Extension dependencies

core/src/main/java/org/geysermc/geyser/extension/GeyserExtensionClassLoader.java

@@ -40,11 +40,11 @@
 
 public class GeyserExtensionClassLoader extends URLClassLoader {
     private final GeyserExtensionLoader loader;
-    private final ExtensionDescription description;
+    private final GeyserExtensionDescription description;
     private final Object2ObjectMap<String, Class<?>> classes = new Object2ObjectOpenHashMap<>();
     private boolean warnedForExternalClassAccess;
 
-    public GeyserExtensionClassLoader(GeyserExtensionLoader loader, ClassLoader parent, Path path, ExtensionDescription description) throws MalformedURLException {
+    public GeyserExtensionClassLoader(GeyserExtensionLoader loader, ClassLoader parent, Path path, GeyserExtensionDescription description) throws MalformedURLException {
         super(new URL[] { path.toUri().toURL() }, parent);
         this.loader = loader;
         this.description = description;
@@ -89,7 +89,7 @@ protected Class<?> findClass(String name, boolean checkGlobal) throws ClassNotFo
                 // If class is not found in current extension, check in the global class loader
                 // This is used for classes that are not in the extension, but are in other extensions
                 if (checkGlobal) {
-                    if (!warnedForExternalClassAccess) {
+                    if (!warnedForExternalClassAccess && this.description.dependencies().isEmpty()) { // Don't warn when the extension has dependencies, it is probably using it's dependencies!
                         GeyserImpl.getInstance().getLogger().warning("Extension " + this.description.name() + " loads class " + name + " from an external source. " +
                                 "This can change at any time and break the extension, additionally to potentially causing unexpected behaviour!");
                         warnedForExternalClassAccess = true;

core/src/main/java/org/geysermc/geyser/extension/GeyserExtensionDescription.java

@@ -47,7 +47,8 @@ public record GeyserExtensionDescription(@NonNull String id,
                                          int majorApiVersion,
                                          int minorApiVersion,
                                          @NonNull String version,
-                                         @NonNull List<String> authors) implements ExtensionDescription {
+                                         @NonNull List<String> authors,
+                                         @NonNull Map<String, Dependency> dependencies) implements ExtensionDescription {
 
     private static final Yaml YAML = new Yaml(new CustomClassLoaderConstructor(Source.class.getClassLoader(), new LoaderOptions()));
 
@@ -94,7 +95,12 @@ public static GeyserExtensionDescription fromYaml(Reader reader) throws InvalidD
             authors.addAll(source.authors);
         }
 
-        return new GeyserExtensionDescription(id, name, main, humanApi, majorApi, minorApi, version, authors);
+        Map<String, Dependency> dependencies = new LinkedHashMap<>();
+        if (source.dependencies != null) {
+            dependencies.putAll(source.dependencies);
+        }
+
+        return new GeyserExtensionDescription(id, name, main, humanApi, majorApi, minorApi, version, authors, dependencies);
     }
 
     @NonNull
@@ -116,5 +122,17 @@ public static class Source {
         String version;
         String author;
         List<String> authors;
+        Map<String, Dependency> dependencies;
+    }
+
+    @Getter
+    @Setter
+    public static class Dependency {
+        boolean required = true; // Defaults to true
+        LoadOrder load = LoadOrder.BEFORE; // Defaults to ensure the dependency loads before this extension
+    }
+
+    public enum LoadOrder {
+        BEFORE, AFTER
     }
 }

core/src/main/java/org/geysermc/geyser/extension/GeyserExtensionLoader.java

@@ -54,11 +54,16 @@
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.BiConsumer;
+import java.util.function.Consumer;
 import java.util.regex.Pattern;
 
 @RequiredArgsConstructor
@@ -167,6 +172,8 @@ protected void loadAllExtensions(@NonNull ExtensionManager extensionManager) {
 
             Map<String, Path> extensions = new LinkedHashMap<>();
             Map<String, GeyserExtensionContainer> loadedExtensions = new LinkedHashMap<>();
+            Map<String, GeyserExtensionDescription> descriptions = new LinkedHashMap<>();
+            Map<String, Path> extensionPaths = new LinkedHashMap<>();
 
             Path updateDirectory = extensionsDirectory.resolve("update");
             if (Files.isDirectory(updateDirectory)) {
@@ -195,10 +202,126 @@ protected void loadAllExtensions(@NonNull ExtensionManager extensionManager) {
                 });
             }
 
