use std::mem::ManuallyDrop;
use std::u64;
use crate::error;
use windows::core::PCSTR;
use windows::Win32::Graphics::Direct3D::Fxc::{
    D3DCompile, D3DCOMPILE_DEBUG, D3DCOMPILE_SKIP_OPTIMIZATION,
};
use windows::Win32::Graphics::Direct3D::ID3DBlob;
use windows::Win32::Graphics::Direct3D12::{ID3D12Device, D3D12_FEATURE_DATA_FORMAT_SUPPORT, D3D12_FEATURE_FORMAT_SUPPORT, ID3D12CommandList, ID3D12GraphicsCommandList, ID3D12Resource, D3D12_RESOURCE_DESC, D3D12_RESOURCE_BARRIER, D3D12_RESOURCE_BARRIER_TYPE_TRANSITION, D3D12_RESOURCE_BARRIER_FLAG_NONE, D3D12_RESOURCE_DESC1, D3D12_RESOURCE_BARRIER_0, D3D12_RESOURCE_TRANSITION_BARRIER, D3D12_RESOURCE_BARRIER_ALL_SUBRESOURCES, D3D12_RESOURCE_STATES, D3D12_PLACED_SUBRESOURCE_FOOTPRINT, D3D12_MEMCPY_DEST, D3D12_SUBRESOURCE_DATA, D3D12_RESOURCE_DIMENSION_BUFFER, D3D12_TEXTURE_COPY_LOCATION, D3D12_TEXTURE_COPY_TYPE_SUBRESOURCE_INDEX, D3D12_TEXTURE_COPY_LOCATION_0, D3D12_TEXTURE_COPY_TYPE_PLACED_FOOTPRINT};
use windows::Win32::Graphics::Dxgi::Common::*;
use crate::error::assume_d3d12_init;

/// wtf retroarch?
const DXGI_FORMAT_EX_A4R4G4B4_UNORM: DXGI_FORMAT = DXGI_FORMAT(1000);

const fn d3d12_format_fallback_list(format: DXGI_FORMAT) -> Option<&'static [DXGI_FORMAT]> {
    match format {
        DXGI_FORMAT_R32G32B32A32_FLOAT => Some(&[
            DXGI_FORMAT_R32G32B32A32_FLOAT,
            DXGI_FORMAT_R16G16B16A16_FLOAT,
            DXGI_FORMAT_R32G32B32_FLOAT,
            DXGI_FORMAT_R11G11B10_FLOAT,
            DXGI_FORMAT_UNKNOWN,
        ]),
        DXGI_FORMAT_R16G16B16A16_FLOAT => Some(&[
            DXGI_FORMAT_R16G16B16A16_FLOAT,
            DXGI_FORMAT_R32G32B32A32_FLOAT,
            DXGI_FORMAT_R32G32B32_FLOAT,
            DXGI_FORMAT_R11G11B10_FLOAT,
            DXGI_FORMAT_UNKNOWN,
        ]),
        DXGI_FORMAT_R8G8B8A8_UNORM => Some(&[
            DXGI_FORMAT_R8G8B8A8_UNORM,
            DXGI_FORMAT_B8G8R8A8_UNORM,
            DXGI_FORMAT_B8G8R8X8_UNORM,
            DXGI_FORMAT_UNKNOWN,
        ]),
        DXGI_FORMAT_R8G8B8A8_UNORM_SRGB => Some(&[
            DXGI_FORMAT_R8G8B8A8_UNORM_SRGB,
            DXGI_FORMAT_R8G8B8A8_UNORM,
            DXGI_FORMAT_B8G8R8A8_UNORM,
            DXGI_FORMAT_B8G8R8X8_UNORM,
            DXGI_FORMAT_UNKNOWN,
        ]),
        DXGI_FORMAT_B8G8R8A8_UNORM => Some(&[
            DXGI_FORMAT_B8G8R8A8_UNORM,
            DXGI_FORMAT_R8G8B8A8_UNORM,
            DXGI_FORMAT_UNKNOWN,
        ]),
        DXGI_FORMAT_B8G8R8X8_UNORM => Some(&[
            DXGI_FORMAT_B8G8R8X8_UNORM,
            DXGI_FORMAT_B8G8R8A8_UNORM,
            DXGI_FORMAT_R8G8B8A8_UNORM,
            DXGI_FORMAT_UNKNOWN,
        ]),
        DXGI_FORMAT_B5G6R5_UNORM => Some(&[
            DXGI_FORMAT_B5G6R5_UNORM,
            DXGI_FORMAT_B8G8R8X8_UNORM,
            DXGI_FORMAT_B8G8R8A8_UNORM,
            DXGI_FORMAT_R8G8B8A8_UNORM,
            DXGI_FORMAT_UNKNOWN,
        ]),
        DXGI_FORMAT_EX_A4R4G4B4_UNORM | DXGI_FORMAT_B4G4R4A4_UNORM => Some(&[
            DXGI_FORMAT_B4G4R4A4_UNORM,
            DXGI_FORMAT_B8G8R8A8_UNORM,
            DXGI_FORMAT_R8G8B8A8_UNORM,
            DXGI_FORMAT_UNKNOWN,
        ]),
        DXGI_FORMAT_A8_UNORM => Some(&[
            DXGI_FORMAT_A8_UNORM,
            DXGI_FORMAT_R8_UNORM,
            DXGI_FORMAT_R8G8_UNORM,
            DXGI_FORMAT_R8G8B8A8_UNORM,
            DXGI_FORMAT_B8G8R8A8_UNORM,
            DXGI_FORMAT_UNKNOWN,
        ]),
        DXGI_FORMAT_R8_UNORM => Some(&[
            DXGI_FORMAT_R8_UNORM,
            DXGI_FORMAT_A8_UNORM,
            DXGI_FORMAT_R8G8_UNORM,
            DXGI_FORMAT_R8G8B8A8_UNORM,
            DXGI_FORMAT_B8G8R8A8_UNORM,
            DXGI_FORMAT_UNKNOWN,
        ]),
        _ => None,
    }
}

