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    // Copyright (c) 2016 The vulkano developers
    // Licensed under the Apache License, Version 2.0
    // <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT
    // license <LICENSE-MIT or http://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.

    //! Stage of a graphics pipeline.
    //!
    //! In Vulkan, shaders are grouped in *shader modules*. Each shader module is built from SPIR-V
    //! code and can contain one or more entry points. Note that for the moment the official
    //! GLSL-to-SPIR-V compiler does not support multiple entry points.
    //!
    //! The vulkano library does not provide any functionality that checks and introspects the SPIR-V
    //! code, therefore the whole shader-related API is unsafe. You are encouraged to use the
    //! `vulkano-shaders` crate that will generate Rust code that wraps around vulkano's shaders API.

    use std::borrow::Cow;
    use std::error;
    use std::ffi::CStr;
    use std::fmt;
    use std::iter;
    use std::iter::Empty as EmptyIter;
    use std::marker::PhantomData;
    use std::mem;
    use std::ops::Range;
    use std::ptr;
    use std::sync::Arc;

    use descriptor::pipeline_layout::EmptyPipelineDesc;
    use descriptor::pipeline_layout::PipelineLayoutDesc;
    use format::Format;
    use pipeline::input_assembly::PrimitiveTopology;

    use OomError;
    use VulkanObject;
    use check_errors;
    use device::Device;
    use vk;

    /// Contains SPIR-V code with one or more entry points.
    ///
    /// Note that it is advised to wrap around a `ShaderModule` with a struct that is different for
    /// each shader.
    #[derive(Debug)]
    pub struct ShaderModule {
        // The module.
        module: vk::ShaderModule,
        // Pointer to the device.
        device: Arc<Device>,
    }

    impl ShaderModule {
        /// Builds a new shader module from SPIR-V bytes.
        ///
        /// # Safety
        ///
        /// - The SPIR-V code is not validated.
        /// - The SPIR-V code may require some features that are not enabled. This isn't checked by
        ///   this function either.
        ///
        pub unsafe fn new(device: Arc<Device>, spirv: &[u8]) -> Result<Arc<ShaderModule>, OomError> {
            debug_assert!((spirv.len() % 4) == 0);
            Self::from_ptr(device, spirv.as_ptr() as *const _, spirv.len())
        }

        /// Builds a new shader module from SPIR-V 32-bit words.
        ///
        /// # Safety
        ///
        /// - The SPIR-V code is not validated.
        /// - The SPIR-V code may require some features that are not enabled. This isn't checked by
        ///   this function either.
        ///
        pub unsafe fn from_words(device: Arc<Device>, spirv: &[u32])
                                 -> Result<Arc<ShaderModule>, OomError> {
            Self::from_ptr(device, spirv.as_ptr(), spirv.len() * mem::size_of::<u32>())
        }

        /// Builds a new shader module from SPIR-V.
        ///
        /// # Safety
        ///
        /// - The SPIR-V code is not validated.
        /// - The SPIR-V code may require some features that are not enabled. This isn't checked by
        ///   this function either.
        ///
        unsafe fn from_ptr(device: Arc<Device>, spirv: *const u32, spirv_len: usize)
                           -> Result<Arc<ShaderModule>, OomError> {
            let module = {
                let infos = vk::ShaderModuleCreateInfo {
                    sType: vk::STRUCTURE_TYPE_SHADER_MODULE_CREATE_INFO,
                    pNext: ptr::null(),
                    flags: 0, // reserved
                    codeSize: spirv_len,
                    pCode: spirv,
                };

                let vk = device.pointers();
                let mut output = mem::uninitialized();
                check_errors(vk.CreateShaderModule(device.internal_object(),
                                                   &infos,
                                                   ptr::null(),
                                                   &mut output))?;
                output
            };

            Ok(Arc::new(ShaderModule {
                            module: module,
                            device: device,
                        }))
        }

