use bevy::{
    ecs::query::QuerySingleError,
    prelude::*,
    render::{
        camera::{ManualTextureView, ManualTextureViewHandle, ManualTextureViews, RenderTarget},
        extract_resource::ExtractResourcePlugin,
        pipelined_rendering::PipelinedRenderingPlugin,
        view::ExtractedView,
        Render, RenderApp, RenderSet,
    },
};
use bevy_xr::camera::{XrCamera, XrCameraBundle, XrProjection};
use openxr::ViewStateFlags;

use crate::{
    init::{session_started, OxrHandleEvents, OxrLast, OxrTrackingRoot},
    layer_builder::ProjectionLayer,
};
use crate::{reference_space::OxrPrimaryReferenceSpace, resources::*};

#[derive(Debug, Hash, PartialEq, Eq, Clone, Copy, SystemSet)]
pub struct OxrRenderBegin;

#[derive(Debug, Hash, PartialEq, Eq, Clone, Copy, SystemSet)]
pub struct OxrRenderEnd;

pub struct OxrRenderPlugin;

impl Plugin for OxrRenderPlugin {
    fn build(&self, app: &mut App) {
        if app.is_plugin_added::<PipelinedRenderingPlugin>() {
            app.init_resource::<Pipelined>();
        }

        app.add_plugins((
            ExtractResourcePlugin::<OxrFrameState>::default(),
            ExtractResourcePlugin::<OxrRootTransform>::default(),
            ExtractResourcePlugin::<OxrGraphicsInfo>::default(),
            ExtractResourcePlugin::<OxrSwapchainImages>::default(),
            ExtractResourcePlugin::<OxrViews>::default(),
        ))
        .add_systems(
            PreUpdate,
            (locate_views, update_views)
                .chain()
                // .run_if(should_render)
                .run_if(session_started),
        )
        .add_systems(
            OxrLast,
            (
                wait_frame.run_if(session_started),
                update_cameras.run_if(session_started),
                init_views.run_if(resource_added::<OxrSession>),
                apply_deferred,
            )
                .chain()
                .after(OxrHandleEvents),
        )
        .init_resource::<OxrViews>();

        let render_app = app.sub_app_mut(RenderApp);
        render_app
            .configure_sets(
                Render,
                OxrRenderBegin
                    .after(RenderSet::ExtractCommands)
                    .before(RenderSet::PrepareAssets)
                    .before(RenderSet::ManageViews),
            )
            .configure_sets(
                Render,
                OxrRenderEnd
                    .after(RenderSet::Render)
                    .before(RenderSet::Cleanup),
            )
            .add_systems(
                Render,
                (
                    begin_frame,
                    insert_texture_views,
                    locate_views,
                    update_views_render_world,
                    wait_image,
                )
                    .chain()
                    .run_if(session_started)
                    .in_set(OxrRenderBegin),
            )
            .add_systems(
                Render,
                (release_image, end_frame)
                    .chain()
                    .run_if(session_started)
                    .in_set(OxrRenderEnd),
            )
            .insert_resource(OxrRenderLayers(vec![Box::new(ProjectionLayer)]));

        // app.add_systems(
        //     PreUpdate,
        //     (
        //         init_views.run_if(resource_added::<OxrGraphicsInfo>),
        //         locate_views.run_if(session_running),
        //         update_views.run_if(session_running),
        //     )
        //         .chain(), // .after(OxrPreUpdateSet::UpdateNonCriticalComponents),
        // )
        // .add_systems(
        //     PostUpdate,
        //     (locate_views, update_views)
        //         .chain()
        //         .run_if(session_running)
        //         .before(TransformSystem::TransformPropagate),
        // )
        // .add_systems(Last, wait_frame.run_if(session_started));
        // app.sub_app_mut(RenderApp)
        //     .add_systems(
        //         Render,
        //         (
        //             (
        //                 insert_texture_views,
        //                 locate_views.run_if(resource_exists::<OxrPrimaryReferenceSpace>),
        //                 update_views_render_world,
        //             )
        //                 .chain()
        //                 .in_set(RenderSet::PrepareAssets),
        //             begin_frame
        //                 .before(RenderSet::Queue)
        //                 .before(insert_texture_views),
        //             wait_image.in_set(RenderSet::Render).before(render_system),
        //             (release_image, end_frame)
        //                 .chain()
        //                 .in_set(RenderSet::Cleanup),
        //         )
        //             .run_if(session_started),
        //     )
        //     .insert_resource(OxrRenderLayers(vec![Box::new(ProjectionLayer)]));
    }
}

