package com.bumptech.glide.load.engine.cache;

import android.content.Context;
import android.support.annotation.Nullable;
import java.io.File;

/**
 * Creates an {@link com.bumptech.glide.disklrucache.DiskLruCache} based disk cache in the external
 * disk cache directory, which falls back to the internal disk cache if no external storage is
 * available. If ever fell back to the internal disk cache, will use that one from that moment on.
 *
 * <p><b>Images can be read by everyone when using external disk cache.</b>
 */
// Public API.
@SuppressWarnings({"unused", "WeakerAccess"})
public final class ExternalPreferredCacheDiskCacheFactory extends DiskLruCacheFactory {

  public ExternalPreferredCacheDiskCacheFactory(Context context) {
    this(context, DiskCache.Factory.DEFAULT_DISK_CACHE_DIR,
        DiskCache.Factory.DEFAULT_DISK_CACHE_SIZE);
  }

  public ExternalPreferredCacheDiskCacheFactory(Context context, long diskCacheSize) {
    this(context, DiskCache.Factory.DEFAULT_DISK_CACHE_DIR, diskCacheSize);
  }

  public ExternalPreferredCacheDiskCacheFactory(final Context context, final String diskCacheName,
                                                final long diskCacheSize) {
    super(new CacheDirectoryGetter() {
      @Nullable
      private File getInternalCacheDirectory() {
        File cacheDirectory = context.getCacheDir();
        if (cacheDirectory == null) {
          return null;
        }
        if (diskCacheName != null) {
          return new File(cacheDirectory, diskCacheName);
        }
        return cacheDirectory;
      }

      @Override
      public File getCacheDirectory() {
        File internalCacheDirectory = getInternalCacheDirectory();

        // Already used internal cache, so keep using that one,
        // thus avoiding using both external and internal with transient errors.
        if ((null != internalCacheDirectory) && internalCacheDirectory.exists()) {
          return internalCacheDirectory;
        }

        File cacheDirectory = context.getExternalCacheDir();

        // Shared storage is not available.
        if ((cacheDirectory == null) || (!cacheDirectory.canWrite())) {
          return internalCacheDirectory;
        }
        if (diskCacheName != null) {
          return new File(cacheDirectory, diskCacheName);
        }
        return cacheDirectory;
      }
    }, diskCacheSize);
  }
}
