/***************************** factoriser.c ***************************** 

  Primarily an exercise in linked lists, this program finds the factors
  of a number input by the user and returns them.

************************************************************************/ 

/* Include some other files */
#include<stdio.h>
#include<limits.h>

/* Define some constants */
#define version 0.1

/* Prototype some fns. */
int getInt();



main () { // START OF MAIN

/* Would be nice to include code to pass number as argument, as well as
 * a feature to get `help' and version information. Have seen it 
 * somewhere but can't find it again. */

/* main() variables. */
int number, i, firstPtr;

/* As I understand this, below defines a set of types ('num' and 'next')
 * under the domain 'prime_node_t', if so, what does 'prime_node_tmp'
 * mean? */
typedef struct prime_node_tmp{
	long num;
	/* Is the following self-referential to its own typedef? */
	struct prime_node_tmp *next; 
} prime_node_t;

/* 'Declares' the pointer as type 'prime_node_t' meaning it can
 * use 'methods' num and next. */
prime_node_t *myPtr;



/* Prompt */
printf("Please enter your number to be factorised: ");
number = getInt(INT_MAX,INT_MIN);

/* Set firstPtr to 0 */
firstPtr = 0;

for (i = 2; i < sqrt(number); i++) {
	if (!number % i) {

		/* Don't fully understand the following, however have tried to
		 * express how I understand it so far, seems to have parrallels
		 * with Perl's 'object orientated' approach so have included
		 * analogies. I'm probably way off base though ;-) */

		/* Allocate some memory of any size 'methods' num and next can
		 * take. myPtr is a pointer the is at start of this memory. */
		myPtr = (prime_node_t *)malloc(sizeof(prime_node_t)); 

		/* Save the pointer to the first node for use in retreival. */
		if (!firstPtr) {
			firstPtr = (int)myPtr;
		}

		/* Uses num 'method' to assign number/i to myPtr address in
		 * memory. */
		myPtr->num = number/i; 

		/* Uses next 'method' to assign next place in memory NULL. */
		myPtr->next = NULL;

	}
}


/* Print out the factors if it has any, else declare it a prime. Note
 * this does not yet inlcude code for vetting numbers 1 and itself */
if (firstPtr) { /* True if a factor was found */
	
	printf("%d has the following factors...\n\n",number);

	printf("%d",firstPtr);

	/*
	while (firstPtr->next) {
		printf("%d",firstPtr*);
	}
	*/

} else {

	printf("%d is a prime number.\n",number);

}

} // END OF MAIN


/************************** getInt() - V0.1 *************************
                    Retrieves an integer from STDIN
Changelog: Version 0.2 
	 Additional max and min set to INT_MAX and INT_MIN.
 ********************************************************************/

int getInt(int max, int min) {

	/* Declare local vars */
	int valid, num; 
	char usrInput[5];

	/* Check to see if within limits */
	if (max > INT_MAX) {
		max == INT_MAX;
		printf("Debug: maximum changed to %d\n", INT_MAX);
	}

	if (min < INT_MIN) {
		min == INT_MIN;
		printf("Debug: lower limit changed to %d\n", INT_MIN);
	}

	do {
		scanf("%s",usrInput);
		num = atoi(usrInput);
		if ((num >= min) && (num <= max)) {
			valid = 1;
		} else {
			valid = 0;
			printf("Valid range is %d-%d, please re-enter: ",min,max);
		}
	} while (!valid);
	return(num);
}