/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef SRC_ANDROID_SDK_NATIVEHELPER_SCOPED_LOCAL_REF_H_
#define SRC_ANDROID_SDK_NATIVEHELPER_SCOPED_LOCAL_REF_H_

// Copied from
// https://cs.android.com/android/platform/superproject/main/+/main:libnativehelper/header_only_include/nativehelper/scoped_local_ref.h;drc=4be05051ef76b2c24d8385732a892401eb45d911

#include <cstddef>

#include <jni.h>

#include "src/android_sdk/nativehelper/nativehelper_utils.h"

// A smart pointer that deletes a JNI local reference when it goes out of scope.
//
// For creating a `ScopedLocalRef<jstring>`, consider using
// `CREATE_UTF_OR_RETURN`.
template <typename T>
class ScopedLocalRef {
 public:
  ScopedLocalRef(JNIEnv* env, T localRef) : mEnv(env), mLocalRef(localRef) {}

  ScopedLocalRef(ScopedLocalRef&& s) noexcept
      : mEnv(s.mEnv), mLocalRef(s.release()) {}

  explicit ScopedLocalRef(JNIEnv* env) : mEnv(env), mLocalRef(nullptr) {}

  ~ScopedLocalRef() { reset(); }

  void reset(T ptr = nullptr) {
    if (ptr != mLocalRef) {
      if (mLocalRef != nullptr) {
        mEnv->DeleteLocalRef(mLocalRef);
      }
      mLocalRef = ptr;
    }
  }

  T release() __attribute__((warn_unused_result)) {
    T localRef = mLocalRef;
    mLocalRef = nullptr;
    return localRef;
  }

  T get() const { return mLocalRef; }

  // We do not expose an empty constructor as it can easily lead to errors
  // using common idioms, e.g.:
  //   ScopedLocalRef<...> ref;
  //   ref.reset(...);

  // Move assignment operator.
  ScopedLocalRef& operator=(ScopedLocalRef&& s) noexcept {
    reset(s.release());
    mEnv = s.mEnv;
    return *this;
  }

  // Allows "if (scoped_ref == nullptr)"
  bool operator==(std::nullptr_t) const { return mLocalRef == nullptr; }

  // Allows "if (scoped_ref != nullptr)"
  bool operator!=(std::nullptr_t) const { return mLocalRef != nullptr; }

 private:
  JNIEnv* mEnv;
  T mLocalRef;

  DISALLOW_COPY_AND_ASSIGN(ScopedLocalRef);
};

#endif  // SRC_ANDROID_SDK_NATIVEHELPER_SCOPED_LOCAL_REF_H_