//! This crates provides bindings between [`egui`](https://github.com/emilk/egui) and [wgpu](https://crates.io/crates/wgpu).
//!
//! If you're targeting WebGL you also need to turn on the
//! `webgl` feature of the `wgpu` crate:
//!
//! ```toml
//! # Enable both WebGL and WebGPU backends on web.
//! wgpu = { version = "*", features = ["webgpu", "webgl"] }
//! ```
//!
//! You can control whether WebGL or WebGPU will be picked at runtime by setting
//! [`WgpuConfiguration::supported_backends`].
//! The default is to prefer WebGPU and fall back on WebGL.
//!
//! ## Feature flags
#![doc = document_features::document_features!()]
//!

#![allow(unsafe_code)]

pub use wgpu;

/// Low-level painting of [`egui`](https://github.com/emilk/egui) on [`wgpu`].
mod renderer;

pub use renderer::*;

/// Module for painting [`egui`](https://github.com/emilk/egui) with [`wgpu`] on [`winit`].
#[cfg(feature = "winit")]
pub mod winit;

use std::sync::Arc;

use epaint::mutex::RwLock;

/// An error produced by egui-wgpu.
#[derive(thiserror::Error, Debug)]
pub enum WgpuError {
    #[error("Failed to create wgpu adapter, no suitable adapter found.")]
    NoSuitableAdapterFound,

    #[error("There was no valid format for the surface at all.")]
    NoSurfaceFormatsAvailable,

    #[error(transparent)]
    RequestDeviceError(#[from] wgpu::RequestDeviceError),

    #[error(transparent)]
    CreateSurfaceError(#[from] wgpu::CreateSurfaceError),

    #[cfg(feature = "winit")]
    #[error(transparent)]
    HandleError(#[from] ::winit::raw_window_handle::HandleError),
}

/// Access to the render state for egui.
#[derive(Clone)]
pub struct RenderState {
    /// Wgpu adapter used for rendering.
    pub adapter: Arc<wgpu::Adapter>,

    /// All the available adapters.
    ///
    /// This is not available on web.
    /// On web, we always select WebGPU is available, then fall back to WebGL if not.
    #[cfg(not(target_arch = "wasm32"))]
    pub available_adapters: Arc<[wgpu::Adapter]>,

    /// Wgpu device used for rendering, created from the adapter.
    pub device: Arc<wgpu::Device>,

    /// Wgpu queue used for rendering, created from the adapter.
    pub queue: Arc<wgpu::Queue>,

    /// The target texture format used for presenting to the window.
    pub target_format: wgpu::TextureFormat,

    /// Egui renderer responsible for drawing the UI.
    pub renderer: Arc<RwLock<Renderer>>,
}

impl RenderState {
    /// Creates a new [`RenderState`], containing everything needed for drawing egui with wgpu.
    ///
    /// # Errors
    /// Wgpu initialization may fail due to incompatible hardware or driver for a given config.
    pub async fn create(
        config: &WgpuConfiguration,
        instance: &wgpu::Instance,
        surface: &wgpu::Surface<'static>,
        depth_format: Option<wgpu::TextureFormat>,
        msaa_samples: u32,
        dithering: bool,
    ) -> Result<Self, WgpuError> {
        crate::profile_scope!("RenderState::create"); // async yield give bad names using `profile_function`

        // This is always an empty list on web.
        #[cfg(not(target_arch = "wasm32"))]
        let available_adapters = instance.enumerate_adapters(wgpu::Backends::all());

        let adapter = {
            crate::profile_scope!("request_adapter");
            instance
                .request_adapter(&wgpu::RequestAdapterOptions {
                    power_preference: config.power_preference,
                    compatible_surface: Some(surface),
                    force_fallback_adapter: false,
                })
                .await
                .ok_or_else(|| {
                    #[cfg(not(target_arch = "wasm32"))]
                    if available_adapters.is_empty() {
                        log::info!("No wgpu adapters found");
                    } else if available_adapters.len() == 1 {
                        log::info!(
                            "The only available wgpu adapter was not suitable: {}",
                            adapter_info_summary(&available_adapters[0].get_info())
                        );
                    } else {
                        log::info!(
                            "No suitable wgpu adapter found out of the {} available ones: {}",
                            available_adapters.len(),
                            describe_adapters(&available_adapters)
                        );
                    }

                    WgpuError::NoSuitableAdapterFound
                })?
        };

        #[cfg(target_arch = "wasm32")]
        log::debug!(
            "Picked wgpu adapter: {}",
            adapter_info_summary(&adapter.get_info())
        );

