//
// 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"

#define PI 3.14
#define SIG_FREQ 100
#define SAM_FREQ 2000

_Noreturn void k_avg(int fd) {
    // Exponential Moving Average should be updated with f = 10Hz (i.e. every 200 samples).
    int samples = 200;
    printf("A k_avg has been called\n");

    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 delay;
    delay.tv_sec = 0;
    delay.tv_nsec = 100000000ULL*1; // 100ms == 100 000 000ns -> 10Hz


    double alpha = 0.1;
    double ema;
    int start_idx = 0;


    while (1) {
        start_idx = buffer->info.free_idx;
        ema = buffer->data[start_idx];
        printf("start_idx = %d\n", start_idx);
        printf("EMA = %lf\n", ema);
        nanosleep(&delay, NULL);
    }



    // while (1) {
    //     start_idx = (buffer->info.free_idx - samples) % buffer->info.size;
    //     printf("start_idx = %d\n", start_idx);
    //     ema = buffer->data[start_idx];
    //     for (int read_idx = start_idx + 1; read_idx < samples; read_idx = ++read_idx % buffer->info.size) {
    //         ema = alpha*buffer->data[read_idx] + (1 - alpha) * ema;
    //         printf("EMA[%d] = %lf\n", read_idx, ema);
    //     }
    //     printf("EMA = %lf\n", ema);
    //     nanosleep(&delay, NULL);
    // }

}

int main(int argc, char *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_avg(fd);

	return 0;
}