#include "fft_stage.hpp"
#include <cstring>

namespace fft_stage {

// cplx_mul — complex elementwise multiply: out = in1 * in2 (conjugated 2nd)
void cplx_mul(double* out, const double* in1, const double* in2, uint32_t n) {
    for (uint32_t i = 0; i < n * 2; i += 2) {
        double re1 = in1[i + 0];
        double im1 = in1[i + 1];
        double re2 = in2[i + 0];
        double im2 = in2[i + 1];
        out[i + 0] = re1 * re2 - im1 * im2;
        out[i + 1] = re1 * im2 + im1 * re2;
    }
}

// stage_complex — reformat: read interleaved complex [re,im][n], write [re][n],[im][n]
void stage_complex(double* out, const double* in, const double* tw, uint32_t n) {
    for (uint32_t i = 0; i < n; i++) {
        double re1 = in[i * 2 + 0];
        double im1 = in[i * 2 + 1];
        double re2 = tw[i * 2 + 0];
        double im2 = tw[i * 2 + 1];
        out[i * 2 + 0] = re1 * re2 - im1 * im2;
        out[i * 2 + 1] = re1 * im2 + im1 * re2;
    }
}

// stage_double — scalar multiply (FUN_180008500): out[i] = in[i] * tw[i]
void stage_double(double* out, const double* in, const double* tw, uint32_t n) {
    for (uint32_t i = 0; i < n; i++) {
        out[i] = in[i] * tw[i];
    }
}

}