/*-------------------------------------------------------------------*/
/* stackdynarray.c (Composition with DynArray)                       */
/*-------------------------------------------------------------------*/

#include "stack.h"
#include "dynarray.h"
#include <stdlib.h>
#include <assert.h>

/*-------------------------------------------------------------------*/

struct Stack
{
   DynArray_T oDynArray;
   int iTop;
};

/*-------------------------------------------------------------------*/

static int Stack_isValid(Stack_T oStack)

/* Return 1 (TRUE) iff oStack is in a valid state. */

{
   if (oStack->oDynArray == NULL) return 0;
   if (oStack->iTop < 0) return 0;
   if (oStack->iTop > DynArray_getLength(oStack->oDynArray)) return 0;
   return 1;
}
/*-------------------------------------------------------------------*/

Stack_T Stack_new(void)

/* Return a new Stack_T. */

{
   Stack_T oStack;
   oStack = (struct Stack*)malloc(sizeof(*oStack)); 
   assert(oStack != NULL);
   oStack->oDynArray = DynArray_new(0);
   oStack->iTop = 0;
   return oStack;
}

/*-------------------------------------------------------------------*/

void Stack_free(Stack_T oStack)

/* Free oStack. */

{
   if (oStack == NULL)
      return;
   DynArray_free(oStack->oDynArray);
   free(oStack);
}

/*-------------------------------------------------------------------*/

void Stack_push(Stack_T oStack, void *pvItem)

/* Push pvItem onto oStack.  
   It is a checked runtime error for oStack to be NULL. */

{
   assert(oStack != NULL);
   assert(Stack_isValid(oStack));
   if (oStack->iTop < DynArray_getLength(oStack->oDynArray))
      DynArray_put(oStack->oDynArray, oStack->iTop, pvItem);
   else
      DynArray_add(oStack->oDynArray, pvItem);
   ++(oStack->iTop);
}

/*-------------------------------------------------------------------*/

void *Stack_pop(Stack_T oStack)

/* Pop oStack, and return the popped item. 
   It is a checked runtime error for oStack to be NULL or empty. */

{
   assert(oStack != NULL);
   assert(Stack_isValid(oStack));
   assert(! Stack_isEmpty(oStack));
   --(oStack->iTop);
   return DynArray_get(oStack->oDynArray, oStack->iTop);
}

/*-------------------------------------------------------------------*/

int Stack_isEmpty(Stack_T oStack)

/* Return 1 (TRUE) iff oStack is empty. 
   It is a checked runtime error for oStack to be NULL. */

{
   assert(oStack != NULL);
   assert(Stack_isValid(oStack));
   return oStack->iTop == 0;
}