//! Common traits and types for egl rendering
//!
//! Large parts of this module are taken from
//! [glutin src/api/egl](https://github.com/tomaka/glutin/tree/044e651edf67a2029eecc650dd42546af1501414/src/api/egl/)
//!
//! It therefore falls under
//! [glutin's Apache 2.0 license](https://github.com/tomaka/glutin/tree/044e651edf67a2029eecc650dd42546af1501414/LICENSE)
//!
//! Wayland specific EGL functionality - EGL based [`WlBuffer`](wayland_server::protocol::wl_buffer::WlBuffer)s.
//!
//! The types of this module can be used to initialize hardware acceleration rendering
//! based on EGL for clients as it may enabled usage of `EGLImage` based [`WlBuffer`](wayland_server::protocol::wl_buffer::WlBuffer)s.
//!
//! To use it bind any backend implementing the [`EGLGraphicsBackend`](::backend::egl::EGLGraphicsBackend) trait, that shall do the
//! rendering (so pick a fast one), to the [`wayland_server::Display`] of your compositor.
//! Note only one backend may be bound to any [`Display`](wayland_server::Display) at any time.
//!
//! You may then use the resulting [`EGLDisplay`](::backend::egl::EGLDisplay) to receive [`EGLImages`](::backend::egl::EGLImages)
//! of an EGL-based [`WlBuffer`](wayland_server::protocol::wl_buffer::WlBuffer) for rendering.

#[cfg(feature = "renderer_gl")]
use crate::backend::graphics::gl::ffi as gl_ffi;
use nix::libc::c_uint;
use std::{
    ffi::CStr,
    fmt,
    rc::{Rc, Weak},
};
use wayland_server::{
    protocol::wl_buffer::{self, WlBuffer},
    Display, Resource,
};
#[cfg(feature = "native_lib")]
use wayland_sys::server::wl_display;

pub mod context;
pub use self::context::EGLContext;
pub mod error;
use self::error::*;

#[allow(non_camel_case_types, dead_code, unused_mut, non_upper_case_globals)]
pub mod ffi;
use self::ffi::egl::types::EGLImage;

pub mod native;
pub mod surface;
pub use self::surface::EGLSurface;

/// Error that can happen on optional EGL features
#[derive(Debug, Clone, PartialEq)]
pub struct EglExtensionNotSupportedError(&'static [&'static str]);

impl fmt::Display for EglExtensionNotSupportedError {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> ::std::result::Result<(), fmt::Error> {
        write!(
            formatter,
            "None of the following EGL extensions is supported by the underlying EGL implementation,
                     at least one is required: {:?}",
            self.0
        )
    }
}

impl ::std::error::Error for EglExtensionNotSupportedError {
    fn description(&self) -> &str {
        "The required EGL extension is not supported by the underlying EGL implementation"
    }

    fn cause(&self) -> Option<&dyn ::std::error::Error> {
        None
    }
}

/// Error that can occur when accessing an EGL buffer
pub enum BufferAccessError {
    /// The corresponding Context is not alive anymore
    ContextLost,
    /// This buffer is not managed by the EGL buffer
    NotManaged(Resource<WlBuffer>),
    /// Failed to create `EGLImages` from the buffer
    EGLImageCreationFailed,
    /// The required EGL extension is not supported by the underlying EGL implementation
    EglExtensionNotSupported(EglExtensionNotSupportedError),
}

impl fmt::Debug for BufferAccessError {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> ::std::result::Result<(), fmt::Error> {
        match *self {
            BufferAccessError::ContextLost => write!(formatter, "BufferAccessError::ContextLost"),
            BufferAccessError::NotManaged(_) => write!(formatter, "BufferAccessError::NotManaged"),
            BufferAccessError::EGLImageCreationFailed => {
                write!(formatter, "BufferAccessError::EGLImageCreationFailed")
            }
            BufferAccessError::EglExtensionNotSupported(ref err) => write!(formatter, "{:?}", err),
        }
    }
}

impl fmt::Display for BufferAccessError {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> ::std::result::Result<(), fmt::Error> {
        use std::error::Error;
        match *self {
            BufferAccessError::ContextLost
            | BufferAccessError::NotManaged(_)
            | BufferAccessError::EGLImageCreationFailed => write!(formatter, "{}", self.description()),
            BufferAccessError::EglExtensionNotSupported(ref err) => err.fmt(formatter),
        }
    }
}

impl ::std::error::Error for BufferAccessError {
    fn description(&self) -> &str {
        match *self {
            BufferAccessError::ContextLost => "The corresponding context was lost",
            BufferAccessError::NotManaged(_) => "This buffer is not managed by EGL",
            BufferAccessError::EGLImageCreationFailed => "Failed to create EGLImages from the buffer",
            BufferAccessError::EglExtensionNotSupported(ref err) => err.description(),
        }
    }

    fn cause(&self) -> Option<&dyn ::std::error::Error> {
        match *self {
            BufferAccessError::EglExtensionNotSupported(ref err) => Some(err),
            _ => None,
        }
    }
}

impl From<EglExtensionNotSupportedError> for BufferAccessError {
    fn from(error: EglExtensionNotSupportedError) -> Self {
        BufferAccessError::EglExtensionNotSupported(error)
    }
}

