/*****************
 *  jims_insertionsort.c
 *
 * Jim's implementation of insertion sort, 
 * using template for sorting in C,
 * class exercise March 17.
 * 
 *  For C syntax and libraries, see 
 *  https://cs.marlboro.college/courses/spring2016/systems/c_refcard.pdf
 *
 *  $ gcc jims_insertsort.c -o jims_insertsort
 *  $ ./jims_insertsort
 *    -- sorting --
 *    (max int is 2147483647 ; max random is 2147483647 ; a random is 613560990 *
 *    initial numbers:
 *      [83, 25, 67, 57, 29, 75, 33, 91, ]
 *     invariant check: i=1, array=[25, ]
 *   Yes, invariant is OK.
 *    invariant check: i=2, array=[25, 67, ]
 *   Yes, invariant is OK.
 *    invariant check: i=3, array=[25, 57, 67, ]
 *   Yes, invariant is OK.
 *    invariant check: i=4, array=[25, 29, 57, 67, ]
 *   Yes, invariant is OK.
 *    invariant check: i=5, array=[25, 29, 57, 67, 75, ]
 *   Yes, invariant is OK.
 *    invariant check: i=6, array=[25, 29, 33, 57, 67, 75, ]
 *   Yes, invariant is OK.
 *    invariant check: i=7, array=[25, 29, 33, 57, 67, 75, 83, ]
 *   Yes, invariant is OK.
 *   sorted numbers:
 *      [25, 29, 33, 57, 67, 75, 83, 91, ]
 *     elapsed time is 0.00008200 seconds
 *
 * Jim Mahoney | cs.bennington.college | MIT License | March 2022
 *****************/

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <time.h>

double get_secs(){
  // return time since program launch
  clock_t ticks = clock();
  double seconds = (double)ticks / (double)CLOCKS_PER_SEC;
  //printf(" ticks since epoch = %lu ; ", ticks);        // debug
  //printf(" ticks per second = %d \n", CLOCKS_PER_SEC); // .
  //printf(" seconds = %.6f \n", seconds);               // .
  return seconds;
}

int* get_randoms(int n, int maxvalue){
    // return array of n random numbers, randoms[0] to randoms[n-1],
    // each random 0 to maxvalue
  int i;
  int* randoms = malloc(n * sizeof(int));
  for (i=0; i<n; i++) randoms[i] = rand() % maxvalue;
  return randoms;
}

void init_randoms(){
  // initialize the pseudo random number generator using the system time
  srand(time(NULL));
}

void print_array(int n, int* array){
  int i;
  printf("[");
  for (i=0; i<n; i++) printf("%d, ", array[i]);
  printf("]\n");
}

int assert_invariant(int i, int* numbers){
    // return 1 if numbers[0] ... numbers[i-1] are in order, 0 otherwise.
    // ... compare numbers[0] with numbers[1]
    //             numbers[1] with numbers[2]
    //             numbers[i-2] with numbers[i-1]
    //     fail if any pair is out of order
    int j;
    int total = 0;
    printf(" invariant check: i=%i, array=", i);
    print_array(i, numbers);
    for (j=1; j<i; j++){
        if (numbers[j-1] > numbers[j]){
            printf("No, invariant is *NOT* OK.\n");            
            return 0;
        }
    }
    printf("Yes, invariant is OK.\n");
    return 1;
}

void sort(int n, int* numbers){
    // sort numbers[0] to numbers[n-1] into increasing order, in place.
    // insertion sort : https://en.wikipedia.org/wiki/Insertion_sort
    int i;
    int j;
    int temp;
    i = 1;
    while (i < n){
        j = i;
        while (j>0 && numbers[j-1] > numbers[j]){
            temp = numbers[j];
            numbers[j] = numbers[j-1];
            numbers[j-1] = temp;
            j = j - 1;

            
        }

        // check loop invariant ... are numbers[0...i] in order?
        if (! assert_invariant(i, numbers)){
            printf(" OOPS - loop invariant failed!! ");
        }
        
        i = i + 1;
        // print_array(n, numbers);
    }
}

int main(){
  int* randoms;
  int n = 8;

  double start, stop;

  start = get_secs();
  
  init_randoms();
  
  printf(" -- sorting -- \n");
  printf(" (max int is %d ;", INT_MAX);
  printf(" max random is %d ;", RAND_MAX);
  printf(" a random is %d.) \n\n", rand());

  randoms = get_randoms(n, 100);
  printf("initial numbers: \n   ");
  print_array(n, randoms);
  printf("\n");

  sort(n, randoms);

  printf("sorted numbers: \n   ");
  print_array(n, randoms);
  printf("\n");

  stop = get_secs();
  printf(" elapsed time is %.8f seconds \n", stop - start);
  
  return 0;
}