
                    .clone(),
            ),
            RenderingCommand::ActivateShader(RenderingObjectId::Asset(shader_asset.id())),
            RenderingCommand::CreateMesh {
                obj_id: mesh_obj_id,
                mesh: AssetOrValue::Value(mesh.clone()),
                usage: MeshUsage::Stream,
            },
        ],
        draw_properties: DrawProperties::default(),
    });

    Some((shader_asset, mesh_obj_id, mesh))
}

fn update_inputs(
    context: &mut Context,
    window: &Window,
    keyboard: &Keyboard,
    mouse: &Mouse,
    mouse_buttons: &MouseButtons,
)
{
    let io = context.ctx.get_io_mut();

    for (key, key_state) in keyboard.new_key_states() {
        if let Some(key) = key_to_imgui_key(key) {
            io.add_key_event(key, key_state.is_pressed());
        }
    }

    for character in keyboard.text_keys().chars() {
        if character == '\u{7f}' {
            continue;
        }

        io.add_input_character(character);
    }

    io.add_mouse_source_event(dear_imgui_rs::input::MouseSource::Mouse);

    let mouse_pos = mouse.position.to_logical::<f64>(window.scale_factor());

    io.add_mouse_pos_event([mouse_pos.x as f32, mouse_pos.y as f32]);

    if !mouse.curr_tick_scroll_delta.is_zero() {
        io.add_mouse_wheel_event([
            mouse.curr_tick_scroll_delta.hor_lines,
            mouse.curr_tick_scroll_delta.vert_lines,
        ]);
    }

    for (mouse_button, mouse_button_state) in mouse_buttons.all_current() {
        if let Some(mouse_button) = mouse_button_to_imgui_mouse_button(mouse_button) {
            io.add_mouse_button_event(mouse_button, mouse_button_state.is_pressed());
        }
    }
}

fn add_drawing_render_pass(
    context: &mut Context,
    render_passes: &mut RenderPasses,
    shader_context: &ShaderContext,
    window_surface_id: SurfaceId,
    shader_asset: AssetHandle<ShaderModuleSource>,
    mesh_obj_id: RenderingObjectId,
    mesh: &mut Mesh,
)
{
    let render_pass = render_passes.passes.push_back_mut(RenderPass {
        commands: Vec::new(),
        draw_properties: DrawProperties {
            blending_enabled: true,
            blending_config: RenderingBlendingConfiguration {
                equation: RenderingBlendingEquation::Add,
                source_factor: RenderingBlendingFactor::SrcAlpha,
                destination_factor: RenderingBlendingFactor::OneMinusSrcAlpha,
            },
            depth_test_enabled: false,
            face_culling_enabled: false,
            scissor_test_enabled: true,
            ..Default::default()
        },
    });

    let shader_program = shader_context
        .get_program(&shader_asset.id())
        .expect("Not possible");

    let shader_cursor = ShaderCursor::new(
        shader_program
            .reflection(0)
            .unwrap()
            .global_params_var_layout()
            .unwrap(),
    );

    let Context { enabled: _, ctx, texture_lookup } = context;

    let draw_data = ctx.render();

    let mut textures = draw_data.textures_mut();

    while let Some(mut texture_data) = textures.next() {
        match texture_data.status() {
            dear_imgui_rs::TextureStatus::WantCreate => {
                let Some(texture_pixels) = texture_data.pixels() else {
                    texture_data.set_status(dear_imgui_rs::TextureStatus::OK);
                    continue;
                };

                if !matches!(texture_data.format(), dear_imgui_rs::TextureFormat::RGBA32)
                {
                    unimplemented!();
                }

                let image =
                    match Image::from_pixels(ImagePixelBuffer::<Rgba<u8>, _>::new(
                        texture_pixels,
                        Dimens {
                            width: texture_data.width(),
                            height: texture_data.height(),
                        },
                    )) {
                        Ok(image) => image,
                        Err(ImagePixelBufferLenIncorrectForSize) => {
                            tracing::error!("Not enough texture pixels for texture size");
                            continue;
                        }
                    };

                let texture_object_id = RenderingObjectId::new_sequential();

                render_pass.commands.push(RenderingCommand::CreateTexture(
                    texture_object_id,
                    AssetOrValue::Value(Texture {
                        image,
                        properties: TextureProperties::default(),
                    }),
                ));

                let texture_lookup_id = TextureLookupId::new();

                texture_data.set_tex_id(texture_lookup_id.into());

                texture_lookup.insert(texture_lookup_id, texture_object_id);