pub const XR_TEXTURE_INDEX: u32 = 3383858418;

pub fn init_views(
    graphics_info: Res<OxrGraphicsInfo>,
    mut manual_texture_views: ResMut<ManualTextureViews>,
    swapchain_images: Res<OxrSwapchainImages>,
    root: Query<Entity, With<OxrTrackingRoot>>,
    mut commands: Commands,
) {
    let _span = info_span!("xr_init_views");
    let temp_tex = swapchain_images.first().unwrap();
    // this for loop is to easily add support for quad or mono views in the future.
    for index in 0..2 {
        info!("{}", graphics_info.resolution);
        let view_handle =
            add_texture_view(&mut manual_texture_views, temp_tex, &graphics_info, index);

        let cam = commands
            .spawn((
                XrCameraBundle {
                    camera: Camera {
                        target: RenderTarget::TextureView(view_handle),
                        ..Default::default()
                    },
                    view: XrCamera(index),
                    ..Default::default()
                },
                // OpenXrTracker,
                // XrRoot::default(),
            ))
            .id();
        match root.get_single() {
            Ok(root) => {
                commands.entity(root).add_child(cam);
            }
            Err(QuerySingleError::NoEntities(_)) => {
                warn!("No OxrTrackingRoot!");
            }
            Err(QuerySingleError::MultipleEntities(_)) => {
                warn!("Multiple OxrTrackingRoots! this is not allowed");
            }
        }
    }
}

pub fn wait_frame(mut frame_waiter: ResMut<OxrFrameWaiter>, mut commands: Commands) {
    let _span = info_span!("xr_wait_frame");
    let state = frame_waiter.wait().expect("Failed to wait frame");
    // Here we insert the predicted display time for when this frame will be displayed.
    // TODO: don't add predicted_display_period if pipelined rendering plugin not enabled
    commands.insert_resource(OxrFrameState(state));
}

pub fn update_cameras(
    frame_state: Res<OxrFrameState>,
    mut cameras: Query<&mut Camera, With<XrCamera>>,
) {
    if frame_state.is_changed() {
        for mut camera in &mut cameras {
            camera.is_active = frame_state.should_render
        }
    }
}

pub fn locate_views(
    session: Res<OxrSession>,
    ref_space: Res<OxrPrimaryReferenceSpace>,
    frame_state: Res<OxrFrameState>,
    mut openxr_views: ResMut<OxrViews>,
    pipelined: Option<Res<Pipelined>>,
) {
    let time = if pipelined.is_some() {
        openxr::Time::from_nanos(
            frame_state.predicted_display_time.as_nanos()
                + frame_state.predicted_display_period.as_nanos(),
        )
    } else {
        frame_state.predicted_display_time
    };
    let (flags, xr_views) = session
        .locate_views(
            openxr::ViewConfigurationType::PRIMARY_STEREO,
            time,
            &ref_space,
        )
        .expect("Failed to locate views");

    match (
        flags & ViewStateFlags::ORIENTATION_VALID == ViewStateFlags::ORIENTATION_VALID,
        flags & ViewStateFlags::POSITION_VALID == ViewStateFlags::POSITION_VALID,
    ) {
        (true, true) => *openxr_views = OxrViews(xr_views),
        (true, false) => {
            for (i, view) in openxr_views.iter_mut().enumerate() {
                let Some(xr_view) = xr_views.get(i) else {
                    break;
                };
                view.pose.orientation = xr_view.pose.orientation;
            }
        }
        (false, true) => {
            for (i, view) in openxr_views.iter_mut().enumerate() {
                let Some(xr_view) = xr_views.get(i) else {
                    break;
                };
                view.pose.position = xr_view.pose.position;
            }
        }
        (false, false) => {}
    }
}

