/*
 * Copyright (C) 2013 Square, Inc.
 *
 * 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.squareup.picasso;

import android.content.Context;
import android.net.Uri;
import android.net.http.HttpResponseCache;
import android.os.Build;
import java.io.File;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;

import static com.squareup.picasso.Utils.parseResponseSourceHeader;

/**
 * A {@link Downloader} which uses {@link HttpURLConnection} to download images. A disk cache of
 * 10MB will automatically be installed in the application's cache directory, when available.
 */
public class UrlConnectionDownloader implements Downloader {
  static final String RESPONSE_SOURCE = "X-Android-Response-Source";

  private static final Object lock = new Object();
  static volatile Object cache;

  private final Context context;

  public UrlConnectionDownloader(Context context) {
    this.context = context.getApplicationContext();
  }

  protected HttpURLConnection openConnection(Uri path) throws IOException {
    HttpURLConnection connection = (HttpURLConnection) new URL(path.toString()).openConnection();
    connection.setConnectTimeout(Utils.DEFAULT_CONNECT_TIMEOUT);
    connection.setReadTimeout(Utils.DEFAULT_READ_TIMEOUT);
    return connection;
  }

  @Override public Response load(Uri uri, boolean localCacheOnly) throws IOException {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
      installCacheIfNeeded(context);
    }

    HttpURLConnection connection = openConnection(uri);
    connection.setUseCaches(true);
    if (localCacheOnly) {
      connection.setRequestProperty("Cache-Control", "only-if-cached");
    }

    boolean fromCache = parseResponseSourceHeader(connection.getHeaderField(RESPONSE_SOURCE));

    return new Response(connection.getInputStream(), fromCache);
  }

  private static void installCacheIfNeeded(Context context) {
    // DCL + volatile should be safe after Java 5.
    if (cache == null) {
      try {
        synchronized (lock) {
          if (cache == null) {
            cache = ResponseCacheIcs.install(context);
          }
        }
      } catch (IOException ignored) {
      }
    }
  }

  private static class ResponseCacheIcs {
    static Object install(Context context) throws IOException {
      File cacheDir = Utils.createDefaultCacheDir(context);
      HttpResponseCache cache = HttpResponseCache.getInstalled();
      if (cache == null) {
        int maxSize = Utils.calculateDiskCacheSize(cacheDir);
        cache = HttpResponseCache.install(cacheDir, maxSize);
      }
      return cache;
    }
  }
}