use std::{marker::PhantomData, ops::Range, sync::Arc, thread};

use crate::context::DynContext;
use crate::*;

#[derive(Debug)]
pub(crate) struct RenderPassInner {
    pub(crate) data: Box<Data>,
    pub(crate) context: Arc<C>,
}

impl Drop for RenderPassInner {
    fn drop(&mut self) {
        if !thread::panicking() {
            self.context.render_pass_end(self.data.as_mut());
        }
    }
}

/// In-progress recording of a render pass: a list of render commands in a [`CommandEncoder`].
///
/// It can be created with [`CommandEncoder::begin_render_pass()`], whose [`RenderPassDescriptor`]
/// specifies the attachments (textures) that will be rendered to.
///
/// Most of the methods on `RenderPass` serve one of two purposes, identifiable by their names:
///
/// * `draw_*()`: Drawing (that is, encoding a render command, which, when executed by the GPU, will
///   rasterize something and execute shaders).
/// * `set_*()`: Setting part of the [render state](https://gpuweb.github.io/gpuweb/#renderstate)
///   for future drawing commands.
///
/// A render pass may contain any number of drawing commands, and before/between each command the
/// render state may be updated however you wish; each drawing command will be executed using the
/// render state that has been set when the `draw_*()` function is called.
///
/// Corresponds to [WebGPU `GPURenderPassEncoder`](
/// https://gpuweb.github.io/gpuweb/#render-pass-encoder).
#[derive(Debug)]
pub struct RenderPass<'encoder> {
    /// The inner data of the render pass, separated out so it's easy to replace the lifetime with 'static if desired.
    pub(crate) inner: RenderPassInner,

    /// This lifetime is used to protect the [`CommandEncoder`] from being used
    /// while the pass is alive.
    pub(crate) encoder_guard: PhantomData<&'encoder ()>,
}

impl<'encoder> RenderPass<'encoder> {
    /// Drops the lifetime relationship to the parent command encoder, making usage of
    /// the encoder while this pass is recorded a run-time error instead.
    ///
    /// Attention: As long as the render pass has not been ended, any mutating operation on the parent
    /// command encoder will cause a run-time error and invalidate it!
    /// By default, the lifetime constraint prevents this, but it can be useful
    /// to handle this at run time, such as when storing the pass and encoder in the same
    /// data structure.
    ///
    /// This operation has no effect on pass recording.
    /// It's a safe operation, since [`CommandEncoder`] is in a locked state as long as the pass is active
    /// regardless of the lifetime constraint or its absence.
    pub fn forget_lifetime(self) -> RenderPass<'static> {
        RenderPass {
            inner: self.inner,
            encoder_guard: PhantomData,
        }
    }

    /// Sets the active bind group for a given bind group index. The bind group layout
    /// in the active pipeline when any `draw_*()` method is called must match the layout of
    /// this bind group.
    ///
    /// If the bind group have dynamic offsets, provide them in binding order.
    /// These offsets have to be aligned to [`Limits::min_uniform_buffer_offset_alignment`]
    /// or [`Limits::min_storage_buffer_offset_alignment`] appropriately.
    ///
    /// Subsequent draw calls’ shader executions will be able to access data in these bind groups.
    pub fn set_bind_group(
        &mut self,
        index: u32,
        bind_group: Option<&BindGroup>,
        offsets: &[DynamicOffset],
    ) {
        let bg = bind_group.map(|x| x.data.as_ref());
        DynContext::render_pass_set_bind_group(
            &*self.inner.context,
            self.inner.data.as_mut(),
            index,
            bg,
            offsets,
        )
    }

    /// Sets the active render pipeline.
    ///
    /// Subsequent draw calls will exhibit the behavior defined by `pipeline`.
    pub fn set_pipeline(&mut self, pipeline: &RenderPipeline) {
        DynContext::render_pass_set_pipeline(
            &*self.inner.context,
            self.inner.data.as_mut(),
            pipeline.data.as_ref(),
        )
    }

