added XML parser

src/xml/XMLParser.java

@@ -0,0 +1,126 @@
+package xml;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import javax.xml.parsers.DocumentBuilderFactory;
+import javax.xml.parsers.ParserConfigurationException;
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+import org.w3c.dom.Node;
+import org.w3c.dom.NodeList;
+import org.xml.sax.SAXException;
+
+public class XMLParser {
+
+
+	private static final String CONFIG_FILE_NAME = "appdata/config.xml";
+
+	// Lists
+	private static final String ADLIST_TAG = "adlist";
+	private static final String URL_ATTRIBUTE_TAG = "url";
+	private static final String LIST_TAG = "list";
+
+	private static void saveDummyDocument(File file) {
+		try {
+			PrintWriter writer = new PrintWriter(file);
+			writer.write("""
+					<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+					<root>
+					  <adlist url="">
+					    <list><!--Put here in which list this Ad-list should be included--></list>
+					    <list><!--The Ad-list can be included in multiple lists--></list>
+					  </adlist>
+					</root>""");
+			writer.close();
+		} catch (IOException e) {
+			e.printStackTrace();
+			System.exit(1);
+		}
+	}
+
+	/**
+	 * Will get the Config.xml or, if not present, create a dummy one and exit
+	 *
+	 * @return The Document
+	 */
+	private static Document getDocument() {
+		try {
+			File inputFile = new File(CONFIG_FILE_NAME);
+			if (inputFile.createNewFile()) {
+				saveDummyDocument(inputFile);
+				System.err.println("There was no " + CONFIG_FILE_NAME
+							 + " available. Created a dummy one. Please fill it out");
+				System.exit(1);
+			}
+			return DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(inputFile);
+		} catch (ParserConfigurationException | IOException e) {
+			e.printStackTrace();
+			System.exit(1);
+		} catch (SAXException e) {
+			xmlFormatException("something went wrong while parsing the xml");
+		}
+		return null; // will never get there
+	}
+
+	/**
+	 * Will get AdLists
+	 *
+	 * @return The AdLists
+	 */
+	public static Map<String, List<String>> getAdList() {
+		NodeList adlist_list = getDocument().getElementsByTagName(ADLIST_TAG);
+		Map<String, List<String>> output = new HashMap<>();
+		for (int i = 0; i < adlist_list.getLength(); i++) {
+			try {
+				Element adlist = (Element) adlist_list.item(i);
+				String url = adlist.getAttribute(URL_ATTRIBUTE_TAG);
+				List<String> lists = new ArrayList<>();
+				NodeList list_list = adlist.getElementsByTagName(LIST_TAG);
+				for (int j = 0; j < list_list.getLength(); j++) {
+					Element countdown = (Element) list_list.item(j);
+					lists.add(readTextElement(countdown));
+				}
+				output.put(url, lists);
+			} catch (NullPointerException e) {
+				xmlFormatException("Tag missing in AdList");
+			}
+		}
+		return output;
+	}
+
+	/**
+	 * Will trim all '\n' and ' ' at the beginning and end of the Text Element
+	 *
+	 * @param node The Node were the Text Element is
+	 *
+	 * @return A String striped of it's unnecessary '\n' and ' '
+	 */
+	private static String readTextElement(Node node) {
+		String text = node.getTextContent();
+		if (text == null || text.equals(""))
+			return "";
+		while (text.charAt(0) == '\n' || text.charAt(0) == ' ') {
+			text = text.substring(1);
+		}
+		while (text.charAt(text.length() - 1) == '\n' || text.charAt(text.length() - 1) == ' ') {
+			text = text.substring(0, text.length() - 1);
+		}
+		return text;
+	}
+
+	/**
+	 * Will output a Error Log and throw a Runtime Exception
+	 *
+	 * @param reason The Message that should be in the Log
+	 */
+	private static void xmlFormatException(String reason) {
+		System.err.println("XML was wrongly formatted: " + reason);
+		throw new RuntimeException("XML was wrongly formatted: " + reason);
+	}
+
+}