import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

/** @author chaynes@indiana.edu */
public class GetText {

   private static final String DEFAULT_TEST_URL = 
      "www.cs.indiana.edu/~chaynes/test.html";
   private static final String DEFAULT_URL_PREFIX = "http://";
   public static final int BUFFER_SIZE = 1000;
   public static final int EOF = -1;

   /**
    * @param url
    * syntax [http://<host domain>[:<port>][/[<path>][?<query>][#<fragment>]]
    * 
    * @return response to GET request on connection with given URL, or null if
    * the URL is malformed for there is a problem with the connection.
    */
   public static String fromUrl(String url) {
      if (!url.startsWith(DEFAULT_URL_PREFIX)) url = DEFAULT_URL_PREFIX + url;
      try {
         HttpURLConnection con = (HttpURLConnection) new URL(url).openConnection();
         con.setUseCaches(false);
         con.setRequestMethod("GET");
         con.connect();
         return readerToString(new InputStreamReader(con.getInputStream()));
      } catch (MalformedURLException e) {
         return null;
      } catch (IOException e) {
         return null;
      }
   }

   /** 
    * @return contents of indicated text file in a string, or null if the
    * file cannot be found or there is an error while reading it.
    */
   public static String fromFile(String fileName) {
      try {
         return readerToString(new FileReader(fileName));
      } catch (FileNotFoundException e) {
         return null;
      }
   }
   
   private static String readerToString(Reader reader) {
      char[] buffer = new char[BUFFER_SIZE];
      StringBuffer sb = new StringBuffer();
      int numCharsRead;
      try {
         while ((numCharsRead = reader.read(buffer)) != EOF) {
            sb.append(buffer, 0, numCharsRead);
         }
      } catch (IOException e) {
         return null;
      }
      return sb.toString();
   }

   /**
    * Usage: java GetText [url] where url defaults to
    * www.cs.indiana.edu/~chaynes/test.html and url prefix http:// is optional.
    * Prints server's response to url GET request.
    */
   public static void main(String[] args) {
      String url;
      if (args.length == 1) {
         url = args[0];
      } else if (args.length == 0) {
         url = DEFAULT_TEST_URL;
      } else {
         System.err.println("Usage: java Http [url]");
         return;
      }
      String s = fromUrl(url);
      System.out.println(s);
   }
}