Add filter interface.

diff --git a/src/main/java/net/pterodactylus/reactor/Filter.java b/src/main/java/net/pterodactylus/reactor/Filter.java
new file mode 100644 (file)
index 0000000..0afb226
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+++ b/src/main/java/net/pterodactylus/reactor/Filter.java
@@ -0,0 +1,43 @@
+/*
+ * Reactor - Filter.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;
+
+/**
+ * Defines a filter that runs between {@link Query}s and {@link Trigger}s and
+ * can be used to convert a {@link State} into another {@link State}. This can
+ * be used to extract further information from a state.
+ * <p>
+ * An example scenario would be a {@link Query} that requests a web site and a
+ * {@link Filter} that extracts content from the web site. That way the same
+ * {@link Query} could be used for multiple {@link Reaction}s without requiring
+ * modifications.
+ *
+ * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+ */
+public interface Filter {
+
+       /**
+        * Converts the given state into a different state.
+        *
+        * @param state
+        *            The state to convert
+        * @return The new state
+        */
+       State filter(State state);
+
+}