/**
 * This program will demonstrate the file transfer from remote to local. If everything works fine, a
 * file 'file1' on 'remotehost' will copied to local 'file1'.
 */
import com.jcraft.jsch.Channel;
import com.jcraft.jsch.ChannelExec;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.Session;
import com.jcraft.jsch.UIKeyboardInteractive;
import com.jcraft.jsch.UserInfo;
import java.awt.Container;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;

public class ScpFrom {
  public static void main(String[] arg) {
    if (arg.length != 2) {
      System.err.println("usage: java ScpFrom user@remotehost:file1 file2");
      System.exit(-1);
    }

    try {

      String user = arg[0].substring(0, arg[0].indexOf('@'));
      arg[0] = arg[0].substring(arg[0].indexOf('@') + 1);
      String host = arg[0].substring(0, arg[0].indexOf(':'));
      String rfile = arg[0].substring(arg[0].indexOf(':') + 1);
      String lfile = arg[1];

      String prefix = null;
      if (new File(lfile).isDirectory()) {
        prefix = lfile + File.separator;
      }

      JSch jsch = new JSch();
      Session session = jsch.getSession(user, host, 22);

      // username and password will be given via UserInfo interface.
      UserInfo ui = new MyUserInfo();
      session.setUserInfo(ui);
      session.connect();

      // exec 'scp -f rfile' remotely
      rfile = rfile.replace("'", "'\"'\"'");
      rfile = "'" + rfile + "'";
      String command = "scp -f " + rfile;
      Channel channel = session.openChannel("exec");
      ((ChannelExec) channel).setCommand(command);

      // get I/O streams for remote scp
      OutputStream out = channel.getOutputStream();
      InputStream in = channel.getInputStream();

      channel.connect();

      byte[] buf = new byte[1024];

      // send '\0'
      buf[0] = 0;
      out.write(buf, 0, 1);
      out.flush();

      while (true) {
        int c = checkAck(in);
        if (c != 'C') {
          break;
        }

        // read '0644 '
        in.read(buf, 0, 5);

        long filesize = 0L;
        while (true) {
          if (in.read(buf, 0, 1) < 0) {
            // error
            break;
          }
          if (buf[0] == ' ')
            break;
          filesize = filesize * 10L + (long) (buf[0] - '0');
        }

        String file = null;
        for (int i = 0;; i++) {
          in.read(buf, i, 1);
          if (buf[i] == (byte) 0x0a) {
            file = new String(buf, 0, i);
            break;
          }
        }

        // System.out.println("filesize=" + filesize + ", file=" + file);

        // send '\0'
        buf[0] = 0;
        out.write(buf, 0, 1);
        out.flush();

        // read a content of lfile
        try (OutputStream fos = new FileOutputStream(prefix == null ? lfile : prefix + file)) {
          int foo;
          while (true) {
            if (buf.length < filesize)
              foo = buf.length;
            else
              foo = (int) filesize;
            foo = in.read(buf, 0, foo);
            if (foo < 0) {
              // error
              break;
            }
            fos.write(buf, 0, foo);
            filesize -= foo;
            if (filesize == 0L)
              break;
          }
        }

        if (checkAck(in) != 0) {
          System.exit(0);
        }

        // send '\0'
        buf[0] = 0;
        out.write(buf, 0, 1);
        out.flush();
      }

      session.disconnect();

      System.exit(0);
    } catch (Exception e) {
      System.out.println(e);
    }
  }

  static int checkAck(InputStream in) throws IOException {
    int b = in.read();
    // b may be 0 for success,
    // 1 for error,
    // 2 for fatal error,
    // -1
    if (b == 0)
      return b;
    if (b == -1)
      return b;

    if (b == 1 || b == 2) {
      StringBuilder sb = new StringBuilder();
      int c;
      do {
        c = in.read();
        sb.append((char) c);
      } while (c != '\n');
      if (b == 1) { // error
        System.out.print(sb);
      }
      if (b == 2) { // fatal error
        System.out.print(sb);
      }
    }
    return b;
  }

  public static class MyUserInfo implements UserInfo, UIKeyboardInteractive {
    @Override
    public String getPassword() {
      return passwd;
    }

    @Override
    public boolean promptYesNo(String str) {
      Object[] options = {"yes", "no"};
      int foo = JOptionPane.showOptionDialog(null, str, "Warning", JOptionPane.DEFAULT_OPTION,
          JOptionPane.WARNING_MESSAGE, null, options, options[0]);
      return foo == 0;
    }

    String passwd;
    JTextField passwordField = new JPasswordField(20);

    @Override
    public String getPassphrase() {
      return null;
    }

    @Override
    public boolean promptPassphrase(String message) {
      return true;
    }

    @Override
    public boolean promptPassword(String message) {
      Object[] ob = {passwordField};
      int result = JOptionPane.showConfirmDialog(null, ob, message, JOptionPane.OK_CANCEL_OPTION);
      if (result == JOptionPane.OK_OPTION) {
        passwd = passwordField.getText();
        return true;
      } else {
        return false;
      }
    }

    @Override
    public void showMessage(String message) {
      JOptionPane.showMessageDialog(null, message);
    }

    final GridBagConstraints gbc = new GridBagConstraints(0, 0, 1, 1, 1, 1,
        GridBagConstraints.NORTHWEST, GridBagConstraints.NONE, new Insets(0, 0, 0, 0), 0, 0);
    private Container panel;

    @Override
    public String[] promptKeyboardInteractive(String destination, String name, String instruction,
        String[] prompt, boolean[] echo) {
      panel = new JPanel();
      panel.setLayout(new GridBagLayout());

      gbc.weightx = 1.0;
      gbc.gridwidth = GridBagConstraints.REMAINDER;
      gbc.gridx = 0;
      panel.add(new JLabel(instruction), gbc);
      gbc.gridy++;

      gbc.gridwidth = GridBagConstraints.RELATIVE;

      JTextField[] texts = new JTextField[prompt.length];
      for (int i = 0; i < prompt.length; i++) {
        gbc.fill = GridBagConstraints.NONE;
        gbc.gridx = 0;
        gbc.weightx = 1;
        panel.add(new JLabel(prompt[i]), gbc);

        gbc.gridx = 1;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.weighty = 1;
        if (echo[i]) {
          texts[i] = new JTextField(20);
        } else {
          texts[i] = new JPasswordField(20);
        }
        panel.add(texts[i], gbc);
        gbc.gridy++;
      }

      if (JOptionPane.showConfirmDialog(null, panel, destination + ": " + name,
          JOptionPane.OK_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE) == JOptionPane.OK_OPTION) {
        String[] response = new String[prompt.length];
        for (int i = 0; i < prompt.length; i++) {
          response[i] = texts[i].getText();
        }
        return response;
      } else {
        return null; // cancel
      }
    }
  }
}