//! HDR desktop -> SDR normalization for Desktop Duplication frames.
//!
//! With HDR enabled Windows composes the desktop as linear scRGB in
//! R16G16B16A16_FLOAT, and SDR "white" sits at the user's SDR content
//! brightness (DISPLAYCONFIG_SDR_WHITE_LEVEL) rather than at 1.0. The legacy
//! DuplicateOutput converts that to BGRA8 by clipping, which is the washed-out
//! picture reported for HDR hosts. This pass divides by the SDR white level,
//! clamps, and applies the sRGB transfer, so SDR content comes out exactly as
//! it would from an SDR desktop.
//!
//! It is a normalization, not a tone map: anything brighter than SDR white
//! (HDR video, HDR games) clips to white on the SDR viewer, where the local
//! HDR display would show it brighter than white. A roll-off would have to
//! move SDR white below 1.0 to make headroom, trading the accuracy of the SDR
//! content this pass exists for, so it is deliberately not done.
//!
//! The conversion is automatic and stays on the controlled side on purpose:
//! the controller renders through Flutter external textures, which are 8-bit
//! on every desktop platform, so there is nothing to gain from sending HDR.
//! Real HDR pass-through, if the renderer ever supports it, should follow the
//! Sunshine/Moonlight pattern instead: an `hdr` capability bit advertised by
//! the controller behind an explicit user toggle, negotiated like i444.

use super::ComPtr;
use hbb_common::log;
use std::{
    io, mem, ptr,
    sync::{atomic::AtomicBool, OnceLock},
    time::{Duration, Instant},
};
use winapi::{
    shared::{
        basetsd::SIZE_T,
        dxgiformat::DXGI_FORMAT_B8G8R8A8_UNORM,
        dxgitype::DXGI_SAMPLE_DESC,
        minwindef::{LPCVOID, UINT, ULONG},
        ntdef::{LONG, LPCSTR, WCHAR},
        winerror::S_OK,
    },
    um::{
        d3d11::*,
        d3dcommon::{ID3DBlob, ID3DInclude, D3D_PRIMITIVE_TOPOLOGY_TRIANGLELIST, D3D_SHADER_MACRO},
        libloaderapi::{GetProcAddress, LoadLibraryW},
        unknwnbase::IUnknown,
        wingdi::{
            DISPLAYCONFIG_DEVICE_INFO_GET_SOURCE_NAME, DISPLAYCONFIG_DEVICE_INFO_HEADER,
            DISPLAYCONFIG_MODE_INFO, DISPLAYCONFIG_PATH_INFO, DISPLAYCONFIG_SOURCE_DEVICE_NAME,
            DISPLAYCONFIG_TOPOLOGY_ID,
        },
        winnt::HRESULT,
    },
};

/// Set once the tone-map can never work in this process (no d3dcompiler, the
/// shaders do not compile). Capturers then stop asking DXGI for float frames.
/// Device-specific failures are not recorded here; the capturer that hit one
/// re-duplicates without the tone-map on its own.
pub static UNAVAILABLE: AtomicBool = AtomicBool::new(false);

/// Failures no capturer on this machine can recover from, as opposed to
/// device-specific ones that a recreated capturer may not hit again.
pub fn is_permanent(err: &io::Error) -> bool {
    err.kind() == io::ErrorKind::Unsupported
}

const VS_SRC: &str = "\
float4 main(uint id : SV_VertexID) : SV_Position {
    float2 uv = float2((id << 1) & 2, id & 2);
    return float4(uv * float2(2.0, -2.0) + float2(-1.0, 1.0), 0.0, 1.0);
}";

const PS_SRC: &str = "\
Texture2D<float4> src : register(t0);
cbuffer Params : register(b0) { float inv_sdr_white; float3 pad; };
float4 main(float4 pos : SV_Position) : SV_Target {
    float3 lin = saturate(src.Load(int3(pos.xy, 0)).rgb * inv_sdr_white);
    float3 lo = lin * 12.92;
    float3 hi = 1.055 * pow(lin, 1.0 / 2.4) - 0.055;
    return float4(lerp(hi, lo, step(lin, 0.0031308)), 1.0);
}";

