/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

use crate::{
    binding_model::{CreateBindGroupLayoutError, CreatePipelineLayoutError},
    device::{DeviceError, RenderPassContext},
    hub::Resource,
    id::{DeviceId, PipelineLayoutId, ShaderModuleId},
    validation, Label, LifeGuard, Stored,
};
use std::borrow::Cow;
use thiserror::Error;

#[derive(Debug)]
pub enum ShaderModuleSource<'a> {
    SpirV(Cow<'a, [u32]>),
    Wgsl(Cow<'a, str>),
    Naga(naga::Module),
}

#[derive(Clone, Debug)]
#[cfg_attr(feature = "trace", derive(serde::Serialize))]
#[cfg_attr(feature = "replay", derive(serde::Deserialize))]
pub struct ShaderModuleDescriptor<'a> {
    pub label: Label<'a>,
    #[cfg_attr(any(feature = "replay", feature = "trace"), serde(default))]
    pub flags: wgt::ShaderFlags,
}

#[derive(Debug)]
pub struct ShaderModule<B: hal::Backend> {
    pub(crate) raw: B::ShaderModule,
    pub(crate) device_id: Stored<DeviceId>,
    pub(crate) interface: Option<validation::Interface>,
    #[cfg(debug_assertions)]
    pub(crate) label: String,
}

impl<B: hal::Backend> Resource for ShaderModule<B> {
    const TYPE: &'static str = "ShaderModule";

    fn life_guard(&self) -> &LifeGuard {
        unreachable!()
    }

    fn label(&self) -> &str {
        #[cfg(debug_assertions)]
        return &self.label;
        #[cfg(not(debug_assertions))]
        return "";
    }
}

#[derive(Clone, Debug, Error)]
pub enum CreateShaderModuleError {
    #[error("Failed to parse WGSL")]
    Parsing,
    #[error(transparent)]
    Device(#[from] DeviceError),
    #[error(transparent)]
    Validation(#[from] naga::proc::ValidationError),
}

/// Describes a programmable pipeline stage.
#[derive(Clone, Debug)]
#[cfg_attr(feature = "trace", derive(serde::Serialize))]
#[cfg_attr(feature = "replay", derive(serde::Deserialize))]
pub struct ProgrammableStageDescriptor<'a> {
    /// The compiled shader module for this stage.
    pub module: ShaderModuleId,
    /// The name of the entry point in the compiled shader. There must be a function that returns
    /// void with this name in the shader.
    pub entry_point: Cow<'a, str>,
}

/// Number of implicit bind groups derived at pipeline creation.
pub type ImplicitBindGroupCount = u8;

#[derive(Clone, Debug, Error)]
pub enum ImplicitLayoutError {
    #[error("missing IDs for deriving {0} bind groups")]
    MissingIds(ImplicitBindGroupCount),
    #[error("unable to reflect the shader {0:?} interface")]
    ReflectionError(wgt::ShaderStage),
    #[error(transparent)]
    BindGroup(#[from] CreateBindGroupLayoutError),
    #[error(transparent)]
    Pipeline(#[from] CreatePipelineLayoutError),
}

/// Describes a compute pipeline.
#[derive(Clone, Debug)]
#[cfg_attr(feature = "trace", derive(serde::Serialize))]
#[cfg_attr(feature = "replay", derive(serde::Deserialize))]
pub struct ComputePipelineDescriptor<'a> {
    pub label: Label<'a>,
    /// The layout of bind groups for this pipeline.
    pub layout: Option<PipelineLayoutId>,
    /// The compiled compute stage and its entry point.
    pub stage: ProgrammableStageDescriptor<'a>,
}

#[derive(Clone, Debug, Error)]
pub enum CreateComputePipelineError {
    #[error(transparent)]
    Device(#[from] DeviceError),
    #[error("pipeline layout is invalid")]
    InvalidLayout,
    #[error("unable to derive an implicit layout")]
    Implicit(#[from] ImplicitLayoutError),
    #[error(transparent)]
    Stage(validation::StageError),
}

#[derive(Debug)]
pub struct ComputePipeline<B: hal::Backend> {
    pub(crate) raw: B::ComputePipeline,
    pub(crate) layout_id: Stored<PipelineLayoutId>,
    pub(crate) device_id: Stored<DeviceId>,
    pub(crate) life_guard: LifeGuard,
}

impl<B: hal::Backend> Resource for ComputePipeline<B> {
    const TYPE: &'static str = "ComputePipeline";

    fn life_guard(&self) -> &LifeGuard {
        &self.life_guard
    }
}

/// Describes how the vertex buffer is interpreted.
#[derive(Clone, Debug)]
#[cfg_attr(feature = "trace", derive(serde::Serialize))]
#[cfg_attr(feature = "replay", derive(serde::Deserialize))]
pub struct VertexBufferLayout<'a> {
    /// The stride, in bytes, between elements of this buffer.
    pub array_stride: wgt::BufferAddress,
    /// How often this vertex buffer is "stepped" forward.
    pub step_mode: wgt::InputStepMode,
    /// The list of attributes which comprise a single vertex.
    pub attributes: Cow<'a, [wgt::VertexAttribute]>,
}

