package stack

type Stack struct {
	st  []interface{}
	len int
}

func New() *Stack {
	stack := &Stack{}
	stack.st = make([]interface{}, 1)
	stack.len = 0
	return stack
}

func (stack *Stack) Length() int {
	return stack.len
}

func (stack *Stack) Pop() {
	stack.st = stack.st[1:]
	stack.len -= 1
}

func (stack *Stack) Peek() interface{} {
	return stack.st[0]
}

func (stack *Stack) IsEmpty() bool {
	return (stack.len == 0)
}

func (stack *Stack) Push(value interface{}) {
	add(stack, value)
}

func add(slice *Stack, value interface{}) {
	slice.len += 1
	var tmpSlice []interface{} = make([]interface{}, slice.len)
	if slice.len == 0 {
		slice.st[0] = value
		return
	}

	for i := 0; i < slice.len; i++ {
		tmpSlice[i] = 0
	}

	for i := 0; i < slice.len; i++ {
		if i == 0 {
			tmpSlice[0] = value
		} else {
			tmpSlice[i] = slice.st[i-1]
		}

		if i == slice.len-1 {
			break
		}
	}

	slice.st = tmpSlice
}