#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <math.h>

#define DATA_L 1024
#define FP_acc 1000

#define PI 3.141592653589793238462643383279502884197169399375105820974944



int64_t cos_delta_FP_arr[DATA_L] = {0,};
int64_t sin_delta_FP_arr[DATA_L] = {0,};
int64_t wr_arr[DATA_L][DATA_L / 2] = {0,};
int64_t wi_arr[DATA_L][DATA_L / 2] = {0,};

void FFT_fp(int64_t* inp, uint32_t inp_L, int64_t* buf){

	    // buf имеет длину inp_L * 2 (Re, Im, Re, Im, ...)
	    // inp содержит inp_L значений uint32_t

	    uint32_t i, j, bit;
//	    uint32_t N = inp_L / 2;  // длина комплексного массива (inp содержит только Re-часть)
	    uint32_t N = inp_L;  // длина комплексного массива (inp содержит только Re-часть)

	    // --- копирование входных данных в буфер ---
	    for (i = 0; i < inp_L; i++) {
	        buf[i * 2]     = inp[i];
	        buf[i * 2 + 1] = 0;
	    }

	    // --- bit-reversal перестановка ---
	    j = 0;
	    for (i = 1; i < N; i++) {
	        bit = N >> 1;
	        while (j & bit) {
	            j ^= bit;
	            bit >>= 1;
	        }
	        j |= bit;
	        if (i < j) {
	            int64_t tmp_re = buf[i * 2];
	            int64_t tmp_im = buf[i * 2 + 1];
	            buf[i * 2]     = buf[j * 2];
	            buf[i * 2 + 1] = buf[j * 2 + 1];
	            buf[j * 2]     = tmp_re;
	            buf[j * 2 + 1] = tmp_im;
	        }
	    }

	    // --- уровни бабочек ---
	    uint32_t m = 2;
	    while (m <= N) {
	        uint32_t half = m >> 1;

	        for (uint32_t start = 0; start < N; start += m) {
            int64_t *twiddle_re = wr_arr[m - 2];
            int64_t *twiddle_im = wi_arr[m - 2];

            for (uint32_t k = 0; k < half; k++) {
                int64_t wr = twiddle_re[k];
                int64_t wi = twiddle_im[k];
                int64_t u_re = buf[(start + k) * 2];
                int64_t u_im = buf[(start + k) * 2 + 1];
                int64_t v_re = buf[(start + k + half) * 2];
                int64_t v_im = buf[(start + k + half) * 2 + 1];

	                // t = w * v  (в фиксированной точке)
	                int64_t t_re = (wr * v_re - wi * v_im) / FP_acc;
	                int64_t t_im = (wr * v_im + wi * v_re) / FP_acc;

	                // верх/низ
	                buf[(start + k) * 2]              = u_re + t_re;
	                buf[(start + k) * 2 + 1]          = u_im + t_im;
	                buf[(start + k + half) * 2]       = u_re - t_re;
	                buf[(start + k + half) * 2 + 1]   = u_im - t_im;

            }
        }
        m <<= 1;
    }
	    for (uint32_t i = 0; i < inp_L; ++i){
	    	//buf[i*2] /= inp_L;
	    	//buf[i*2+1] /= inp_L;
	    	printf("re,im: %lld, %lld\n", (long long)buf[i*2], (long long)buf[i*2 +1]);
	    }

}

void imagery2abs(int64_t* inp, uint32_t inp_L, int64_t *out){
	printf("+++++++++++++++++++++\n");
	printf("calculating abs^2\n");
	for (uint32_t i = 0; i < inp_L; ++i){
		int64_t re = inp[i*2];
		int64_t im = inp[i*2 +1];
		int64_t val = (re * re + im * im) / FP_acc;
		printf("%lld\n", (long long)val);
		out[i] = val;
	}
}



void sin_cos_filler(int64_t* sin_arr, int64_t* cos_arr, uint32_t L){
	//[int(-sin(2.0 * pi / m) * FP_acc) for m in range(2,inp_L//2 + 2)]
	for (uint32_t i = 0; i < L; ++i){
		int m = i + 2;
		double angle = 2.0* PI/m;
		sin_arr[i] = lround(-sin(angle) * FP_acc);
		cos_arr[i] = lround(cos(angle) * FP_acc);
		uint32_t half = m >> 1;
		for (uint32_t k = 0; k < half; ++k){
			double tw_angle = angle * k;
			wr_arr[i][k] = lround(cos(tw_angle) * FP_acc);
			wi_arr[i][k] = lround(-sin(tw_angle) * FP_acc);
		}
		printf("i, angle, sin, cos: %d %g %lld %lld\n", i, angle, (long long)sin_arr[i], (long long)cos_arr[i]);
	}
}

void data_generator(int64_t* X, int64_t* Y, uint32_t N){
	for (int i = 0; i < N; ++i){
		X[i] = (int64_t)i;
		Y[i] = lround(sin(((double)i)*2.0* PI/(N/10))*FP_acc);
		Y[i] += 1*FP_acc;
	}
}

void main(){
	char* logfilename = "tmp";
	int64_t data_X[DATA_L] = {0,};
	int64_t data_Y[DATA_L] = {0,};
	int64_t data_res_FFT_imag[DATA_L*2] = {0,};
	int64_t data_res_FFT_abs[DATA_L] = {0,};

	sin_cos_filler(sin_delta_FP_arr, cos_delta_FP_arr, DATA_L);

	data_generator(data_X, data_Y, DATA_L);


	FFT_fp(data_Y, DATA_L, data_res_FFT_imag);


	imagery2abs(data_res_FFT_imag, DATA_L, data_res_FFT_abs);

	FILE *logfile_ptr;
    logfile_ptr = fopen(logfilename, "w");
    fprintf(logfile_ptr, "X, Y, FFT\n");
	for (uint32_t i = 0; i < DATA_L; ++i){
		fprintf(logfile_ptr, "%lld, %lg, %lg \n", (long long)data_X[i], ((double)data_Y[i])/(double)FP_acc , (double)data_res_FFT_abs[i]/(double)FP_acc);
	}
	fclose(logfile_ptr);
}