Resource gatherer to extract data from Minecraft's server jar instead of distributing our own

.gitignore

@@ -42,6 +42,9 @@ gradle-app.setting
 # Cache of project
 .gradletasknamecache
 
+# IDEA files
+.idea/
+
 # # Work around https://youtrack.jetbrains.com/issue/IDEA-116898
 # gradle/wrapper/gradle-wrapper.properties
 

src/main/java/net/minestom/server/MinecraftServer.java

@@ -15,10 +15,13 @@ import net.minestom.server.network.packet.server.play.ServerDifficultyPacket;
 import net.minestom.server.ping.ResponseDataConsumer;
 import net.minestom.server.recipe.RecipeManager;
 import net.minestom.server.registry.RegistryMain;
+import net.minestom.server.registry.ResourceGatherer;
 import net.minestom.server.scoreboard.TeamManager;
 import net.minestom.server.timer.SchedulerManager;
 import net.minestom.server.world.Difficulty;
 
+import java.io.IOException;
+
 public class MinecraftServer {
 
     // Threads
@@ -103,6 +106,12 @@ public class MinecraftServer {
         nettyServer = new NettyServer(packetProcessor);
 
         // Registry
+        try {
+            ResourceGatherer.ensureResourcesArePresent(null); // TODO: provide a way to give a path override, probably via launch arguments?
+        } catch (IOException e) {
+            System.err.println("An error happened during resource gathering. Minestom will attempt to load anyway, but things may not work, and crashes can happen.");
+            e.printStackTrace();
+        }
         RegistryMain.registerBlocks();
         RegistryMain.registerItems();
         RegistryMain.registerEntities();

src/main/java/net/minestom/server/registry/RegistryMain.java

@@ -23,12 +23,12 @@ import java.util.Set;
 
 public class RegistryMain {
 
-    public static final String BLOCKS_PATH = "registry/blocks.json";
-    public static final String ITEMS_PATH = "registry/registries.json";
-    public static final String ENTITIES_PATH = "registry/registries.json";
-    public static final String SOUNDS_PATH = "registry/registries.json";
-    public static final String PARTICLES_PATH = "registry/registries.json";
-    public static final String STATS_PATH = "registry/registries.json";
+    public static final String BLOCKS_PATH = "minecraft_data/reports/blocks.json";
+    public static final String ITEMS_PATH = "minecraft_data/reports/registries.json";
+    public static final String ENTITIES_PATH = "minecraft_data/reports/registries.json";
+    public static final String SOUNDS_PATH = "minecraft_data/reports/registries.json";
+    public static final String PARTICLES_PATH = "minecraft_data/reports/registries.json";
+    public static final String STATS_PATH = "minecraft_data/reports/registries.json";
 
     public static void main(String[] args) {
         List<RegistryBlock> blocks = parseBlocks(BLOCKS_PATH);

