package stacks

/* ---------------------------------------------------------------- *
 * IMPORTS
 * ---------------------------------------------------------------- */

import (
	"fmt"
	"strings"
)

/* ---------------------------------------------------------------- *
 * GLOBAL VARIABLES/CONSTANTS
 * ---------------------------------------------------------------- */

//

/* ---------------------------------------------------------------- *
 * TYPE
 * ---------------------------------------------------------------- */

type StackInt struct {
	values *[]int
}

/* ---------------------------------------------------------------- *
 * METHODS stacks
 * ---------------------------------------------------------------- */

func CREATE() StackInt {
	return StackInt{}
}

func (S *StackInt) INIT() {
	S.values = &[]int{}
}

func (S StackInt) Length() int {
	if S.values == nil {
		return 0
	}
	return len(*S.values)
}

func (S StackInt) String() string {
	if S.EMPTY() {
		return "-"
	}
	values := []string{}
	for _, value := range *S.values {
		values = append(values, fmt.Sprintf("%v", value))
	}
	return fmt.Sprintf(strings.Join(values, ", "))
}

func (S StackInt) EMPTY() bool {
	return S.Length() == 0
}

func (S *StackInt) PUSH(x int) {
	if S.values == nil {
		panic("Stack not initialised!")
	}
	*S.values = append(*S.values, x)
}

func (S *StackInt) TOP() int {
	if S.EMPTY() {
		panic("Cannot read from empty stack!")
	}
	n := S.Length()
	return (*S.values)[n-1]
}

func (S *StackInt) POP() {
	if S.EMPTY() {
		panic("Cannot remove from empty stack!")
	}
	n := S.Length()
	*S.values = (*S.values)[:(n - 1)]
}