/*
 * Copyright (C) 2017 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.source.ads;

import androidx.annotation.Nullable;
import android.view.ViewGroup;
import com.google.android.exoplayer2.C;
import com.google.android.exoplayer2.Player;
import com.google.android.exoplayer2.source.ads.AdsMediaSource.AdLoadException;
import com.google.android.exoplayer2.upstream.DataSpec;
import java.io.IOException;

/**
 * Interface for loaders of ads, which can be used with {@link AdsMediaSource}.
 *
 * <p>Ad loaders notify the {@link AdsMediaSource} about events via {@link EventListener}. In
 * particular, implementations must call {@link EventListener#onAdPlaybackState(AdPlaybackState)}
 * with a new copy of the current {@link AdPlaybackState} whenever further information about ads
 * becomes known (for example, when an ad media URI is available, or an ad has played to the end).
 *
 * <p>{@link #start(EventListener, ViewGroup)} will be called when the ads media source first
 * initializes, at which point the loader can request ads. If the player enters the background,
 * {@link #stop()} will be called. Loaders should maintain any ad playback state in preparation for
 * a later call to {@link #start(EventListener, ViewGroup)}. If an ad is playing when the player is
 * detached, update the ad playback state with the current playback position using {@link
 * AdPlaybackState#withAdResumePositionUs(long)}.
 *
 * <p>If {@link EventListener#onAdPlaybackState(AdPlaybackState)} has been called, the
 * implementation of {@link #start(EventListener, ViewGroup)} should invoke the same listener to
 * provide the existing playback state to the new player.
 */
public interface AdsLoader {

  /**
   * Listener for ad loader events. All methods are called on the main thread.
   */
  interface EventListener {

    /**
     * Called when the ad playback state has been updated.
     *
     * @param adPlaybackState The new ad playback state.
     */
    void onAdPlaybackState(AdPlaybackState adPlaybackState);

    /**
     * Called when there was an error loading ads.
     *
     * @param error The error.
     * @param dataSpec The data spec associated with the load error.
     */
    void onAdLoadError(AdLoadException error, DataSpec dataSpec);

    /**
     * Called when the user clicks through an ad (for example, following a 'learn more' link).
     */
    void onAdClicked();

    /**
     * Called when the user taps a non-clickthrough part of an ad.
     */
    void onAdTapped();

  }

  // Methods called by the application.

  /**
   * Sets the player that will play the loaded ads.
   *
   * <p>This method must be called before the player is prepared with media using this ads loader.
   *
   * <p>This method must also be called on the main thread and only players which are accessed on
   * the main thread are supported ({@code player.getApplicationLooper() ==
   * Looper.getMainLooper()}).
   *
   * @param player The player instance that will play the loaded ads. May be null to delete the
   *     reference to a previously set player.
   */
  void setPlayer(@Nullable Player player);

  /**
   * Releases the loader. Must be called by the application on the main thread when the instance is
   * no longer needed.
   */
  void release();

  // Methods called by AdsMediaSource.

  /**
   * Sets the supported content types for ad media. Must be called before the first call to {@link
   * #start(EventListener, ViewGroup)}. Subsequent calls may be ignored. Called on the main thread
   * by {@link AdsMediaSource}.
   *
   * @param contentTypes The supported content types for ad media. Each element must be one of
   *     {@link C#TYPE_DASH}, {@link C#TYPE_HLS}, {@link C#TYPE_SS} and {@link C#TYPE_OTHER}.
   */
  void setSupportedContentTypes(@C.ContentType int... contentTypes);

  /**
   * Starts using the ads loader for playback. Called on the main thread by {@link AdsMediaSource}.
   *
   * @param eventListener Listener for ads loader events.
   * @param adUiViewGroup A {@link ViewGroup} on top of the player that will show any ad UI.
   */
  void start(EventListener eventListener, ViewGroup adUiViewGroup);

  /**
   * Stops using the ads loader for playback and deregisters the event listener. Called on the main
   * thread by {@link AdsMediaSource}.
   */
  void stop();

  /**
   * Notifies the ads loader that the player was not able to prepare media for a given ad.
   * Implementations should update the ad playback state as the specified ad has failed to load.
   * Called on the main thread by {@link AdsMediaSource}.
   *
   * @param adGroupIndex The index of the ad group.
   * @param adIndexInAdGroup The index of the ad in the ad group.
   * @param exception The preparation error.
   */
  void handlePrepareError(int adGroupIndex, int adIndexInAdGroup, IOException exception);
}
