/*
 * Copyright (c) 2026 Roger Seguin <rgrsgn@gmail.com>
 *				(https://frogzie.duckdns.org)
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

// $Id: fibonacci.c,v 1.2 2026/02/07 01:54:54 RogerSeguin Exp $

/* gcc -O3 -o cfibonacci -Wall fibonacci.c */

#include <stdio.h>
#include <stdint.h>
#include <time.h>
#include <string.h>
#include <stdbool.h>

const clockid_t CLOCK_ID =
//    CLOCK_PROCESS_CPUTIME_ID
    CLOCK_TAI
    ;

int usage(char *cmd)
{
    fprintf (stderr, "Usage: %s {--recursive|--loop} number\n", cmd);
    return (0);
}

static uint64_t recursiveCalls = 0;

uint64_t fibonacciRecursive(uint32_t n)
{
//    ++recursiveCalls;
    if (n == 0) return (0);
    if (n == 1) return (1);
    return (fibonacciRecursive(n - 1) + fibonacciRecursive(n - 2));
}

uint64_t fibonacciLoop(uint32_t n)
{
    uint64_t prev2 = 0;
    uint64_t prev1 = 1;
    uint64_t r = 0;
    if (n == 1)
        return (1);
    for (int i = 1; i < n; i++) {
        r = prev2 + prev1;
        prev2 = prev1;
        prev1 = r;
    }
    return (r);
}

int displaySequenceRecursive(uint32_t n)
{
    for (int i  = 0; i < n; i++)
        printf ("%ld ", fibonacciRecursive (i));
    puts("");
    return (0);
}

int displaySequenceLoop(uint32_t n)
{
    for (int i  = 0; i < n; i++) {
        printf ("%ld ", fibonacciLoop (i));
    }
    puts("");
    return (0);
}

int main(int argc, char** argv)
{
    if (argc < 3) {
        usage (argv[0]);
        return (1);
    }
    bool recursiveAlgo = false;
    if (strcmp (argv[1], "--recursive") == 0)
        recursiveAlgo = true;
    else if (strcmp (argv[1], "--loop") != 0) {
        usage(argv[0]);
        return (1);
    }
    uint32_t n;
    sscanf (argv[2], "%u", &n);
    struct timespec startTime, endTime;
    int status;

    //displaySequenceRecursive(n);
    //displaySequenceLoop(n);

    status = clock_gettime(CLOCK_ID, &startTime);
    if (status == -1)
        perror ("Start time");
    uint64_t r = (recursiveAlgo ? fibonacciRecursive (n) : fibonacciLoop (n));
    status = clock_gettime(CLOCK_ID, &endTime);
    if (status == -1)
        perror ("End time");

    const char *unit = "ns";
    double duration = 1000000000 * endTime.tv_sec + endTime.tv_nsec
                      - 1000000000 * startTime.tv_sec - startTime.tv_nsec;
    if (duration >= 1000) {
        unit = "us";
        duration /= 1000;
    }
    if (duration >= 1000) {
        unit = "ms";
        duration /= 1000;
    }
    if (duration >= 1000) {
        unit = "s";
        duration /= 1000;
    }

    printf ("Fibonacci(%d)=%lu", n, r);
    if (recursiveCalls)
        printf("\t%lu recursions", recursiveCalls);
    printf("\tCPU time: %lf %s\n", (double) duration, unit);
    return (0);
}