pub fn d3d12_get_closest_format(
    device: &ID3D12Device,
    format: DXGI_FORMAT,
    format_support: D3D12_FEATURE_DATA_FORMAT_SUPPORT,
) -> DXGI_FORMAT {
    let default_list = [format, DXGI_FORMAT_UNKNOWN];
    let format_support_list = d3d12_format_fallback_list(format).unwrap_or(&default_list);

    for supported in format_support_list {
        unsafe {
            let mut support = D3D12_FEATURE_DATA_FORMAT_SUPPORT {
                Format: format,
                ..Default::default()
            };
            if device
                .CheckFeatureSupport(
                    D3D12_FEATURE_FORMAT_SUPPORT,
                    &mut support as *mut _ as *mut _,
                    std::mem::size_of::<D3D12_FEATURE_DATA_FORMAT_SUPPORT>() as u32,
                )
                .is_ok()
                && (support.Support1 & format_support.Support1) == format_support.Support1
                && (support.Support2 & format_support.Support2) == format_support.Support2
            {
                return *supported;
            }
        }
    }
    DXGI_FORMAT_UNKNOWN
}

pub fn d3d_compile_shader(source: &[u8], entry: &[u8], version: &[u8]) -> error::Result<ID3DBlob> {
    unsafe {
        let mut blob = None;
        D3DCompile(
            source.as_ptr().cast(),
            source.len(),
            None,
            None,
            None,
            PCSTR(entry.as_ptr()),
            PCSTR(version.as_ptr()),
            if cfg!(feature = "debug-shader") {
                D3DCOMPILE_DEBUG | D3DCOMPILE_SKIP_OPTIMIZATION
            } else {
                0
            },
            0,
            &mut blob,
            None,
        )?;

        Ok(blob.unwrap())
    }
}

pub fn d3d12_resource_transition(cmd: &ID3D12GraphicsCommandList,
    resource: &ID3D12Resource,
    before: D3D12_RESOURCE_STATES,
    after: D3D12_RESOURCE_STATES
) {
    let barrier = [D3D12_RESOURCE_BARRIER {
        Type: D3D12_RESOURCE_BARRIER_TYPE_TRANSITION,
        Flags: D3D12_RESOURCE_BARRIER_FLAG_NONE,
        Anonymous: D3D12_RESOURCE_BARRIER_0 {
            Transition: ManuallyDrop::new(D3D12_RESOURCE_TRANSITION_BARRIER {
                pResource: windows::core::ManuallyDrop::new(resource),
                Subresource: D3D12_RESOURCE_BARRIER_ALL_SUBRESOURCES,
                StateBefore: before,
                StateAfter: after,
            })
        },
    }];

    unsafe {
        cmd.ResourceBarrier(&barrier)
    }
}

pub fn d3d12_update_subresources(cmd: &ID3D12GraphicsCommandList,
                                 destination_resource: &ID3D12Resource,
                                 intermediate_resource: &ID3D12Resource,
                                 intermediate_offset: u64,
                                 first_subresouce: u32,
                                 num_subresources: u32,
    source: &[D3D12_SUBRESOURCE_DATA]
) -> error::Result<u64> {

