1 files changed, 63 insertions, 0 deletions
diff --git a/JPratt/src/main/java/com/ashardalon/pratt/blocks/TriggeredParseBlock.java b/JPratt/src/main/java/com/ashardalon/pratt/blocks/TriggeredParseBlock.java
new file mode 100644
index 0000000..1aeabdb
--- /dev/null
+++ b/JPratt/src/main/java/com/ashardalon/pratt/blocks/TriggeredParseBlock.java
@@ -0,0 +1,63 @@
+package com.ashardalon.pratt.blocks;
+
+import java.util.function.UnaryOperator;
+
+import com.ashardalon.pratt.ParserContext;
+import com.ashardalon.pratt.commands.CommandResult;
+import com.ashardalon.pratt.commands.CommandResult.Status;
+
+import bjc.utils.parserutils.ParserException;
+
+/**
+ * A parse block that can adjust the state before handling its context.
+ *
+ * @author bjculkin
+ *
+ * @param <K>
+ *        The key type of the tokens.
+ * @param <V>
+ *        The value type of the tokens.
+ * @param <C>
+ *        The state type of the parser.
+ */
+public class TriggeredParseBlock<K, V, C> implements ParseBlock<K, V, C> {
+	private final UnaryOperator<C> onEntr;
+	private final UnaryOperator<C> onExt;
+
+	private final ParseBlock<K, V, C> sourc;
+
+	/**
+	 * Create a new triggered parse block.
+	 *
+	 * @param onEnter
+	 *        The action to fire before parsing the block.
+	 *
+	 * @param onExit
+	 *        The action to fire after parsing the block.
+	 *
+	 * @param source
+	 *        The block to use for parsing.
+	 */
+	public TriggeredParseBlock(final UnaryOperator<C> onEnter, final UnaryOperator<C> onExit,
+			final ParseBlock<K, V, C> source) {
+		onEntr = onEnter;
+		onExt = onExit;
+		sourc = source;
+	}
+
+	@Override
+	public CommandResult<K, V> parse(final ParserContext<K, V, C> ctx) throws ParserException {
+		final C newState = onEntr.apply(ctx.state);
+
+		final ParserContext<K, V, C> newCtx = new ParserContext<>(ctx.tokens, ctx.parse, newState);
+
+		final CommandResult<K,V> res = sourc.parse(newCtx);
+
+		if (res.status != Status.SUCCESS) return res;
+		
+		ctx.state = onExt.apply(newState);
+
+		return res;
+	}
+
+}