                texture_data.set_status(dear_imgui_rs::TextureStatus::OK);
            }
            dear_imgui_rs::TextureStatus::WantUpdates => {
                if texture_data.tex_id().is_null() {
                    tracing::error!(concat!(
                        "Update was requested for texture with a null ID. Did you forget ",
                        "to set the texture status to TextureStatus::WantCreate?"));

                    continue;
                }

                if texture_data.pixels().is_none() {
                    texture_data.set_status(dear_imgui_rs::TextureStatus::OK);
                    continue;
                }

                let mut rects: Vec<dear_imgui_rs::texture::TextureRect> =
                    texture_data.updates().collect();

                if rects.is_empty() {
                    let rect = texture_data.update_rect();
                    if rect.w > 0 && rect.h > 0 {
                        rects.push(rect);
                    }
                }

                if rects.is_empty() {
                    texture_data.set_status(dear_imgui_rs::TextureStatus::OK);
                    continue;
                }

                let Some(texture_object_id) =
                    texture_lookup.get(&TextureLookupId::from(texture_data.tex_id()))
                else {
                    tracing::error!(
                        "Unknown texture {}. Skipping update",
                        texture_data.tex_id().id()
                    );
                    texture_data.set_status(dear_imgui_rs::TextureStatus::OK);
                    continue;
                };

                render_pass.commands.extend(rects.iter().filter_map(|rect| {
                    let Some(rect_image) = get_texture_rect_image(&texture_data, rect)
                    else {
                        return None;
                    };

                    Some(RenderingCommand::UpdateTexture {
                        obj_id: texture_object_id.clone(),
                        image: rect_image,
                        offset: Vec2 { x: rect.x as u32, y: rect.y as u32 },
                    })
                }));

                texture_data.set_status(dear_imgui_rs::TextureStatus::OK);
            }
            dear_imgui_rs::TextureStatus::WantDestroy => {
                let Some(texture_object_id) =
                    texture_lookup.remove(TextureLookupId::from(texture_data.tex_id()))
                else {
                    tracing::error!(
                        "Unknown texture {}. Skipping destroyal",
                        texture_data.tex_id().id()
                    );
                    texture_data.set_status(dear_imgui_rs::TextureStatus::OK);
                    continue;
                };

                render_pass
                    .commands
                    .push(RenderingCommand::RemoveTexture(texture_object_id));
            }
            _ => {}
        }
    }

    let [display_width, display_height] = draw_data.display_size;

    // let [scale_width, scale_height] = draw_data.framebuffer_scale;

    render_pass.commands.extend([
        RenderingCommand::MakeCurrent(window_surface_id),
        RenderingCommand::ActivateShader(RenderingObjectId::Asset(shader_asset.id())),
        RenderingCommand::SetShaderBinding(
            shader_cursor
                .field("Uniforms")
                .field("projection")
                .into_binding_location(),
            ShaderBindingValue::FMat4x4(
                OrthographicProjection::builder()
                    .near(1.0)
                    .far(-1.0)
                    .viewport_origin(Vec2 { x: 0.0, y: 1.0 })
                    .size(crate::projection::OrthographicSize::WindowSize)
                    .build()
                    .to_matrix_rh(
                        Dimens {
                            width: display_width,
                            height: -display_height,
                        },
                        ProjectionClipVolume::NegOneToOne,
                    ),
            ),
        ),
    ]);

    for draw_list in draw_data.draw_lists() {
        mesh.vertex_buf_mut().clear();

        for vertex in draw_list.vtx_buffer() {
            mesh.vertex_buf_mut().push((
                MeshNamedVertexAttr::<[f32; 3]> {
                    name: POSITION_VERTEX_ATTRIB_NAME,
                    value: [vertex.pos[0], vertex.pos[1], 0.0],
                },
                MeshNamedVertexAttr {
                    name: "color",
                    value: vertex.rgba().map(|elem| (elem as f32) / 255.0),
                },
                MeshNamedVertexAttr {
                    name: "texture_coords",
                    value: vertex.uv,
                },
            ));
        }

        mesh.set_indices(draw_list.idx_buffer().iter().map(|index| (*index).into()));

        render_pass.commands.push(RenderingCommand::UpdateMesh {
            obj_id: mesh_obj_id,
            mesh: mesh.clone(),
            usage: MeshUsage::Stream,
        });

        for command in draw_list.commands() {
            match command {
                ImguiDrawCmd::Elements { count, cmd_params, raw_cmd } => {
                    let Some(scissor_box) =
                        calc_draw_cmd_scissor_box(draw_data, &cmd_params)
                    else {
                        continue;
                    };

                    let tex_id = dear_imgui_rs::TextureId::new(u64::from(unsafe {
                        let mut cmd_copy = *raw_cmd;

