//
// Written for Computer Networks and Systems lab classes
// AUTHOR : Sergiusz Warga

#include <fcntl.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <unistd.h>
#include <time.h>

#include "CircBuffer.h"
#include "funs.h"

void handle_arguments(int argc, char *argv[]) {
    if (argc != 3) {
        fprintf(stderr, "Usage: %s SAMPLING_FREQUENCY REFRESHING_FREQUENCY\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    if (strtol(argv[1], NULL, 10) < 2) {
        fprintf(stderr, "Sampling frequency should be at least 400Hz!\n");
        exit(EXIT_FAILURE);
    }

    if (strtol(argv[2], NULL, 10) > 1 || strtod(argv[2], NULL) < 0) {
        fprintf(stderr, "Refreshing frequency should be at least 1Hz!\n");
        exit(EXIT_FAILURE);
    }
}

int crosses_zero(double prev, double curr) {
	// let's just ignore 0 for now
	return (prev > 0 && curr < 0) || (prev < 0 && curr > 0);
}

_Noreturn void k_f0(int fd, int sampling_frequency, int refreshing_frequency) {
    printf("A k_f0 has been called\n");

	//----- Initialize the buffer -----
    struct CircBuffer *buffer;
    buffer = mmap(NULL, sizeof(struct CircBuffer), PROT_READ, MAP_SHARED, fd, 0);
    if (buffer == MAP_FAILED) {
        fprintf(stderr, "mmap: ");
        exit(EXIT_FAILURE);
    }

    struct timespec tic, toc;
    unsigned long long delay = NSEC_PER_SEC*1./refreshing_frequency;
    clock_gettime(CLOCK_REALTIME, &tic);

    int transitions = 0;
    int samples = 0;
    int read_idx;
    
    read_idx = buffer->info.free_idx - 1;

    while (1) {
    	clock_gettime(CLOCK_REALTIME, &toc);
    	if (timespec_diff_nano(&toc, &tic) > delay) {
    		double t_samp = 1./sampling_frequency;
        	// printf("t_samp = %fs\n", t_samp);
        	// printf("n_samp = %d\n", samples);
        	double t_anal = t_samp*samples;
        	// printf("t_anal = %fs\n", t_anal);
        	// printf("n_tran = %d\n", transitions);
        	printf("f = %fHz\n", transitions/(2*t_anal));
        	transitions = 0;
        	samples = 0;
        	clock_gettime(CLOCK_REALTIME, &tic);
    	}

    	if (crosses_zero(buffer->data[read_idx-1], buffer->data[read_idx])) {
    		++transitions;
    	}
    	while (read_idx == ((buffer->info.free_idx - 1) % buffer->info.size)) {};
        read_idx = ++read_idx % buffer->info.size;
        ++samples;
    }
}

int main(int argc, char *argv[]) {

	handle_arguments(argc, argv);

    //----- Open a shared memory -----
	const char *memory_name = "/dsp";
	int fd = shm_open(memory_name, O_RDONLY, 0777);
    if (fd < 0) {
        fprintf(stderr, "shm_open: ");
        exit(EXIT_FAILURE);
    }
    printf("Shared memory file descriptor: %d\n", fd);

    k_f0(fd, strtol(argv[1], NULL, 10), strtol(argv[2], NULL, 10));

	return 0;
}