/// DISPLAYCONFIG units: 1000 == 80 nits == scRGB 1.0.
const DEFAULT_SDR_WHITE_LEVEL: u32 = 1000;
const SDR_WHITE_LEVEL_REFRESH: Duration = Duration::from_secs(1);

pub struct HdrToSdr {
    device: ComPtr<ID3D11Device>,
    context: ComPtr<ID3D11DeviceContext>,
    vs: ComPtr<ID3D11VertexShader>,
    ps: ComPtr<ID3D11PixelShader>,
    params: ComPtr<ID3D11Buffer>,
    target: ComPtr<ID3D11Texture2D>,
    rtv: ComPtr<ID3D11RenderTargetView>,
    srv: ComPtr<ID3D11ShaderResourceView>,
    // Texture `srv` was created for. The view keeps it alive, so the address
    // cannot be recycled behind our back.
    srv_source: *mut ID3D11Texture2D,
    width: u32,
    height: u32,
    device_name: [WCHAR; 32],
    sdr_white_level: u32,
    queried_at: Instant,
}

impl HdrToSdr {
    pub fn new(
        device: *mut ID3D11Device,
        context: *mut ID3D11DeviceContext,
        device_name: &[WCHAR; 32],
    ) -> io::Result<Self> {
        unsafe {
            if device.is_null() || context.is_null() {
                return Err(other("no d3d11 device"));
            }
            (*device).AddRef();
            let device = ComPtr(device);
            (*context).AddRef();
            let context = ComPtr(context);

            let compile = load_d3d_compile()?;
            let vs_code = compile_shader(compile, VS_SRC, b"vs_4_0\0")?;
            let ps_code = compile_shader(compile, PS_SRC, b"ps_4_0\0")?;
            let mut vs = ptr::null_mut();
            check(
                (*device.0).CreateVertexShader(
                    (*vs_code.0).GetBufferPointer(),
                    (*vs_code.0).GetBufferSize(),
                    ptr::null_mut(),
                    &mut vs,
                ),
                "CreateVertexShader",
            )?;
            let vs = ComPtr(vs);
            let mut ps = ptr::null_mut();
            check(
                (*device.0).CreatePixelShader(
                    (*ps_code.0).GetBufferPointer(),
                    (*ps_code.0).GetBufferSize(),
                    ptr::null_mut(),
                    &mut ps,
                ),
                "CreatePixelShader",
            )?;
            let ps = ComPtr(ps);

            let sdr_white_level =
                query_sdr_white_level(device_name).unwrap_or(DEFAULT_SDR_WHITE_LEVEL);
            let init = params_data(sdr_white_level);
            let desc = D3D11_BUFFER_DESC {
                ByteWidth: mem::size_of_val(&init) as _,
                Usage: D3D11_USAGE_DEFAULT,
                BindFlags: D3D11_BIND_CONSTANT_BUFFER,
                CPUAccessFlags: 0,
                MiscFlags: 0,
                StructureByteStride: 0,
            };
            let data = D3D11_SUBRESOURCE_DATA {
                pSysMem: init.as_ptr() as _,
                SysMemPitch: 0,
                SysMemSlicePitch: 0,
            };
            let mut params = ptr::null_mut();
            check(
                (*device.0).CreateBuffer(&desc, &data, &mut params),
                "CreateBuffer",
            )?;
            let params = ComPtr(params);
            log::info!("HDR tone-map ready, sdr white level {sdr_white_level}");

            Ok(Self {
                device,
                context,
                vs,
                ps,
                params,
                target: ComPtr(ptr::null_mut()),
                rtv: ComPtr(ptr::null_mut()),
                srv: ComPtr(ptr::null_mut()),
                srv_source: ptr::null_mut(),
                width: 0,
                height: 0,
                device_name: *device_name,
                sdr_white_level,
                queried_at: Instant::now(),
            })
        }
    }