                        dear_imgui_rs::sys::ImDrawCmd_GetTexID(&mut cmd_copy)
                    }));

                    let Some(texture_object_id) =
                        texture_lookup.get(&TextureLookupId::from(tex_id))
                    else {
                        tracing::error!(
                            "Unknown texture {}. Skipping skipping draw command",
                            tex_id.id()
                        );
                        continue;
                    };

                    render_pass.commands.extend([
                        RenderingCommand::UpdateDrawProperties(
                            DrawProperties { scissor_box, ..Default::default() },
                            DrawPropertiesUpdateFlags::SCISSOR_BOX,
                        ),
                        RenderingCommand::SetShaderBinding(
                            shader_cursor.field("main_texture").into_binding_location(),
                            ShaderBindingValue::Texture(texture_object_id.clone()),
                        ),
                        RenderingCommand::DrawMesh(
                            mesh_obj_id,
                            DrawMeshOptions::builder()
                                .element_offset(cmd_params.idx_offset.try_into().unwrap())
                                .vertex_offset(cmd_params.vtx_offset.try_into().unwrap())
                                .element_cnt(count.try_into().unwrap())
                                .build(),
                        ),
                    ]);
                }
                _ => {}
            }
        }
    }
}

fn get_texture_rect_image(
    texture_data: &dear_imgui_rs::TextureData,
    rect: &dear_imgui_rs::TextureRect,
) -> Option<Image>
{
    let texture_pixels = texture_data.pixels()?;

    let tex_width = texture_data.width();
    let tex_height = texture_data.height();

    if tex_width == 0 || tex_height == 0 {
        return None;
    }

    let rect_pos = Vec2::<u32> { x: rect.x.into(), y: rect.y.into() };

    let rect_size = Dimens::<u32> {
        width: rect.w.into(),
        height: rect.h.into(),
    };

    if rect_size.width == 0
        || rect_size.height == 0
        || rect_pos.x >= tex_width
        || rect_pos.y >= tex_height
    {
        return None;
    }

    let rect_size = Dimens {
        width: rect_size.width.min(tex_width.saturating_sub(rect_pos.x)),
        height: rect_size.height.min(tex_height.saturating_sub(rect_pos.y)),
    };

    match texture_data.format() {
        dear_imgui_rs::TextureFormat::RGBA32 => {
            let Ok(texture_image) =
                Image::from_pixels(ImagePixelBuffer::<Rgba<u8>, _>::new(
                    texture_pixels,
                    Dimens { width: tex_width, height: tex_height },
                ))
            else {
                return None;
            };

            Some(texture_image.sub_view(rect_pos, rect_size).to_image())
        }
        dear_imgui_rs::TextureFormat::Alpha8 => {
            unimplemented!();
        }
    }
}

fn calc_draw_cmd_scissor_box(
    draw_data: &dear_imgui_rs::DrawData,
    cmd_params: &dear_imgui_rs::DrawCmdParams,
) -> Option<ScissorBox>
{
    let clip_rect = cmd_params.clip_rect;

    let clip_min_x =
        (clip_rect[0] - draw_data.display_pos[0]) * draw_data.framebuffer_scale[0];

    let clip_min_y =
        (clip_rect[1] - draw_data.display_pos[1]) * draw_data.framebuffer_scale[1];

    let clip_max_x =
        (clip_rect[2] - draw_data.display_pos[0]) * draw_data.framebuffer_scale[0];

    let clip_max_y =
        (clip_rect[3] - draw_data.display_pos[1]) * draw_data.framebuffer_scale[1];

    if clip_max_x <= clip_min_x || clip_max_y <= clip_min_y {
        return None;
    }

    let fb_height = draw_data.display_size[1] * draw_data.framebuffer_scale[1];

    Some(ScissorBox {
        size: Some(Dimens {
            width: (clip_max_x - clip_min_x) as u16,
            height: (clip_max_y - clip_min_y) as u16,
        }),
        lower_left_corner_pos: Vec2 {
            x: clip_min_x as u16,
            y: (fb_height - clip_max_y) as u16,
        },
    })
}