    // let allocation_size = std::mem::size_of::<D3D12_PLACED_SUBRESOURCE_FOOTPRINT>()
    //     + std::mem::size_of::<u32>()
    //     + std::mem::size_of::<u64>() * num_subresources;

    unsafe {
        let destination_desc = destination_resource.GetDesc();
        let mut device: Option<ID3D12Device> = None;
        destination_resource.GetDevice(&mut device)?;
        assume_d3d12_init!(device, "GetDevice");


        let mut layouts = vec![D3D12_PLACED_SUBRESOURCE_FOOTPRINT::default(); num_subresources as usize];
        let mut num_rows = vec![0; num_subresources as usize];
        let mut row_sizes_in_bytes =  vec![0; num_subresources as usize];
        let mut required_size = 0;
        // texture upload
        unsafe {
            device.GetCopyableFootprints(
                &destination_desc,
                first_subresouce,
                num_subresources,
                intermediate_offset,
                Some(layouts.as_mut_ptr()),
                Some(num_rows.as_mut_ptr()),
                Some(row_sizes_in_bytes.as_mut_ptr()),
                Some(&mut required_size),
            );
        }

        update_subresources(
            cmd,
            destination_resource,
            intermediate_resource,
            first_subresouce,
            num_subresources,
            required_size,
            &layouts,
            &num_rows,
            &row_sizes_in_bytes,
            source,
        )
    }
}

#[allow(clippy::too_many_arguments)]
fn update_subresources(
    cmd: &ID3D12GraphicsCommandList,
    destination_resource: &ID3D12Resource,
    intermediate_resource: &ID3D12Resource,
    first_subresouce: u32,
    num_subresources: u32,
    required_size: u64,
    layouts: &[D3D12_PLACED_SUBRESOURCE_FOOTPRINT],
    num_rows: &[u32],
    row_sizes_in_bytes: &[u64],
    source_data: &[D3D12_SUBRESOURCE_DATA],
) -> error::Result<u64> {
    // ToDo: implement validation as in the original function


    unsafe {
        let mut data = std::ptr::null_mut();
        intermediate_resource.Map(0, None, Some(&mut data))?;

        for i in 0..num_subresources as usize {
            let dest_data = D3D12_MEMCPY_DEST {
                pData: data.offset(layouts[i].Offset as isize)
                    as *mut std::ffi::c_void,
                RowPitch: layouts[i].Footprint.RowPitch as usize,
                SlicePitch: ((layouts[i].Footprint.RowPitch)
                    * num_rows[i]) as usize,
            };

            memcpy_subresource(
                &dest_data,
                &source_data[i],
                row_sizes_in_bytes[i],
                num_rows[i],
                layouts[i].Footprint.Depth,
            );
        }
        intermediate_resource.Unmap(0, None);
    }

    unsafe {
        let destination_desc = destination_resource.GetDesc();
        if destination_desc.Dimension == D3D12_RESOURCE_DIMENSION_BUFFER {
            cmd.CopyBufferRegion(
                destination_resource,
                0,
                intermediate_resource,
                layouts[0].Offset,
                layouts[0].Footprint.Width as u64,
            );
        } else {
            for i in 0..num_subresources as usize {

                let dest_location = D3D12_TEXTURE_COPY_LOCATION {
                    pResource: windows::core::ManuallyDrop::new(destination_resource),
                    Type: D3D12_TEXTURE_COPY_TYPE_SUBRESOURCE_INDEX,
                    Anonymous: D3D12_TEXTURE_COPY_LOCATION_0 {
                        SubresourceIndex: i as u32 + first_subresouce
                    },
                };

                let source_location = D3D12_TEXTURE_COPY_LOCATION {
                    pResource: windows::core::ManuallyDrop::new(intermediate_resource),
                    Type: D3D12_TEXTURE_COPY_TYPE_PLACED_FOOTPRINT,
                    Anonymous: D3D12_TEXTURE_COPY_LOCATION_0 {
                        PlacedFootprint: layouts[i]
                    },
                };

                cmd.CopyTextureRegion(
                    &dest_location,
                    0,
                    0,
                    0,
                    &source_location,
                    None,
                );
            }
        }
        Ok(required_size)
    }

}

// this function should not leak to the public API, so
// there is no point in using struct wrappers
unsafe fn memcpy_subresource(
    dest: &D3D12_MEMCPY_DEST,
    src: &D3D12_SUBRESOURCE_DATA,
    row_sizes_in_bytes: u64,
    num_rows: u32,
    num_slices: u32,
) {
    for z in 0..num_slices  as usize {
        let dest_slice =
            dest.pData.offset((dest.SlicePitch * z) as isize);
        let src_slice = src.pData.offset((src.SlicePitch * z as isize) as isize);

        for y in 0..num_rows as usize {
            std::ptr::copy_nonoverlapping(
                src_slice.offset((src.RowPitch * y as isize) as isize),
                dest_slice.offset((dest.RowPitch * y) as isize),
                row_sizes_in_bytes as usize,
            );
        }
    }
}