UnivrReader.java

package com.cellasoft.univrapp.reader;

import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import com.cellasoft.univrapp.Config;
import com.cellasoft.univrapp.model.Channel;
import com.cellasoft.univrapp.model.Department;
import com.cellasoft.univrapp.rss.RSSFeed;
import com.cellasoft.univrapp.rss.RSSHandler.OnNewEntryCallback;
import com.cellasoft.univrapp.utils.ErrorResponse;
import com.cellasoft.univrapp.utils.HandlerException;
import com.cellasoft.univrapp.utils.JSONHandler;
import com.cellasoft.univrapp.utils.StreamUtils;
import com.cellasoft.univrapp.widget.ContactItemInterface;
import com.google.gson.Gson;
import com.google.gson.JsonSyntaxException;

import java.io.IOException;
import java.io.InputStream;
import java.io.Serializable;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.List;

import static com.cellasoft.univrapp.utils.LogUtils.*;

public class UnivrReader implements Serializable {

    protected static final int DEFAULT_RETRY_HANDLER_SLEEP_TIME = 3 * 1000;
    private static final String TAG = makeLogTag(UnivrReader.class);
    private static final long serialVersionUID = 5743213346852835282L;
    private static final int DEFAULT_NUM_RETRIES = 3;
    protected static int numRetries = DEFAULT_NUM_RETRIES;
    private String userAgent;

    public UnivrReader(Context context) {
        userAgent = buildUserAgent(context);
    }

    /**
     * Build and return a user-agent string that can identify this application
     * to remote servers. Contains the package name and version code.
     */
    private static String buildUserAgent(Context context) {
        String versionName = "unknown";
        int versionCode = 0;

        try {
            final PackageInfo info = context.getPackageManager()
                    .getPackageInfo(context.getPackageName(), 0);
            versionName = info.versionName;
            versionCode = info.versionCode;
        } catch (PackageManager.NameNotFoundException ignored) {
        }

        return context.getPackageName() + "/" + versionName + " ("
                + versionCode + ") (gzip)";
    }

    public RSSFeed fetchEntriesOfFeed(Channel channel, int maxItems,
                                      OnNewEntryCallback callback) throws IOException {

        StreamUtils.disableConnectionReuseIfNecessary();
        URL url = new URL(channel.url);
        HttpURLConnection urlConnection = (HttpURLConnection) url
                .openConnection();
        urlConnection.setRequestProperty("User-Agent", userAgent);
        urlConnection.setRequestProperty("Content-Type", "application/rss+xml");
        urlConnection.setDoOutput(true);

        urlConnection.connect();
        throwErrors(urlConnection);

        InputStream is = urlConnection.getInputStream();
        return RSSFeed.parse(is, maxItems, callback);
    }

    public List<ContactItemInterface> executeGetJSON(Department uni,
                                                     JSONHandler handler) throws IOException {
        LOGI(TAG, "get Json (dest = " + uni.dest + ")");

        StreamUtils.disableConnectionReuseIfNecessary();

        String serverUrl = Config.Links.SERVER + "/lecturers.php?format=json&dest="
                + uni.dest;

        URL url = new URL(serverUrl);
        HttpURLConnection urlConnection = (HttpURLConnection) url
                .openConnection();
        urlConnection.setRequestProperty("User-Agent", userAgent);
        urlConnection.setRequestProperty("Content-Type", "application/json");

        urlConnection.connect();
        throwErrors(urlConnection);

        InputStream is = urlConnection.getInputStream();
        String response = StreamUtils.readAllText(is);

        LOGV(TAG, "HTTP response: " + response);
        return handler.parse(response);
    }

    private void throwErrors(HttpURLConnection urlConnection)
            throws IOException {
        final int status = urlConnection.getResponseCode();
        if (status < 200 || status >= 300) {
            String errorMessage = null;
            try {
                String errorContent = StreamUtils.readAllText(urlConnection
                        .getErrorStream());
                LOGV(TAG, "Error content: " + errorContent);
                ErrorResponse errorResponse = new Gson().fromJson(errorContent,
                        ErrorResponse.class);
                errorMessage = errorResponse.error.message;
            } catch (JsonSyntaxException ignored) {
            }

            String exceptionMessage = "Error response " + status + " "
                    + urlConnection.getResponseMessage()
                    + (errorMessage == null ? "" : (": " + errorMessage))
                    + " for " + urlConnection.getURL();

            // TODO: the API should return 401, and we shouldn't have to parse
            // the message
            if (errorMessage != null)
                throw new HandlerException(exceptionMessage);
        }
    }
}