/*
 * [Download.java]
 *
 * Summary: command line automated download a file from the Internet.
 *
 * Copyright: (c) 1999-2017 Roedy Green, Canadian Mind Products, http://mindprod.com
 *
 * Licence: This software may be copied and used freely for any purpose but military.
 *          http://mindprod.com/contact/nonmil.html
 *
 * Requires: JDK 1.8+
 *
 * Created with: JetBrains IntelliJ IDEA IDE http://www.jetbrains.com/idea/
 *
 * Version History:
 *  2.5 2008-08-10 add setReadTimeout and setConnectTimeout methods.
 */
package com.mindprod.filetransfer;

import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;

import static java.lang.System.*;

/**
 * command line automated download a file from the Internet.
 * <p/>
 * use:
 * java com.mindprod.filetransfer.Download http://x.com/y.html C:\y.txt
 *
 * @author Roedy Green, Canadian Mind Products
 * @version 2.5 2008-08-10 add setReadTimeout and setConnectTimeout methods.
 * @since 1999
 */
public final class Download
    {
    public static final String USAGE = "Syntax is: Download [-sni] {source URL of file to download} {target file name}";

    /**
     * 64K is size buffer for file transfer
     */
    private static final int BUFFSIZE = 64 * 1024;

    static
        {
        System.setProperty( "java.net.preferIPv4Stack", "true" );
        System.setProperty( "jsse.enableSNIExtension", "false" );
        System.setProperty( "jdk.tls.ephemeralDHKeySize", "2048" );
        }

    /**
     * private constructor not used. Only use this class via static main.
     */
    private Download()
        {
        }

    /**
     * Download one file
     *
     * @param urlString source URL of file to download
     *                  e.g."http://www.billabong.com:80/songs/lyrics.txt"
     *                  works with  http:, https:,  file: and possibly others.
     * @param filename  target name of file to save on hard disk.
     * @param sni       true if should use server name identification
     *
     * @return true if download succeeded
     * @see com.mindprod.http.Fetch
     */
    @SuppressWarnings( { "BooleanMethodNameMustStartWithQuestion" } )
    public static boolean downloadOneFile( String urlString, String filename, boolean sni )
        {
        URL url;
        try
            {
            url = new URL( urlString );
            }
        catch ( MalformedURLException e )
            {
            throw new IllegalArgumentException( "Malformed URL: " + urlString );
            }
        final File file;
        try
            {
            file = new File( filename );
            if ( file.exists() )
                {
                if ( !file.canWrite() )
                    {
                    // canWrite true implies file exists.
                    throw new IllegalArgumentException( "Cannot write file: "
                                                        + filename );
                    }
                }
            else
                {
                // create file safely before we fool with URL
                file.createNewFile();
                }
            }
        catch ( IOException e )
            {
            throw new IllegalArgumentException( "Cannot write file: "
                                                + filename );
            }
        FileTransfer downloader = new FileTransfer( BUFFSIZE/* buffsize */ );
        // FileTransfer.download does the actual work.
        return downloader.download( url, file, sni );
        }

    /**
     * Command line Download
     *
     * @param args source url, target file
     *             source URL of file to download
     *             e.g."http://www.billabong.com:80/songs/lyrics.txt"
     *             works with  http:, https:,  file: and possibly others.
     */
    public static void main( String[] args )
        {
        if ( args.length < 1 )
            {
            throw new IllegalArgumentException( USAGE );
            }
        final boolean sni;
        final String source;
        final String target;
        if ( args[ 0 ].equals( "-sni" ) )
            {
            sni = true;
            if ( args.length < 3 )
                {
                throw new IllegalArgumentException( USAGE );
                }
            source = args[ 1 ];
            target = args[ 2 ];
            }
        else
            {
            sni = false;
            if ( args.length < 2 )
                {
                throw new IllegalArgumentException( USAGE );
                }
            source = args[ 0 ];
            target = args[ 1 ];
            }
        boolean success = downloadOneFile( source, target, sni );
        if ( success )
            {
            out.println( "Download of "
                         + source
                         + " to "
                         + target
                         + " succeeded." );
            }
        else
            {
            err.println( "Download of "
                         + source
                         + " to "
                         + target
                         + " failed. "
                         + FileTransfer.why );
            System.exit( 1 );
            }
        }
    }