/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef txStack_h___
#define txStack_h___

#include "nsTArray.h"

class txStack : private nsTArray<void*> {
 public:
  /**
   * Returns the specified object from the top of this stack,
   * without removing it from the stack.
   *
   * @return a pointer to the object that is the top of this stack.
   */
  inline void* peek() {
    NS_ASSERTION(!isEmpty(), "peeking at empty stack");
    return !isEmpty() ? ElementAt(Length() - 1) : nullptr;
  }

  /**
   * Adds the specified object to the top of this stack.
   *
   * @param obj a pointer to the object that is to be added to the
   * top of this stack.
   */
  inline nsresult push(void* aObject) {
    // XXX(Bug 1631371) Check if this should use a fallible operation as it
    // pretended earlier, or change the return type to void.
    AppendElement(aObject);
    return NS_OK;
  }

  /**
   * Removes and returns the specified object from the top of this
   * stack.
   *
   * @return a pointer to the object that was the top of this stack.
   */
  inline void* pop() {
    void* object = nullptr;
    NS_ASSERTION(!isEmpty(), "popping from empty stack");
    if (!isEmpty()) {
      object = PopLastElement();
    }
    return object;
  }

  /**
   * Returns true if there are no objects in the stack.
   *
   * @return true if there are no objects in the stack.
   */
  inline bool isEmpty() { return IsEmpty(); }

  /**
   * Returns the number of elements in the Stack.
   *
   * @return the number of elements in the Stack.
   */
  inline int32_t size() { return Length(); }

 private:
  friend class txStackIterator;
};

class txStackIterator {
 public:
  /**
   * Creates an iterator for the given stack.
   *
   * @param aStack the stack to create an iterator for.
   */
  inline explicit txStackIterator(txStack* aStack)
      : mStack(aStack), mPosition(0) {}

  /**
   * Returns true if there is more objects on the stack.
   *
   * @return .
   */
  inline bool hasNext() { return (mPosition < mStack->Length()); }

  /**
   * Returns the next object pointer from the stack.
   *
   * @return .
   */
  inline void* next() {
    if (mPosition == mStack->Length()) {
      return nullptr;
    }
    return mStack->ElementAt(mPosition++);
  }

 private:
  txStack* mStack;
  uint32_t mPosition;
};

#endif /* txStack_h___ */