pub fn update_views(
    mut query: Query<(&mut Transform, &mut XrProjection, &XrCamera)>,
    views: ResMut<OxrViews>,
) {
    for (mut transform, mut projection, camera) in query.iter_mut() {
        let Some(view) = views.get(camera.0 as usize) else {
            continue;
        };

        let projection_matrix = calculate_projection(projection.near, view.fov);
        projection.projection_matrix = projection_matrix;

        let openxr::Quaternionf { x, y, z, w } = view.pose.orientation;
        let rotation = Quat::from_xyzw(x, y, z, w);
        transform.rotation = rotation;
        let openxr::Vector3f { x, y, z } = view.pose.position;
        let translation = Vec3::new(x, y, z);
        transform.translation = translation;
    }
}

pub fn update_views_render_world(
    views: Res<OxrViews>,
    root: Res<OxrRootTransform>,
    mut query: Query<(&mut ExtractedView, &XrCamera)>,
) {
    for (mut extracted_view, camera) in query.iter_mut() {
        let Some(view) = views.get(camera.0 as usize) else {
            continue;
        };
        let mut transform = Transform::IDENTITY;
        let openxr::Quaternionf { x, y, z, w } = view.pose.orientation;
        let rotation = Quat::from_xyzw(x, y, z, w);
        transform.rotation = rotation;
        let openxr::Vector3f { x, y, z } = view.pose.position;
        let translation = Vec3::new(x, y, z);
        transform.translation = translation;
        extracted_view.transform = root.0.mul_transform(transform);
    }
}

fn calculate_projection(near_z: f32, fov: openxr::Fovf) -> Mat4 {
    //  symmetric perspective for debugging
    // let x_fov = (self.fov.angle_left.abs() + self.fov.angle_right.abs());
    // let y_fov = (self.fov.angle_up.abs() + self.fov.angle_down.abs());
    // return Mat4::perspective_infinite_reverse_rh(y_fov, x_fov / y_fov, self.near);

    let is_vulkan_api = false; // FIXME wgpu probably abstracts this
    let far_z = -1.; //   use infinite proj
                     // let far_z = self.far;

    let tan_angle_left = fov.angle_left.tan();
    let tan_angle_right = fov.angle_right.tan();

    let tan_angle_down = fov.angle_down.tan();
    let tan_angle_up = fov.angle_up.tan();

    let tan_angle_width = tan_angle_right - tan_angle_left;

    // Set to tanAngleDown - tanAngleUp for a clip space with positive Y
    // down (Vulkan). Set to tanAngleUp - tanAngleDown for a clip space with
    // positive Y up (OpenGL / D3D / Metal).
    // const float tanAngleHeight =
    //     graphicsApi == GRAPHICS_VULKAN ? (tanAngleDown - tanAngleUp) : (tanAngleUp - tanAngleDown);
    let tan_angle_height = if is_vulkan_api {
        tan_angle_down - tan_angle_up
    } else {
        tan_angle_up - tan_angle_down
    };

    // Set to nearZ for a [-1,1] Z clip space (OpenGL / OpenGL ES).
    // Set to zero for a [0,1] Z clip space (Vulkan / D3D / Metal).
    // const float offsetZ =
    //     (graphicsApi == GRAPHICS_OPENGL || graphicsApi == GRAPHICS_OPENGL_ES) ? nearZ : 0;
    // FIXME handle enum of graphics apis
    let offset_z = 0.;

    let mut cols: [f32; 16] = [0.0; 16];

    if far_z <= near_z {
        // place the far plane at infinity
        cols[0] = 2. / tan_angle_width;
        cols[4] = 0.;
        cols[8] = (tan_angle_right + tan_angle_left) / tan_angle_width;
        cols[12] = 0.;

        cols[1] = 0.;
        cols[5] = 2. / tan_angle_height;
        cols[9] = (tan_angle_up + tan_angle_down) / tan_angle_height;
        cols[13] = 0.;

        cols[2] = 0.;
        cols[6] = 0.;
        cols[10] = -1.;
        cols[14] = -(near_z + offset_z);

        cols[3] = 0.;
        cols[7] = 0.;
        cols[11] = -1.;
        cols[15] = 0.;

