/*
 *   linkList.c
 *   create, initialize, and free a simple Linked List
 *   of dynamic structs
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_NAME_LENGTH 10

typedef struct {
    char *name;
    int  age;
} Person;  /* Person is now a data type */

/* typedef struct list_node * ListNodePtr; */

typedef struct list_node {
    Person data;
    struct list_node *next;
} ListNode;  /* ListNode is another data type */

void printList(ListNode *hd);
void freeList(ListNode *hd);
void fatalError(char *msg);


int main(int argc, char *argv[])
{
    FILE *inFile;
    ListNode *head = NULL;
    ListNode *tmp; /* doubles for new element pointer and iterator */

    /* temp variables to read data from file */
    char name[MAX_NAME_LENGTH];
    int age;

    if (!(inFile  = fopen("input.txt", "r")))
        fatalError("Can't open input.txt");

    /* Build list via insert at front with each name/age from infile */
    while(fscanf(inFile,"%s %d",name,&age) == 2)
    {
        if ((tmp = (ListNode *)malloc(sizeof(ListNode))) == NULL)
            fatalError("malloc of tmp failed");

        if ((tmp->data.name = (char *)malloc((strlen(name) + 1) * sizeof(char))) == NULL)
            fatalError("malloc of tmp->name failed");
        strcpy(tmp->data.name,name);
        tmp->data.age = age;

	/* insert the new node in front of the current head node */
	tmp->next = head;
	head = tmp;
    }
    fclose(inFile);

    printf("printing the list:\n");
    printList(head);

    freeList(head);

    return 0;
}


/* Notice we use our incoming head pointer as an iterator!
 * We are not corrupting the real head in main - this is just a copy
 * Some folks like this style, some would rather use an explicit temp ptr
*/
void printList(ListNode *hd)
{
    for ( ; hd != NULL; hd = hd->next)
    {
        printf("[%s,%d]", hd->data.name, hd->data.age);
        if (hd->next)
            printf(" -> ");
    }
    printf("\n");
}


/* use recursion to free string and struct on the way back up the list.
 * Doing this going forward would be cutting our bridge off in front of us
*/
void freeList(ListNode *hd)
{
    if (hd == NULL)
        return;

    freeList(hd->next);  /* recurse to the end of list */
    free(hd->data.name);  /* free the string */
    free(hd);  /* then the struct */
}


/* a convenient function to print a fatal error msg and exit the program
 * Note we don't bother cleaning up memory. It will be done for us
 * when our program exits.
*/
void fatalError(char *msg)
{
    fprintf(stderr,"\nFATAL ERROR: %s!!\n\n", msg);
    exit(EXIT_FAILURE);
}