/*------------------------------------------------------------------------------
  stack.c - Operations on an expansion data stack

  Create the stack with new_stack().

  When you are finished with the stack, it must be deallocated with 
  delete_stack().

  Other functions are:
    is_empty() - Determine if a stack is empty
    pop()      - Pop an expansion data record from the stack
    push()     - Push an expansion data record onto the stack
------------------------------------------------------------------------------*/
#include <stdlib.h>
#include "stack.h"

#define INITIAL_CAPACITY 16

/*------------------------------------------------------------------------------
  delete_stack - Deallocate an expansion data stack

  stack = A pointer to the stack to be deallocated
------------------------------------------------------------------------------*/
void delete_stack (expansion_stack *stack) {
  if (stack != NULL) {
    for (int i = 0; i <= stack->top; i++) free (stack->data[i]);
    free (stack);
  }
}

/*------------------------------------------------------------------------------
  is_empty - Determine if a stack is empty
------------------------------------------------------------------------------*/
int is_empty (expansion_stack *stack) {
  if (stack == NULL) return 1;
  return stack->top < 0;
}

/*------------------------------------------------------------------------------
  new_stack - Create an expansion data stack
------------------------------------------------------------------------------*/
expansion_stack *new_stack () {
  expansion_stack *result = malloc (sizeof (expansion_stack) + sizeof (expansion_data *) * INITIAL_CAPACITY);
  if (result != NULL) {
    result->capacity = INITIAL_CAPACITY;
    result->top      = -1;
  }
  return result;
}

/*------------------------------------------------------------------------------
  pop - Pop an expansion data record from the stack
------------------------------------------------------------------------------*/
void pop (expansion_stack **stack) {
  if (stack != NULL && (*stack)->top >= 0 && (*stack)->top < (*stack)->capacity) {
    delete_expansion_data ((*stack)->data[(*stack)->top]);
    (*stack)->data[(*stack)->top] = NULL;
    (*stack)->top--;
    if ((*stack)->capacity > INITIAL_CAPACITY && (*stack)->top < (*stack)->capacity >> 2) {
      int newsize = (*stack)->capacity >> 1;
      if (newsize < INITIAL_CAPACITY) newsize = INITIAL_CAPACITY;
      expansion_stack *new = malloc (sizeof (expansion_stack) + sizeof (expansion_data *) * newsize);
      if (new != NULL) {
        *stack = new;
        (*stack)->capacity = newsize;
      }
    }
  }
}

/*------------------------------------------------------------------------------
  push - Push an expansion data record onto the stack
------------------------------------------------------------------------------*/
int push (expansion_stack **stack, expansion_data *data) {
  int i, newtop;

  if ((*stack)->top + 1 >= (*stack)->capacity) {
    int newsize = sizeof (expansion_stack) + sizeof (expansion_data *) * ((*stack)->capacity << 1);
    expansion_stack *new = realloc (*stack, newsize);
    if (new == NULL) return FALSE;
    *stack = new;
    (*stack)->capacity <<= 1;
  }

  newtop = (*stack)->top + 1;
  (*stack)->data[newtop] = new_expansion_data (data->part_starts_at);
  if ((*stack)->data[newtop] == NULL) return FALSE;
  for (i = 0; i < data->expansions->length; i++) {
    append_string_to_list (&(*stack)->data[newtop]->expansions, data->expansions->list[i]);
  }
  (*stack)->top = newtop;
  return TRUE;
}