// Copyright 2014 The Gfx-rs Developers.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Command Buffer device interface

use std::ops::Deref;
use std::collections::hash_set::{self, HashSet};
use {Resources, IndexType, InstanceCount, VertexCount,
     SubmissionResult, SubmissionError};
use {state, target, pso, shade, texture, handle};

/// A universal clear color supporting integet formats
/// as well as the standard floating-point.
#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
#[cfg_attr(feature = "serialize", derive(Serialize, Deserialize))]
pub enum ClearColor {
    /// Standard floating-point vec4 color
    Float([f32; 4]),
    /// Integer vector to clear ivec4 targets.
    Int([i32; 4]),
    /// Unsigned int vector to clear uvec4 targets.
    Uint([u32; 4]),
}

/// Optional instance parameters: (instance count, buffer offset)
pub type InstanceParams = (InstanceCount, VertexCount);

/// An interface of the abstract command buffer. It collects commands in an
/// efficient API-specific manner, to be ready for execution on the device.
#[allow(missing_docs)]
pub trait Buffer<R: Resources>: 'static + Send {
    /// Reset the command buffer contents, retain the allocated storage
    fn reset(&mut self);
    /// Bind a pipeline state object
    fn bind_pipeline_state(&mut self, R::PipelineStateObject);
    /// Bind a complete set of vertex buffers
    fn bind_vertex_buffers(&mut self, pso::VertexBufferSet<R>);
    /// Bind a complete set of constant buffers
    fn bind_constant_buffers(&mut self, &[pso::ConstantBufferParam<R>]);
    /// Bind a global constant
    fn bind_global_constant(&mut self, shade::Location, shade::UniformValue);
    /// Bind a complete set of shader resource views
    fn bind_resource_views(&mut self, &[pso::ResourceViewParam<R>]);
    /// Bind a complete set of unordered access views
    fn bind_unordered_views(&mut self, &[pso::UnorderedViewParam<R>]);
    /// Bind a complete set of samplers
    fn bind_samplers(&mut self, &[pso::SamplerParam<R>]);
    /// Bind a complete set of pixel targets, including multiple
    /// colors views and an optional depth/stencil view.
    fn bind_pixel_targets(&mut self, pso::PixelTargetSet<R>);
    /// Bind an index buffer
    fn bind_index(&mut self, R::Buffer, IndexType);
    /// Set scissor rectangle
    fn set_scissor(&mut self, target::Rect);
    /// Set reference values for the blending and stencil front/back
    fn set_ref_values(&mut self, state::RefValues);
    /// Copy part of a buffer to another
    fn copy_buffer(&mut self, src: R::Buffer, dst: R::Buffer,
                   src_offset_bytes: usize, dst_offset_bytes: usize,
                   size_bytes: usize);
    /// Copy part of a buffer to a texture
    fn copy_buffer_to_texture(&mut self,
                              src: R::Buffer, src_offset_bytes: usize,
                              dst: texture::TextureCopyRegion<R::Texture>);
    /// Copy part of a texture to a buffer
    fn copy_texture_to_buffer(&mut self,
                              src: texture::TextureCopyRegion<R::Texture>,
                              dst: R::Buffer, dst_offset_bytes: usize);
    /// Copy part of one texture into another
    fn copy_texture_to_texture(&mut self,
                               src: texture::TextureCopyRegion<R::Texture>,
                               dst: texture::TextureCopyRegion<R::Texture>);
    /// Update a vertex/index/uniform buffer
    fn update_buffer(&mut self, R::Buffer, data: &[u8], offset: usize);
    /// Update a texture
    fn update_texture(&mut self, texture::TextureCopyRegion<R::Texture>, data: &[u8]);
    fn generate_mipmap(&mut self, R::ShaderResourceView);
    /// Clear color target
    fn clear_color(&mut self, R::RenderTargetView, ClearColor);
    fn clear_depth_stencil(&mut self, R::DepthStencilView,
                           Option<target::Depth>, Option<target::Stencil>);
    /// Draw a primitive
    fn call_draw(&mut self, VertexCount, VertexCount, Option<InstanceParams>);
    /// Draw a primitive with index buffer
    fn call_draw_indexed(&mut self, VertexCount, VertexCount, VertexCount, Option<InstanceParams>);
}

macro_rules! impl_clear {
    { $( $ty:ty = $sub:ident[$a:expr, $b:expr, $c:expr, $d:expr], )* } => {
        $(
            impl From<$ty> for ClearColor {
                fn from(v: $ty) -> ClearColor {
                    ClearColor::$sub([v[$a], v[$b], v[$c], v[$d]])
                }
            }
        )*
    }
}

impl_clear! {
    [f32; 4] = Float[0, 1, 2, 3],
    [f32; 3] = Float[0, 1, 2, 0],
    [f32; 2] = Float[0, 1, 0, 0],
    [i32; 4] = Int  [0, 1, 2, 3],
    [i32; 3] = Int  [0, 1, 2, 0],
    [i32; 2] = Int  [0, 1, 0, 0],
    [u32; 4] = Uint [0, 1, 2, 3],
    [u32; 3] = Uint [0, 1, 2, 0],
    [u32; 2] = Uint [0, 1, 0, 0],
}

impl From<f32> for ClearColor {
    fn from(v: f32) -> Self {
        ClearColor::Float([v, 0.0, 0.0, 0.0])
    }
}
impl From<i32> for ClearColor {
    fn from(v: i32) -> Self {
        ClearColor::Int([v, 0, 0, 0])
    }
}
impl From<u32> for ClearColor {
    fn from(v: u32) -> Self {
        ClearColor::Uint([v, 0, 0, 0])
    }
}