        //  bevy uses the _reverse_ infinite projection
        //  https://dev.theomader.com/depth-precision/
        let z_reversal = Mat4::from_cols_array_2d(&[
            [1f32, 0., 0., 0.],
            [0., 1., 0., 0.],
            [0., 0., -1., 0.],
            [0., 0., 1., 1.],
        ]);

        return z_reversal * Mat4::from_cols_array(&cols);
    } else {
        // normal projection
        cols[0] = 2. / tan_angle_width;
        cols[4] = 0.;
        cols[8] = (tan_angle_right + tan_angle_left) / tan_angle_width;
        cols[12] = 0.;

        cols[1] = 0.;
        cols[5] = 2. / tan_angle_height;
        cols[9] = (tan_angle_up + tan_angle_down) / tan_angle_height;
        cols[13] = 0.;

        cols[2] = 0.;
        cols[6] = 0.;
        cols[10] = -(far_z + offset_z) / (far_z - near_z);
        cols[14] = -(far_z * (near_z + offset_z)) / (far_z - near_z);

        cols[3] = 0.;
        cols[7] = 0.;
        cols[11] = -1.;
        cols[15] = 0.;
    }

    Mat4::from_cols_array(&cols)
}

/// # Safety
/// Images inserted into texture views here should not be written to until [`wait_image`] is ran
pub fn insert_texture_views(
    swapchain_images: Res<OxrSwapchainImages>,
    mut swapchain: ResMut<OxrSwapchain>,
    mut manual_texture_views: ResMut<ManualTextureViews>,
    graphics_info: Res<OxrGraphicsInfo>,
) {
    let _span = info_span!("xr_insert_texture_views");
    let index = swapchain.acquire_image().expect("Failed to acquire image");
    let image = &swapchain_images[index as usize];

    for i in 0..2 {
        add_texture_view(&mut manual_texture_views, image, &graphics_info, i);
    }
}

pub fn wait_image(mut swapchain: ResMut<OxrSwapchain>) {
    swapchain
        .wait_image(openxr::Duration::INFINITE)
        .expect("Failed to wait image");
}

pub fn add_texture_view(
    manual_texture_views: &mut ManualTextureViews,
    texture: &wgpu::Texture,
    info: &OxrGraphicsInfo,
    index: u32,
) -> ManualTextureViewHandle {
    let view = texture.create_view(&wgpu::TextureViewDescriptor {
        dimension: Some(wgpu::TextureViewDimension::D2),
        array_layer_count: Some(1),
        base_array_layer: index,
        ..default()
    });
    let view = ManualTextureView {
        texture_view: view.into(),
        size: info.resolution,
        format: info.format,
    };
    let handle = ManualTextureViewHandle(XR_TEXTURE_INDEX + index);
    manual_texture_views.insert(handle, view);
    handle
}

pub fn begin_frame(mut frame_stream: ResMut<OxrFrameStream>) {
    frame_stream.begin().expect("Failed to begin frame")
}

pub fn release_image(mut swapchain: ResMut<OxrSwapchain>) {
    let _span = info_span!("xr_release_image");
    #[cfg(target_os = "android")]
    {
        let ctx = ndk_context::android_context();
        let vm = unsafe { jni::JavaVM::from_raw(ctx.vm().cast()) }.unwrap();
        let env = vm.attach_current_thread_as_daemon();
    }
    swapchain.release_image().unwrap();
}

pub fn end_frame(world: &mut World) {
    let _span = info_span!("xr_end_frame");
    #[cfg(target_os = "android")]
    {
        let ctx = ndk_context::android_context();
        let vm = unsafe { jni::JavaVM::from_raw(ctx.vm().cast()) }.unwrap();
        let env = vm.attach_current_thread_as_daemon();
    }
    world.resource_scope::<OxrFrameStream, ()>(|world, mut frame_stream| {
        let mut layers = vec![];
        let frame_state = world.resource::<OxrFrameState>();
        if frame_state.should_render {
            for layer in world.resource::<OxrRenderLayers>().iter() {
                if let Some(layer) = layer.get(world) {
                    layers.push(layer);
                }
            }
        }
        let layers: Vec<_> = layers.iter().map(Box::as_ref).collect();
        frame_stream
            .end(
                frame_state.predicted_display_time,
                world.resource::<OxrGraphicsInfo>().blend_mode,
                &layers,
            )
            .expect("Failed to end frame");
    });
}