// 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.

//! Factory extension.
//!
//! This module serves as an extension to the `factory` module in the `gfx` crate. This module
//! exposes extension functions and shortcuts to aid with creating and managing graphics resources.
//! See the `FactoryExt` trait for more information.

use std::error::Error;
use std::fmt;
use core::{buffer, format, handle, texture, state};
use core::{Primitive, Resources, ShaderSet};
use core::factory::Factory;
use core::pso::{CreationError, Descriptor};
use core::memory::{Bind, Pod, Usage};
use slice::{Slice, IndexBuffer, IntoIndexBuffer};
use pso;
use shade::ProgramError;

/// Error creating a PipelineState
#[derive(Clone, PartialEq, Debug)]
pub enum PipelineStateError<S> {
    /// Shader program failed to link.
    Program(ProgramError),
    /// Unable to create PSO descriptor due to mismatched formats.
    DescriptorInit(pso::InitError<S>),
    /// Device failed to create the handle give the descriptor.
    DeviceCreate(CreationError),
}

impl<'a> From<PipelineStateError<&'a str>> for PipelineStateError<String> {
    fn from(pse: PipelineStateError<&'a str>) -> PipelineStateError<String> {
        match pse {
            PipelineStateError::Program(e) => PipelineStateError::Program(e),
            PipelineStateError::DescriptorInit(e) => PipelineStateError::DescriptorInit(e.into()),
            PipelineStateError::DeviceCreate(e) => PipelineStateError::DeviceCreate(e),
        }
    }
}

impl<S: fmt::Debug + fmt::Display> fmt::Display for PipelineStateError<S> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            PipelineStateError::Program(ref e) => write!(f, "{}: {}", self.description(), e),
            PipelineStateError::DescriptorInit(ref e) => write!(f, "{}: {}", self.description(), e),
            PipelineStateError::DeviceCreate(ref e) => write!(f, "{}: {}", self.description(), e),
        }
    }
}

impl<S: fmt::Debug + fmt::Display> Error for PipelineStateError<S> {
    fn description(&self) -> &str {
        match *self {
            PipelineStateError::Program(_) => "Shader program failed to link",
            PipelineStateError::DescriptorInit(_) =>
                "Unable to create PSO descriptor due to mismatched formats",
            PipelineStateError::DeviceCreate(_) => "Device failed to create the handle give the descriptor",
        }
    }

    fn cause(&self) -> Option<&dyn Error> {
        match *self {
            PipelineStateError::Program(ref program_error) => Some(program_error),
            PipelineStateError::DescriptorInit(ref init_error) => Some(init_error),
            PipelineStateError::DeviceCreate(ref creation_error) => Some(creation_error),
        }
    }
}

impl<S> From<ProgramError> for PipelineStateError<S> {
    fn from(e: ProgramError) -> Self {
        PipelineStateError::Program(e)
    }
}

impl<S> From<pso::InitError<S>> for PipelineStateError<S> {
    fn from(e: pso::InitError<S>) -> Self {
        PipelineStateError::DescriptorInit(e)
    }
}

impl<S> From<CreationError> for PipelineStateError<S> {
    fn from(e: CreationError) -> Self {
        PipelineStateError::DeviceCreate(e)
    }
}

/// This trait is responsible for creating and managing graphics resources, much like the `Factory`
/// trait in the `gfx` crate. Every `Factory` automatically implements `FactoryExt`.
pub trait FactoryExt<R: Resources>: Factory<R> {
    /// Creates an immutable vertex buffer from the supplied vertices.
    /// A `Slice` will have to manually be constructed.
    fn create_vertex_buffer<T>(&mut self, vertices: &[T])
                               -> handle::Buffer<R, T>
        where T: Pod + pso::buffer::Structure<format::Format>
    {
        //debug_assert!(nv <= self.get_capabilities().max_vertex_count);
        self.create_buffer_immutable(vertices, buffer::Role::Vertex, Bind::empty())
            .unwrap()
    }

