Add Dependency Injection Support for WorldGen Plugins

engine/src/main/java/org/terasology/engine/world/generator/plugin/UnresolvedWorldGeneratorPluginException.java

@@ -0,0 +1,22 @@
+// Copyright 2021 The Terasology Foundation
+// SPDX-License-Identifier: Apache-2.0
+package org.terasology.engine.world.generator.plugin;
+
+import java.io.Serial;
+
+public class UnresolvedWorldGeneratorPluginException extends Exception {
+
+    @Serial
+    private static final long serialVersionUID = 2096504461776129337L;
+
+    public UnresolvedWorldGeneratorPluginException() {
+    }
+
+    public UnresolvedWorldGeneratorPluginException(String message) {
+        super(message);
+    }
+
+    public UnresolvedWorldGeneratorPluginException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}

engine/src/main/java/org/terasology/engine/world/generator/plugin/WorldGeneratorPluginManager.java

@@ -0,0 +1,87 @@
+// Copyright 2024 The Terasology Foundation
+// SPDX-License-Identifier: Apache-2.0
+
+package org.terasology.engine.world.generator.plugin;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.terasology.engine.context.Context;
+import org.terasology.engine.core.module.ModuleManager;
+import org.terasology.engine.registry.InjectionHelper;
+import org.terasology.gestalt.assets.ResourceUrn;
+import org.terasology.gestalt.module.Module;
+import org.terasology.gestalt.module.ModuleEnvironment;
+import org.terasology.gestalt.module.dependencyresolution.DependencyResolver;
+import org.terasology.gestalt.module.dependencyresolution.ResolutionResult;
+
+import java.lang.reflect.InvocationTargetException;
+
+public class WorldGeneratorPluginManager {
+
+    private static final Logger logger = LoggerFactory.getLogger(WorldGeneratorPluginManager.class);
+
+    private final Context context;
+
+    public WorldGeneratorPluginManager(Context context) {
+        this.context = context;
+    }
+
+    /**
+     * @param urn urn of the world generator to create.
+     * @param context objects from this context will be injected into the world generator plugin
+     * @return The instantiated world generator plugin.
+     */
+    public static WorldGeneratorPlugin createGeneratorPlugin(ResourceUrn urn, Context context) throws UnresolvedWorldGeneratorPluginException {
+        ModuleManager moduleManager = context.get(ModuleManager.class);
+        Module module = moduleManager.getEnvironment().get(urn.getModuleName());
+        if (module == null) {
+            DependencyResolver resolver = new DependencyResolver(moduleManager.getRegistry());
+            ResolutionResult result = resolver.resolve(urn.getModuleName());
+            if (!result.isSuccess()) {
+                if (moduleManager.getRegistry().getLatestModuleVersion(urn.getModuleName()) == null) {
+                    throw new UnresolvedWorldGeneratorPluginException("Unable to resolve world generator plugin'"
+                            + urn + "' - not found");
+                } else {
+                    throw new UnresolvedWorldGeneratorPluginException("Unable to resolve world generator plugin'"
+                            + urn + "' - unable to resolve module dependencies");
+                }
+            }
+            try (ModuleEnvironment environment = moduleManager.loadEnvironment(result.getModules(), false)) {
+                return createWorldGeneratorPlugin(urn, context, environment);
+            }
+        } else {
+            return createWorldGeneratorPlugin(urn, context, moduleManager.getEnvironment());
+        }
+    }
+
+    /**
+     * @param urn urn of the world generator plugin to create.
+     * @param context that will be used to inject the world generator plugin.
+     * @param environment to be searched for the world generator plugin class.
+     * @return a new world generator plugin with the specified urn.
+     */
+    public static WorldGeneratorPlugin createWorldGeneratorPlugin(ResourceUrn urn, Context context, ModuleEnvironment environment)
+            throws UnresolvedWorldGeneratorPluginException {
+        for (Class<?> entry : environment.getTypesAnnotatedWith(RegisterPlugin.class)) {
+            ResourceUrn generatorUrn = new ResourceUrn(environment.getModuleProviding(entry).toString(), entry.getSimpleName());
+            if (generatorUrn.equals(urn)) {
+                WorldGeneratorPlugin worldGeneratorPlugin = loadGeneratorPlugin(entry, generatorUrn);
+                InjectionHelper.inject(worldGeneratorPlugin, context);
+                return worldGeneratorPlugin;
+            }
+        }
+        throw new UnresolvedWorldGeneratorPluginException("Unable to resolve world generator '" + urn + "' - not found");
+    }
+
+    private static WorldGeneratorPlugin loadGeneratorPlugin(Class<?> generatorClass, ResourceUrn urn) throws UnresolvedWorldGeneratorPluginException {
+        if (WorldGeneratorPlugin.class.isAssignableFrom(generatorClass)) {
+            try {
+                return (WorldGeneratorPlugin) generatorClass.getConstructor(ResourceUrn.class).newInstance(urn);
+            } catch (InstantiationException | IllegalAccessException | InvocationTargetException | NoSuchMethodException e) {
+                throw new UnresolvedWorldGeneratorPluginException("Failed to instantiate world generator plugin '" + urn + "'", e);
+            }
+        } else {
+            throw new UnresolvedWorldGeneratorPluginException(urn + " is not a valid world generator plugin");
+        }
+    }
+}