    /// Sets the blend color as used by some of the blending modes.
    ///
    /// Subsequent blending tests will test against this value.
    /// If this method has not been called, the blend constant defaults to [`Color::TRANSPARENT`]
    /// (all components zero).
    pub fn set_blend_constant(&mut self, color: Color) {
        DynContext::render_pass_set_blend_constant(
            &*self.inner.context,
            self.inner.data.as_mut(),
            color,
        )
    }

    /// Sets the active index buffer.
    ///
    /// Subsequent calls to [`draw_indexed`](RenderPass::draw_indexed) on this [`RenderPass`] will
    /// use `buffer` as the source index buffer.
    pub fn set_index_buffer(&mut self, buffer_slice: BufferSlice<'_>, index_format: IndexFormat) {
        DynContext::render_pass_set_index_buffer(
            &*self.inner.context,
            self.inner.data.as_mut(),
            buffer_slice.buffer.data.as_ref(),
            index_format,
            buffer_slice.offset,
            buffer_slice.size,
        )
    }

    /// Assign a vertex buffer to a slot.
    ///
    /// Subsequent calls to [`draw`] and [`draw_indexed`] on this
    /// [`RenderPass`] will use `buffer` as one of the source vertex buffers.
    ///
    /// The `slot` refers to the index of the matching descriptor in
    /// [`VertexState::buffers`].
    ///
    /// [`draw`]: RenderPass::draw
    /// [`draw_indexed`]: RenderPass::draw_indexed
    pub fn set_vertex_buffer(&mut self, slot: u32, buffer_slice: BufferSlice<'_>) {
        DynContext::render_pass_set_vertex_buffer(
            &*self.inner.context,
            self.inner.data.as_mut(),
            slot,
            buffer_slice.buffer.data.as_ref(),
            buffer_slice.offset,
            buffer_slice.size,
        )
    }

    /// Sets the scissor rectangle used during the rasterization stage.
    /// After transformation into [viewport coordinates](https://www.w3.org/TR/webgpu/#viewport-coordinates).
    ///
    /// Subsequent draw calls will discard any fragments which fall outside the scissor rectangle.
    /// If this method has not been called, the scissor rectangle defaults to the entire bounds of
    /// the render targets.
    ///
    /// The function of the scissor rectangle resembles [`set_viewport()`](Self::set_viewport),
    /// but it does not affect the coordinate system, only which fragments are discarded.
    pub fn set_scissor_rect(&mut self, x: u32, y: u32, width: u32, height: u32) {
        DynContext::render_pass_set_scissor_rect(
            &*self.inner.context,
            self.inner.data.as_mut(),
            x,
            y,
            width,
            height,
        );
    }

    /// Sets the viewport used during the rasterization stage to linearly map
    /// from [normalized device coordinates](https://www.w3.org/TR/webgpu/#ndc) to [viewport coordinates](https://www.w3.org/TR/webgpu/#viewport-coordinates).
    ///
    /// Subsequent draw calls will only draw within this region.
    /// If this method has not been called, the viewport defaults to the entire bounds of the render
    /// targets.
    pub fn set_viewport(&mut self, x: f32, y: f32, w: f32, h: f32, min_depth: f32, max_depth: f32) {
        DynContext::render_pass_set_viewport(
            &*self.inner.context,
            self.inner.data.as_mut(),
            x,
            y,
            w,
            h,
            min_depth,
            max_depth,
        );
    }

    /// Sets the stencil reference.
    ///
    /// Subsequent stencil tests will test against this value.
    /// If this method has not been called, the stencil reference value defaults to `0`.
    pub fn set_stencil_reference(&mut self, reference: u32) {
        DynContext::render_pass_set_stencil_reference(
            &*self.inner.context,
            self.inner.data.as_mut(),
            reference,
        );
    }

    /// Inserts debug marker.
    pub fn insert_debug_marker(&mut self, label: &str) {
        DynContext::render_pass_insert_debug_marker(
            &*self.inner.context,
            self.inner.data.as_mut(),
            label,
        );
    }

