import java.net.*;
import java.io.*;
import java.util.regex.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class WebCrawler {

    public static void main( String[] argv )
    {
        //regex setup
        ArrayList<String> inputs = new ArrayList<String>();
        String re = "http(s)*://(\\w+\\.)*(\\w+)" ;
        Pattern pat = Pattern.compile( re );
        String re2 = "(../)+index.html" ;
        Pattern pat2 = Pattern.compile( re2 );


        String urlName = null;
        if( argv.length < 1 )
            {
                System.out.print( "Enter URL (w/protocol) => " );
                BufferedReader cin = new BufferedReader( new InputStreamReader( System.in ));
            try {
                urlName = cin.readLine();
            } catch (IOException e) {
                System.err.println( "IO Error.  Exiting." );
                System.exit( 1 );
            }
        }
        else {
            urlName = argv[0];
        }//end get URL

        try {

        URL url = new URL( urlName );
        String file = slurp( url.openStream() );
        //System.out.println(file);

        List<String> inputlist = Arrays.asList(file);

        for( String s : inputlist )
        {
            Matcher matcher = pat.matcher( s );

            //System.out.println( "\nregex: " + re );
            //System.out.println( "input: " + s );
            //System.out.println( "----------------------------------" );

            while( matcher.find() )
            {
                System.out.println( "This link is: " + matcher.group() );

                    // Note on groupings:
                    // 0 is the entire string.  Groupings can be pulled out.  They are
                    // simply enumerated, even nested parentheses, by counting the
                    // opening left parenthesis (start at 1).
            }

            Matcher matcher2 = pat2.matcher( s );

            while( matcher2.find() )
            {
                System.out.println( "This link is: " + matcher2.group() );

                    // Note on groupings:
                    // 0 is the entire string.  Groupings can be pulled out.  They are
                    // simply enumerated, even nested parentheses, by counting the
                    // opening left parenthesis (start at 1).
            }
        }

        } catch( MalformedURLException e ) {
            System.err.println( "Poorly formed URL:" );
            System.out.println( e );
            System.exit( 2 );
        } catch( UnknownHostException e ) {
            System.err.println( "Unknown Host:" );
            System.out.println( e );
            System.exit( 3 );
        } catch( IOException e ) {
            System.err.println( ":" );
            System.out.println( e );
            System.exit( 4 );
        } // try
    } //end main

    public static String slurp (InputStream in) throws IOException
    {
        int n;
        StringBuffer out = new StringBuffer();
        byte[] b = new byte[4096];
        n = in.read( b );
        while( n != -1 )
        {
            out.append(new String(b, 0, n));
            n = in.read( b );
        }
        return out.toString();
    }   // slurp


}