Adds some still not working code for building spigot and bukkit .jar files

src/main/java/net/knarcraft/minecraftserverlauncher/utility/CommonFunctions.java

@@ -202,6 +202,8 @@ public final class CommonFunctions {
             if (reader.read(readCharacters) > 0) {
                 text.append(readCharacters);
                 readCharacters = new char[1000];
+            } else {
+                return text.toString().trim();
             }
         }
         return text.toString().trim();

src/main/java/net/knarcraft/minecraftserverlauncher/utility/JarBuilder.java

@@ -0,0 +1,141 @@
+package net.knarcraft.minecraftserverlauncher.utility;
+
+import net.knarcraft.minecraftserverlauncher.Main;
+
+import java.io.BufferedReader;
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.OutputStreamWriter;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+public class JarBuilder {
+
+    private String downloadedBuildToolsVersion = "#124";
+    private String buildDirectory;
+    private String jarDirectory;
+
+    public JarBuilder(String buildDirectory, String jarDirectory) {
+        this.buildDirectory = buildDirectory;
+        this.jarDirectory = jarDirectory;
+    }
+
+    /**
+     * Builds the latest version of the spigot .jar file
+     */
+    public void buildSpigotJar() {
+        downloadBuildTools();
+        ProcessBuilder processBuilder = new ProcessBuilder("java", "-jar", "BuildTools.jar", "--rev",
+                "latest", "--output-dir", jarDirectory);
+        executeBuildProcess(processBuilder);
+        System.out.println("Finished building spigot .jar. Moving it to the correct location");
+        moveBuiltJar("spigot-", "SpigotLatest.jar");
+        System.out.println("Finished moving spigot .jar");
+    }
+
+    /**
+     * Builds the latest version of the craftbukkit .jar file
+     */
+    public void buildBukkitJar() {
+        downloadBuildTools();
+        ProcessBuilder processBuilder = new ProcessBuilder("java", "-jar", "BuildTools.jar", "--compile",
+                "craftbukkit", "--rev", "latest", "--output-dir", jarDirectory);
+        executeBuildProcess(processBuilder);
+        System.out.println("Finished building craftbukkit .jar. Moving it to the correct location");
+        moveBuiltJar("craftbukkit-", "BukkitLatest.jar");
+        System.out.println("Finished moving craftbukkit .jar");
+    }
+
+    /**
+     * Downloads the latest BuildTools version
+     */
+    public void downloadBuildTools() {
+        try {
+            String latestVersion = getLatestBuildToolsVersion();
+            if (!latestVersion.equals(downloadedBuildToolsVersion)) {
+                boolean success = CommonFunctions.downloadFile("https://hub.spigotmc.org/jenkins/job/BuildTools/" +
+                        "lastSuccessfulBuild/artifact/target/BuildTools.jar", Paths.get(buildDirectory + "BuildTools.jar"));
+                if (!success) {
+                    Main.getController().getGUI().setStatus("Unable to download the latest BuildTools");
+                }
+            }
+        } catch (IOException e) {
+            Main.getController().getGUI().setStatus("Unable to download the latest BuildTools");
+        }
+    }
+
+    /**
+     * Moves a built .jar file to its target file
+     * @param searchString <p>The start of the name of the built file used to find it</p>
+     * @param newName <p>The new name of the built file</p>
+     */
+    private void moveBuiltJar(String searchString, String newName) {
+        File[] foundFiles = new File(jarDirectory).listFiles((file) -> file.isFile() && file.getName().startsWith(searchString));
+        if (foundFiles != null && foundFiles.length == 1) {
+            File newFileLocation = new File(jarDirectory + File.separator + newName);
+            if (newFileLocation.exists()) {
+                if (!newFileLocation.delete()) {
+                    throw new IllegalArgumentException("Unable to delete previously built .jar");
+                }
+            }
+            if (!foundFiles[0].renameTo(newFileLocation)) {
+                throw new IllegalArgumentException("Unable to move built .jar");
+            }
+        }
+    }
+
+    /**
+     * Starts the build process and initializes
+     * @param processBuilder <p>The process builder to execute</p>
+     */
+    private void executeBuildProcess(ProcessBuilder processBuilder) {
+        processBuilder.directory(new File(buildDirectory));
+        processBuilder.redirectErrorStream(true);
+        try {
+            Process process = processBuilder.start();
+            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(System.out));
+            BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
+            ScheduledExecutorService builderOutputExecutor = Executors.newSingleThreadScheduledExecutor();
+            builderOutputExecutor.scheduleAtFixedRate(() -> {
+                try {
+                    String readText = CommonFunctions.readBufferedReader(reader);
+                    if (!readText.equals("")) {
+                        writer.write(readText);
+                        writer.flush();
+                    }
+                    if (!process.isAlive()) {
+                        writer.write("Closing process");
+                        writer.flush();
+                        builderOutputExecutor.shutdown();
+                        writer.close();
+                        reader.close();
+                        process.destroyForcibly();
+                    }
+                } catch (IOException e) {
+                    e.printStackTrace();
+                }
+            }, 1000, 5000, TimeUnit.MILLISECONDS);
+            process.waitFor();
+            System.out.println("Stopped waiting for process");
+        } catch (IOException | InterruptedException e) {
+            e.printStackTrace();
+        }
+    }
+
+    /**
+     * Gets the latest build tools version available
+     * @return <p>The latest build tools version available</p>
+     * @throws IOException <p>If unable to read the version file</p>
+     */
+    String getLatestBuildToolsVersion() throws IOException {
+        String versionDocument;
+        versionDocument = CommonFunctions.readFile("https://hub.spigotmc.org/jenkins/job/BuildTools/lastSuccessfulBuild/");
+        return CommonFunctions.stringBetween(versionDocument, "BuildTools #", " [");
+    }
+
+}