    /// Start record commands and group it into debug marker group.
    pub fn push_debug_group(&mut self, label: &str) {
        DynContext::render_pass_push_debug_group(
            &*self.inner.context,
            self.inner.data.as_mut(),
            label,
        );
    }

    /// Stops command recording and creates debug group.
    pub fn pop_debug_group(&mut self) {
        DynContext::render_pass_pop_debug_group(&*self.inner.context, self.inner.data.as_mut());
    }

    /// Draws primitives from the active vertex buffer(s).
    ///
    /// The active vertex buffer(s) can be set with [`RenderPass::set_vertex_buffer`].
    /// Does not use an Index Buffer. If you need this see [`RenderPass::draw_indexed`]
    ///
    /// Panics if vertices Range is outside of the range of the vertices range of any set vertex buffer.
    ///
    /// vertices: The range of vertices to draw.
    /// instances: Range of Instances to draw. Use 0..1 if instance buffers are not used.
    /// E.g.of how its used internally
    /// ```rust ignore
    /// for instance_id in instance_range {
    ///     for vertex_id in vertex_range {
    ///         let vertex = vertex[vertex_id];
    ///         vertex_shader(vertex, vertex_id, instance_id);
    ///     }
    /// }
    /// ```
    ///
    /// This drawing command uses the current render state, as set by preceding `set_*()` methods.
    /// It is not affected by changes to the state that are performed after it is called.
    pub fn draw(&mut self, vertices: Range<u32>, instances: Range<u32>) {
        DynContext::render_pass_draw(
            &*self.inner.context,
            self.inner.data.as_mut(),
            vertices,
            instances,
        )
    }

    /// Draws indexed primitives using the active index buffer and the active vertex buffers.
    ///
    /// The active index buffer can be set with [`RenderPass::set_index_buffer`]
    /// The active vertex buffers can be set with [`RenderPass::set_vertex_buffer`].
    ///
    /// Panics if indices Range is outside of the range of the indices range of any set index buffer.
    ///
    /// indices: The range of indices to draw.
    /// base_vertex: value added to each index value before indexing into the vertex buffers.
    /// instances: Range of Instances to draw. Use 0..1 if instance buffers are not used.
    /// E.g.of how its used internally
    /// ```rust ignore
    /// for instance_id in instance_range {
    ///     for index_index in index_range {
    ///         let vertex_id = index_buffer[index_index];
    ///         let adjusted_vertex_id = vertex_id + base_vertex;
    ///         let vertex = vertex[adjusted_vertex_id];
    ///         vertex_shader(vertex, adjusted_vertex_id, instance_id);
    ///     }
    /// }
    /// ```
    ///
    /// This drawing command uses the current render state, as set by preceding `set_*()` methods.
    /// It is not affected by changes to the state that are performed after it is called.
    pub fn draw_indexed(&mut self, indices: Range<u32>, base_vertex: i32, instances: Range<u32>) {
        DynContext::render_pass_draw_indexed(
            &*self.inner.context,
            self.inner.data.as_mut(),
            indices,
            base_vertex,
            instances,
        );
    }

    /// Draws primitives from the active vertex buffer(s) based on the contents of the `indirect_buffer`.
    ///
    /// This is like calling [`RenderPass::draw`] but the contents of the call are specified in the `indirect_buffer`.
    /// The structure expected in `indirect_buffer` must conform to [`DrawIndirectArgs`](crate::util::DrawIndirectArgs).
    ///
    /// Indirect drawing has some caveats depending on the features available. We are not currently able to validate
    /// these and issue an error.
    /// - If [`Features::INDIRECT_FIRST_INSTANCE`] is not present on the adapter,
    ///   [`DrawIndirect::first_instance`](crate::util::DrawIndirectArgs::first_instance) will be ignored.
    /// - If [`DownlevelFlags::VERTEX_AND_INSTANCE_INDEX_RESPECTS_RESPECTIVE_FIRST_VALUE_IN_INDIRECT_DRAW`] is not present on the adapter,
    ///   any use of `@builtin(vertex_index)` or `@builtin(instance_index)` in the vertex shader will have different values.
    ///
    /// See details on the individual flags for more information.
    pub fn draw_indirect(&mut self, indirect_buffer: &Buffer, indirect_offset: BufferAddress) {
        DynContext::render_pass_draw_indirect(
            &*self.inner.context,
            self.inner.data.as_mut(),
            indirect_buffer.data.as_ref(),
            indirect_offset,
        );
    }