src/main/java/net/minestom/server/registry/ResourceGatherer.java

@@ -0,0 +1,164 @@
+package net.minestom.server.registry;
+
+import com.google.gson.Gson;
+
+import java.io.BufferedInputStream;
+import java.io.File;
+import java.io.FileReader;
+import java.io.IOException;
+import java.net.URL;
+import java.nio.file.*;
+import java.nio.file.attribute.BasicFileAttributes;
+import java.util.stream.Collectors;
+
+/**
+ * Responsible for making sure Minestom has the necessary files to run (notably registry files)
+ */
+public class ResourceGatherer {
+
+    public static final File DATA_FOLDER = new File("./minecraft_data/");
+    private static final File TMP_FOLDER = new File("./.minestom_tmp/");
+
+    /**
+     * Checks if registry/ folder is present
+     * If it is not, download the minecraft server jar, run the data generator and extract the wanted files
+     * If it is already present, directly return
+     */
+    public static void ensureResourcesArePresent(File minecraftFolderOverride) throws IOException {
+        if(DATA_FOLDER.exists()) {
+            return;
+        }
+        System.out.println(DATA_FOLDER +" folder does not exist. Minestom will now generate the necessary files.");
+
+        if(!TMP_FOLDER.exists() && !TMP_FOLDER.mkdirs()) {
+            throw new IOException("Failed to create tmp folder.");
+        }
+
+        final String version = "1.15.2"; // TODO: Do not hardcode
+
+        System.out.println("Starting download of Minecraft server jar for version "+version+" from Mojang servers...");
+        File minecraftFolder = getMinecraftFolder(minecraftFolderOverride);
+        if(!minecraftFolder.exists()) {
+            throw new IOException("Could not find Minecraft installation folder, attempted location "+minecraftFolder+". If this location is not the correct one, please supply the correct one as argument of ResourceGatherer#ensureResourcesArePresent");
+        }
+        File serverJar = downloadServerJar(minecraftFolder, version);
+        System.out.println("Download complete.");
+
+        runDataGenerator(serverJar);
+
+        moveAndCleanup(version);
+        System.out.println("Resource gathering done!");
+    }
+
+    private static void moveAndCleanup(String version) throws IOException {
+        Path dataFolderPath = DATA_FOLDER.toPath();
+        Path tmpFolderPath = TMP_FOLDER.toPath();
+        Path generatedFolder = tmpFolderPath.resolve("generated");
+        System.out.println("Data generator successful, removing server jar");
+        Files.delete(tmpFolderPath.resolve("server_"+version+".jar"));
+        System.out.println("Removal successful, now moving data to "+DATA_FOLDER);
+        Files.walkFileTree(tmpFolderPath, new SimpleFileVisitor<>() {
+
+            @Override
+            public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
+                Path relativePath = generatedFolder.relativize(dir);
+                if(dir.startsWith(generatedFolder)) { // don't copy logs
+                    Path resolvedPath = dataFolderPath.resolve(relativePath);
+                    System.out.println("> Creating sub-folder "+relativePath);
+                    Files.createDirectories(resolvedPath);
+                }
+                return FileVisitResult.CONTINUE;
+            }
+
+            @Override
+            public FileVisitResult postVisitDirectory(Path dir, IOException exc) throws IOException {
+                System.out.println("> Deleting folder "+dir);
+                Files.delete(dir);
+                return FileVisitResult.CONTINUE;
+            }
+
+            @Override
+            public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
+                Path relativePath = generatedFolder.relativize(file);
+                if(file.startsWith(generatedFolder)) { // don't copy logs
+                    Path resolvedPath = dataFolderPath.resolve(relativePath);
+                    System.out.println("> Moving "+relativePath);
+                    Files.move(file, resolvedPath);
+                } else {
+                    System.out.println("> Deleting "+relativePath);
+                    Files.delete(file);
+                }
+                return FileVisitResult.CONTINUE;
+            }
+        });
+    }
+
+    private static void runDataGenerator(File serverJar) throws IOException {
+        ProcessBuilder dataGenerator = new ProcessBuilder("java", "-cp", serverJar.getName(), "net.minecraft.data.Main", "--all", "--server", "--dev");
+        dataGenerator.directory(TMP_FOLDER);
+        dataGenerator.inheritIO();
+        System.out.println("Now running data generator with options '--dev', '--server', '--all'");
+        System.out.println("Executing: "+dataGenerator.command().stream().collect(Collectors.joining(" ")));
+        System.out.println("Minestom will now wait for it to finish, here's its output:");
+        Process dataGeneratorProcess = dataGenerator.start();
+        try {
+            int resultCode = dataGeneratorProcess.waitFor();
+            if(resultCode != 0) {
+                throw new IOException("Data generator finished with non-zero return code "+resultCode);
+            }
+        } catch (InterruptedException e) {
+            throw new IOException("Data generator was interrupted.", e);
+        }
+    }
+
+    /**
+     * Finds the URL for the server jar inside the versions/ folder of the game installation and download the .jar file from there
+     * @param minecraftFolder
+     * @param version
+     * @return
+     */
+    private static File downloadServerJar(File minecraftFolder, String version) throws IOException {
+        File versionInfoFile = new File(minecraftFolder, "versions/"+version+"/"+version+".json");
+        if(!versionInfoFile.exists()) {
+            throw new IOException("Could not find "+version+".json in your Minecraft installation. Make sure to launch this version at least once before running Minestom");
+        }
+
+        try(FileReader fileReader = new FileReader(versionInfoFile)) {
+            Gson gson = new Gson();
+            VersionInfo versionInfo = gson.fromJson(fileReader, VersionInfo.class);
+            VersionInfo.DownloadObject serverJarInfo = versionInfo.getDownloadableFiles().get("server");
+            String downloadURL = serverJarInfo.getUrl();
+
+            System.out.println("Found URL, starting download from "+downloadURL+"...");
+            return download(version, downloadURL);
+        }
+    }
+
+    private static File download(String version, String url) throws IOException {
+        File target = new File(TMP_FOLDER, "server_"+version+".jar");
+        try(BufferedInputStream in = new BufferedInputStream(new URL(url).openStream())) {
+            Files.copy(in, target.toPath(), StandardCopyOption.REPLACE_EXISTING);
+        } catch (IOException e) {
+            throw new IOException("Failed to download Minecraft server jar.", e);
+        }
+        return target;
+    }
+
+    private static File getMinecraftFolder(File minecraftFolderOverride) {
+        if(minecraftFolderOverride != null) {
+            return minecraftFolderOverride;
+        }
+
+        // https://help.minecraft.net/hc/en-us/articles/360035131551-Where-are-Minecraft-files-stored-
+        String os = System.getProperty("os.name").toLowerCase();
+        if(os.contains("win")) {
+            String user = System.getProperty("user.name");
+            return new File("C:/Users/"+user+"/AppData/Roaming/.minecraft/");
+        }
+        if(os.contains("mac")) {
+            return new File("~/Library/Application Support/minecraft");
+        }
+
+        return new File("~/.minecraft");
+    }
+}

src/main/java/net/minestom/server/registry/VersionInfo.java

@@ -0,0 +1,39 @@
+package net.minestom.server.registry;
+
+import java.util.Map;
+
+/**
+ * Class used to represent the contents of a versions/{version}/{version}.json file
+ * Structured in a way that makes loading with Gson easy.
+ * Only concerned with helping extracting data from the server jar, lots of features may be missing.
+ */
+class VersionInfo {
+
+    private Map<String, DownloadObject> downloads;
+
+    private VersionInfo() {
+
+    }
+
+    public Map<String, DownloadObject> getDownloadableFiles() {
+        return downloads;
+    }
+
+    class DownloadObject {
+        private String url;
+        private String sha1;
+        private long size;
+
+        public String getUrl() {
+            return url;
+        }
+
+        public long getSize() {
+            return size;
+        }
+
+        public String getSha1() {
+            return sha1;
+        }
+    }
+}