fn key_to_imgui_key(key: Key) -> Option<ImguiKey>
{
    match key {
        Key::Backquote => Some(ImguiKey::GraveAccent),
        Key::Backslash => Some(ImguiKey::Backslash),
        Key::BracketLeft => Some(ImguiKey::LeftBracket),
        Key::BracketRight => Some(ImguiKey::RightBracket),
        Key::Comma => Some(ImguiKey::Comma),
        Key::Digit0 => Some(ImguiKey::Key0),
        Key::Digit1 => Some(ImguiKey::Key1),
        Key::Digit2 => Some(ImguiKey::Key2),
        Key::Digit3 => Some(ImguiKey::Key3),
        Key::Digit4 => Some(ImguiKey::Key4),
        Key::Digit5 => Some(ImguiKey::Key5),
        Key::Digit6 => Some(ImguiKey::Key6),
        Key::Digit7 => Some(ImguiKey::Key7),
        Key::Digit8 => Some(ImguiKey::Key8),
        Key::Digit9 => Some(ImguiKey::Key9),
        Key::Equal => Some(ImguiKey::Equal),
        Key::A => Some(ImguiKey::A),
        Key::B => Some(ImguiKey::B),
        Key::C => Some(ImguiKey::C),
        Key::D => Some(ImguiKey::D),
        Key::E => Some(ImguiKey::E),
        Key::F => Some(ImguiKey::F),
        Key::G => Some(ImguiKey::G),
        Key::H => Some(ImguiKey::H),
        Key::I => Some(ImguiKey::I),
        Key::J => Some(ImguiKey::J),
        Key::K => Some(ImguiKey::K),
        Key::L => Some(ImguiKey::L),
        Key::M => Some(ImguiKey::M),
        Key::N => Some(ImguiKey::N),
        Key::O => Some(ImguiKey::O),
        Key::P => Some(ImguiKey::P),
        Key::Q => Some(ImguiKey::Q),
        Key::R => Some(ImguiKey::R),
        Key::S => Some(ImguiKey::S),
        Key::T => Some(ImguiKey::T),
        Key::U => Some(ImguiKey::U),
        Key::V => Some(ImguiKey::V),
        Key::W => Some(ImguiKey::W),
        Key::X => Some(ImguiKey::X),
        Key::Y => Some(ImguiKey::Y),
        Key::Z => Some(ImguiKey::Z),
        Key::Minus => Some(ImguiKey::Minus),
        Key::Period => Some(ImguiKey::Period),
        Key::Quote => Some(ImguiKey::Apostrophe),
        Key::Semicolon => Some(ImguiKey::Semicolon),
        Key::Slash => Some(ImguiKey::Slash),
        Key::AltLeft => Some(ImguiKey::LeftAlt),
        Key::AltRight => Some(ImguiKey::RightAlt),
        Key::Backspace => Some(ImguiKey::Backspace),
        Key::CapsLock => Some(ImguiKey::CapsLock),
        Key::ControlLeft => Some(ImguiKey::LeftCtrl),
        Key::ControlRight => Some(ImguiKey::RightCtrl),
        Key::Enter => Some(ImguiKey::Enter),
        Key::SuperLeft => Some(ImguiKey::LeftSuper),
        Key::SuperRight => Some(ImguiKey::RightSuper),
        Key::ShiftLeft => Some(ImguiKey::LeftShift),
        Key::ShiftRight => Some(ImguiKey::RightShift),
        Key::Space => Some(ImguiKey::Space),
        Key::Tab => Some(ImguiKey::Tab),
        Key::Delete => Some(ImguiKey::Delete),
        Key::End => Some(ImguiKey::End),
        Key::Home => Some(ImguiKey::Home),
        Key::Insert => Some(ImguiKey::Insert),
        Key::PageDown => Some(ImguiKey::PageDown),
        Key::PageUp => Some(ImguiKey::PageUp),
        Key::ArrowDown => Some(ImguiKey::DownArrow),
        Key::ArrowLeft => Some(ImguiKey::LeftArrow),
        Key::ArrowRight => Some(ImguiKey::RightArrow),
        Key::ArrowUp => Some(ImguiKey::UpArrow),
        Key::NumLock => Some(ImguiKey::NumLock),
        Key::Numpad0 => Some(ImguiKey::Keypad0),
        Key::Numpad1 => Some(ImguiKey::Keypad1),
        Key::Numpad2 => Some(ImguiKey::Keypad2),
        Key::Numpad3 => Some(ImguiKey::Keypad3),
        Key::Numpad4 => Some(ImguiKey::Keypad4),
        Key::Numpad5 => Some(ImguiKey::Keypad5),
        Key::Numpad6 => Some(ImguiKey::Keypad6),
        Key::Numpad7 => Some(ImguiKey::Keypad7),
        Key::Numpad8 => Some(ImguiKey::Keypad8),
        Key::Numpad9 => Some(ImguiKey::Keypad9),
        Key::NumpadAdd => Some(ImguiKey::KeypadAdd),
        Key::NumpadDecimal => Some(ImguiKey::KeypadDecimal),
        Key::NumpadDivide => Some(ImguiKey::KeypadDivide),
        Key::NumpadEnter => Some(ImguiKey::KeypadEnter),
        Key::NumpadEqual => Some(ImguiKey::KeypadEqual),
        Key::NumpadMultiply => Some(ImguiKey::KeypadMultiply),
        Key::NumpadSubtract => Some(ImguiKey::KeypadSubtract),
        Key::Escape => Some(ImguiKey::Escape),
        Key::PrintScreen => Some(ImguiKey::PrintScreen),
        Key::ScrollLock => Some(ImguiKey::ScrollLock),
        Key::Pause => Some(ImguiKey::Pause),
        Key::Meta => Some(ImguiKey::ModSuper),
        Key::F1 => Some(ImguiKey::F1),
        Key::F2 => Some(ImguiKey::F2),
        Key::F3 => Some(ImguiKey::F3),
        Key::F4 => Some(ImguiKey::F4),
        Key::F5 => Some(ImguiKey::F5),
        Key::F6 => Some(ImguiKey::F6),
        Key::F7 => Some(ImguiKey::F7),
        Key::F8 => Some(ImguiKey::F8),
        Key::F9 => Some(ImguiKey::F9),
        Key::F10 => Some(ImguiKey::F10),
        Key::F11 => Some(ImguiKey::F11),
        Key::F12 => Some(ImguiKey::F12),
        _ => None,
    }
}

