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// Copyright (c) 2016 The vulkano developers
// Licensed under the Apache License, Version 2.0
// <LICENSE-APACHE or
// https://www.apache.org/licenses/LICENSE-2.0> or the MIT
// license <LICENSE-MIT or https://opensource.org/licenses/MIT>,
// at your option. All files in the project carrying such
// notice may not be copied, modified, or distributed except
// according to those terms.

use crate::descriptor_set::layout::DescriptorType;

/// In-memory layout of the pixel data of an image.
///
/// The pixel data of a Vulkan image is arranged in a particular way, which is called its *layout*.
/// Each image subresource (mipmap level and array layer) in an image can have a different layout,
/// but usually the whole image has its data in the same layout. Layouts are abstract in the sense
/// that the user does not know the specific details of each layout; the device driver is free to
/// implement each layout in the way it sees fit.
///
/// The layout of a newly created image is either `Undefined` or `Preinitialized`. Every operation
/// that can be performed on an image is only possible with specific layouts, so before the
/// operation is performed, the user must perform a *layout transition* on the image. This
/// rearranges the pixel data from one layout into another. Layout transitions are performed as part
/// of pipeline barriers in a command buffer.
///
/// The `General` layout is compatible with any operation, so layout transitions are never needed.
/// However, the other layouts, while more restricted, are usually better optimised for a particular
/// type of operation than `General`, so they are usually preferred.
///
/// Vulkan does not keep track of layouts itself, so it is the responsibility of the user to keep
/// track of this information. When performing a layout transition, the previous layout must be
/// specified as well. Some operations allow for different layouts, but require the user to specify
/// which one. Vulkano helps with this by providing sensible defaults, automatically tracking the
/// layout of each image when creating a command buffer, and adding layout transitions where needed.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
#[repr(i32)]
pub enum ImageLayout {
    /// The layout of the data is unknown, and the image is treated as containing no valid data.
    /// Transitioning from `Undefined` will discard any existing pixel data.
    Undefined = ash::vk::ImageLayout::UNDEFINED.as_raw(),

    /// A general-purpose layout that can be used for any operation. Some operations may only allow
    /// `General`, such as storage images, but many have a more specific layout that is better
    /// optimized for that purpose.
    General = ash::vk::ImageLayout::GENERAL.as_raw(),

    /// For a color image used as a color or resolve attachment in a framebuffer. Images that are
    /// transitioned into this layout must have the `color_attachment` usage enabled.
    ColorAttachmentOptimal = ash::vk::ImageLayout::COLOR_ATTACHMENT_OPTIMAL.as_raw(),

    /// For a depth/stencil image used as a depth/stencil attachment in a framebuffer.
    DepthStencilAttachmentOptimal = ash::vk::ImageLayout::DEPTH_STENCIL_ATTACHMENT_OPTIMAL.as_raw(),

    /// For a depth/stencil image used as a read-only depth/stencil attachment in a framebuffer, or
    /// as a (combined) sampled image or input attachment in a shader.
    DepthStencilReadOnlyOptimal = ash::vk::ImageLayout::DEPTH_STENCIL_READ_ONLY_OPTIMAL.as_raw(),

    /// For a color image used as a (combined) sampled image or input attachment in a shader.
    /// Images that are transitioned into this layout must have the `sampled` or `input_attachment`
    /// usages enabled.
    ShaderReadOnlyOptimal = ash::vk::ImageLayout::SHADER_READ_ONLY_OPTIMAL.as_raw(),

    /// For operations that transfer data from an image (copy, blit).
    TransferSrcOptimal = ash::vk::ImageLayout::TRANSFER_SRC_OPTIMAL.as_raw(),

    /// For operations that transfer data to an image (copy, blit, clear).
    TransferDstOptimal = ash::vk::ImageLayout::TRANSFER_DST_OPTIMAL.as_raw(),

    /// When creating an image, this specifies that the initial data is going to be directly
    /// written to from the CPU. Unlike `Undefined`, the image is assumed to contain valid data when
    /// transitioning from this layout. However, this only works right when the image has linear
    /// tiling, optimal tiling gives undefined results.
    Preinitialized = ash::vk::ImageLayout::PREINITIALIZED.as_raw(),

    /// The layout of images that are held in a swapchain. Images are in this layout when they are
    /// acquired from the swapchain, and must be transitioned back into this layout before
    /// presenting them.
    PresentSrc = ash::vk::ImageLayout::PRESENT_SRC_KHR.as_raw(),
}

impl From<ImageLayout> for ash::vk::ImageLayout {
    #[inline]
    fn from(val: ImageLayout) -> Self {
        Self::from_raw(val as i32)
    }
}

/// The set of layouts to use for an image when used in descriptor of various kinds.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct ImageDescriptorLayouts {
    /// The image layout to use in a descriptor as a storage image.
    pub storage_image: ImageLayout,
    /// The image layout to use in a descriptor as a combined image sampler.
    pub combined_image_sampler: ImageLayout,
    /// The image layout to use in a descriptor as a sampled image.
    pub sampled_image: ImageLayout,
    /// The image layout to use in a descriptor as an input attachment.
    pub input_attachment: ImageLayout,
}

impl ImageDescriptorLayouts {
    /// Returns the layout for the given descriptor type. Panics if `descriptor_type` is not an
    /// image descriptor type.
    #[inline]
    pub fn layout_for(&self, descriptor_type: DescriptorType) -> ImageLayout {
        match descriptor_type {
            DescriptorType::CombinedImageSampler => self.combined_image_sampler,
            DescriptorType::SampledImage => self.sampled_image,
            DescriptorType::StorageImage => self.storage_image,
            DescriptorType::InputAttachment => self.input_attachment,
            _ => panic!("{:?} is not an image descriptor type", descriptor_type),
        }
    }
}