    /// Renders `source` (R16G16B16A16_FLOAT) into an owned B8G8R8A8_UNORM
    /// texture of the same size and returns it. The texture stays valid until
    /// the next call.
    pub fn convert(
        &mut self,
        source: *mut ID3D11Texture2D,
        desc: &D3D11_TEXTURE2D_DESC,
    ) -> io::Result<*mut ID3D11Texture2D> {
        unsafe {
            self.refresh_sdr_white_level();
            self.ensure_target(desc.Width, desc.Height)?;
            self.ensure_source_view(source)?;

            let ctx = self.context.0;
            let rtv = self.rtv.0;
            let srv = self.srv.0;
            let params = self.params.0;
            let viewport = D3D11_VIEWPORT {
                TopLeftX: 0.0,
                TopLeftY: 0.0,
                Width: self.width as f32,
                Height: self.height as f32,
                MinDepth: 0.0,
                MaxDepth: 1.0,
            };
            (*ctx).OMSetRenderTargets(1, &rtv, ptr::null_mut());
            (*ctx).OMSetBlendState(ptr::null_mut(), &[0.0; 4], 0xffff_ffff);
            (*ctx).OMSetDepthStencilState(ptr::null_mut(), 0);
            (*ctx).RSSetState(ptr::null_mut());
            (*ctx).RSSetViewports(1, &viewport);
            (*ctx).IASetInputLayout(ptr::null_mut());
            (*ctx).IASetPrimitiveTopology(D3D_PRIMITIVE_TOPOLOGY_TRIANGLELIST);
            (*ctx).VSSetShader(self.vs.0, ptr::null(), 0);
            (*ctx).PSSetShader(self.ps.0, ptr::null(), 0);
            (*ctx).PSSetConstantBuffers(0, 1, &params);
            (*ctx).PSSetShaderResources(0, 1, &srv);
            (*ctx).Draw(3, 0);
            // Unbind so the next frame's copy and the encoder never see the
            // target as a live render target or the desktop image as a bound
            // shader input.
            let no_srv: *mut ID3D11ShaderResourceView = ptr::null_mut();
            (*ctx).PSSetShaderResources(0, 1, &no_srv);
            (*ctx).OMSetRenderTargets(0, ptr::null(), ptr::null_mut());
            Ok(self.target.0)
        }
    }

    unsafe fn ensure_target(&mut self, width: u32, height: u32) -> io::Result<()> {
        if !self.target.is_null() && self.width == width && self.height == height {
            return Ok(());
        }
        let desc = D3D11_TEXTURE2D_DESC {
            Width: width,
            Height: height,
            MipLevels: 1,
            ArraySize: 1,
            Format: DXGI_FORMAT_B8G8R8A8_UNORM,
            SampleDesc: DXGI_SAMPLE_DESC {
                Count: 1,
                Quality: 0,
            },
            Usage: D3D11_USAGE_DEFAULT,
            BindFlags: D3D11_BIND_RENDER_TARGET | D3D11_BIND_SHADER_RESOURCE,
            CPUAccessFlags: 0,
            MiscFlags: D3D11_RESOURCE_MISC_SHARED,
        };
        let mut target = ptr::null_mut();
        check(
            (*self.device.0).CreateTexture2D(&desc, ptr::null(), &mut target),
            "CreateTexture2D",
        )?;
        let target = ComPtr(target);
        let mut rtv = ptr::null_mut();
        check(
            (*self.device.0).CreateRenderTargetView(target.0 as *mut _, ptr::null(), &mut rtv),
            "CreateRenderTargetView",
        )?;
        self.rtv = ComPtr(rtv);
        self.target = target;
        self.width = width;
        self.height = height;
        Ok(())
    }

    unsafe fn ensure_source_view(&mut self, source: *mut ID3D11Texture2D) -> io::Result<()> {
        if !self.srv.is_null() && self.srv_source == source {
            return Ok(());
        }
        let mut srv = ptr::null_mut();
        check(
            (*self.device.0).CreateShaderResourceView(source as *mut _, ptr::null(), &mut srv),
            "CreateShaderResourceView",
        )?;
        self.srv = ComPtr(srv);
        self.srv_source = source;
        Ok(())
    }

