content: /*
   * 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.server;
  
  import android.annotation.NonNull;
  import android.annotation.Nullable;
  import android.os.FileUtils;
  import android.util.Slog;
  
  import java.io.File;
  import java.io.IOException;
  
  /**
   * A specialized ExtconUEventObserver that on receiving a {@link UEvent} calls {@link
   * #updateState(ExtconInfo, String, S)} with the value of{@link #parseState(ExtconInfo, String)}.
   *
   * @param <S> the type of state to parse and update
   * @hide
   */
  public abstract class ExtconStateObserver<S> extends ExtconUEventObserver {
      private static final String TAG = "ExtconStateObserver";
      private static final boolean LOG = false;
  
      /**
       * Parses the current state from the state file for {@code extconInfo}.
       *
       * @param extconInfo the extconInfo to parse state for
       * @see #parseState(ExtconInfo, String)
       * @see ExtconInfo#getStatePath()
       */
      @Nullable
      public S parseStateFromFile(ExtconInfo extconInfo) throws IOException {
          String statePath = extconInfo.getStatePath();
          return parseState(
                  extconInfo,
                  FileUtils.readTextFile(new File(statePath), 0, null).trim());
      }
  
      @Override
      public void onUEvent(ExtconInfo extconInfo, UEvent event) {
          if (LOG) Slog.d(TAG, extconInfo.getName() + " UEVENT: " + event);
          String name = event.get("NAME");
          S state = parseState(extconInfo, event.get("STATE"));
          if (state != null) {
              updateState(extconInfo, name, state);
          }
      }
  
      /**
       * Subclasses of ExtconStateObserver should override this method update state for {@code
       * exconInfo} from an {@code UEvent}.
       *
       * @param extconInfo the external connection
       * @param eventName the {@code NAME} of the {@code UEvent}
       * @param state the{@code STATE} as parsed by {@link #parseState(ExtconInfo, String)}.
       */
      public abstract void updateState(ExtconInfo extconInfo, String eventName, @NonNull S state);
  
      /**
       * Subclasses of ExtconStateObserver should override this method to parse the {@code STATE} from
       * an UEvent.
       *
       * @param extconInfo that matches the {@code DEVPATH} of {@code event}
       * @param state the {@code STATE} from a {@code UEvent}.
       * @return the parsed state. Return null if the state can not be parsed.
       */
      @Nullable
      public abstract S parseState(ExtconInfo extconInfo, String state);
  }
  