/* Program to reverse a list of names using the stack package */

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

void fatal(char message[]);
int can_load_name(stack stk);
void unload_name(stack stk);

main() {
    stack s;                            /* Declare stack variable */
    s = stack_init(100);                /* Initialise */
    if (s == NULL) {
        fatal("Cannot initialise stack");
    }
    printf("Enter names:\n");
    while (can_load_name(s)) {          /* Try to load another name */
        /* Try again */
    }
    printf("Names are:\n");

    /* Here all names are loaded into stack; now unload and output. */
    while (! stack_empty(s)) {          /* Still more in stack? */
        unload_name(s);                 /* yes - pop and print */
    }
    stack_free(s);    /* Not necessary in this program, but good practice
                         to free any memory not required further. */
    return 0;
}

/* fatal: print error and stop */
void fatal(char message[]) {
    fprintf(stderr, "ERROR:%s!\n", message);
    exit(EXIT_FAILURE);
}

/* can_load_name: Read a name & push; return 1 (success), or 0 (fail) */
int can_load_name(stack s) {
    char buf[80], *nam;     /* Temporary buffer, and pointer for the name */

    if (scanf("%79[^\n]%*[^\n]", buf) < 1) {  /* Try to read name. Fail? */
        return 0;                             /* Report failure */
    }
    getchar();                  /* Input '\n', ready for next name input */

    nam = (char*)malloc((strlen(buf)+1) * sizeof(char)); /* get space */
    if (nam == NULL) {                                   /* fail? */
        fatal("No space for name");
    }

    strcpy(nam, buf);            /* copy string into nam */
    if (! stack_push(s, nam)) {  /* Try pushing buffer's address - fail? */
        fatal("No room on stack");
    }
    return 1;                    /* Report success */
}

/* unload_name: Assumes there is a name in the stack; removes & prints it */
void unload_name(stack stk) {
    char * buf;
    buf = (char*)stack_pop(stk);
    printf("%s\n", buf);
    free(buf);                   /* Reclaim space malloc'ed above. */
}