    unsafe fn refresh_sdr_white_level(&mut self) {
        if self.queried_at.elapsed() < SDR_WHITE_LEVEL_REFRESH {
            return;
        }
        self.queried_at = Instant::now();
        let Some(level) = query_sdr_white_level(&self.device_name) else {
            return;
        };
        if level == self.sdr_white_level || level == 0 {
            return;
        }
        log::info!(
            "sdr white level changed {} -> {level}",
            self.sdr_white_level
        );
        self.sdr_white_level = level;
        let data = params_data(level);
        (*self.context.0).UpdateSubresource(
            self.params.0 as *mut _,
            0,
            ptr::null(),
            data.as_ptr() as _,
            0,
            0,
        );
    }
}

fn params_data(sdr_white_level: u32) -> [f32; 4] {
    [1000.0 / sdr_white_level.max(1) as f32, 0.0, 0.0, 0.0]
}

fn other(msg: impl Into<String>) -> io::Error {
    io::Error::new(io::ErrorKind::Other, msg.into())
}

fn check(hr: HRESULT, what: &str) -> io::Result<()> {
    if hr == S_OK {
        Ok(())
    } else {
        Err(other(format!("{what} failed: {hr:#x}")))
    }
}

// D3DCompile(pSrcData, SrcDataSize, pSourceName, pDefines, pInclude,
//            pEntrypoint, pTarget, Flags1, Flags2, ppCode, ppErrorMsgs)
type D3DCompileFn = unsafe extern "system" fn(
    LPCVOID,
    SIZE_T,
    LPCSTR,
    *const D3D_SHADER_MACRO,
    *mut ID3DInclude,
    LPCSTR,
    LPCSTR,
    UINT,
    UINT,
    *mut *mut ID3DBlob,
    *mut *mut ID3DBlob,
) -> HRESULT;

static D3D_COMPILE: OnceLock<Result<D3DCompileFn, String>> = OnceLock::new();

// Loaded once per process and kept: the compiler DLL is only needed on HDR
// desktops, and an import-time link would make every install depend on it.
fn load_d3d_compile() -> io::Result<D3DCompileFn> {
    D3D_COMPILE
        .get_or_init(|| unsafe { find_d3d_compile() })
        .clone()
        .map_err(|e| io::Error::new(io::ErrorKind::Unsupported, e))
}

unsafe fn find_d3d_compile() -> Result<D3DCompileFn, String> {
    let name: Vec<u16> = "d3dcompiler_47.dll\0".encode_utf16().collect();
    let module = LoadLibraryW(name.as_ptr());
    if module.is_null() {
        return Err("d3dcompiler_47.dll not available".into());
    }
    let f = GetProcAddress(module, b"D3DCompile\0".as_ptr() as _);
    if f.is_null() {
        return Err("D3DCompile not exported".into());
    }
    Ok(mem::transmute::<_, D3DCompileFn>(f))
}

unsafe fn compile_shader(
    compile: D3DCompileFn,
    src: &str,
    target: &[u8],
) -> io::Result<ComPtr<ID3DBlob>> {
    let mut code = ptr::null_mut();
    let mut errors = ptr::null_mut();
    let hr = compile(
        src.as_ptr() as _,
        src.len(),
        ptr::null(),
        ptr::null(),
        ptr::null_mut(),
        b"main\0".as_ptr() as _,
        target.as_ptr() as _,
        0,
        0,
        &mut code,
        &mut errors,
    );
    let errors = ComPtr(errors);
    if hr != S_OK || code.is_null() {
        let msg = if errors.is_null() {
            String::new()
        } else {
            let bytes = std::slice::from_raw_parts(
                (*errors.0).GetBufferPointer() as *const u8,
                (*errors.0).GetBufferSize(),
            );
            String::from_utf8_lossy(bytes).into_owned()
        };
        if !code.is_null() {
            (*(code as *mut IUnknown)).Release();
        }
        return Err(io::Error::new(
            io::ErrorKind::Unsupported,
            format!("D3DCompile failed: {hr:#x} {msg}"),
        ));
    }
    Ok(ComPtr(code))
}

const DISPLAYCONFIG_DEVICE_INFO_GET_SDR_WHITE_LEVEL: u32 = 11;
const QDC_ONLY_ACTIVE_PATHS: u32 = 2;