    /// Draws indexed primitives using the active index buffer and the active vertex buffers,
    /// based on the contents of the `indirect_buffer`.
    ///
    /// This is like calling [`RenderPass::draw_indexed`] but the contents of the call are specified in the `indirect_buffer`.
    /// The structure expected in `indirect_buffer` must conform to [`DrawIndexedIndirectArgs`](crate::util::DrawIndexedIndirectArgs).
    ///
    /// Indirect drawing has some caveats depending on the features available. We are not currently able to validate
    /// these and issue an error.
    /// - If [`Features::INDIRECT_FIRST_INSTANCE`] is not present on the adapter,
    ///   [`DrawIndexedIndirect::first_instance`](crate::util::DrawIndexedIndirectArgs::first_instance) will be ignored.
    /// - If [`DownlevelFlags::VERTEX_AND_INSTANCE_INDEX_RESPECTS_RESPECTIVE_FIRST_VALUE_IN_INDIRECT_DRAW`] is not present on the adapter,
    ///   any use of `@builtin(vertex_index)` or `@builtin(instance_index)` in the vertex shader will have different values.
    ///
    /// See details on the individual flags for more information.
    pub fn draw_indexed_indirect(
        &mut self,
        indirect_buffer: &Buffer,
        indirect_offset: BufferAddress,
    ) {
        DynContext::render_pass_draw_indexed_indirect(
            &*self.inner.context,
            self.inner.data.as_mut(),
            indirect_buffer.data.as_ref(),
            indirect_offset,
        );
    }

    /// Execute a [render bundle][RenderBundle], which is a set of pre-recorded commands
    /// that can be run together.
    ///
    /// Commands in the bundle do not inherit this render pass's current render state, and after the
    /// bundle has executed, the state is **cleared** (reset to defaults, not the previous state).
    pub fn execute_bundles<'a, I: IntoIterator<Item = &'a RenderBundle>>(
        &mut self,
        render_bundles: I,
    ) {
        let mut render_bundles = render_bundles.into_iter().map(|rb| rb.data.as_ref());

        DynContext::render_pass_execute_bundles(
            &*self.inner.context,
            self.inner.data.as_mut(),
            &mut render_bundles,
        )
    }
}

/// [`Features::MULTI_DRAW_INDIRECT`] must be enabled on the device in order to call these functions.
impl<'encoder> RenderPass<'encoder> {
    /// Dispatches multiple draw calls from the active vertex buffer(s) based on the contents of the `indirect_buffer`.
    /// `count` draw calls are issued.
    ///
    /// The active vertex buffers can be set with [`RenderPass::set_vertex_buffer`].
    ///
    /// The structure expected in `indirect_buffer` must conform to [`DrawIndirectArgs`](crate::util::DrawIndirectArgs).
    /// These draw structures are expected to be tightly packed.
    ///
    /// This drawing command uses the current render state, as set by preceding `set_*()` methods.
    /// It is not affected by changes to the state that are performed after it is called.
    pub fn multi_draw_indirect(
        &mut self,
        indirect_buffer: &Buffer,
        indirect_offset: BufferAddress,
        count: u32,
    ) {
        DynContext::render_pass_multi_draw_indirect(
            &*self.inner.context,
            self.inner.data.as_mut(),
            indirect_buffer.data.as_ref(),
            indirect_offset,
            count,
        );
    }

