shared/src/main/java/com/android/tools/analytics/HostData.kt

/*
 * Copyright (C) 2018 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.
 */
package com.android.tools.analytics

import com.sun.management.OperatingSystemMXBean
import java.awt.GraphicsEnvironment
import java.lang.management.*
import kotlin.reflect.KProperty

/**
 * Entry point to various host data classes such as MxBeans and GraphicsEnvironment. Used to allow
 * stubbing these out in tests.
 */
object HostData {

  @JvmStatic
  var osBean: OperatingSystemMXBean? by stubbable {
    ManagementFactory.getOperatingSystemMXBean() as OperatingSystemMXBean
  }

  @JvmStatic
  var runtimeBean: RuntimeMXBean? by stubbable {
    ManagementFactory.getRuntimeMXBean()
  }

  @JvmStatic
  var graphicsEnvironment: GraphicsEnvironment? by stubbable {
    GraphicsEnvironment.getLocalGraphicsEnvironment()
  }

  @JvmStatic
  var memoryBean: MemoryMXBean? by stubbable {
    ManagementFactory.getMemoryMXBean()
  }

  @JvmStatic
  var classLoadingBean: ClassLoadingMXBean? by stubbable {
    ManagementFactory.getClassLoadingMXBean()
  }

  @JvmStatic
  var garbageCollectorBeans: List<GarbageCollectorMXBean>? by stubbable {
    ManagementFactory.getGarbageCollectorMXBeans()

  }

  @JvmStatic
  var threadBean: ThreadMXBean? by stubbable {
    ManagementFactory.getThreadMXBean()
  }
}

/**
 * stubbable is like lazy but provides a setter so the property can be stubbed out in tests
 * TODO(jvg): consider moving this to a utility library so other parts of our codebase can benefit from this pattern.
 */
internal fun <T> stubbable(initializer: () -> T): StubbableLazy<T> = StubbableLazy(initializer)

internal class StubbableLazy<T>(val initializer: () -> T) : Lazy<T> {
  private var _value: T? = null

  override val value: T
    get() {
      val current = _value
      if (current != null) {
        return current
      }

      return synchronized(this) {
        _value = initializer()
        _value!!
      }
    }

  override fun isInitialized(): Boolean = _value !== null
  operator fun getValue(thisRef: Any?, property: KProperty<*>): T = value
  operator fun setValue(hisRef: Any?, property: KProperty<*>, t: T) {
    _value = t
  }
}