    /// Creates an immutable index buffer from the supplied vertices.
    ///
    /// The paramater `indices` is typically a &[u16] or &[u32] slice.
    fn create_index_buffer<T>(&mut self, indices: T)
                              -> IndexBuffer<R>
        where T: IntoIndexBuffer<R>
    {
        indices.into_index_buffer(self)
    }

    /// Creates an immutable vertex buffer from the supplied vertices,
    /// together with a `Slice` from the supplied indices.
    fn create_vertex_buffer_with_slice<B, V>(&mut self, vertices: &[V], indices: B)
                                             -> (handle::Buffer<R, V>, Slice<R>)
        where V: Pod + pso::buffer::Structure<format::Format>,
              B: IntoIndexBuffer<R>
    {
        let vertex_buffer = self.create_vertex_buffer(vertices);
        let index_buffer = self.create_index_buffer(indices);
        let buffer_length = match index_buffer {
            IndexBuffer::Auto => vertex_buffer.len(),
            IndexBuffer::Index16(ref ib) => ib.len(),
            IndexBuffer::Index32(ref ib) => ib.len(),
        };

        (vertex_buffer, Slice {
            start: 0,
            end: buffer_length as u32,
            base_vertex: 0,
            instances: None,
            buffer: index_buffer
        })
    }

    /// Creates a constant buffer for `num` identical elements of type `T`.
    fn create_constant_buffer<T>(&mut self, num: usize) -> handle::Buffer<R, T>
        where T: Copy
    {
        self.create_buffer(num,
                           buffer::Role::Constant,
                           Usage::Dynamic,
                           Bind::empty()).unwrap()
    }

    /// Creates an upload buffer for `num` elements of type `T`.
    fn create_upload_buffer<T>(&mut self, num: usize)
                               -> Result<handle::Buffer<R, T>, buffer::CreationError>
    {
        self.create_buffer(num,
                           buffer::Role::Staging,
                           Usage::Upload,
                           Bind::TRANSFER_SRC)
    }

    /// Creates a download buffer for `num` elements of type `T`.
    fn create_download_buffer<T>(&mut self, num: usize)
                                 -> Result<handle::Buffer<R, T>, buffer::CreationError>
    {
        self.create_buffer(num,
                           buffer::Role::Staging,
                           Usage::Download,
                           Bind::TRANSFER_DST)
    }

    /// Creates a `ShaderSet` from the supplied vertex and pixel shader source code.
    fn create_shader_set(&mut self, vs_code: &[u8], ps_code: &[u8])
                         -> Result<ShaderSet<R>, ProgramError> {
        let vs = self.create_shader_vertex(vs_code).map_err(ProgramError::Vertex)?;
        let ps = self.create_shader_pixel(ps_code).map_err(ProgramError::Pixel)?;
        Ok(ShaderSet::Simple(vs, ps))
    }

    /// Creates a `ShaderSet` from the supplied vertex, geometry, and pixel
    /// shader source code. Mainly used for testing.
    fn create_shader_set_geometry(&mut self, vs_code: &[u8], gs_code: &[u8], ps_code: &[u8])
                         -> Result<ShaderSet<R>, ProgramError> {
        let vs = self.create_shader_vertex(vs_code).map_err(ProgramError::Vertex)?;
        let gs = self.create_shader_geometry(gs_code).map_err(ProgramError::Geometry)?;
        let ps = self.create_shader_pixel(ps_code).map_err(ProgramError::Pixel)?;
        Ok(ShaderSet::Geometry(vs, gs, ps))
    }

    /// Creates a `ShaderSet` from the supplied vertex, hull, domain, and pixel
    /// shader source code. Mainly used for testing.
    fn create_shader_set_tessellation(&mut self, vs_code: &[u8], hs_code: &[u8], ds_code: &[u8], ps_code: &[u8])
                         -> Result<ShaderSet<R>, ProgramError> {
        let vs = self.create_shader_vertex(vs_code).map_err(ProgramError::Vertex)?;
        let hs = self.create_shader_hull(hs_code).map_err(ProgramError::Hull)?;
        let ds = self.create_shader_domain(ds_code).map_err(ProgramError::Domain)?;
        let ps = self.create_shader_pixel(ps_code).map_err(ProgramError::Pixel)?;
        Ok(ShaderSet::Tessellated(vs, hs, ds, ps))
    }

