/* 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 mozilla_a11y_relation_h_
#define mozilla_a11y_relation_h_

#include <memory>

#include "AccIterator.h"

namespace mozilla {
namespace a11y {

/**
 * A collection of relation targets of a certain type.  Targets are computed
 * lazily while enumerating.
 */
class Relation {
 public:
  Relation() : mFirstIter(nullptr), mLastIter(nullptr) {}

  explicit Relation(AccIterable* aIter) : mFirstIter(aIter), mLastIter(aIter) {}

  explicit Relation(Accessible* aAcc)
      : mFirstIter(nullptr), mLastIter(nullptr) {
    AppendTarget(aAcc);
  }

  Relation(DocAccessible* aDocument, nsIContent* aContent)
      : mFirstIter(nullptr), mLastIter(nullptr) {
    AppendTarget(aDocument, aContent);
  }

  Relation(Relation&& aOther)
      : mFirstIter(std::move(aOther.mFirstIter)), mLastIter(aOther.mLastIter) {
    aOther.mLastIter = nullptr;
  }

  Relation& operator=(Relation&& aRH) {
    mFirstIter = std::move(aRH.mFirstIter);
    mLastIter = aRH.mLastIter;
    aRH.mLastIter = nullptr;
    return *this;
  }

  inline void AppendIter(AccIterable* aIter) {
    if (mLastIter) {
      mLastIter->mNextIter.reset(aIter);
    } else {
      mFirstIter.reset(aIter);
    }

    mLastIter = aIter;
  }

  /**
   * Append the given accessible to the set of related accessibles.
   */
  inline void AppendTarget(Accessible* aAcc) {
    if (aAcc) AppendIter(new SingleAccIterator(aAcc));
  }

  /**
   * Append the one accessible for this content node to the set of related
   * accessibles.
   */
  void AppendTarget(DocAccessible* aDocument, nsIContent* aContent) {
    if (aContent) AppendTarget(aDocument->GetAccessible(aContent));
  }

  /**
   * compute and return the next related accessible.
   */
  inline Accessible* Next() {
    Accessible* target = nullptr;

    while (mFirstIter && !(target = mFirstIter->Next())) {
      mFirstIter = std::move(mFirstIter->mNextIter);
    }

    if (!mFirstIter) mLastIter = nullptr;

    return target;
  }

  inline LocalAccessible* LocalNext() {
    Accessible* next = Next();
    return next ? next->AsLocal() : nullptr;
  }

 private:
  Relation& operator=(const Relation&) = delete;
  Relation(const Relation&) = delete;

  std::unique_ptr<AccIterable> mFirstIter;
  AccIterable* mLastIter;
};

}  // namespace a11y
}  // namespace mozilla

#endif