/// Error that might happen when binding an `EGLImage` to a GL texture
#[derive(Debug, Clone, PartialEq)]
pub enum TextureCreationError {
    /// The given plane index is out of bounds
    PlaneIndexOutOfBounds,
    /// The OpenGL context has been lost and needs to be recreated.
    ///
    /// All the objects associated to it (textures, buffers, programs, etc.)
    /// need to be recreated from scratch.
    ///
    /// Operations will have no effect. Functions that read textures, buffers, etc.
    /// from OpenGL will return uninitialized data instead.
    ///
    /// A context loss usually happens on mobile devices when the user puts the
    /// application on sleep and wakes it up later. However any OpenGL implementation
    /// can theoretically lose the context at any time.
    ContextLost,
    /// Required OpenGL Extension for texture creation is missing
    GLExtensionNotSupported(&'static str),
    /// Failed to bind the `EGLImage` to the given texture
    ///
    /// The given argument is the GL error code
    TextureBindingFailed(u32),
}

impl fmt::Display for TextureCreationError {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> ::std::result::Result<(), fmt::Error> {
        use std::error::Error;
        match *self {
            TextureCreationError::ContextLost => write!(formatter, "{}", self.description()),
            TextureCreationError::PlaneIndexOutOfBounds => write!(formatter, "{}", self.description()),
            TextureCreationError::GLExtensionNotSupported(ext) => {
                write!(formatter, "{}: {:}", self.description(), ext)
            }
            TextureCreationError::TextureBindingFailed(code) => {
                write!(formatter, "{}. Gl error code: {:?}", self.description(), code)
            }
        }
    }
}

impl ::std::error::Error for TextureCreationError {
    fn description(&self) -> &str {
        match *self {
            TextureCreationError::ContextLost => "The context has been lost, it needs to be recreated",
            TextureCreationError::PlaneIndexOutOfBounds => "This buffer is not managed by EGL",
            TextureCreationError::GLExtensionNotSupported(_) => {
                "Required OpenGL Extension for texture creation is missing"
            }
            TextureCreationError::TextureBindingFailed(_) => "Failed to create EGLImages from the buffer",
        }
    }

    fn cause(&self) -> Option<&dyn ::std::error::Error> {
        None
    }
}

/// Texture format types
#[repr(i32)]
#[allow(non_camel_case_types)]
#[derive(Debug)]
pub enum Format {
    /// RGB format
    RGB = ffi::egl::TEXTURE_RGB as i32,
    /// RGB + alpha channel format
    RGBA = ffi::egl::TEXTURE_RGBA as i32,
    /// External format
    External = ffi::egl::TEXTURE_EXTERNAL_WL,
    /// 2-plane Y and UV format
    Y_UV = ffi::egl::TEXTURE_Y_UV_WL,
    /// 3-plane Y, U and V format
    Y_U_V = ffi::egl::TEXTURE_Y_U_V_WL,
    /// 2-plane Y and XUXV format
    Y_XUXV = ffi::egl::TEXTURE_Y_XUXV_WL,
}

impl Format {
    /// Amount of planes this format uses
    pub fn num_planes(&self) -> usize {
        match *self {
            Format::RGB | Format::RGBA | Format::External => 1,
            Format::Y_UV | Format::Y_XUXV => 2,
            Format::Y_U_V => 3,
        }
    }
}

/// Images of the EGL-based [`WlBuffer`].
pub struct EGLImages {
    display: Weak<ffi::egl::types::EGLDisplay>,
    /// Width in pixels
    pub width: u32,
    /// Height in pixels
    pub height: u32,
    /// If the y-axis is inverted or not
    pub y_inverted: bool,
    /// Format of these images
    pub format: Format,
    images: Vec<EGLImage>,
    buffer: Resource<WlBuffer>,
    #[cfg(feature = "renderer_gl")]
    gl: gl_ffi::Gles2,
    #[cfg(feature = "renderer_gl")]
    egl_to_texture_support: bool,
}

impl EGLImages {
    /// Amount of planes of these `EGLImages`
    pub fn num_planes(&self) -> usize {
        self.format.num_planes()
    }