        /// Gets access to an entry point contained in this module.
        ///
        /// This is purely a *logical* operation. It returns a struct that *represents* the entry
        /// point but doesn't actually do anything.
        ///
        /// # Safety
        ///
        /// - The user must check that the entry point exists in the module, as this is not checked
        ///   by Vulkan.
        /// - The input, output and layout must correctly describe the input, output and layout used
        ///   by this stage.
        ///
        pub unsafe fn graphics_entry_point<'a, S, I, O, L>(&'a self, name: &'a CStr, input: I,
                                                           output: O, layout: L,
                                                           ty: GraphicsShaderType)
                                                           -> GraphicsEntryPoint<'a, S, I, O, L> {
            GraphicsEntryPoint {
                module: self,
                name: name,
                input: input,
                output: output,
                layout: layout,
                ty: ty,
                marker: PhantomData,
            }
        }

        /// Gets access to an entry point contained in this module.
        ///
        /// This is purely a *logical* operation. It returns a struct that *represents* the entry
        /// point but doesn't actually do anything.
        ///
        /// # Safety
        ///
        /// - The user must check that the entry point exists in the module, as this is not checked
        ///   by Vulkan.
        /// - The layout must correctly describe the layout used by this stage.
        ///
        #[inline]
        pub unsafe fn compute_entry_point<'a, S, L>(&'a self, name: &'a CStr, layout: L)
                                                    -> ComputeEntryPoint<'a, S, L> {
            ComputeEntryPoint {
                module: self,
                name: name,
                layout: layout,
                marker: PhantomData,
            }
        }
    }

    unsafe impl VulkanObject for ShaderModule {
        type Object = vk::ShaderModule;

        const TYPE: vk::DebugReportObjectTypeEXT = vk::DEBUG_REPORT_OBJECT_TYPE_SHADER_MODULE_EXT;

        #[inline]
        fn internal_object(&self) -> vk::ShaderModule {
            self.module
        }
    }

    impl Drop for ShaderModule {
        #[inline]
        fn drop(&mut self) {
            unsafe {
                let vk = self.device.pointers();
                vk.DestroyShaderModule(self.device.internal_object(), self.module, ptr::null());
            }
        }
    }

    pub unsafe trait GraphicsEntryPointAbstract: EntryPointAbstract {
        type InputDefinition: ShaderInterfaceDef;
        type OutputDefinition: ShaderInterfaceDef;

        /// Returns the input attributes used by the shader stage.
        fn input(&self) -> &Self::InputDefinition;

        /// Returns the output attributes used by the shader stage.
        fn output(&self) -> &Self::OutputDefinition;

        /// Returns the type of shader.
        fn ty(&self) -> GraphicsShaderType;
    }

    /// Represents a shader entry point in a shader module.
    ///
    /// Can be obtained by calling `entry_point()` on the shader module.
    #[derive(Debug, Copy, Clone)]
    pub struct GraphicsEntryPoint<'a, S, I, O, L> {
        module: &'a ShaderModule,
        name: &'a CStr,
        input: I,
        layout: L,
        output: O,
        ty: GraphicsShaderType,
        marker: PhantomData<S>,
    }

    unsafe impl<'a, S, I, O, L> EntryPointAbstract for GraphicsEntryPoint<'a, S, I, O, L>
        where L: PipelineLayoutDesc,
              I: ShaderInterfaceDef,
              O: ShaderInterfaceDef,
              S: SpecializationConstants
    {
        type PipelineLayout = L;
        type SpecializationConstants = S;

        #[inline]
        fn module(&self) -> &ShaderModule {
            self.module
        }

        #[inline]
        fn name(&self) -> &CStr {
            self.name
        }

        #[inline]
        fn layout(&self) -> &L {
            &self.layout
        }
    }

    unsafe impl<'a, S, I, O, L> GraphicsEntryPointAbstract for GraphicsEntryPoint<'a, S, I, O, L>
        where L: PipelineLayoutDesc,
              I: ShaderInterfaceDef,
              O: ShaderInterfaceDef,
              S: SpecializationConstants
    {
        type InputDefinition = I;
        type OutputDefinition = O;

        #[inline]
        fn input(&self) -> &I {
            &self.input
        }

        #[inline]
        fn output(&self) -> &O {
            &self.output
        }

        #[inline]
        fn ty(&self) -> GraphicsShaderType {
            self.ty
        }
    }

    #[derive(Debug, Copy, Clone, PartialEq, Eq)]
    pub enum GraphicsShaderType {
        Vertex,
        TessellationControl,
        TessellationEvaluation,
        Geometry(GeometryShaderExecutionMode),
        Fragment,
    }

