#include "position_stack.h"
#include <stdio.h>
#include <stdlib.h>

// Error handler for stack errors
void stack_error(int err)
{
	switch (err)
	{
	case STACK_ERR_OVERFLOW:
		printf("Error: Stack overflow\nBe kind and report this problem.");
		break;
	case STACK_ERR_UNDERFLOW:
		printf("Error: Stack underflow\nBe kind and report this problem.");
		break;
	}

	exit(1);
}

// Creates a new stack
struct PositionStack *create_pos_stack(int capacity)
{
	struct PositionStack *stack_pt = malloc(sizeof(struct PositionStack));

	stack_pt->capacity = capacity;
	stack_pt->top = -1;
	stack_pt->items = malloc(sizeof(struct Position) * capacity);

	return stack_pt;
}

// Adds a new item to a stack
void pos_stack_push(struct PositionStack *stack_pt, struct Position pos)
{
	// Avoid a overflow by checking if the stack is full
	if (stack_pt->top == stack_pt->capacity - 1)
	{
		stack_error(STACK_ERR_OVERFLOW);
	}

	// Add an element and increase the top index
	stack_pt->items[++stack_pt->top] = pos;
}

// Returns the topmost item of a stack
struct Position pos_stack_peek(struct PositionStack *stack_pt)
{
	// Avoid a underflow by checking if the stack is empty
	if (stack_pt->top == -1)
	{
		stack_error(STACK_ERR_UNDERFLOW);
	}

	return stack_pt->items[stack_pt->top];
}

// Deletes the topmost item of a stack
struct Position pos_stack_pop(struct PositionStack *stack_pt)
{
	// Avoid a underflow by checking if the stack is empty
	if (stack_pt->top == -1)
	{
		stack_error(STACK_ERR_UNDERFLOW);
	}

	// Decrease the stack size by 1 and return the popped element
	return stack_pt->items[stack_pt->top--];
}