/*
 * 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 androidx.media3.datasource.cache;

import androidx.annotation.Nullable;
import androidx.media3.common.C;
import androidx.media3.common.util.UnstableApi;
import java.io.File;

/** Defines a span of data that may or may not be cached (as indicated by {@link #isCached}). */
@UnstableApi
public class CacheSpan implements Comparable<CacheSpan> {

  /** The cache key that uniquely identifies the resource. */
  public final String key;

  /** The position of the {@link CacheSpan} in the resource. */
  public final long position;

  /**
   * The length of the {@link CacheSpan}, or {@link C#LENGTH_UNSET} if this is an open-ended hole.
   */
  public final long length;

  /** Whether the {@link CacheSpan} is cached. */
  public final boolean isCached;

  /** The file corresponding to this {@link CacheSpan}, or null if {@link #isCached} is false. */
  @Nullable public final File file;

  /** The last touch timestamp, or {@link C#TIME_UNSET} if {@link #isCached} is false. */
  public final long lastTouchTimestamp;

  /**
   * Creates a hole CacheSpan which isn't cached, has no last touch timestamp and no file
   * associated.
   *
   * @param key The cache key that uniquely identifies the resource.
   * @param position The position of the {@link CacheSpan} in the resource.
   * @param length The length of the {@link CacheSpan}, or {@link C#LENGTH_UNSET} if this is an
   *     open-ended hole.
   */
  public CacheSpan(String key, long position, long length) {
    this(key, position, length, C.TIME_UNSET, null);
  }

  /**
   * Creates a CacheSpan.
   *
   * @param key The cache key that uniquely identifies the resource.
   * @param position The position of the {@link CacheSpan} in the resource.
   * @param length The length of the {@link CacheSpan}, or {@link C#LENGTH_UNSET} if this is an
   *     open-ended hole.
   * @param lastTouchTimestamp The last touch timestamp, or {@link C#TIME_UNSET} if {@link
   *     #isCached} is false.
   * @param file The file corresponding to this {@link CacheSpan}, or null if it's a hole.
   */
  public CacheSpan(
      String key, long position, long length, long lastTouchTimestamp, @Nullable File file) {
    this.key = key;
    this.position = position;
    this.length = length;
    this.isCached = file != null;
    this.file = file;
    this.lastTouchTimestamp = lastTouchTimestamp;
  }

  /** Returns whether this is an open-ended {@link CacheSpan}. */
  public boolean isOpenEnded() {
    return length == C.LENGTH_UNSET;
  }

  /** Returns whether this is a hole {@link CacheSpan}. */
  public boolean isHoleSpan() {
    return !isCached;
  }

  @Override
  public int compareTo(CacheSpan another) {
    if (!key.equals(another.key)) {
      return key.compareTo(another.key);
    }
    long startOffsetDiff = position - another.position;
    return startOffsetDiff == 0 ? 0 : ((startOffsetDiff < 0) ? -1 : 1);
  }

  @Override
  public String toString() {
    return "[" + position + ", " + length + "]";
  }
}