    /// Bind plane to an OpenGL texture id
    ///
    /// This does only temporarily modify the OpenGL state any changes are reverted before returning.
    ///
    /// # Unsafety
    ///
    /// The given `tex_id` needs to be a valid GL texture otherwise undefined behavior might occur.
    #[cfg(feature = "renderer_gl")]
    pub unsafe fn bind_to_texture(
        &self,
        plane: usize,
        tex_id: c_uint,
    ) -> ::std::result::Result<(), TextureCreationError> {
        if self.display.upgrade().is_some() {
            if !self.egl_to_texture_support {
                return Err(TextureCreationError::GLExtensionNotSupported("GL_OES_EGL_image"));
            }

            let mut old_tex_id: i32 = 0;
            self.gl.GetIntegerv(gl_ffi::TEXTURE_BINDING_2D, &mut old_tex_id);
            self.gl.BindTexture(gl_ffi::TEXTURE_2D, tex_id);
            self.gl.EGLImageTargetTexture2DOES(
                gl_ffi::TEXTURE_2D,
                *self
                    .images
                    .get(plane)
                    .ok_or(TextureCreationError::PlaneIndexOutOfBounds)?,
            );
            let res = match ffi::egl::GetError() as u32 {
                ffi::egl::SUCCESS => Ok(()),
                err => Err(TextureCreationError::TextureBindingFailed(err)),
            };
            self.gl.BindTexture(gl_ffi::TEXTURE_2D, old_tex_id as u32);
            res
        } else {
            Err(TextureCreationError::ContextLost)
        }
    }
}

impl Drop for EGLImages {
    fn drop(&mut self) {
        if let Some(display) = self.display.upgrade() {
            for image in self.images.drain(..) {
                unsafe {
                    ffi::egl::DestroyImageKHR(*display, image);
                }
            }
        }
        self.buffer.send(wl_buffer::Event::Release);
    }
}

/// Trait any backend type may implement that allows binding a [`Display`](wayland_server::Display)
/// to create an [`EGLDisplay`] for EGL-based [`WlBuffer`]s.
#[cfg(feature = "native_lib")]
pub trait EGLGraphicsBackend {
    /// Binds this EGL context to the given Wayland display.
    ///
    /// This will allow clients to utilize EGL to create hardware-accelerated
    /// surfaces. The server will need to be able to handle EGL-[`WlBuffer`]s.
    ///
    /// ## Errors
    ///
    /// This might return [`EglExtensionNotSupported`](ErrorKind::EglExtensionNotSupported)
    /// if binding is not supported by the EGL implementation.
    ///
    /// This might return [`OtherEGLDisplayAlreadyBound`](ErrorKind::OtherEGLDisplayAlreadyBound)
    /// if called for the same [`Display`] multiple times, as only one context may be bound at any given time.
    fn bind_wl_display(&self, display: &Display) -> Result<EGLDisplay>;
}

/// Type to receive [`EGLImages`] for EGL-based [`WlBuffer`]s.
///
/// Can be created by using [`EGLGraphicsBackend::bind_wl_display`].
#[cfg(feature = "native_lib")]
pub struct EGLDisplay {
    egl: Weak<ffi::egl::types::EGLDisplay>,
    wayland: *mut wl_display,
    #[cfg(feature = "renderer_gl")]
    gl: gl_ffi::Gles2,
    #[cfg(feature = "renderer_gl")]
    egl_to_texture_support: bool,
}

#[cfg(feature = "native_lib")]
impl EGLDisplay {
    fn new<B: native::Backend, N: native::NativeDisplay<B>>(
        context: &EGLContext<B, N>,
        display: *mut wl_display,
    ) -> EGLDisplay {
        #[cfg(feature = "renderer_gl")]
        let gl = gl_ffi::Gles2::load_with(|s| unsafe { context.get_proc_address(s) as *const _ });

        EGLDisplay {
            egl: Rc::downgrade(&context.display),
            wayland: display,
            #[cfg(feature = "renderer_gl")]
            egl_to_texture_support: {
                // the list of gl extensions supported by the context
                let data = unsafe { CStr::from_ptr(gl.GetString(gl_ffi::EXTENSIONS) as *const _) }
                    .to_bytes()
                    .to_vec();
                let list = String::from_utf8(data).unwrap();
                list.split(' ')
                    .any(|s| s == "GL_OES_EGL_image" || s == "GL_OES_EGL_image_base")
            },
            #[cfg(feature = "renderer_gl")]
            gl,
        }
    }

