/*
 * Copyright (C) 2016 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.google.android.exoplayer2.util;

/**
 * Configurable loader for native libraries.
 */
public final class LibraryLoader {

  private String[] nativeLibraries;
  private boolean loadAttempted;
  private boolean isAvailable;

  /**
   * @param libraries The names of the libraries to load.
   */
  public LibraryLoader(String... libraries) {
    nativeLibraries = libraries;
  }

  /**
   * Overrides the names of the libraries to load. Must be called before any call to
   * {@link #isAvailable()}.
   */
  public synchronized void setLibraries(String... libraries) {
    Assertions.checkState(!loadAttempted, "Cannot set libraries after loading");
    nativeLibraries = libraries;
  }

  /**
   * Returns whether the underlying libraries are available, loading them if necessary.
   */
  public synchronized boolean isAvailable() {
    if (loadAttempted) {
      return isAvailable;
    }
    loadAttempted = true;
    try {
      for (String lib : nativeLibraries) {
        System.loadLibrary(lib);
      }
      isAvailable = true;
    } catch (UnsatisfiedLinkError exception) {
      // Do nothing.
    }
    return isAvailable;
  }

}