#[repr(C)]
#[allow(non_snake_case)]
struct DISPLAYCONFIG_SDR_WHITE_LEVEL {
    header: DISPLAYCONFIG_DEVICE_INFO_HEADER,
    SDRWhiteLevel: ULONG,
}

#[link(name = "user32")]
extern "system" {
    fn GetDisplayConfigBufferSizes(
        flags: u32,
        numPathArrayElements: *mut u32,
        numModeInfoArrayElements: *mut u32,
    ) -> LONG;
    fn QueryDisplayConfig(
        flags: u32,
        numPathArrayElements: *mut u32,
        pathArray: *mut DISPLAYCONFIG_PATH_INFO,
        numModeInfoArrayElements: *mut u32,
        modeInfoArray: *mut DISPLAYCONFIG_MODE_INFO,
        currentTopologyId: *mut DISPLAYCONFIG_TOPOLOGY_ID,
    ) -> LONG;
    fn DisplayConfigGetDeviceInfo(requestPacket: *mut DISPLAYCONFIG_DEVICE_INFO_HEADER) -> LONG;
}

/// SDR white level of the output whose GDI name is `device_name`
/// (e.g. `\\.\DISPLAY1`), in DISPLAYCONFIG units (1000 == 80 nits).
fn query_sdr_white_level(device_name: &[WCHAR; 32]) -> Option<u32> {
    unsafe {
        let mut n_paths = 0u32;
        let mut n_modes = 0u32;
        if GetDisplayConfigBufferSizes(QDC_ONLY_ACTIVE_PATHS, &mut n_paths, &mut n_modes) != 0 {
            return None;
        }
        let mut paths: Vec<DISPLAYCONFIG_PATH_INFO> = vec![mem::zeroed(); n_paths as usize];
        let mut modes: Vec<DISPLAYCONFIG_MODE_INFO> = vec![mem::zeroed(); n_modes as usize];
        if QueryDisplayConfig(
            QDC_ONLY_ACTIVE_PATHS,
            &mut n_paths,
            paths.as_mut_ptr(),
            &mut n_modes,
            modes.as_mut_ptr(),
            ptr::null_mut(),
        ) != 0
        {
            return None;
        }
        for path in &paths[..n_paths as usize] {
            let mut source: DISPLAYCONFIG_SOURCE_DEVICE_NAME = mem::zeroed();
            source.header._type = DISPLAYCONFIG_DEVICE_INFO_GET_SOURCE_NAME;
            source.header.size = mem::size_of::<DISPLAYCONFIG_SOURCE_DEVICE_NAME>() as _;
            source.header.adapterId = path.sourceInfo.adapterId;
            source.header.id = path.sourceInfo.id;
            if DisplayConfigGetDeviceInfo(&mut source.header) != 0
                || !wide_eq(&source.viewGdiDeviceName, device_name)
            {
                continue;
            }
            let mut white: DISPLAYCONFIG_SDR_WHITE_LEVEL = mem::zeroed();
            white.header._type = DISPLAYCONFIG_DEVICE_INFO_GET_SDR_WHITE_LEVEL;
            white.header.size = mem::size_of::<DISPLAYCONFIG_SDR_WHITE_LEVEL>() as _;
            white.header.adapterId = path.targetInfo.adapterId;
            white.header.id = path.targetInfo.id;
            if DisplayConfigGetDeviceInfo(&mut white.header) == 0 {
                return Some(white.SDRWhiteLevel);
            }
        }
        None
    }
}

fn wide_eq(a: &[WCHAR], b: &[WCHAR]) -> bool {
    let end = |s: &[WCHAR]| s.iter().position(|&c| c == 0).unwrap_or(s.len());
    a[..end(a)] == b[..end(b)]
}