/// Informations about what is accessed by a bunch of commands.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct AccessInfo<R: Resources> {
    mapped_reads: HashSet<handle::RawBuffer<R>>,
    mapped_writes: HashSet<handle::RawBuffer<R>>,
}

impl<R: Resources> AccessInfo<R> {
    /// Creates empty access informations
    pub fn new() -> Self {
        AccessInfo {
            mapped_reads: HashSet::new(),
            mapped_writes: HashSet::new(),
        }
    }

    /// Clear access informations
    pub fn clear(&mut self) {
        self.mapped_reads.clear();
        self.mapped_writes.clear();
    }

    /// Register a buffer read access
    pub fn buffer_read(&mut self, buffer: &handle::RawBuffer<R>) {
        if buffer.is_mapped() {
            self.mapped_reads.insert(buffer.clone());
        }
    }

    /// Register a buffer write access
    pub fn buffer_write(&mut self, buffer: &handle::RawBuffer<R>) {
        if buffer.is_mapped() {
            self.mapped_writes.insert(buffer.clone());
        }
    }

    /// Returns the mapped buffers that The GPU will read from
    pub fn mapped_reads(&self) -> AccessInfoBuffers<R> {
        self.mapped_reads.iter()
    }

    /// Returns the mapped buffers that The GPU will write to
    pub fn mapped_writes(&self) -> AccessInfoBuffers<R> {
        self.mapped_writes.iter()
    }

    /// Is there any mapped buffer reads ?
    pub fn has_mapped_reads(&self) -> bool {
        !self.mapped_reads.is_empty()
    }

    /// Is there any mapped buffer writes ?
    pub fn has_mapped_writes(&self) -> bool {
        !self.mapped_writes.is_empty()
    }

    /// Takes all the accesses necessary for submission
    pub fn take_accesses(&self) -> SubmissionResult<AccessGuard<R>> {
        for buffer in self.mapped_reads().chain(self.mapped_writes()) {
            unsafe {
                if !buffer.mapping().unwrap().take_access() {
                    return Err(SubmissionError::AccessOverlap);
                }
            }
        }
        Ok(AccessGuard { inner: self })
    }
}

#[allow(missing_docs)]
pub type AccessInfoBuffers<'a, R> = hash_set::Iter<'a, handle::RawBuffer<R>>;

#[allow(missing_docs)]
#[derive(Debug)]
pub struct AccessGuard<'a, R: Resources> {
    inner: &'a AccessInfo<R>,
}

#[allow(missing_docs)]
impl<'a, R: Resources> AccessGuard<'a, R> {
    /// Returns the mapped buffers that The GPU will read from,
    /// with exclusive acces to their mapping
    pub fn access_mapped_reads(&mut self) -> AccessGuardBuffers<R> {
        AccessGuardBuffers {
            buffers: self.inner.mapped_reads()
        }
    }

    /// Returns the mapped buffers that The GPU will write to,
    /// with exclusive acces to their mapping
    pub fn access_mapped_writes(&mut self) -> AccessGuardBuffers<R> {
        AccessGuardBuffers {
            buffers: self.inner.mapped_writes()
        }
    }

    pub fn access_mapped(&mut self) -> AccessGuardBuffersChain<R> {
        AccessGuardBuffersChain {
            fst: self.inner.mapped_reads(),
            snd: self.inner.mapped_writes(),
        }
    }
}

impl<'a, R: Resources> Deref for AccessGuard<'a, R> {
    type Target = AccessInfo<R>;
    fn deref(&self) -> &Self::Target {
        &self.inner
    }
}

impl<'a, R: Resources> Drop for AccessGuard<'a, R> {
    fn drop(&mut self) {
        for buffer in self.inner.mapped_reads().chain(self.inner.mapped_writes()) {
            unsafe {
                buffer.mapping().unwrap().release_access();
            }
        }
    }
}

#[allow(missing_docs)]
#[derive(Debug)]
pub struct AccessGuardBuffers<'a, R: Resources> {
    buffers: AccessInfoBuffers<'a, R>
}

impl<'a, R: Resources> Iterator for AccessGuardBuffers<'a, R> {
    type Item = (&'a handle::RawBuffer<R>, &'a mut R::Mapping);

    fn next(&mut self) -> Option<Self::Item> {
        self.buffers.next().map(|buffer| unsafe {
            (buffer, buffer.mapping().unwrap().use_access())
        })
    }
}

#[allow(missing_docs)]
#[derive(Debug)]
pub struct AccessGuardBuffersChain<'a, R: Resources> {
    fst: AccessInfoBuffers<'a, R>,
    snd: AccessInfoBuffers<'a, R>
}

impl<'a, R: Resources> Iterator for AccessGuardBuffersChain<'a, R> {
    type Item = (&'a handle::RawBuffer<R>, &'a mut R::Mapping);

    fn next(&mut self) -> Option<Self::Item> {
        self.fst.next().or_else(|| self.snd.next())
            .map(|buffer| unsafe {
                (buffer, buffer.mapping().unwrap().use_access())
            })
    }
}