    /// Dispatches multiple draw calls from the active index buffer and the active vertex buffers,
    /// based on the contents of the `indirect_buffer`. `count` draw calls are issued.
    ///
    /// The active index buffer can be set with [`RenderPass::set_index_buffer`], while the active
    /// vertex buffers can be set with [`RenderPass::set_vertex_buffer`].
    ///
    /// The structure expected in `indirect_buffer` must conform to [`DrawIndexedIndirectArgs`](crate::util::DrawIndexedIndirectArgs).
    /// These draw structures are expected to be tightly packed.
    ///
    /// This drawing command uses the current render state, as set by preceding `set_*()` methods.
    /// It is not affected by changes to the state that are performed after it is called.
    pub fn multi_draw_indexed_indirect(
        &mut self,
        indirect_buffer: &Buffer,
        indirect_offset: BufferAddress,
        count: u32,
    ) {
        DynContext::render_pass_multi_draw_indexed_indirect(
            &*self.inner.context,
            self.inner.data.as_mut(),
            indirect_buffer.data.as_ref(),
            indirect_offset,
            count,
        );
    }
}

/// [`Features::MULTI_DRAW_INDIRECT_COUNT`] must be enabled on the device in order to call these functions.
impl<'encoder> RenderPass<'encoder> {
    /// Dispatches multiple draw calls from the active vertex buffer(s) based on the contents of the `indirect_buffer`.
    /// The count buffer is read to determine how many draws to issue.
    ///
    /// The indirect buffer must be long enough to account for `max_count` draws, however only `count`
    /// draws will be read. If `count` is greater than `max_count`, `max_count` will be used.
    ///
    /// The active vertex buffers can be set with [`RenderPass::set_vertex_buffer`].
    ///
    /// The structure expected in `indirect_buffer` must conform to [`DrawIndirectArgs`](crate::util::DrawIndirectArgs).
    /// These draw structures are expected to be tightly packed.
    ///
    /// The structure expected in `count_buffer` is the following:
    ///
    /// ```rust
    /// #[repr(C)]
    /// struct DrawIndirectCount {
    ///     count: u32, // Number of draw calls to issue.
    /// }
    /// ```
    ///
    /// This drawing command uses the current render state, as set by preceding `set_*()` methods.
    /// It is not affected by changes to the state that are performed after it is called.
    pub fn multi_draw_indirect_count(
        &mut self,
        indirect_buffer: &Buffer,
        indirect_offset: BufferAddress,
        count_buffer: &Buffer,
        count_offset: BufferAddress,
        max_count: u32,
    ) {
        DynContext::render_pass_multi_draw_indirect_count(
            &*self.inner.context,
            self.inner.data.as_mut(),
            indirect_buffer.data.as_ref(),
            indirect_offset,
            count_buffer.data.as_ref(),
            count_offset,
            max_count,
        );
    }

    /// Dispatches multiple draw calls from the active index buffer and the active vertex buffers,
    /// based on the contents of the `indirect_buffer`. The count buffer is read to determine how many draws to issue.
    ///
    /// The indirect buffer must be long enough to account for `max_count` draws, however only `count`
    /// draws will be read. If `count` is greater than `max_count`, `max_count` will be used.
    ///
    /// The active index buffer can be set with [`RenderPass::set_index_buffer`], while the active
    /// vertex buffers can be set with [`RenderPass::set_vertex_buffer`].
    ///
    ///
    /// The structure expected in `indirect_buffer` must conform to [`DrawIndexedIndirectArgs`](crate::util::DrawIndexedIndirectArgs).
    ///
    /// These draw structures are expected to be tightly packed.
    ///
    /// The structure expected in `count_buffer` is the following:
    ///
    /// ```rust
    /// #[repr(C)]
    /// struct DrawIndexedIndirectCount {
    ///     count: u32, // Number of draw calls to issue.
    /// }
    /// ```
    ///
    /// This drawing command uses the current render state, as set by preceding `set_*()` methods.
    /// It is not affected by changes to the state that are performed after it is called.
    pub fn multi_draw_indexed_indirect_count(
        &mut self,
        indirect_buffer: &Buffer,
        indirect_offset: BufferAddress,
        count_buffer: &Buffer,
        count_offset: BufferAddress,
        max_count: u32,
    ) {
        DynContext::render_pass_multi_draw_indexed_indirect_count(
            &*self.inner.context,
            self.inner.data.as_mut(),
            indirect_buffer.data.as_ref(),
            indirect_offset,
            count_buffer.data.as_ref(),
            count_offset,
            max_count,
        );
    }
}