/// Describes the vertex process in a render pipeline.
#[derive(Clone, Debug)]
#[cfg_attr(feature = "trace", derive(serde::Serialize))]
#[cfg_attr(feature = "replay", derive(serde::Deserialize))]
pub struct VertexState<'a> {
    /// The compiled vertex stage and its entry point.
    pub stage: ProgrammableStageDescriptor<'a>,
    /// The format of any vertex buffers used with this pipeline.
    pub buffers: Cow<'a, [VertexBufferLayout<'a>]>,
}

/// Describes fragment processing in a render pipeline.
#[derive(Clone, Debug)]
#[cfg_attr(feature = "trace", derive(serde::Serialize))]
#[cfg_attr(feature = "replay", derive(serde::Deserialize))]
pub struct FragmentState<'a> {
    /// The compiled fragment stage and its entry point.
    pub stage: ProgrammableStageDescriptor<'a>,
    /// The effect of draw calls on the color aspect of the output target.
    pub targets: Cow<'a, [wgt::ColorTargetState]>,
}

/// Describes a render (graphics) pipeline.
#[derive(Clone, Debug)]
#[cfg_attr(feature = "trace", derive(serde::Serialize))]
#[cfg_attr(feature = "replay", derive(serde::Deserialize))]
pub struct RenderPipelineDescriptor<'a> {
    pub label: Label<'a>,
    /// The layout of bind groups for this pipeline.
    pub layout: Option<PipelineLayoutId>,
    /// The vertex processing state for this pipeline.
    pub vertex: VertexState<'a>,
    /// The properties of the pipeline at the primitive assembly and rasterization level.
    #[cfg_attr(any(feature = "replay", feature = "trace"), serde(default))]
    pub primitive: wgt::PrimitiveState,
    /// The effect of draw calls on the depth and stencil aspects of the output target, if any.
    #[cfg_attr(any(feature = "replay", feature = "trace"), serde(default))]
    pub depth_stencil: Option<wgt::DepthStencilState>,
    /// The multi-sampling properties of the pipeline.
    #[cfg_attr(any(feature = "replay", feature = "trace"), serde(default))]
    pub multisample: wgt::MultisampleState,
    /// The fragment processing state for this pipeline.
    pub fragment: Option<FragmentState<'a>>,
}

#[derive(Clone, Debug, Error)]
pub enum CreateRenderPipelineError {
    #[error(transparent)]
    Device(#[from] DeviceError),
    #[error("pipelie layout is invalid")]
    InvalidLayout,
    #[error("unable to derive an implicit layout")]
    Implicit(#[from] ImplicitLayoutError),
    #[error("missing output at index {index}")]
    MissingOutput { index: u8 },
    #[error("incompatible output format at index {index}")]
    IncompatibleOutputFormat { index: u8 },
    #[error("invalid sample count {0}")]
    InvalidSampleCount(u32),
    #[error("vertex buffer {index} stride {stride} does not respect `VERTEX_STRIDE_ALIGNMENT`")]
    UnalignedVertexStride {
        index: u32,
        stride: wgt::BufferAddress,
    },
    #[error("vertex attribute at location {location} has invalid offset {offset}")]
    InvalidVertexAttributeOffset {
        location: wgt::ShaderLocation,
        offset: wgt::BufferAddress,
    },
    #[error("missing required device features {0:?}")]
    MissingFeature(wgt::Features),
    #[error("error in stage {flag:?}")]
    Stage {
        flag: wgt::ShaderStage,
        #[source]
        error: validation::StageError,
    },
}

bitflags::bitflags! {
    #[repr(transparent)]
    pub struct PipelineFlags: u32 {
        const BLEND_COLOR = 1;
        const STENCIL_REFERENCE = 2;
        const WRITES_DEPTH_STENCIL = 4;
    }
}

#[derive(Debug)]
pub struct RenderPipeline<B: hal::Backend> {
    pub(crate) raw: B::GraphicsPipeline,
    pub(crate) layout_id: Stored<PipelineLayoutId>,
    pub(crate) device_id: Stored<DeviceId>,
    pub(crate) pass_context: RenderPassContext,
    pub(crate) flags: PipelineFlags,
    pub(crate) strip_index_format: Option<wgt::IndexFormat>,
    pub(crate) vertex_strides: Vec<(wgt::BufferAddress, wgt::InputStepMode)>,
    pub(crate) life_guard: LifeGuard,
}

impl<B: hal::Backend> Resource for RenderPipeline<B> {
    const TYPE: &'static str = "RenderPipeline";

    fn life_guard(&self) -> &LifeGuard {
        &self.life_guard
    }
}