        #[cfg(not(target_arch = "wasm32"))]
        if available_adapters.len() == 1 {
            log::debug!(
                "Picked the only available wgpu adapter: {}",
                adapter_info_summary(&adapter.get_info())
            );
        } else {
            log::info!(
                "There were {} available wgpu adapters: {}",
                available_adapters.len(),
                describe_adapters(&available_adapters)
            );
            log::debug!(
                "Picked wgpu adapter: {}",
                adapter_info_summary(&adapter.get_info())
            );
        }

        let capabilities = {
            crate::profile_scope!("get_capabilities");
            surface.get_capabilities(&adapter).formats
        };
        let target_format = crate::preferred_framebuffer_format(&capabilities)?;

        let (device, queue) = {
            crate::profile_scope!("request_device");
            adapter
                .request_device(&(*config.device_descriptor)(&adapter), None)
                .await?
        };

        let renderer = Renderer::new(
            &device,
            target_format,
            depth_format,
            msaa_samples,
            dithering,
        );

        Ok(Self {
            adapter: Arc::new(adapter),
            #[cfg(not(target_arch = "wasm32"))]
            available_adapters: available_adapters.into(),
            device: Arc::new(device),
            queue: Arc::new(queue),
            target_format,
            renderer: Arc::new(RwLock::new(renderer)),
        })
    }
}

#[cfg(not(target_arch = "wasm32"))]
fn describe_adapters(adapters: &[wgpu::Adapter]) -> String {
    if adapters.is_empty() {
        "(none)".to_owned()
    } else if adapters.len() == 1 {
        adapter_info_summary(&adapters[0].get_info())
    } else {
        let mut list_string = String::new();
        for adapter in adapters {
            if !list_string.is_empty() {
                list_string += ", ";
            }
            list_string += &format!("{{{}}}", adapter_info_summary(&adapter.get_info()));
        }
        list_string
    }
}

/// Specifies which action should be taken as consequence of a [`wgpu::SurfaceError`]
pub enum SurfaceErrorAction {
    /// Do nothing and skip the current frame.
    SkipFrame,

    /// Instructs egui to recreate the surface, then skip the current frame.
    RecreateSurface,
}

/// Configuration for using wgpu with eframe or the egui-wgpu winit feature.
///
/// This can also be configured with the environment variables:
/// * `WGPU_BACKEND`: `vulkan`, `dx11`, `dx12`, `metal`, `opengl`, `webgpu`
/// * `WGPU_POWER_PREF`: `low`, `high` or `none`
#[derive(Clone)]
pub struct WgpuConfiguration {
    /// Backends that should be supported (wgpu will pick one of these).
    ///
    /// For instance, if you only want to support WebGL (and not WebGPU),
    /// you can set this to [`wgpu::Backends::GL`].
    ///
    /// By default on web, WebGPU will be used if available.
    /// WebGL will only be used as a fallback,
    /// and only if you have enabled the `webgl` feature of crate `wgpu`.
    pub supported_backends: wgpu::Backends,

    /// Configuration passed on device request, given an adapter
    pub device_descriptor: Arc<dyn Fn(&wgpu::Adapter) -> wgpu::DeviceDescriptor<'static>>,

    /// Present mode used for the primary surface.
    pub present_mode: wgpu::PresentMode,

    /// Desired maximum number of frames that the presentation engine should queue in advance.
    ///
    /// Use `1` for low-latency, and `2` for high-throughput.
    ///
    /// See [`wgpu::SurfaceConfiguration::desired_maximum_frame_latency`] for details.
    ///
    /// `None` = `wgpu` default.
    pub desired_maximum_frame_latency: Option<u32>,

    /// Power preference for the adapter.
    pub power_preference: wgpu::PowerPreference,

    /// Callback for surface errors.
    pub on_surface_error: Arc<dyn Fn(wgpu::SurfaceError) -> SurfaceErrorAction>,
}

impl std::fmt::Debug for WgpuConfiguration {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let Self {
            supported_backends,
            device_descriptor: _,
            present_mode,
            desired_maximum_frame_latency,
            power_preference,
            on_surface_error: _,
        } = self;
        f.debug_struct("WgpuConfiguration")
            .field("supported_backends", &supported_backends)
            .field("present_mode", &present_mode)
            .field(
                "desired_maximum_frame_latency",
                &desired_maximum_frame_latency,
            )
            .field("power_preference", &power_preference)
            .finish_non_exhaustive()
    }
}

impl Default for WgpuConfiguration {
    fn default() -> Self {
        Self {
            // Add GL backend, primarily because WebGPU is not stable enough yet.
            // (note however, that the GL backend needs to be opted-in via the wgpu feature flag "webgl")
            supported_backends: wgpu::util::backend_bits_from_env()
                .unwrap_or(wgpu::Backends::PRIMARY | wgpu::Backends::GL),

            device_descriptor: Arc::new(|adapter| {
                let base_limits = if adapter.get_info().backend == wgpu::Backend::Gl {
                    wgpu::Limits::downlevel_webgl2_defaults()
                } else {
                    wgpu::Limits::default()
                };

                wgpu::DeviceDescriptor {
                    label: Some("egui wgpu device"),
                    required_features: wgpu::Features::default(),
                    required_limits: wgpu::Limits {
                        // When using a depth buffer, we have to be able to create a texture
                        // large enough for the entire surface, and we want to support 4k+ displays.
                        max_texture_dimension_2d: 8192,
                        ..base_limits
                    },
                }
            }),