/// [`Features::PUSH_CONSTANTS`] must be enabled on the device in order to call these functions.
impl<'encoder> RenderPass<'encoder> {
    /// Set push constant data for subsequent draw calls.
    ///
    /// Write the bytes in `data` at offset `offset` within push constant
    /// storage, all of which are accessible by all the pipeline stages in
    /// `stages`, and no others.  Both `offset` and the length of `data` must be
    /// multiples of [`PUSH_CONSTANT_ALIGNMENT`], which is always 4.
    ///
    /// For example, if `offset` is `4` and `data` is eight bytes long, this
    /// call will write `data` to bytes `4..12` of push constant storage.
    ///
    /// # Stage matching
    ///
    /// Every byte in the affected range of push constant storage must be
    /// accessible to exactly the same set of pipeline stages, which must match
    /// `stages`. If there are two bytes of storage that are accessible by
    /// different sets of pipeline stages - say, one is accessible by fragment
    /// shaders, and the other is accessible by both fragment shaders and vertex
    /// shaders - then no single `set_push_constants` call may affect both of
    /// them; to write both, you must make multiple calls, each with the
    /// appropriate `stages` value.
    ///
    /// Which pipeline stages may access a given byte is determined by the
    /// pipeline's [`PushConstant`] global variable and (if it is a struct) its
    /// members' offsets.
    ///
    /// For example, suppose you have twelve bytes of push constant storage,
    /// where bytes `0..8` are accessed by the vertex shader, and bytes `4..12`
    /// are accessed by the fragment shader. This means there are three byte
    /// ranges each accessed by a different set of stages:
    ///
    /// - Bytes `0..4` are accessed only by the fragment shader.
    ///
    /// - Bytes `4..8` are accessed by both the fragment shader and the vertex shader.
    ///
    /// - Bytes `8..12` are accessed only by the vertex shader.
    ///
    /// To write all twelve bytes requires three `set_push_constants` calls, one
    /// for each range, each passing the matching `stages` mask.
    ///
    /// [`PushConstant`]: https://docs.rs/naga/latest/naga/enum.StorageClass.html#variant.PushConstant
    pub fn set_push_constants(&mut self, stages: ShaderStages, offset: u32, data: &[u8]) {
        DynContext::render_pass_set_push_constants(
            &*self.inner.context,
            self.inner.data.as_mut(),
            stages,
            offset,
            data,
        );
    }
}

/// [`Features::TIMESTAMP_QUERY_INSIDE_PASSES`] must be enabled on the device in order to call these functions.
impl<'encoder> RenderPass<'encoder> {
    /// Issue a timestamp command at this point in the queue. The
    /// timestamp will be written to the specified query set, at the specified index.
    ///
    /// Must be multiplied by [`Queue::get_timestamp_period`] to get
    /// the value in nanoseconds. Absolute values have no meaning,
    /// but timestamps can be subtracted to get the time it takes
    /// for a string of operations to complete.
    pub fn write_timestamp(&mut self, query_set: &QuerySet, query_index: u32) {
        DynContext::render_pass_write_timestamp(
            &*self.inner.context,
            self.inner.data.as_mut(),
            query_set.data.as_ref(),
            query_index,
        )
    }
}

impl<'encoder> RenderPass<'encoder> {
    /// Start a occlusion query on this render pass. It can be ended with
    /// `end_occlusion_query`. Occlusion queries may not be nested.
    pub fn begin_occlusion_query(&mut self, query_index: u32) {
        DynContext::render_pass_begin_occlusion_query(
            &*self.inner.context,
            self.inner.data.as_mut(),
            query_index,
        );
    }