fn mouse_button_to_imgui_mouse_button(
    mouse_button: MouseButton,
) -> Option<ImguiMouseButton>
{
    match mouse_button {
        MouseButton::Left | MouseButton::Other(0) => Some(ImguiMouseButton::Left),
        MouseButton::Right | MouseButton::Other(1) => Some(ImguiMouseButton::Right),
        MouseButton::Middle | MouseButton::Other(2) => Some(ImguiMouseButton::Middle),
        MouseButton::Other(3) => Some(ImguiMouseButton::Extra1),
        MouseButton::Other(4) => Some(ImguiMouseButton::Extra2),
        _ => None,
    }
}

mod inner_context_wrapper
{
    use std::path::PathBuf;
    use std::pin::Pin;
    use std::ptr::null_mut;

    pub struct InnerContextWrapper
    {
        ctx: Pin<Box<dear_imgui_rs::Context>>,
        frame: *mut dear_imgui_rs::Ui,
    }

    impl InnerContextWrapper
    {
        pub fn new() -> Self
        {
            let mut ctx = Box::pin(dear_imgui_rs::Context::create());

            let _ = ctx.set_platform_name(Some("engine-windowing"));
            let _ = ctx.set_renderer_name(Some("engine-rendering"));

            ctx.io_mut()
                .set_backend_flags(dear_imgui_rs::BackendFlags::RENDERER_HAS_TEXTURES);

            Self { ctx, frame: null_mut() }
        }

        pub fn set_settings_ini_file_path(
            &mut self,
            path: Option<PathBuf>,
        ) -> Result<(), dear_imgui_rs::ImGuiError>
        {
            self.ctx.set_ini_filename(path)
        }

        pub fn register_texture(
            &mut self,
            texture_data: &mut dear_imgui_rs::texture::OwnedTextureData,
        )
        {
            self.ctx.register_user_texture(texture_data);
        }

        pub fn get_io_mut(&mut self) -> &mut dear_imgui_rs::Io
        {
            self.ctx.io_mut()
        }

        pub fn render(&mut self) -> &mut dear_imgui_rs::DrawData
        {
            self.ctx.render()
        }

        pub fn new_frame(&mut self)
        {
            let frame = &raw mut *self.ctx.frame();

            self.frame = frame;
        }

        pub fn get_frame(&mut self) -> Option<&mut dear_imgui_rs::Ui>
        {
            unsafe { self.frame.as_mut() }
        }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
struct TextureLookupId
{
    inner: u64,
}

impl TextureLookupId
{
    fn new() -> Self
    {
        static NEXT: AtomicU64 = AtomicU64::new(1);

        Self {
            inner: NEXT.fetch_add(1, Ordering::Relaxed),
        }
    }
}

impl From<dear_imgui_rs::TextureId> for TextureLookupId
{
    fn from(texture_id: dear_imgui_rs::TextureId) -> Self
    {
        assert!(!texture_id.is_null(), "Bad texture ID: is null");

        Self { inner: texture_id.id() }
    }
}

impl From<TextureLookupId> for dear_imgui_rs::TextureId
{
    fn from(texture_id: TextureLookupId) -> Self
    {
        Self::new(texture_id.inner)
    }
}