#include "stack.h"

int StackNotEmpty(stk_stack * theStack) {
  return( theStack ? (int) theStack->top : 0);
}

stk_stack * StackJoin(stk_stack * stack1, stk_stack * stack2) {
  if (!stack1->tail) {
    free(stack1);
    return(stack2);
  } else {
    stack1->tail->next=stack2->top;
    stack1->tail=stack2->tail;
    free(stack2);
    return(stack1);
  }
}

stk_stack * StackCreate() {
  stk_stack * newStack;
  
  newStack=(stk_stack *) SafeMalloc(sizeof(stk_stack));
  newStack->top=newStack->tail=NULL;
  return(newStack);
}


void StackPush(stk_stack * theStack, DATA_TYPE newInfoPointer) {
  stk_stack_node * newNode;

  if(!theStack->top) {
    newNode=(stk_stack_node *) SafeMalloc(sizeof(stk_stack_node));
    newNode->info=newInfoPointer;
    newNode->next=theStack->top;
    theStack->top=newNode;
    theStack->tail=newNode;
  } else {
    newNode=(stk_stack_node *) SafeMalloc(sizeof(stk_stack_node));
    newNode->info=newInfoPointer;
    newNode->next=theStack->top;
    theStack->top=newNode;
  }
  
}

DATA_TYPE StackPop(stk_stack * theStack) {
  DATA_TYPE popInfo;
  stk_stack_node * oldNode;

  if(theStack->top) {
    popInfo=theStack->top->info;
    oldNode=theStack->top;
    theStack->top=theStack->top->next;
    free(oldNode);
    if (!theStack->top) theStack->tail=NULL;
  } else {
    popInfo=NULL;
  }
  return(popInfo);
}

void StackDestroy(stk_stack * theStack,void DestFunc(void * a)) {
  stk_stack_node * x=theStack->top;
  stk_stack_node * y;

  if(theStack) {
    while(x) {
      y=x->next;
      DestFunc(x->info);
      free(x);
      x=y;
    }
    free(theStack);
  }
}