Add loader for reactions from chains.

diff --git a/src/main/java/net/pterodactylus/reactor/loader/ReactionLoader.java b/src/main/java/net/pterodactylus/reactor/loader/ReactionLoader.java
new file mode 100644 (file)
index 0000000..7016edb
--- /dev/null
+++ b/src/main/java/net/pterodactylus/reactor/loader/ReactionLoader.java
@@ -0,0 +1,177 @@
+/*
+ * Reactor - Loader.java - Copyright © 2013 David Roden
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package net.pterodactylus.reactor.loader;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+import net.pterodactylus.reactor.Action;
+import net.pterodactylus.reactor.Filter;
+import net.pterodactylus.reactor.Query;
+import net.pterodactylus.reactor.Reaction;
+import net.pterodactylus.reactor.Trigger;
+import net.pterodactylus.reactor.loader.Chain.Parameter;
+import net.pterodactylus.reactor.loader.Chain.Part;
+
+/**
+ * Creates {@link Reaction}s from {@link Chain}s.
+ *
+ * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+ */
+public class ReactionLoader {
+
+       /**
+        * Creates a {@link Reaction} from the given {@link Chain}.
+        *
+        * @param chain
+        *            The chain to create a reaction from
+        * @return The created reaction
+        * @throws LoaderException
+        *             if a class can not be loaded
+        */
+       @SuppressWarnings("static-method")
+       public Reaction loadReaction(Chain chain) throws LoaderException {
+
+               /* check if chain is enabled. */
+               if (!chain.enabled()) {
+                       throw new IllegalArgumentException("Chain is not enabled.");
+               }
+
+               /* create query. */
+               Query query = createObject(chain.query().name(), "net.pterodactylus.reactor.queries", extractParameters(chain.query().parameters()));
+
+               /* create filters. */
+               List<Filter> filters = new ArrayList<Filter>();
+               for (Part filterPart : chain.filters()) {
+                       filters.add(ReactionLoader.<Filter> createObject(filterPart.name(), "net.pterodactylus.reactor.filters", extractParameters(filterPart.parameters())));
+               }
+
+               /* create trigger. */
+               Trigger trigger = createObject(chain.trigger().name(), "net.pterodactylus.reactor.triggers", extractParameters(chain.trigger().parameters()));
+
+               /* create action. */
+               Action action = createObject(chain.action().name(), "net.pterodactylus.reactor.actions", extractParameters(chain.action().parameters()));
+
+               return new Reaction(query, filters, trigger, action).setUpdateInterval(TimeUnit.SECONDS.toMillis(chain.updateInterval()));
+       }
+
+       //
+       // STATIC METHODS
+       //
+
+       /**
+        * Extracts all parameter values from the given parameters.
+        *
+        * @param parameters
+        *            The parameters to extract the values from
+        * @return The extracted values
+        */
+       private static List<String> extractParameters(List<Parameter> parameters) {
+               List<String> parameterValues = new ArrayList<String>();
+
+               for (Parameter parameter : parameters) {
+                       parameterValues.add(parameter.value());
+               }
+
+               return parameterValues;
+       }
+
+       /**
+        * Creates a new object.
+        * <p>
+        * First, {@code className} is used to try to load a {@link Class} with that
+        * name. If that fails, {@code packageName} is prepended to the class name.
+        * If no class can be found, a {@link LoaderException} will be thrown.
+        * <p>
+        * If a class could be located using the described method, a constructor
+        * will be searched that has the same number of {@link String} parameters as
+        * the given parameters. The parameters from the given parameters are then
+        * used in a constructor call to create the new object.
+        *
+        * @param className
+        *            The name of the class
+        * @param packageName
+        *            The optional name of the package to prepend
+        * @param parameters
+        *            The parameters for the constructor call
+        * @return The created object
+        * @throws LoaderException
+        *             if the object can not be created
+        */
+       @SuppressWarnings("unchecked")
+       private static <T> T createObject(String className, String packageName, List<String> parameters) throws LoaderException {
+
+               /* try to load class without package name. */
+               Class<?> objectClass = null;
+               try {
+                       objectClass = Class.forName(className);
+               } catch (ClassNotFoundException cnfe1) {
+                       /* ignore, we’ll try again. */
+               }
+
+               if (objectClass == null) {
+                       try {
+                               objectClass = Class.forName(packageName + "." + className);
+                       } catch (ClassNotFoundException cnfe1) {
+                               /* okay, now we need to throw. */
+                               throw new LoaderException(String.format("Could find neither class “%s” nor class “%s.”", className, packageName + "." + className), cnfe1);
+                       }
+               }
+
+               /* locate an eligible constructor. */
+               Constructor<?> wantedConstructor = null;
+               for (Constructor<?> constructor : objectClass.getConstructors()) {
+                       Class<?>[] parameterTypes = constructor.getParameterTypes();
+                       if (parameterTypes.length != parameters.size()) {
+                               continue;
+                       }
+                       boolean compatibleTypes = true;
+                       for (Class<?> parameterType : parameterTypes) {
+                               if (parameterType != String.class) {
+                                       compatibleTypes = false;
+                                       break;
+                               }
+                       }
+                       if (!compatibleTypes) {
+                               continue;
+                       }
+                       wantedConstructor = constructor;
+               }
+
+               if (wantedConstructor == null) {
+                       throw new LoaderException("Could not find eligible constructor.");
+               }
+
+               try {
+                       return (T) wantedConstructor.newInstance(parameters.toArray());
+               } catch (IllegalArgumentException iae1) {
+                       throw new LoaderException("Could not invoke constructor.", iae1);
+               } catch (InstantiationException ie1) {
+                       throw new LoaderException("Could not invoke constructor.", ie1);
+               } catch (IllegalAccessException iae1) {
+                       throw new LoaderException("Could not invoke constructor.", iae1);
+               } catch (InvocationTargetException ite1) {
+                       throw new LoaderException("Could not invoke constructor.", ite1);
+               }
+
+       }
+
+}