#pragma once
#include <cstddef>
#include <cstdint>
#include <vector>
#include <complex>
#include "fft_plan.hpp"

// Real-time FFT-convolution stage mirroring the plugin per-band FFT-conv
// (NOTES_LEVEL 2026-08-19d, FUN_18052b550 steps 3-6):
//   FIR built from the captured WIN_WINDOW tail (step 5 memcpy),
//   then overlap-save convolution applied to the audio.
// Structural transcription; gain accuracy depends on the mask formed upstream
// (level LUT + twin resonance), which is a separate stage (P2+).
namespace fftconv {

// Builds the per-band FIR from the captured window: copies window[N/2..N-1]
// into FIR[0..N/2-1] and fills the upper half with zero (xmm9 fill), N = nfft.
// Mirrors the decompiled step 5 exactly.
void build_fir_from_window(double* fir, const float* window, size_t nfft);

// FIR impulse response from an arbitrary spectrum buffer (input `spec` of
// nfft/2+1 complex doubles) via forward FFT + step-5 window blend + inverse.
void fir_from_mask(std::complex<double>* fir,
                   const std::complex<double>* mask,
                   const float* window,
                   size_t nfft,
                   const FFTPlan* plan);

// Overlap-save convolution of `in` (frames) with real FIR `ir` (nfft samples).
// out pre-sized to frames. lat: zero-pad/initial delay applied internally.
void conv_overlap_save(const double* ir, size_t nfft, size_t hop,
                       const float* in, float* out, size_t frames,
                       const FFTPlan* plan);

}  // namespace fftconv