    /// Creates a `ShaderSet` from the supplied vertex, hull, domain, geometry and pixel
    /// shader source code. Mainly used for testing.
    fn create_shader_set_tessellation_with_geometry(&mut self, vs_code: &[u8], hs_code: &[u8], ds_code: &[u8], gs_code: &[u8], ps_code: &[u8])
                         -> Result<ShaderSet<R>, ProgramError> {
        let vs = self.create_shader_vertex(vs_code).map_err(ProgramError::Vertex)?;
        let hs = self.create_shader_hull(hs_code).map_err(ProgramError::Hull)?;
        let ds = self.create_shader_domain(ds_code).map_err(ProgramError::Domain)?;
        let gs = self.create_shader_geometry(gs_code).map_err(ProgramError::Geometry)?;
        let ps = self.create_shader_pixel(ps_code).map_err(ProgramError::Pixel)?;
        Ok(ShaderSet::TessellatedGeometry(vs, hs, ds, gs, ps))
    }

    /// Creates a basic shader `Program` from the supplied vertex and pixel shader source code.
    fn link_program(&mut self, vs_code: &[u8], ps_code: &[u8])
                    -> Result<handle::Program<R>, ProgramError> {

        let set = try!(self.create_shader_set(vs_code, ps_code));
        self.create_program(&set).map_err(|e| ProgramError::Link(e))
    }

    /// Similar to `create_pipeline_from_program(..)`, but takes a `ShaderSet` as opposed to a
    /// shader `Program`.
    fn create_pipeline_state<I: pso::PipelineInit>(&mut self, shaders: &ShaderSet<R>,
                             primitive: Primitive, rasterizer: state::Rasterizer, init: I)
                             -> Result<pso::PipelineState<R, I::Meta>, PipelineStateError<String>>
    {
        let program = try!(self.create_program(shaders).map_err(|e| ProgramError::Link(e)));
        self.create_pipeline_from_program(&program, primitive, rasterizer, init).map_err(|error| {
            use self::PipelineStateError::*;
            match error {
                Program(e) => Program(e),
                DescriptorInit(e) => DescriptorInit(e.into()),
                DeviceCreate(e) => DeviceCreate(e),
            }
        })
    }

    /// Creates a strongly typed `PipelineState` from its `Init` structure, a shader `Program`, a
    /// primitive type and a `Rasterizer`.
    fn create_pipeline_from_program<'a, I: pso::PipelineInit>(&mut self, program: &'a handle::Program<R>,
                                    primitive: Primitive, rasterizer: state::Rasterizer, init: I)
                                    -> Result<pso::PipelineState<R, I::Meta>, PipelineStateError<&'a str>>
    {
        let mut descriptor = Descriptor::new(primitive, rasterizer);
        let meta = try!(init.link_to(&mut descriptor, program.get_info()));
        let raw = try!(self.create_pipeline_state_raw(program, &descriptor));

        Ok(pso::PipelineState::new(raw, primitive, meta))
    }

    /// Creates a strongly typed `PipelineState` from its `Init` structure. Automatically creates a
    /// shader `Program` from a vertex and pixel shader source, as well as a `Rasterizer` capable
    /// of rendering triangle faces without culling.
    fn create_pipeline_simple<I: pso::PipelineInit>(&mut self, vs: &[u8], ps: &[u8], init: I)
                              -> Result<pso::PipelineState<R, I::Meta>, PipelineStateError<String>>
    {
        let set = try!(self.create_shader_set(vs, ps));
        self.create_pipeline_state(&set, Primitive::TriangleList, state::Rasterizer::new_fill(),
                                   init)
    }

    /// Create a linear sampler with clamping to border.
    fn create_sampler_linear(&mut self) -> handle::Sampler<R> {
        self.create_sampler(texture::SamplerInfo::new(
            texture::FilterMethod::Trilinear,
            texture::WrapMode::Clamp,
        ))
    }
}

impl<R: Resources, F: Factory<R>> FactoryExt<R> for F {}