/*!

Handles bindless textures.




*/
use texture::any::TextureAny;
use TextureExt;
use GlObject;

use ContextExt;
use gl;

use std::marker::PhantomData;
use std::ops::{Deref, DerefMut};

use program::BlockLayout;
use uniforms::AsUniformValue;
use uniforms::LayoutMismatchError;
use uniforms::UniformBlock;
use uniforms::UniformValue;
use uniforms::UniformType;
use uniforms::SamplerBehavior;

/// A texture that is resident in video memory. This allows you to use bindless textures in your
/// shaders.
pub struct ResidentTexture {
    texture: Option<TextureAny>,
    handle: gl::types::GLuint64,
}

impl ResidentTexture {
    /// Takes ownership of the given texture and makes it resident.
    // TODO: sampler
    pub fn new(texture: TextureAny) -> Result<ResidentTexture, BindlessTexturesNotSupportedError> {
        let handle = {
            let mut ctxt = texture.get_context().make_current();

            if !ctxt.extensions.gl_arb_bindless_texture {
                return Err(BindlessTexturesNotSupportedError);
            }

            let handle = unsafe { ctxt.gl.GetTextureHandleARB(texture.get_id()) };
            unsafe { ctxt.gl.MakeTextureHandleResidentARB(handle) };
            ctxt.resident_texture_handles.push(handle);
            handle
        };

        // store the handle in the context
        Ok(ResidentTexture {
            texture: Some(texture),
            handle: handle,
        })
    }

    /// Unwraps the texture and restores it.
    pub fn into_inner(mut self) -> TextureAny {
        self.into_inner_impl()
    }

    /// Implementation of `into_inner`. Also called by the destructor.
    fn into_inner_impl(&mut self) -> TextureAny {
        let texture = self.texture.take().unwrap();

        {
            let mut ctxt = texture.get_context().make_current();
            unsafe { ctxt.gl.MakeTextureHandleNonResidentARB(self.handle) };
            ctxt.resident_texture_handles.retain(|&t| t != self.handle);
        }

        texture
    }
}

impl Deref for ResidentTexture {
    type Target = TextureAny;

    fn deref(&self) -> &TextureAny {
        self.texture.as_ref().unwrap()
    }
}

impl DerefMut for ResidentTexture {
    fn deref_mut(&mut self) -> &mut TextureAny {
        self.texture.as_mut().unwrap()
    }
}

impl Drop for ResidentTexture {
    fn drop(&mut self) {
        self.into_inner_impl();
    }
}

/// Handle to a texture.
#[derive(Copy, Clone)]
pub struct TextureHandle<'a> {
    value: gl::types::GLuint64,
    marker: PhantomData<&'a ResidentTexture>,
}

impl<'a> TextureHandle<'a> {
    /// Builds a new handle.
    pub fn new(texture: &'a ResidentTexture, _: &SamplerBehavior) -> TextureHandle<'a> {
        // FIXME: take sampler into account
        TextureHandle {
            value: texture.handle,
            marker: PhantomData,
        }
    }

    /// Sets the value to the given texture.
    pub fn set(&mut self, texture: &'a ResidentTexture, _: &SamplerBehavior) {
        // FIXME: take sampler into account
        self.value = texture.handle;
    }
}

impl<'a> AsUniformValue for TextureHandle<'a> {
    fn as_uniform_value(&self) -> UniformValue {
        // TODO: u64
        unimplemented!();
    }
}

impl<'a> UniformBlock for TextureHandle<'a> {
    fn matches(layout: &BlockLayout, base_offset: usize)
               -> Result<(), LayoutMismatchError>
    {
        if let &BlockLayout::BasicType { ty, offset_in_buffer } = layout {
            // TODO: unfortunately we have no idea what the exact type of this handle is
            //       strong typing should be considered
            //
            //       however there is no safety problem here ; the worse that can happen in case of
            //       wrong type is zeroes or undefined data being returned when sampling
            match ty {
                UniformType::Sampler1d => (),
                UniformType::ISampler1d => (),
                UniformType::USampler1d => (),
                UniformType::Sampler2d => (),
                UniformType::ISampler2d => (),
                UniformType::USampler2d => (),
                UniformType::Sampler3d => (),
                UniformType::ISampler3d => (),
                UniformType::USampler3d => (),
                UniformType::Sampler1dArray => (),
                UniformType::ISampler1dArray => (),
                UniformType::USampler1dArray => (),
                UniformType::Sampler2dArray => (),
                UniformType::ISampler2dArray => (),
                UniformType::USampler2dArray => (),
                UniformType::SamplerCube => (),
                UniformType::ISamplerCube => (),
                UniformType::USamplerCube => (),
                UniformType::Sampler2dRect => (),
                UniformType::ISampler2dRect => (),
                UniformType::USampler2dRect => (),
                UniformType::Sampler2dRectShadow => (),
                UniformType::SamplerCubeArray => (),
                UniformType::ISamplerCubeArray => (),
                UniformType::USamplerCubeArray => (),
                UniformType::SamplerBuffer => (),
                UniformType::ISamplerBuffer => (),
                UniformType::USamplerBuffer => (),
                UniformType::Sampler2dMultisample => (),
                UniformType::ISampler2dMultisample => (),
                UniformType::USampler2dMultisample => (),
                UniformType::Sampler2dMultisampleArray => (),
                UniformType::ISampler2dMultisampleArray => (),
                UniformType::USampler2dMultisampleArray => (),
                UniformType::Sampler1dShadow => (),
                UniformType::Sampler2dShadow => (),
                UniformType::SamplerCubeShadow => (),
                UniformType::Sampler1dArrayShadow => (),
                UniformType::Sampler2dArrayShadow => (),
                UniformType::SamplerCubeArrayShadow => (),

                _ => return Err(LayoutMismatchError::TypeMismatch {
                    expected: ty,
                    obtained: UniformType::Sampler2d,       // TODO: wrong
                })
            }

            if offset_in_buffer != base_offset {
                return Err(LayoutMismatchError::OffsetMismatch {
                    expected: offset_in_buffer,
                    obtained: base_offset,
                });
            }

            Ok(())

        } else if let &BlockLayout::Struct { ref members } = layout {
            if members.len() == 1 {
                <TextureHandle as UniformBlock>::matches(&members[0].1, base_offset)

            } else {
                Err(LayoutMismatchError::LayoutMismatch {
                    expected: layout.clone(),
                    obtained: BlockLayout::BasicType {
                        ty: UniformType::Sampler2d,       // TODO: wrong
                        offset_in_buffer: base_offset,
                    }
                })
            }

        } else {
            Err(LayoutMismatchError::LayoutMismatch {
                expected: layout.clone(),
                obtained: BlockLayout::BasicType {
                    ty: UniformType::Sampler2d,       // TODO: wrong
                    offset_in_buffer: base_offset,
                }
            })
        }
    }

    fn build_layout(base_offset: usize) -> BlockLayout {
        BlockLayout::BasicType {
            ty: UniformType::Sampler2d,       // TODO: wrong
            offset_in_buffer: base_offset,
        }
    }
}

// TODO: implement `vertex::Attribute` on `TextureHandle`

/// Bindless textures are not supported.
#[derive(Debug, Copy, Clone)]
pub struct BindlessTexturesNotSupportedError;

#[cfg(test)]
mod test {
    use std::mem;
    use super::TextureHandle;

    #[test]
    fn texture_handle_size() {
        assert_eq!(mem::size_of::<TextureHandle>(), 8);
    }
}