    /// End the occlusion query on this render pass. It can be started with
    /// `begin_occlusion_query`. Occlusion queries may not be nested.
    pub fn end_occlusion_query(&mut self) {
        DynContext::render_pass_end_occlusion_query(&*self.inner.context, self.inner.data.as_mut());
    }
}

/// [`Features::PIPELINE_STATISTICS_QUERY`] must be enabled on the device in order to call these functions.
impl<'encoder> RenderPass<'encoder> {
    /// Start a pipeline statistics query on this render pass. It can be ended with
    /// `end_pipeline_statistics_query`. Pipeline statistics queries may not be nested.
    pub fn begin_pipeline_statistics_query(&mut self, query_set: &QuerySet, query_index: u32) {
        DynContext::render_pass_begin_pipeline_statistics_query(
            &*self.inner.context,
            self.inner.data.as_mut(),
            query_set.data.as_ref(),
            query_index,
        );
    }

    /// End the pipeline statistics query on this render pass. It can be started with
    /// `begin_pipeline_statistics_query`. Pipeline statistics queries may not be nested.
    pub fn end_pipeline_statistics_query(&mut self) {
        DynContext::render_pass_end_pipeline_statistics_query(
            &*self.inner.context,
            self.inner.data.as_mut(),
        );
    }
}

/// Operation to perform to the output attachment at the start of a render pass.
///
/// Corresponds to [WebGPU `GPULoadOp`](https://gpuweb.github.io/gpuweb/#enumdef-gpuloadop),
/// plus the corresponding clearValue.
#[derive(Copy, Clone, Debug, Hash, Eq, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum LoadOp<V> {
    /// Loads the specified value for this attachment into the render pass.
    ///
    /// On some GPU hardware (primarily mobile), "clear" is significantly cheaper
    /// because it avoids loading data from main memory into tile-local memory.
    ///
    /// On other GPU hardware, there isn’t a significant difference.
    ///
    /// As a result, it is recommended to use "clear" rather than "load" in cases
    /// where the initial value doesn’t matter
    /// (e.g. the render target will be cleared using a skybox).
    Clear(V),
    /// Loads the existing value for this attachment into the render pass.
    Load,
}

impl<V: Default> Default for LoadOp<V> {
    fn default() -> Self {
        Self::Clear(Default::default())
    }
}

/// Operation to perform to the output attachment at the end of a render pass.
///
/// Corresponds to [WebGPU `GPUStoreOp`](https://gpuweb.github.io/gpuweb/#enumdef-gpustoreop).
#[derive(Copy, Clone, Debug, Hash, Eq, PartialEq, Default)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum StoreOp {
    /// Stores the resulting value of the render pass for this attachment.
    #[default]
    Store,
    /// Discards the resulting value of the render pass for this attachment.
    ///
    /// The attachment will be treated as uninitialized afterwards.
    /// (If only either Depth or Stencil texture-aspects is set to `Discard`,
    /// the respective other texture-aspect will be preserved.)
    ///
    /// This can be significantly faster on tile-based render hardware.
    ///
    /// Prefer this if the attachment is not read by subsequent passes.
    Discard,
}

/// Pair of load and store operations for an attachment aspect.
///
/// This type is unique to the Rust API of `wgpu`. In the WebGPU specification,
/// separate `loadOp` and `storeOp` fields are used instead.
#[derive(Copy, Clone, Debug, Hash, Eq, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Operations<V> {
    /// How data should be read through this attachment.
    pub load: LoadOp<V>,
    /// Whether data will be written to through this attachment.
    ///
    /// Note that resolve textures (if specified) are always written to,
    /// regardless of this setting.
    pub store: StoreOp,
}

impl<V: Default> Default for Operations<V> {
    #[inline]
    fn default() -> Self {
        Self {
            load: LoadOp::<V>::default(),
            store: StoreOp::default(),
        }
    }
}

