ImageUrlsFetcher.java

/*
 * This file provided by Facebook is for non-commercial testing and evaluation
 * purposes only.  Facebook reserves all rights not expressly granted.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package com.facebook.fresco.sample.urlsfetcher;

import android.os.AsyncTask;

import com.facebook.common.internal.Preconditions;
import com.facebook.common.logging.FLog;

import org.apache.http.HttpStatus;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.StringWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

import javax.annotation.Nullable;

/**
 * Helper that asynchronously fetches the list of image URIs from Imgur.
 */
public class ImageUrlsFetcher {

  /**
   * Imgur license key for use by the Fresco project.
   *
   * The rest of this class may be used freely according to the licence file, with the sole
   * exception of this variable. Any fork of this code or use in any other application,
   * whether open- or closed-source, must use a different client ID obtained from Imgur.
   * See the <a href="https://api.imgur.com/#register">Imgur API documentation</a>.
   */
  private static final String IMGUR_CLIENT_ID = "Client-ID ccc6ca6a65ecdd8";

  private static final String TAG = "FrescoSample";

  public interface Callback {
    public void onFinish(List<String> results);
  }

  public static void getImageUrls(final ImageUrlsRequest request, final Callback callback) {
    new AsyncTask<Void, Void, List<String>>() {
      @Override
      protected List<String> doInBackground(Void... params) {
        return getImageUrls(request);
      }
      @Override
      protected void onPostExecute(List<String> result) {
        callback.onFinish(result);
      }
    }.execute();
  }

  private static List<String> getImageUrls(ImageUrlsRequest request) {
    List<String> urls = new ArrayList<String>();
    try {
      String rawJson = downloadContentAsString(request.getEndpointUrl());
      if (rawJson == null) {
        return urls;
      }
      JSONObject json = new JSONObject(rawJson);
      JSONArray data = json.getJSONArray("data");
      for (int i = 0; i < data.length(); i++) {
        JSONObject item = data.getJSONObject(i);
        if (!item.has("type")) {
          continue;
        }
        ImageFormat imageFormat = ImageFormat.getImageFormatForMime(item.getString("type"));
        ImageSize imageSize = request.getImageSize(imageFormat);
        if (imageSize != null) {
          urls.add(getThumbnailLink(item, imageSize));
        }
      }
    } catch (Exception e) {
      FLog.e(TAG, "Exception fetching album", e);
    }
    return urls;
  }

  @Nullable
  private static String downloadContentAsString(String urlString) throws IOException {
    InputStream is = null;
    try {
      URL url = new URL(urlString);
      HttpURLConnection conn = (HttpURLConnection) url.openConnection();
      conn.setRequestProperty("Authorization", IMGUR_CLIENT_ID);
      conn.setReadTimeout(10000 /* milliseconds */);
      conn.setConnectTimeout(15000 /* milliseconds */);
      conn.setRequestMethod("GET");
      conn.setDoInput(true);
      // Starts the query
      conn.connect();
      int response = conn.getResponseCode();
      if (response != HttpStatus.SC_OK) {
        FLog.e(TAG, "Album request returned %s", response);
        return null;
      }
      is = conn.getInputStream();
      return readAsString(is);
    } finally {
      if (is != null) {
        is.close();
      }
    }
  }

  /** Reads an InputStream and converts it to a String. */
  private static String readAsString(InputStream stream) throws IOException {
    StringWriter writer = new StringWriter();
    Reader reader = new BufferedReader(new InputStreamReader(stream, "UTF-8"));
    while (true) {
      int c = reader.read();
      if (c < 0) {
        break;
      }
      writer.write(c);
    }
    return writer.toString();
  }

  private static String getThumbnailLink(
      final JSONObject json,
      final ImageSize imageSize) throws JSONException {
    Preconditions.checkNotNull(imageSize);
    final String originalUrl = json.getString("link");
    if (imageSize == ImageSize.ORIGINAL_IMAGE) {
      return originalUrl;
    }

    final int dotPos = originalUrl.lastIndexOf('.');
    final StringBuilder linkBuilder = new StringBuilder(originalUrl.length() + 1);
    return linkBuilder
      .append(originalUrl)
      .insert(dotPos, imageSize.suffix)
      .toString();
  }
}