    /// Declares which type of primitives are expected by the geometry shader.
    #[derive(Debug, Copy, Clone, PartialEq, Eq)]
    pub enum GeometryShaderExecutionMode {
        Points,
        Lines,
        LinesWithAdjacency,
        Triangles,
        TrianglesWithAdjacency,
    }

    impl GeometryShaderExecutionMode {
        /// Returns true if the given primitive topology can be used with this execution mode.
        #[inline]
        pub fn matches(&self, input: PrimitiveTopology) -> bool {
            match (*self, input) {
                (GeometryShaderExecutionMode::Points, PrimitiveTopology::PointList) => true,
                (GeometryShaderExecutionMode::Lines, PrimitiveTopology::LineList) => true,
                (GeometryShaderExecutionMode::Lines, PrimitiveTopology::LineStrip) => true,
                (GeometryShaderExecutionMode::LinesWithAdjacency,
                 PrimitiveTopology::LineListWithAdjacency) => true,
                (GeometryShaderExecutionMode::LinesWithAdjacency,
                 PrimitiveTopology::LineStripWithAdjacency) => true,
                (GeometryShaderExecutionMode::Triangles, PrimitiveTopology::TriangleList) => true,
                (GeometryShaderExecutionMode::Triangles, PrimitiveTopology::TriangleStrip) => true,
                (GeometryShaderExecutionMode::Triangles, PrimitiveTopology::TriangleFan) => true,
                (GeometryShaderExecutionMode::TrianglesWithAdjacency,
                 PrimitiveTopology::TriangleListWithAdjacency) => true,
                (GeometryShaderExecutionMode::TrianglesWithAdjacency,
                 PrimitiveTopology::TriangleStripWithAdjacency) => true,
                _ => false,
            }
        }
    }

    pub unsafe trait EntryPointAbstract {
        type PipelineLayout: PipelineLayoutDesc;
        type SpecializationConstants: SpecializationConstants;

        /// Returns the module this entry point comes from.
        fn module(&self) -> &ShaderModule;

        /// Returns the name of the entry point.
        fn name(&self) -> &CStr;

        /// Returns the pipeline layout used by the shader stage.
        fn layout(&self) -> &Self::PipelineLayout;
    }

    /// Represents the entry point of a compute shader in a shader module.
    ///
    /// Can be obtained by calling `compute_shader_entry_point()` on the shader module.
    #[derive(Debug, Copy, Clone)]
    pub struct ComputeEntryPoint<'a, S, L> {
        module: &'a ShaderModule,
        name: &'a CStr,
        layout: L,
        marker: PhantomData<S>,
    }

    unsafe impl<'a, S, L> EntryPointAbstract for ComputeEntryPoint<'a, S, L>
        where L: PipelineLayoutDesc,
              S: SpecializationConstants
    {
        type PipelineLayout = L;
        type SpecializationConstants = S;

        #[inline]
        fn module(&self) -> &ShaderModule {
            self.module
        }

        #[inline]
        fn name(&self) -> &CStr {
            self.name
        }

        #[inline]
        fn layout(&self) -> &L {
            &self.layout
        }
    }

    /// A dummy that implements `GraphicsEntryPointAbstract` and `EntryPointAbstract`.
    ///
    /// When a function has a signature like: `fn foo<S: EntryPointAbstract>(shader: Option<S>)`, you
    /// can pass `None::<EmptyEntryPointDummy>`.
    ///
    /// This object is meant to be a replacement to `!` before it is stabilized.
    // TODO: ^
    #[derive(Debug, Copy, Clone)]
    pub enum EmptyEntryPointDummy {
    }

    unsafe impl EntryPointAbstract for EmptyEntryPointDummy {
        type PipelineLayout = EmptyPipelineDesc;
        type SpecializationConstants = ();

        #[inline]
        fn module(&self) -> &ShaderModule {
            unreachable!()
        }

        #[inline]
        fn name(&self) -> &CStr {
            unreachable!()
        }

        #[inline]
        fn layout(&self) -> &EmptyPipelineDesc {
            unreachable!()
        }
    }

    unsafe impl GraphicsEntryPointAbstract for EmptyEntryPointDummy {
        type InputDefinition = EmptyShaderInterfaceDef;
        type OutputDefinition = EmptyShaderInterfaceDef;