-            // Step 3: Load the extensions
+            // Step 3: Order the extensions to allow dependencies to load in the correct order
             this.processExtensionsFolder(extensionsDirectory, (path, description) -> {
-                String name = description.name();
                 String id = description.id();
+                descriptions.put(id, description);
+                extensionPaths.put(id, path);
+
+            }, (path, e) -> {
+                logger.error(GeyserLocale.getLocaleStringLog("geyser.extensions.load.failed_with_name", path.getFileName(), path.toAbsolutePath()), e);
+            });
+
+            // The graph to back out loading order (Funny I just learnt these too)
+            Map<String, List<String>> loadOrderGraph = new HashMap<>();
+
+            // Looks like the graph needs to be prepopulated otherwise issues happen
+            for (String id : descriptions.keySet()) {
+                loadOrderGraph.putIfAbsent(id, new ArrayList<>());
+            }
+
+            for (GeyserExtensionDescription description : descriptions.values()) {
+                for (Map.Entry<String, GeyserExtensionDescription.Dependency> dependency : description.dependencies().entrySet()) {
+                    String from = null;
+                    String to = null; // Java complains if this isn't initialised, but not from, so, both null.
+
+                    // Check if the extension is even loaded
+                    if (!descriptions.containsKey(dependency.getKey())) {
+                        if (dependency.getValue().isRequired()) { // Only disable the extension if this dependency is required
+                            // The extension we are checking is missing 1 or more dependencies
+                            logger.error(
+                                GeyserLocale.getLocaleStringLog(
+                                    "geyser.extensions.load.failed_dependency_missing",
+                                    description.id(),
+                                    dependency.getKey()
+                                )
+                            );
+
+                            descriptions.remove(description.id()); // Prevents it from being loaded later
+                        }
+
+                        continue;
+                    }
+
+                    if (
+                        !(description.humanApiVersion() >= 2 &&
+                            description.majorApiVersion() >= 9 &&
+                            description.minorApiVersion() >= 0)
+                    ) {
+                        logger.error(
+                            GeyserLocale.getLocaleStringLog(
+                                "geyser.extensions.load.failed_cannot_use_dependencies",
+                                description.id(),
+                                description.apiVersion()
+                            )
+                        );
+
+                        descriptions.remove(description.id()); // Prevents it from being loaded later
+
+                        continue;
+                    }
+
+                    // Determine which way they should go in the graph
+                    switch (dependency.getValue().getLoad()) {
+                        case BEFORE -> {
+                            from = dependency.getKey();
+                            to = description.id();
+                        }
+                        case AFTER -> {
+                            from = description.id();
+                            to = dependency.getKey();
+                        }
+                    }
+
+                    loadOrderGraph.get(from).add(to);
+                }
+            }
+
+            Set<String> visited = new HashSet<>();
+            List<String> visiting = new ArrayList<>();
+            List<String> loadOrder = new ArrayList<>();
+
+            AtomicReference<Consumer<String>> sortMethod = new AtomicReference<>(); // yay, lambdas. This doesn't feel to suited to be a method
+            sortMethod.set((node) -> {
+                if (visiting.contains(node)) {
+                    logger.error(
+                        GeyserLocale.getLocaleStringLog(
+                            "geyser.extensions.load.failed_cyclical_dependencies",
+                            node,
+                            visiting.get(visiting.indexOf(node) - 1)
+                        )
+                    );
+
+                    visiting.remove(node);
+                    return;
+                }
+
+                if (visited.contains(node)) return;
+
+                visiting.add(node);
+                for (String neighbor : loadOrderGraph.get(node)) {
+                    sortMethod.get().accept(neighbor);
+                }
+                visiting.remove(node);
+                visited.add(node);
+                loadOrder.add(node);
+            });
+
+            for (String ext : descriptions.keySet()) {
+                if (!visited.contains(ext)) {
+                    // Time to sort the graph to get a load order, this reveals any cycles we may have
+                    sortMethod.get().accept(ext);
+                }
+            }
+            Collections.reverse(loadOrder); // This is inverted due to how the graph is created
+
+            // Step 4: Load the extensions
+            for (String id : loadOrder) {
+                // Grab path and description found from before, since we want a custom load order now
+                Path path = extensionPaths.get(id);
+                GeyserExtensionDescription description = descriptions.get(id);
+
+                String name = description.name();
                 if (extensions.containsKey(id) || extensionManager.extension(id) != null) {
                     logger.warning(GeyserLocale.getLocaleStringLog("geyser.extensions.load.duplicate", name, path.toString()));
                     return;
@@ -222,20 +345,22 @@ protected void loadAllExtensions(@NonNull ExtensionManager extensionManager) {
                     }
                 }
 
-                GeyserExtensionContainer container = this.loadExtension(path, description);
-                extensions.put(id, path);
-                loadedExtensions.put(id, container);
-            }, (path, e) -> {
-                logger.error(GeyserLocale.getLocaleStringLog("geyser.extensions.load.failed_with_name", path.getFileName(), path.toAbsolutePath()), e);
-            });
+                try {
+                    GeyserExtensionContainer container = this.loadExtension(path, description);
+                    extensions.put(id, path);
+                    loadedExtensions.put(id, container);
+                } catch (Throwable e) {
+                    logger.error(GeyserLocale.getLocaleStringLog("geyser.extensions.load.failed_with_name", path.getFileName(), path.toAbsolutePath()), e);
+                }
+            }
 
-            // Step 4: Register the extensions
+            // Step 5: Register the extensions
             for (GeyserExtensionContainer container : loadedExtensions.values()) {
                 this.extensionContainers.put(container.extension(), container);
                 this.register(container.extension(), extensionManager);
             }
         } catch (IOException ex) {
-            ex.printStackTrace();
+            logger.error("Unable to read extensions.", ex);
         }
     }