Add reactor engine.

diff --git a/src/main/java/net/pterodactylus/reactor/engine/Engine.java b/src/main/java/net/pterodactylus/reactor/engine/Engine.java
new file mode 100644 (file)
index 0000000..123781f
--- /dev/null
+++ b/src/main/java/net/pterodactylus/reactor/engine/Engine.java
@@ -0,0 +1,235 @@
+/*
+ * Reactor - Engine.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.engine;
+
+import java.util.Map;
+import java.util.Set;
+import java.util.SortedMap;
+import java.util.concurrent.TimeUnit;
+
+import net.pterodactylus.reactor.Query;
+import net.pterodactylus.reactor.Reaction;
+import net.pterodactylus.reactor.Trigger;
+import net.pterodactylus.reactor.states.AbstractState;
+
+import org.apache.log4j.Logger;
+
+import com.google.common.collect.Maps;
+import com.google.common.collect.Sets;
+import com.google.common.util.concurrent.AbstractExecutionThreadService;
+import com.google.common.util.concurrent.Uninterruptibles;
+
+/**
+ * Reactor main engine.
+ *
+ * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+ */
+public class Engine extends AbstractExecutionThreadService {
+
+       /** The logger. */
+       private static final Logger logger = Logger.getLogger(Engine.class);
+
+       /** All defined reactions. */
+       private final Set<Reaction> reactions = Sets.newHashSet();
+
+       /** Reaction states. */
+       private final Map<Reaction, ReactionExecution> reactionExecutions = Maps.newHashMap();
+
+       //
+       // ACCESSORS
+       //
+
+       /**
+        * Adds the given reaction to this engine.
+        *
+        * @param reaction
+        *            The reaction to add to this engine
+        */
+       @SuppressWarnings("synthetic-access")
+       public void addReaction(Reaction reaction) {
+               reactions.add(reaction);
+               reactionExecutions.put(reaction, new ReactionExecution());
+       }
+
+       //
+       // ABSTRACTSERVICE METHODS
+       //
+
+       /**
+        * {@inheritDoc}
+        */
+       @Override
+       public void run() {
+               while (isRunning()) {
+
+                       /* delay if we have no reactions. */
+                       if (reactions.isEmpty()) {
+                               logger.trace("Sleeping for 1 second while no Reactions available.");
+                               Uninterruptibles.sleepUninterruptibly(1, TimeUnit.SECONDS);
+                               continue;
+                       }
+
+                       /* find next reaction. */
+                       SortedMap<Long, Reaction> nextReactions = Maps.newTreeMap();
+                       for (Reaction reaction : reactions) {
+                               ReactionExecution reactionExecution = reactionExecutions.get(reaction);
+                               nextReactions.put(reactionExecution.lastExecutionTime() + reaction.updateInterval(), reaction);
+                       }
+                       Reaction nextReaction = nextReactions.get(nextReactions.firstKey());
+                       ReactionExecution reactionExecution = reactionExecutions.get(nextReaction);
+                       logger.debug(String.format("Next Reaction: %s.", nextReaction));
+
+                       /* wait until the next reaction has to run. */
+                       while (isRunning()) {
+                               long waitTime = (reactionExecution.lastExecutionTime() + nextReaction.updateInterval()) - System.currentTimeMillis();
+                               logger.debug(String.format("Time to wait for next Reaction: %d millseconds.", waitTime));
+                               if (waitTime <= 0) {
+                                       break;
+                               }
+                               try {
+                                       logger.debug(String.format("Waiting for %d milliseconds.", waitTime));
+                                       TimeUnit.MILLISECONDS.sleep(waitTime);
+                               } catch (InterruptedException ie1) {
+                                       /* we’re looping! */
+                               }
+                       }
+
+                       /* are we still running? */
+                       if (!isRunning()) {
+                               break;
+                       }
+
+                       /* run reaction. */
+                       reactionExecution.setLastExecutionTime(System.currentTimeMillis());
+                       Query query = nextReaction.query();
+                       net.pterodactylus.reactor.State state;
+                       try {
+                               logger.debug("Querying system...");
+                               state = query.state();
+                               logger.debug("System queried.");
+                       } catch (Throwable t1) {
+                               logger.warn("Querying system failed!", t1);
+                               state = new AbstractState(t1) {
+                                       /* no further state. */
+                               };
+                       }
+                       logger.debug(String.format("State is %s.", state));
+                       reactionExecution.addState(state);
+
+                       /* only run trigger if we have collected two states. */
+                       boolean triggerHit = false;
+                       if (reactionExecution.previousState() != null) {
+                               Trigger trigger = nextReaction.trigger();
+                               logger.debug("Checking Trigger for changes...");
+                               triggerHit = trigger.triggers(reactionExecution.currentState(), reactionExecution.previousState());
+                       }
+
+                       /* run action if trigger was hit. */
+                       logger.debug(String.format("Trigger was hit: %s.", triggerHit));
+                       if (triggerHit) {
+                               logger.info("Executing Action...");
+                               nextReaction.action().execute(reactionExecution.currentState(), reactionExecution.previousState());
+                       }
+               }
+       }
+
+       /**
+        * Stores execution states of a {@link Reaction}.
+        *
+        * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+        */
+       private static class ReactionExecution {
+
+               /** The time the reaction was last executed. */
+               private long lastExecutionTime;
+
+               /** The previous state of the reaction. */
+               private net.pterodactylus.reactor.State previousState;
+
+               /** The current state of the reaction. */
+               private net.pterodactylus.reactor.State currentState;
+
+               //
+               // ACCESSORS
+               //
+
+               /**
+                * Returns the time the reaction was last executed. If the reaction was
+                * not yet executed, this method returns {@code 0}.
+                *
+                * @return The last execution time of the reaction (in milliseconds
+                *         since Jan 1, 1970 UTC)
+                */
+               public long lastExecutionTime() {
+                       return lastExecutionTime;
+               }
+
+               /**
+                * Returns the current state of the reaction. If the reaction was not
+                * yet executed, this method returns {@code null}.
+                *
+                * @return The current state of the reaction
+                */
+               public net.pterodactylus.reactor.State currentState() {
+                       return currentState;
+               }
+
+               /**
+                * Returns the previous state of the reaction. If the reaction was not
+                * yet executed at least twice, this method returns {@code null}.
+                *
+                * @return The previous state of the reaction
+                */
+               public net.pterodactylus.reactor.State previousState() {
+                       return previousState;
+               }
+
+               /**
+                * Sets the last execution time of the reaction.
+                *
+                * @param lastExecutionTime
+                *            The last execution time of the reaction (in milliseconds
+                *            since Jan 1, 1970 UTC)
+                * @return This execution
+                */
+               public ReactionExecution setLastExecutionTime(long lastExecutionTime) {
+                       this.lastExecutionTime = lastExecutionTime;
+                       return this;
+               }
+
+               //
+               // ACTIONS
+               //
+
+               /**
+                * Adds the given state as current state and moves the current state
+                * into the previous state.
+                *
+                * @param state
+                *            The new current state
+                * @return This execution
+                */
+               public ReactionExecution addState(net.pterodactylus.reactor.State state) {
+                       previousState = currentState;
+                       currentState = state;
+                       return this;
+               }
+
+       }
+
+}