            present_mode: wgpu::PresentMode::AutoVsync,

            desired_maximum_frame_latency: None,

            power_preference: wgpu::util::power_preference_from_env()
                .unwrap_or(wgpu::PowerPreference::HighPerformance),

            on_surface_error: Arc::new(|err| {
                if err == wgpu::SurfaceError::Outdated {
                    // This error occurs when the app is minimized on Windows.
                    // Silently return here to prevent spamming the console with:
                    // "The underlying surface has changed, and therefore the swap chain must be updated"
                } else {
                    log::warn!("Dropped frame with error: {err}");
                }
                SurfaceErrorAction::SkipFrame
            }),
        }
    }
}

/// Find the framebuffer format that egui prefers
///
/// # Errors
/// Returns [`WgpuError::NoSurfaceFormatsAvailable`] if the given list of formats is empty.
pub fn preferred_framebuffer_format(
    formats: &[wgpu::TextureFormat],
) -> Result<wgpu::TextureFormat, WgpuError> {
    for &format in formats {
        if matches!(
            format,
            wgpu::TextureFormat::Rgba8Unorm | wgpu::TextureFormat::Bgra8Unorm
        ) {
            return Ok(format);
        }
    }

    formats
        .first()
        .copied()
        .ok_or(WgpuError::NoSurfaceFormatsAvailable)
}

/// Take's epi's depth/stencil bits and returns the corresponding wgpu format.
pub fn depth_format_from_bits(depth_buffer: u8, stencil_buffer: u8) -> Option<wgpu::TextureFormat> {
    match (depth_buffer, stencil_buffer) {
        (0, 8) => Some(wgpu::TextureFormat::Stencil8),
        (16, 0) => Some(wgpu::TextureFormat::Depth16Unorm),
        (24, 0) => Some(wgpu::TextureFormat::Depth24Plus),
        (24, 8) => Some(wgpu::TextureFormat::Depth24PlusStencil8),
        (32, 0) => Some(wgpu::TextureFormat::Depth32Float),
        (32, 8) => Some(wgpu::TextureFormat::Depth32FloatStencil8),
        _ => None,
    }
}

// ---------------------------------------------------------------------------

/// A human-readable summary about an adapter
pub fn adapter_info_summary(info: &wgpu::AdapterInfo) -> String {
    let wgpu::AdapterInfo {
        name,
        vendor,
        device,
        device_type,
        driver,
        driver_info,
        backend,
    } = &info;

    // Example values:
    // > name: "llvmpipe (LLVM 16.0.6, 256 bits)", device_type: Cpu, backend: Vulkan, driver: "llvmpipe", driver_info: "Mesa 23.1.6-arch1.4 (LLVM 16.0.6)"
    // > name: "Apple M1 Pro", device_type: IntegratedGpu, backend: Metal, driver: "", driver_info: ""
    // > name: "ANGLE (Apple, Apple M1 Pro, OpenGL 4.1)", device_type: IntegratedGpu, backend: Gl, driver: "", driver_info: ""

    let mut summary = format!("backend: {backend:?}, device_type: {device_type:?}");

    if !name.is_empty() {
        summary += &format!(", name: {name:?}");
    }
    if !driver.is_empty() {
        summary += &format!(", driver: {driver:?}");
    }
    if !driver_info.is_empty() {
        summary += &format!(", driver_info: {driver_info:?}");
    }
    if *vendor != 0 {
        // TODO(emilk): decode using https://github.com/gfx-rs/wgpu/blob/767ac03245ee937d3dc552edc13fe7ab0a860eec/wgpu-hal/src/auxil/mod.rs#L7
        summary += &format!(", vendor: 0x{vendor:04X}");
    }
    if *device != 0 {
        summary += &format!(", device: 0x{device:02X}");
    }

    summary
}

// ---------------------------------------------------------------------------

mod profiling_scopes {
    #![allow(unused_macros)]
    #![allow(unused_imports)]

    /// Profiling macro for feature "puffin"
    macro_rules! profile_function {
        ($($arg: tt)*) => {
            #[cfg(feature = "puffin")]
            #[cfg(not(target_arch = "wasm32"))] // Disabled on web because of the coarse 1ms clock resolution there.
            puffin::profile_function!($($arg)*);
        };
    }
    pub(crate) use profile_function;

    /// Profiling macro for feature "puffin"
    macro_rules! profile_scope {
        ($($arg: tt)*) => {
            #[cfg(feature = "puffin")]
            #[cfg(not(target_arch = "wasm32"))] // Disabled on web because of the coarse 1ms clock resolution there.
            puffin::profile_scope!($($arg)*);
        };
    }
    pub(crate) use profile_scope;
}

#[allow(unused_imports)]
pub(crate) use profiling_scopes::*;