    /// Try to receive [`EGLImages`] from a given [`WlBuffer`].
    ///
    /// In case the buffer is not managed by EGL (but e.g. the [`wayland::shm` module](::wayland::shm))
    /// a [`BufferAccessError::NotManaged`](::backend::egl::BufferAccessError::NotManaged) is returned with the original buffer
    /// to render it another way.
    pub fn egl_buffer_contents(
        &self,
        buffer: Resource<WlBuffer>,
    ) -> ::std::result::Result<EGLImages, BufferAccessError> {
        if let Some(display) = self.egl.upgrade() {
            let mut format: i32 = 0;
            if unsafe {
                ffi::egl::QueryWaylandBufferWL(
                    *display,
                    buffer.c_ptr() as *mut _,
                    ffi::egl::EGL_TEXTURE_FORMAT,
                    &mut format as *mut _,
                ) == 0
            } {
                return Err(BufferAccessError::NotManaged(buffer));
            }
            let format = match format {
                x if x == ffi::egl::TEXTURE_RGB as i32 => Format::RGB,
                x if x == ffi::egl::TEXTURE_RGBA as i32 => Format::RGBA,
                ffi::egl::TEXTURE_EXTERNAL_WL => Format::External,
                ffi::egl::TEXTURE_Y_UV_WL => Format::Y_UV,
                ffi::egl::TEXTURE_Y_U_V_WL => Format::Y_U_V,
                ffi::egl::TEXTURE_Y_XUXV_WL => Format::Y_XUXV,
                _ => panic!("EGL returned invalid texture type"),
            };

            let mut width: i32 = 0;
            if unsafe {
                ffi::egl::QueryWaylandBufferWL(
                    *display,
                    buffer.c_ptr() as *mut _,
                    ffi::egl::WIDTH as i32,
                    &mut width as *mut _,
                ) == 0
            } {
                return Err(BufferAccessError::NotManaged(buffer));
            }

            let mut height: i32 = 0;
            if unsafe {
                ffi::egl::QueryWaylandBufferWL(
                    *display,
                    buffer.c_ptr() as *mut _,
                    ffi::egl::HEIGHT as i32,
                    &mut height as *mut _,
                ) == 0
            } {
                return Err(BufferAccessError::NotManaged(buffer));
            }

            let mut inverted: i32 = 0;
            if unsafe {
                ffi::egl::QueryWaylandBufferWL(
                    *display,
                    buffer.c_ptr() as *mut _,
                    ffi::egl::WAYLAND_Y_INVERTED_WL,
                    &mut inverted as *mut _,
                ) != 0
            } {
                inverted = 1;
            }

            let mut images = Vec::with_capacity(format.num_planes());
            for i in 0..format.num_planes() {
                let mut out = Vec::with_capacity(3);
                out.push(ffi::egl::WAYLAND_PLANE_WL as i32);
                out.push(i as i32);
                out.push(ffi::egl::NONE as i32);

                images.push({
                    let image = unsafe {
                        ffi::egl::CreateImageKHR(
                            *display,
                            ffi::egl::NO_CONTEXT,
                            ffi::egl::WAYLAND_BUFFER_WL,
                            buffer.c_ptr() as *mut _,
                            out.as_ptr(),
                        )
                    };
                    if image == ffi::egl::NO_IMAGE_KHR {
                        return Err(BufferAccessError::EGLImageCreationFailed);
                    } else {
                        image
                    }
                });
            }

            Ok(EGLImages {
                display: Rc::downgrade(&display),
                width: width as u32,
                height: height as u32,
                y_inverted: inverted != 0,
                format,
                images,
                buffer,
                #[cfg(feature = "renderer_gl")]
                gl: self.gl.clone(),
                #[cfg(feature = "renderer_gl")]
                egl_to_texture_support: self.egl_to_texture_support,
            })
        } else {
            Err(BufferAccessError::ContextLost)
        }
    }
}

#[cfg(feature = "native_lib")]
impl Drop for EGLDisplay {
    fn drop(&mut self) {
        if let Some(display) = self.egl.upgrade() {
            if !self.wayland.is_null() {
                unsafe {
                    ffi::egl::UnbindWaylandDisplayWL(*display, self.wayland as *mut _);
                }
            }
        }
    }
}

#[cfg(feature = "native_lib")]
impl<E: EGLGraphicsBackend> EGLGraphicsBackend for Rc<E> {
    fn bind_wl_display(&self, display: &Display) -> Result<EGLDisplay> {
        (**self).bind_wl_display(display)
    }
}

#[cfg(feature = "native_lib")]
impl<B: native::Backend, N: native::NativeDisplay<B>> EGLGraphicsBackend for EGLContext<B, N> {
    fn bind_wl_display(&self, display: &Display) -> Result<EGLDisplay> {
        if !self.wl_drm_support {
            bail!(ErrorKind::EglExtensionNotSupported(&[
                "EGL_WL_bind_wayland_display"
            ]));
        }
        let res = unsafe { ffi::egl::BindWaylandDisplayWL(*self.display, display.c_ptr() as *mut _) };
        if res == 0 {
            bail!(ErrorKind::OtherEGLDisplayAlreadyBound);
        }
        Ok(EGLDisplay::new(self, display.c_ptr()))
    }
}