        #[inline]
        fn input(&self) -> &EmptyShaderInterfaceDef {
            unreachable!()
        }

        #[inline]
        fn output(&self) -> &EmptyShaderInterfaceDef {
            unreachable!()
        }

        #[inline]
        fn ty(&self) -> GraphicsShaderType {
            unreachable!()
        }
    }

    /// Types that contain the definition of an interface between two shader stages, or between
    /// the outside and a shader stage.
    ///
    /// # Safety
    ///
    /// - Must only provide one entry per location.
    /// - The format of each element must not be larger than 128 bits.
    ///
    pub unsafe trait ShaderInterfaceDef {
        /// Iterator returned by `elements`.
        type Iter: ExactSizeIterator<Item = ShaderInterfaceDefEntry>;

        /// Iterates over the elements of the interface.
        fn elements(&self) -> Self::Iter;
    }

    /// Entry of a shader interface definition.
    #[derive(Debug, Clone)]
    pub struct ShaderInterfaceDefEntry {
        /// Range of locations covered by the element.
        pub location: Range<u32>,
        /// Format of a each location of the element.
        pub format: Format,
        /// Name of the element, or `None` if the name is unknown.
        pub name: Option<Cow<'static, str>>,
    }

    /// Description of an empty shader interface.
    #[derive(Debug, Copy, Clone)]
    pub struct EmptyShaderInterfaceDef;

    unsafe impl ShaderInterfaceDef for EmptyShaderInterfaceDef {
        type Iter = EmptyIter<ShaderInterfaceDefEntry>;

        #[inline]
        fn elements(&self) -> Self::Iter {
            iter::empty()
        }
    }

    /// Extension trait for `ShaderInterfaceDef` that specifies that the interface is potentially
    /// compatible with another one.
    pub unsafe trait ShaderInterfaceDefMatch<I>: ShaderInterfaceDef
        where I: ShaderInterfaceDef
    {
        /// Returns `Ok` if the two definitions match.
        fn matches(&self, other: &I) -> Result<(), ShaderInterfaceMismatchError>;
    }

    // TODO: turn this into a default impl that can be specialized
    unsafe impl<T, I> ShaderInterfaceDefMatch<I> for T
        where T: ShaderInterfaceDef,
              I: ShaderInterfaceDef
    {
        fn matches(&self, other: &I) -> Result<(), ShaderInterfaceMismatchError> {
            if self.elements().len() != other.elements().len() {
                return Err(ShaderInterfaceMismatchError::ElementsCountMismatch {
                    self_elements: self.elements().len() as u32,
                    other_elements: other.elements().len() as u32,
                });
            }

            for a in self.elements() {
                for loc in a.location.clone() {
                    let b = match other
                        .elements()
                        .find(|e| loc >= e.location.start && loc < e.location.end) {
                        None => return Err(ShaderInterfaceMismatchError::MissingElement {
                                               location: loc,
                                           }),
                        Some(b) => b,
                    };

                    if a.format != b.format {
                        return Err(ShaderInterfaceMismatchError::FormatMismatch {
                            location: loc,
                            self_format: a.format,
                            other_format: b.format,
                        });
                    }

                    // TODO: enforce this?
                    /*match (a.name, b.name) {
                        (Some(ref an), Some(ref bn)) => if an != bn { return false },
                        _ => ()
                    };*/
                }
            }

            // Note: since we check that the number of elements is the same, we don't need to iterate
            // over b's elements.

            Ok(())
        }
    }

    /// Error that can happen when the interface mismatches between two shader stages.
    #[derive(Clone, Debug, PartialEq, Eq)]
    pub enum ShaderInterfaceMismatchError {
        /// The number of elements is not the same between the two shader interfaces.
        ElementsCountMismatch {
            /// Number of elements in the first interface.
            self_elements: u32,
            /// Number of elements in the second interface.
            other_elements: u32,
        },

        /// An element is missing from one of the interfaces.
        MissingElement {
            /// Location of the missing element.
            location: u32,
        },

