// Copyright © SixtyFPS GmbH <info@slint.dev>
// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0

#[cfg(feature = "unstable-wgpu-28")]
use i_slint_core::api::GraphicsAPI;
use i_slint_core::api::{PhysicalSize as PhysicalWindowSize, Window};
use i_slint_core::graphics::RequestedGraphicsAPI;
use i_slint_core::partial_renderer::DirtyRegion;
use i_slint_core::platform::PlatformError;
use i_slint_core::renderer::DrawOutcome;

use std::cell::RefCell;
use std::sync::Arc;

use wgpu_28 as wgpu;

use crate::SkiaSharedContext;

#[cfg(target_family = "windows")]
mod dx12;
#[cfg(target_vendor = "apple")]
mod metal;
#[cfg(all(target_family = "unix", not(target_vendor = "apple")))]
mod vulkan;

/// Skia rendering surface backed by WGPU. Supports both on-screen rendering (with a
/// window surface) and offscreen rendering into caller-provided textures.
pub struct WGPUSurface {
    pub(crate) gr_context: RefCell<skia_safe::gpu::DirectContext>,
    instance: wgpu::Instance,
    device: wgpu::Device,
    queue: wgpu::Queue,
    surface_config: RefCell<Option<wgpu::SurfaceConfiguration>>,
    surface: Option<wgpu::Surface<'static>>,
    textures_to_transition_for_sampling: RefCell<Vec<wgpu::Texture>>,
    pub(crate) backend: Backend,
}

impl WGPUSurface {
    pub fn new_with_surface(
        surface_target: impl Into<i_slint_core::graphics::wgpu_28::SurfaceTarget>,
        size: PhysicalWindowSize,
        requested_graphics_api: Option<RequestedGraphicsAPI>,
    ) -> Result<Self, PlatformError> {
        let (instance, adapter, device, queue, surface) =
            i_slint_core::graphics::wgpu_28::init_instance_adapter_device_queue_surface(
                surface_target,
                requested_graphics_api,
                wgpu::Backends::GL /* we're not mapping that to skia because we can't save/restore state */
                    .union(if cfg!(target_os = "windows") {
                        wgpu::Backends::VULKAN
                    } else {
                        wgpu::Backends::empty()
                    }),
            )?;

        let mut surface_config =
            surface.get_default_config(&adapter, size.width, size.height).unwrap();

        let swapchain_capabilities = surface.get_capabilities(&adapter);
        let swapchain_format = swapchain_capabilities
            .formats
            .iter()
            .find(|f| {
                matches!(f, wgpu::TextureFormat::Rgba8Unorm | wgpu::TextureFormat::Bgra8Unorm)
            })
            .copied()
            .unwrap_or_else(|| swapchain_capabilities.formats[0]);
        surface_config.format = swapchain_format;
        surface.configure(&device, &surface_config);

        let backend: Backend = adapter.get_info().backend.try_into()?;

        let gr_context = backend.make_context(&adapter, &device, &queue);

        Ok(Self {
            gr_context: RefCell::new(
                gr_context.ok_or_else(|| {
                    PlatformError::from("Failed to create Skia context from WGPU")
                })?,
            ),
            instance,
            device,
            queue,
            surface_config: Some(surface_config).into(),
            surface: Some(surface),
            textures_to_transition_for_sampling: RefCell::new(Vec::new()),
            backend,
        })
    }

    // Only used by SkiaWGPURenderer, which is gated on wgpu-29 — the wgpu-28
    // path doesn't currently expose an offscreen renderer publicly.
    #[allow(dead_code)]
    pub(crate) fn new_offscreen(
        instance: wgpu::Instance,
        device: wgpu::Device,
        queue: wgpu::Queue,
        backend: Backend,
        gr_context: skia_safe::gpu::DirectContext,
    ) -> Self {
        Self {
            gr_context: RefCell::new(gr_context),
            instance,
            device,
            queue,
            surface_config: None.into(),
            surface: None,
            textures_to_transition_for_sampling: RefCell::new(Vec::new()),
            backend,
        }
    }

    /// Transitions any imported wgpu textures to sampling state and flushes
    /// the Skia graphics context. Must be called after rendering to ensure
    /// Skia's GPU work is submitted.
    pub(crate) fn flush_and_submit(&self, gr_context: &mut skia_safe::gpu::DirectContext) {
        let textures_to_transition = self.textures_to_transition_for_sampling.take();
        if !textures_to_transition.is_empty() {
            let mut encoder = self.device.create_command_encoder(&wgpu::CommandEncoderDescriptor {
                label: Some("Skia texture transition encoder"),
            });
            encoder.transition_resources(
                std::iter::empty(),
                textures_to_transition.iter().map(|texture| wgpu::TextureTransition {
                    texture,
                    selector: None,
                    state: wgpu::TextureUses::RESOURCE,
                }),
            );
            self.queue.submit(Some(encoder.finish()));
        }

