import javax.swing.*;
import javax.swing.event.HyperlinkEvent;
import javax.swing.event.HyperlinkListener;
import javax.swing.text.html.HTMLDocument;
import javax.swing.text.html.HTMLFrameHyperlinkEvent;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Stack;

public class SimpleBrowser extends JFrame implements HyperlinkListener
{
    private JTextField addressBar = new JTextField(40);

    private JEditorPane webPane = new JEditorPane();

    private URL currentURL = null;

    private static Stack<URL> historyBack = new Stack<>();;

    private static Stack<URL> historyForward = new Stack<>();;

    public SimpleBrowser()
    {
        setSize(800, 600);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel navigationPanel = new JPanel();
        navigationPanel.setLayout(new BorderLayout());

        addressBar.addActionListener((ActionEvent e) -> {
            if (addressBar.getText().equals(""))
                return;
            search();
        });

        navigationPanel.add(addressBar, BorderLayout.CENTER);

        JButton backButton = new JButton("<");
        backButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent b) {
                back();
            }
        });

        JButton forwardButton = new JButton(">");
        forwardButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent f) {
                forward();
            }
        });

        navigationPanel.add(backButton, BorderLayout.NORTH);
        navigationPanel.add(forwardButton, BorderLayout.SOUTH);

        JButton goButton = new JButton("Suche");
        goButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                search();
            }
        });

        navigationPanel.add(goButton, BorderLayout.EAST);

        webPane.setContentType("text/html");
        webPane.setEditable(false);
        webPane.addHyperlinkListener(this);

        getContentPane().setLayout(new BorderLayout());
        getContentPane().add(navigationPanel, BorderLayout.NORTH);
        getContentPane().add(new JScrollPane(webPane), BorderLayout.CENTER);
    }

    public void back()
    {
        if (historyBack.empty())
        {
            System.out.println("Cannot got back. Stack is empty");
            return;
        }
        URL poppedURL = historyBack.pop();
        historyForward.push(currentURL);
        showPage(poppedURL);
    }

    public void forward()
    {
        if (historyForward.empty())
        {
            System.out.println("Cannot got forward. Stack is empty");
            return;
        }
        URL poppedURL = historyForward.pop();
        historyBack.push(currentURL);
        showPage(poppedURL);
    }

    public void search()
    {
        URL verifiedURL = checkURL(addressBar.getText());

        if (verifiedURL != null)
        {
            showPage(verifiedURL);
            historyForward.clear();
        }
        else
        {
            System.out.println("Fehler in der URL");
        }
    }

    public void showPage(URL url)
    {
        if (currentURL!=null)
            historyBack.push(currentURL);
        currentURL = url;
        String content = null;
        URLConnection connection;

        try
        {
            connection = url.openConnection();

            boolean textSite = connection.getHeaderField("Content-Type").contains("text/html") || connection.getHeaderField("Content-Type").contains("text/plain");


            webPane.setContentType(connection.getHeaderField("Content-Type"));

            if (textSite)
            {
                try (BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(connection.getInputStream())))
                {
                    String inputLine;
                    StringBuilder stringBuilder = new StringBuilder();
                    while ((inputLine = bufferedReader.readLine()) != null)
                    {
                        stringBuilder.append(inputLine);
                    }

                    content = stringBuilder.toString();
                }
            }
        }
        catch (Exception e)
        {

        }

        System.out.println(content);

        webPane.setText(content);
    }

    public URL checkURL(String urlString)
    {
        if (urlString.toLowerCase().startsWith("https://"))
        {
            return null;
        }

        if (!urlString.toLowerCase().startsWith("http://"))
        {
            urlString = "http://" + urlString;
        }

        URL validURL;

        try
        {
            validURL = new URL(urlString);
        }
        catch (MalformedURLException e)
        {
            return null;
        }

        return validURL;
    }

    public void hyperlinkUpdate(HyperlinkEvent e)
    {
        HyperlinkEvent.EventType eventType = e.getEventType();

        if (eventType == HyperlinkEvent.EventType.ACTIVATED)
        {
            if (e instanceof HTMLFrameHyperlinkEvent)
            {
                HTMLFrameHyperlinkEvent linkEvent = (HTMLFrameHyperlinkEvent) e;
                HTMLDocument document = (HTMLDocument) webPane.getDocument();
                document.processHTMLFrameHyperlinkEvent(linkEvent);
            }
            else
            {
                showPage(e.getURL());
            }
        }
    }

    public static void main(String[] args)
    {
        SimpleBrowser browser = new SimpleBrowser();
        browser.setVisible(true);
    }
}