#pragma once
// FAITHFUL mask-shaping chain (22w) — transcription of FUN_180529fe0 per
// handoff/BLOCKMAP_529fe0.md (raw asm). Replaces process_band_structural
// when RT_FAITHFUL=1.
//
//   band = lvl * s                      (s = RT_FAITH_SCALE, decomp: /0x1a0*0x870*0x88c)
//   mask = exp2(-band)                  (bigkernel exp2 family)
//   bidir(mask, A);  bidir(mask, A)     // states reset each pass (52d650 + inline)
//   bidir(mask, B)                      // pass #3
//   bidir(mask, C);  bidir(mask, C)     // pass #4 x2
//   mirror upper half; dry/wet identity.
//
// Bidirectional one-pole per FUN_18052d650: acc = up[i]*acc + down[i]*x[i],
// forward over all bins, backward n-2..1 with persistent acc, reset per call.
// Coefficients per FUN_180533340 (freq-warped): fc_bin = C/(sr/2)*nbin;
// g = fc/i below crossover, powf(fc/i, p) above; c = 1/(g*tau/mult+1);
// up[i] = exp(-2*pi*kappa*c*g*tau), down[i] = 1-up[i].
//
// Decoded defaults (FUN_180530b60 log-interp @ live 0x540878/87c = 0.5):
//   setA/B tau=19.03 mult=360 ; set3/set4 tau=10.68 mult=2400 ; p=0.822 ;
//   C=1000 Hz ; kappa = 1/T8 ~ 0.0094 (T8 unknown -> env).

#include <cstddef>
#include <vector>

namespace fnfaith {

struct Params {
    double scale;   // RT_FAITH_SCALE
    double kappa;   // RT_FAITH_KAPPA
    double p;       // RT_FAITH_P
    double tau1, mult1;   // state A (#1,#2)
    double tau3, mult3;   // state B (#3)
    double tau4, mult4;   // state C (#4 x2)
    double C_hz;    // crossover (1000)
};

Params params_from_env();

// Compute lower-half mask [0, nbin) for one band from lvl_raw = am/res*scale_factor.
void band_mask_faithful(const float* am, const float* res, size_t nbin,
                        float sample_rate, float scale_factor, const Params& pr,
                        float* mask_out /* nbin */);

}  // namespace fnfaith