/// Describes the timestamp writes of a render pass.
///
/// For use with [`RenderPassDescriptor`].
/// At least one of `beginning_of_pass_write_index` and `end_of_pass_write_index` must be `Some`.
///
/// Corresponds to [WebGPU `GPURenderPassTimestampWrite`](
/// https://gpuweb.github.io/gpuweb/#dictdef-gpurenderpasstimestampwrites).
#[derive(Clone, Debug)]
pub struct RenderPassTimestampWrites<'a> {
    /// The query set to write to.
    pub query_set: &'a QuerySet,
    /// The index of the query set at which a start timestamp of this pass is written, if any.
    pub beginning_of_pass_write_index: Option<u32>,
    /// The index of the query set at which an end timestamp of this pass is written, if any.
    pub end_of_pass_write_index: Option<u32>,
}
#[cfg(send_sync)]
static_assertions::assert_impl_all!(RenderPassTimestampWrites<'_>: Send, Sync);

/// Describes a color attachment to a [`RenderPass`].
///
/// For use with [`RenderPassDescriptor`].
///
/// Corresponds to [WebGPU `GPURenderPassColorAttachment`](
/// https://gpuweb.github.io/gpuweb/#color-attachments).
#[derive(Clone, Debug)]
pub struct RenderPassColorAttachment<'tex> {
    /// The view to use as an attachment.
    pub view: &'tex TextureView,
    /// The view that will receive the resolved output if multisampling is used.
    ///
    /// If set, it is always written to, regardless of how [`Self::ops`] is configured.
    pub resolve_target: Option<&'tex TextureView>,
    /// What operations will be performed on this color attachment.
    pub ops: Operations<Color>,
}
#[cfg(send_sync)]
static_assertions::assert_impl_all!(RenderPassColorAttachment<'_>: Send, Sync);

/// Describes a depth/stencil attachment to a [`RenderPass`].
///
/// For use with [`RenderPassDescriptor`].
///
/// Corresponds to [WebGPU `GPURenderPassDepthStencilAttachment`](
/// https://gpuweb.github.io/gpuweb/#depth-stencil-attachments).
#[derive(Clone, Debug)]
pub struct RenderPassDepthStencilAttachment<'tex> {
    /// The view to use as an attachment.
    pub view: &'tex TextureView,
    /// What operations will be performed on the depth part of the attachment.
    pub depth_ops: Option<Operations<f32>>,
    /// What operations will be performed on the stencil part of the attachment.
    pub stencil_ops: Option<Operations<u32>>,
}
#[cfg(send_sync)]
static_assertions::assert_impl_all!(RenderPassDepthStencilAttachment<'_>: Send, Sync);

/// Describes the attachments of a render pass.
///
/// For use with [`CommandEncoder::begin_render_pass`].
///
/// Corresponds to [WebGPU `GPURenderPassDescriptor`](
/// https://gpuweb.github.io/gpuweb/#dictdef-gpurenderpassdescriptor).
#[derive(Clone, Debug, Default)]
pub struct RenderPassDescriptor<'a> {
    /// Debug label of the render pass. This will show up in graphics debuggers for easy identification.
    pub label: Label<'a>,
    /// The color attachments of the render pass.
    pub color_attachments: &'a [Option<RenderPassColorAttachment<'a>>],
    /// The depth and stencil attachment of the render pass, if any.
    pub depth_stencil_attachment: Option<RenderPassDepthStencilAttachment<'a>>,
    /// Defines which timestamp values will be written for this pass, and where to write them to.
    ///
    /// Requires [`Features::TIMESTAMP_QUERY`] to be enabled.
    pub timestamp_writes: Option<RenderPassTimestampWrites<'a>>,
    /// Defines where the occlusion query results will be stored for this pass.
    pub occlusion_query_set: Option<&'a QuerySet>,
}
#[cfg(send_sync)]
static_assertions::assert_impl_all!(RenderPassDescriptor<'_>: Send, Sync);