use std::ops::Range;
use windows::Win32::Graphics::Direct3D12::{D3D12_CONSTANT_BUFFER_VIEW_DESC, D3D12_CPU_PAGE_PROPERTY_UNKNOWN, D3D12_HEAP_FLAG_NONE, D3D12_HEAP_PROPERTIES, D3D12_HEAP_TYPE_UPLOAD, D3D12_MEMORY_POOL_UNKNOWN, D3D12_RANGE, D3D12_RESOURCE_DESC, D3D12_RESOURCE_DIMENSION, D3D12_RESOURCE_DIMENSION_BUFFER, D3D12_RESOURCE_STATE_GENERIC_READ, D3D12_TEXTURE_LAYOUT_ROW_MAJOR, ID3D12Device, ID3D12Resource};
use windows::Win32::Graphics::Dxgi::Common::DXGI_SAMPLE_DESC;
use crate::error;
use crate::error::assume_d3d12_init;

pub struct D3D12ConstantBuffer {
    buffer: D3D12Buffer,
    desc: D3D12_CONSTANT_BUFFER_VIEW_DESC,
}

pub struct D3D12Buffer {
    handle: ID3D12Resource,
    size: usize
}

pub struct D3D12BufferMapHandle<'a> {
    pub slice: &'a mut [u8],
    pub handle: &'a ID3D12Resource,
}

impl<'a> Drop for D3D12BufferMapHandle<'a> {
    fn drop(&mut self) {
        unsafe {
            self.handle.Unmap(0, None)
        }
    }
}

impl D3D12Buffer {
    pub fn new(device: &ID3D12Device, size: usize) -> error::Result<D3D12Buffer> {
        unsafe {
            let mut buffer: Option<ID3D12Resource> = None;
            device.CreateCommittedResource(
                &D3D12_HEAP_PROPERTIES {
                    Type: D3D12_HEAP_TYPE_UPLOAD,
                    CPUPageProperty: D3D12_CPU_PAGE_PROPERTY_UNKNOWN,
                    MemoryPoolPreference: D3D12_MEMORY_POOL_UNKNOWN,
                    ..Default::default()
                },
                D3D12_HEAP_FLAG_NONE,
                &D3D12_RESOURCE_DESC {
                    Dimension: D3D12_RESOURCE_DIMENSION_BUFFER,
                    Width: size as u64,
                    Height: 1,
                    DepthOrArraySize: 1,
                    MipLevels: 1,
                    Layout: D3D12_TEXTURE_LAYOUT_ROW_MAJOR,
                    SampleDesc: DXGI_SAMPLE_DESC {
                        Count: 1,
                        Quality: 0
                    },
                    ..Default::default()
                },
                D3D12_RESOURCE_STATE_GENERIC_READ,
                None,
                &mut buffer
            )?;

            assume_d3d12_init!(buffer, "CreateCommittedResource");

            Ok(D3D12Buffer {
                handle: buffer,
                size
            })
        }
    }

    pub fn gpu_address(&self) -> u64 {
        unsafe {
            self.handle.GetGPUVirtualAddress()
        }
    }

    pub fn into_raw(self) -> ID3D12Resource {
        self.handle
    }

    pub fn map(&mut self, range: Option<Range<usize>>) -> error::Result<D3D12BufferMapHandle> {
        let (range, size) = range.map(|range| {
            (D3D12_RANGE {
                Begin: range.start,
                End: range.end
            }, range.end - range.start)
        }).unwrap_or((D3D12_RANGE {
            Begin: 0,
            End: 0
        }, self.size));

        unsafe {
            let mut ptr = std::ptr::null_mut();
            self.handle.Map(0, Some(&range), Some(&mut ptr))?;
            let slice = std::slice::from_raw_parts_mut(ptr.cast(), size);
            Ok(D3D12BufferMapHandle {
                handle: &self.handle,
                slice,
            })
        }
    }
}


impl D3D12ConstantBuffer {
    pub fn new(buffer: D3D12Buffer) -> D3D12ConstantBuffer {
        unsafe {
            let desc = D3D12_CONSTANT_BUFFER_VIEW_DESC {
                BufferLocation: buffer.handle.GetGPUVirtualAddress(),
                SizeInBytes: buffer.size as u32,
            };

            D3D12ConstantBuffer {
                buffer,
                desc,
            }
        }
    }
}