        gr_context.submit(None);
    }
}

impl crate::Surface for WGPUSurface {
    fn new(
        _shared_context: &SkiaSharedContext,
        window_handle: Arc<dyn raw_window_handle::HasWindowHandle + Send + Sync>,
        display_handle: Arc<dyn raw_window_handle::HasDisplayHandle + Send + Sync>,
        size: PhysicalWindowSize,
        requested_graphics_api: Option<RequestedGraphicsAPI>,
    ) -> Result<Self, PlatformError> {
        Self::new_with_surface(
            Box::new(WindowAndDisplayHandle(window_handle, display_handle))
                as Box<dyn wgpu::WindowHandle + 'static>,
            size,
            requested_graphics_api,
        )
    }

    fn name(&self) -> &'static str {
        if self.surface.is_some() { "wgpu" } else { "wgpu-texture" }
    }

    fn resize_event(&self, size: PhysicalWindowSize) -> Result<(), PlatformError> {
        let mut surface_config_opt = self.surface_config.borrow_mut();
        let (Some(surface_config), Some(surface)) = (surface_config_opt.as_mut(), &self.surface)
        else {
            return Ok(());
        };

        // Skip reconfigure if size hasn't changed — DRM/KMS surfaces don't
        // support being reconfigured.
        if surface_config.width == size.width && surface_config.height == size.height {
            return Ok(());
        }

        {
            let gr_context = &mut self.gr_context.borrow_mut();
            // This is brute force, but for the lack of access to the fences this seems to work: Avoid any pending work so that
            // IDXGISwapChain::ResizeBuffers doesn't complain that the surface is still in use.
            gr_context.flush_submit_and_sync_cpu();
        }

        // Prefer FIFO modes over possible Mailbox setting for frame pacing and better energy efficiency.
        surface_config.present_mode = wgpu::PresentMode::AutoVsync;
        surface_config.width = size.width;
        surface_config.height = size.height;

        surface.configure(&self.device, surface_config);
        Ok(())
    }

    fn render(
        &self,
        _window: &Window,
        _size: PhysicalWindowSize,
        callback: &dyn Fn(
            &skia_safe::Canvas,
            Option<&mut skia_safe::gpu::DirectContext>,
            u8,
        ) -> Option<DirtyRegion>,
        pre_present_callback: &RefCell<Option<Box<dyn FnMut()>>>,
    ) -> Result<DrawOutcome, PlatformError> {
        let (Some(surface), Some(surface_config)) = (&self.surface, &*self.surface_config.borrow())
        else {
            return Err("WGPUSurface::render() called on offscreen surface".into());
        };

        let gr_context = &mut self.gr_context.borrow_mut();

        let frame = match surface.get_current_texture() {
            Ok(texture) => texture,
            Err(wgpu::SurfaceError::Timeout) => return Ok(DrawOutcome::Timeout),
            // Outdated or lost: re-configure and try once. If the surface still
            // doesn't yield a texture, treat it as occluded so the caller re-arms.
            Err(_) => {
                surface.configure(&self.device, surface_config);
                match surface.get_current_texture() {
                    Ok(texture) => texture,
                    Err(_) => return Ok(DrawOutcome::Occluded),
                }
            }
        };

        let skia_surface = self.backend.make_surface(gr_context, &frame.texture);

        let mut skia_surface = skia_surface
            .ok_or_else(|| PlatformError::from("Failed to create Skia surface from WGPU"))?;

        callback(skia_surface.canvas(), Some(gr_context), 0);

        self.flush_and_submit(gr_context);

        if let Some(pre_present_callback) = pre_present_callback.borrow_mut().as_mut() {
            pre_present_callback();
        }

        frame.present();

        Ok(DrawOutcome::Success)
    }

    fn bits_per_pixel(&self) -> Result<u8, PlatformError> {
        if let Some(surface_config) = &*self.surface_config.borrow() {
            Ok(match surface_config.format {
                wgpu_28::TextureFormat::Rgba8Unorm
                | wgpu_28::TextureFormat::Rgba8UnormSrgb
                | wgpu_28::TextureFormat::Bgra8Unorm
                | wgpu_28::TextureFormat::Bgra8UnormSrgb => 32,
                fmt => return Err(format!("Unsupported surface format {:#?}", fmt).into()),
            })
        } else {
            // All supported render-target formats (Rgba8Unorm, Bgra8Unorm, and sRGB variants) are 32bpp.
            Ok(32)
        }
    }

    #[cfg(feature = "unstable-wgpu-28")]
    fn with_graphics_api(&self, callback: &mut dyn FnMut(GraphicsAPI<'_>)) {
        let api = i_slint_core::graphics::create_graphics_api_wgpu_28(
            self.instance.clone(),
            self.device.clone(),
            self.queue.clone(),
        );
        callback(api)
    }