        /// The format of an element does not match.
        FormatMismatch {
            /// Location of the element that mismatches.
            location: u32,
            /// Format in the first interface.
            self_format: Format,
            /// Format in the second interface.
            other_format: Format
        },
    }

    impl error::Error for ShaderInterfaceMismatchError {
        #[inline]
        fn description(&self) -> &str {
            match *self {
                ShaderInterfaceMismatchError::ElementsCountMismatch { .. } => {
                    "the number of elements mismatches"
                },
                ShaderInterfaceMismatchError::MissingElement { .. } => {
                    "an element is missing"
                },
                ShaderInterfaceMismatchError::FormatMismatch { .. } => {
                    "the format of an element does not match"
                },
            }
        }
    }

    impl fmt::Display for ShaderInterfaceMismatchError {
        #[inline]
        fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
            write!(fmt, "{}", error::Error::description(self))
        }
    }

    /// Trait for types that contain specialization data for shaders.
    ///
    /// Shader modules can contain what is called *specialization constants*. They are the same as
    /// constants except that their values can be defined when you create a compute pipeline or a
    /// graphics pipeline. Doing so is done by passing a type that implements the
    /// `SpecializationConstants` trait and that stores the values in question. The `descriptors()`
    /// method of this trait indicates how to grab them.
    ///
    /// Boolean specialization constants must be stored as 32bits integers, where `0` means `false` and
    /// any non-zero value means `true`. Integer and floating-point specialization constants are
    /// stored as their Rust equivalent.
    ///
    /// This trait is implemented on `()` for shaders that don't have any specialization constant.
    ///
    /// Note that it is the shader module that chooses which type that implements
    /// `SpecializationConstants` it is possible to pass when creating the pipeline, through [the
    /// `EntryPointAbstract` trait](trait.EntryPointAbstract.html). Therefore there is generally no
    /// point to implement this trait yourself, unless you are also writing your own implementation of
    /// `EntryPointAbstract`.
    ///
    /// # Example
    ///
    /// ```rust
    /// use vulkano::pipeline::shader::SpecializationConstants;
    /// use vulkano::pipeline::shader::SpecializationMapEntry;
    ///
    /// #[repr(C)]      // `#[repr(C)]` guarantees that the struct has a specific layout
    /// struct MySpecConstants {
    ///     my_integer_constant: i32,
    ///     a_boolean: u32,
    ///     floating_point: f32,
    /// }
    ///
    /// unsafe impl SpecializationConstants for MySpecConstants {
    ///     fn descriptors() -> &'static [SpecializationMapEntry] {
    ///         static DESCRIPTORS: [SpecializationMapEntry; 3] = [
    ///             SpecializationMapEntry {
    ///                 constant_id: 0,
    ///                 offset: 0,
    ///                 size: 4,
    ///             },
    ///             SpecializationMapEntry {
    ///                 constant_id: 1,
    ///                 offset: 4,
    ///                 size: 4,
    ///             },
    ///             SpecializationMapEntry {
    ///                 constant_id: 2,
    ///                 offset: 8,
    ///                 size: 4,
    ///             },
    ///         ];
    ///
    ///         &DESCRIPTORS
    ///     }
    /// }
    /// ```
    ///
    /// # Safety
    ///
    /// - The `SpecializationMapEntry` returned must contain valid offsets and sizes.
    /// - The size of each `SpecializationMapEntry` must match the size of the corresponding constant
    ///   (`4` for booleans).
    ///
    pub unsafe trait SpecializationConstants {
        /// Returns descriptors of the struct's layout.
        fn descriptors() -> &'static [SpecializationMapEntry];
    }

    unsafe impl SpecializationConstants for () {
        #[inline]
        fn descriptors() -> &'static [SpecializationMapEntry] {
            &[]
        }
    }

    /// Describes an individual constant to set in the shader. Also a field in the struct.
    // Implementation note: has the same memory representation as a `VkSpecializationMapEntry`.
    #[repr(C)]
    pub struct SpecializationMapEntry {
        /// Identifier of the constant in the shader that corresponds to this field.
        ///
        /// For SPIR-V, this must be the value of the `SpecId` decoration applied to the specialization
        /// constant.
        /// For GLSL, this must be the value of `N` in the `layout(constant_id = N)` attribute applied
        /// to a constant.
        pub constant_id: u32,

        /// Offset within the struct where the data can be found.
        pub offset: u32,

        /// Size of the data in bytes. Must match the size of the constant (`4` for booleans).
        pub size: usize,
    }

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