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/*
 * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
 * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
 */

package org.jetbrains.kotlin.fir.resolve.dfa

abstract class Stack {
    abstract val size: Int
    abstract fun top(): T
    abstract fun pop(): T
    abstract fun push(value: T)
    abstract fun reset()

    /**
     * returns all elements of the stack in order of retrieval
     */
    abstract fun all(): List
}

fun  stackOf(vararg values: T): Stack = StackImpl(*values)
val Stack<*>.isEmpty: Boolean get() = size == 0
val Stack<*>.isNotEmpty: Boolean get() = size != 0
fun  Stack.topOrNull(): T? = if (size == 0) null else top()

private class StackImpl(vararg values: T) : Stack() {
    private val stack = mutableListOf(*values)

    override fun top(): T = stack[stack.size - 1]
    override fun pop(): T = stack.removeAt(stack.size - 1)

    override fun push(value: T) {
        stack.add(value)
    }

    override val size: Int get() = stack.size
    override fun reset() {
        stack.clear()
    }

    override fun all(): List = stack.asReversed()
}