    #[cfg(any(feature = "unstable-wgpu-28", feature = "unstable-wgpu-29"))]
    fn import_wgpu_texture(
        &self,
        canvas: &skia_safe::Canvas,
        any_wgpu_texture: &i_slint_core::graphics::WGPUTexture,
    ) -> Option<skia_safe::Image> {
        let texture = match any_wgpu_texture {
            #[cfg(feature = "unstable-wgpu-28")]
            i_slint_core::graphics::WGPUTexture::WGPU28Texture(texture) => texture.clone(),
            #[cfg(feature = "unstable-wgpu-29")]
            i_slint_core::graphics::WGPUTexture::WGPU29Texture(..) => return None,
        };

        // Skia won't submit commands right away, so remember the texture and transition before
        // submitting.
        self.textures_to_transition_for_sampling.borrow_mut().push(texture.clone());

        self.backend.import_texture(canvas, texture)
    }
}

struct WindowAndDisplayHandle(
    Arc<dyn raw_window_handle::HasWindowHandle + Send + Sync>,
    Arc<dyn raw_window_handle::HasDisplayHandle + Send + Sync>,
);

impl raw_window_handle::HasWindowHandle for WindowAndDisplayHandle {
    fn window_handle(
        &self,
    ) -> Result<raw_window_handle::WindowHandle<'_>, raw_window_handle::HandleError> {
        self.0.window_handle()
    }
}

impl raw_window_handle::HasDisplayHandle for WindowAndDisplayHandle {
    fn display_handle(
        &self,
    ) -> Result<raw_window_handle::DisplayHandle<'_>, raw_window_handle::HandleError> {
        self.1.display_handle()
    }
}

pub(crate) enum Backend {
    #[cfg(target_vendor = "apple")]
    Metal,
    #[cfg(target_family = "windows")]
    Dx12,
    #[cfg(all(target_family = "unix", not(target_vendor = "apple")))]
    Vulkan,
}

impl TryFrom<wgpu::Backend> for Backend {
    type Error = PlatformError;

    fn try_from(wgpu_backend: wgpu::Backend) -> Result<Self, Self::Error> {
        match wgpu_backend {
            wgpu_28::Backend::Noop => {
                Err(PlatformError::from("Cannot use WGPU Noop backend with Skia"))
            }
            #[cfg(all(target_family = "unix", not(target_vendor = "apple")))]
            wgpu_28::Backend::Vulkan => Ok(Self::Vulkan),
            #[cfg(target_vendor = "apple")]
            wgpu_28::Backend::Metal => Ok(Self::Metal),
            #[cfg(target_family = "windows")]
            wgpu_28::Backend::Dx12 => Ok(Self::Dx12),
            other => Err(PlatformError::from(format!(
                "Unsupported WGPU backend for use with Skia: {}",
                other
            ))),
        }
    }
}

impl Backend {
    pub(crate) fn make_context(
        &self,
        _adapter: &wgpu::Adapter,
        device: &wgpu::Device,
        queue: &wgpu::Queue,
    ) -> Option<skia_safe::gpu::DirectContext> {
        match self {
            #[cfg(target_vendor = "apple")]
            Self::Metal => metal::make_metal_context(device, queue),
            #[cfg(target_family = "windows")]
            Self::Dx12 => unsafe { dx12::make_dx12_context(&_adapter, &device, &queue) },
            #[cfg(all(target_family = "unix", not(target_vendor = "apple")))]
            Self::Vulkan => unsafe { vulkan::make_vulkan_context(device, queue) },
        }
    }

    pub(crate) fn make_surface(
        &self,
        gr_context: &mut skia_safe::gpu::DirectContext,
        texture: &wgpu::Texture,
    ) -> Option<skia_safe::Surface> {
        match self {
            #[cfg(target_vendor = "apple")]
            Self::Metal => unsafe { metal::make_metal_surface(gr_context, texture) },
            #[cfg(target_family = "windows")]
            Self::Dx12 => unsafe { dx12::make_dx12_surface(gr_context, texture) },
            #[cfg(all(target_family = "unix", not(target_vendor = "apple")))]
            Self::Vulkan => unsafe { vulkan::make_vulkan_surface(gr_context, texture) },
        }
    }

    pub(crate) fn import_texture(
        &self,
        canvas: &skia_safe::Canvas,
        texture: wgpu::Texture,
    ) -> Option<skia_safe::Image> {
        match self {
            #[cfg(target_vendor = "apple")]
            Self::Metal => unsafe { metal::import_metal_texture(canvas, texture) },
            #[cfg(target_family = "windows")]
            Self::Dx12 => unsafe { dx12::import_dx12_texture(canvas, texture) },
            #[cfg(all(target_family = "unix", not(target_vendor = "apple")))]
            Self::Vulkan => unsafe { vulkan::import_vulkan_texture(canvas, texture) },
        }
    }
}