content: /*
   * 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;
  
  import android.os.Looper;
  import android.text.TextUtils;
  import com.google.android.exoplayer2.ExoPlayerLibraryInfo;
  
  /**
   * Provides methods for asserting the truth of expressions and properties.
   */
  public final class Assertions {
  
    private Assertions() {}
  
    /**
     * Throws {@link IllegalArgumentException} if {@code expression} evaluates to false.
     *
     * @param expression The expression to evaluate.
     * @throws IllegalArgumentException If {@code expression} is false.
     */
    public static void checkArgument(boolean expression) {
      if (ExoPlayerLibraryInfo.ASSERTIONS_ENABLED && !expression) {
        throw new IllegalArgumentException();
      }
    }
  
    /**
     * Throws {@link IllegalArgumentException} if {@code expression} evaluates to false.
     *
     * @param expression The expression to evaluate.
     * @param errorMessage The exception message if an exception is thrown. The message is converted
     *     to a {@link String} using {@link String#valueOf(Object)}.
     * @throws IllegalArgumentException If {@code expression} is false.
     */
    public static void checkArgument(boolean expression, Object errorMessage) {
      if (ExoPlayerLibraryInfo.ASSERTIONS_ENABLED && !expression) {
        throw new IllegalArgumentException(String.valueOf(errorMessage));
      }
    }
  
    /**
     * Throws {@link IndexOutOfBoundsException} if {@code index} falls outside the specified bounds.
     *
     * @param index The index to test.
     * @param start The start of the allowed range (inclusive).
     * @param limit The end of the allowed range (exclusive).
     * @return The {@code index} that was validated.
     * @throws IndexOutOfBoundsException If {@code index} falls outside the specified bounds.
     */
    public static int checkIndex(int index, int start, int limit) {
      if (index < start || index >= limit) {
        throw new IndexOutOfBoundsException();
      }
      return index;
    }
  
    /**
     * Throws {@link IllegalStateException} if {@code expression} evaluates to false.
     *
     * @param expression The expression to evaluate.
     * @throws IllegalStateException If {@code expression} is false.
     */
    public static void checkState(boolean expression) {
      if (ExoPlayerLibraryInfo.ASSERTIONS_ENABLED && !expression) {
        throw new IllegalStateException();
      }
    }
  
    /**
     * Throws {@link IllegalStateException} if {@code expression} evaluates to false.
     *
     * @param expression The expression to evaluate.
     * @param errorMessage The exception message if an exception is thrown. The message is converted
     *     to a {@link String} using {@link String#valueOf(Object)}.
     * @throws IllegalStateException If {@code expression} is false.
     */
    public static void checkState(boolean expression, Object errorMessage) {
      if (ExoPlayerLibraryInfo.ASSERTIONS_ENABLED && !expression) {
        throw new IllegalStateException(String.valueOf(errorMessage));
      }
    }
  
    /**
     * Throws {@link NullPointerException} if {@code reference} is null.
     *
     * @param <T> The type of the reference.
     * @param reference The reference.
     * @return The non-null reference that was validated.
     * @throws NullPointerException If {@code reference} is null.
     */
    public static <T> T checkNotNull(T reference) {
      if (ExoPlayerLibraryInfo.ASSERTIONS_ENABLED && reference == null) {
        throw new NullPointerException();
      }
      return reference;
    }
  
    /**
     * Throws {@link NullPointerException} if {@code reference} is null.
     *
     * @param <T> The type of the reference.
     * @param reference The reference.
     * @param errorMessage The exception message to use if the check fails. The message is converted
     *     to a string using {@link String#valueOf(Object)}.
     * @return The non-null reference that was validated.
     * @throws NullPointerException If {@code reference} is null.
     */
    public static <T> T checkNotNull(T reference, Object errorMessage) {
      if (ExoPlayerLibraryInfo.ASSERTIONS_ENABLED && reference == null) {
        throw new NullPointerException(String.valueOf(errorMessage));
      }
      return reference;
    }
  
    /**
     * Throws {@link IllegalArgumentException} if {@code string} is null or zero length.
     *
     * @param string The string to check.
     * @return The non-null, non-empty string that was validated.
     * @throws IllegalArgumentException If {@code string} is null or 0-length.
     */
    public static String checkNotEmpty(String string) {
      if (ExoPlayerLibraryInfo.ASSERTIONS_ENABLED && TextUtils.isEmpty(string)) {
        throw new IllegalArgumentException();
      }
      return string;
    }
  
    /**
     * Throws {@link IllegalArgumentException} if {@code string} is null or zero length.
     *
     * @param string The string to check.
     * @param errorMessage The exception message to use if the check fails. The message is converted
     *     to a string using {@link String#valueOf(Object)}.
     * @return The non-null, non-empty string that was validated.
     * @throws IllegalArgumentException If {@code string} is null or 0-length.
     */
    public static String checkNotEmpty(String string, Object errorMessage) {
      if (ExoPlayerLibraryInfo.ASSERTIONS_ENABLED && TextUtils.isEmpty(string)) {
        throw new IllegalArgumentException(String.valueOf(errorMessage));
      }
      return string;
    }
  
    /**
     * Throws {@link IllegalStateException} if the calling thread is not the application's main
     * thread.
     *
     * @throws IllegalStateException If the calling thread is not the application's main thread.
     */
    public static void checkMainThread() {
      if (ExoPlayerLibraryInfo.ASSERTIONS_ENABLED && Looper.myLooper() != Looper.getMainLooper()) {
        throw new IllegalStateException("Not in applications main thread");
      }
    }
  
  }
  