Implement pattern guards

Pattern guards allow you to say that a particular pair should only be
replaced when the input matches a particular regular expression.

It is tied to the 'G' or 'Guard' control on the pair header, and is one
of the 3 or so major features I want to implement before a 1.0 release

As an aside, the other two features I want to add are:

Multibody Support
=================
This will allow a pair to replace to a few different things, based on
various conditions (the two main ones I want are some sort of cyclic
behavior, and some sort of guards for these)

Sub-application
================
Allow the application of a stage to the result of applying a pair/parts
of applying a pair. This will likely entail several sub-features such
as:

Named Stages
------------
A named stage is a collection of pairs that isn't applied by default,
but is instead used for convenient grouping of related pages together.

Custom Replacement
------------------
Instead of using replaceAll, I'll probably go for something using
appendReplacement etc. on Matcher and roll some sort of custom thing, so
as to provide for a convenient syntax for anything special I want to do
while running the replacement.

I'll also want to add some documentation, in addition to maybe doing
some restructuring to make how things are laid out more obvious.

3 files changed, 47 insertions, 9 deletions

diff --git a/data/test/test10.rp b/data/test/test10.rp
new file mode 100644
index 0000000..a647a3a
--- /dev/null
+++ b/data/test/test10.rp
@@ -0,0 +1,3 @@
+# Test pair guards
+//G/aaa//a
+b
diff --git a/src/main/java/bjc/everge/ReplPair.java b/src/main/java/bjc/everge/ReplPair.java
index 11ca3ef..4425da9 100644
--- a/src/main/java/bjc/everge/ReplPair.java
+++ b/src/main/java/bjc/everge/ReplPair.java
@@ -1,13 +1,10 @@
 package bjc.everge;
 
-import java.util.ArrayList;
-import java.util.List;
-import java.util.Scanner;
+import java.util.*;
+import java.util.function.*;
+import java.util.regex.*;
 
-import java.util.function.UnaryOperator;
-
-import bjc.everge.ControlledString.Control;
-import bjc.everge.ControlledString.ParseStrings;
+import bjc.everge.ControlledString.*;
 
 /**
  * String pairs for replacements.
@@ -37,6 +34,14 @@ public class ReplPair implements Comparable<ReplPair>, UnaryOperator<String> {
 	public String name;
 
 	/**
+	 * The guard for this replacement.
+	 *
+	 * The guard of the replacement is a regex that has to match before the pair will be considered.
+	 * Defaults to being blank.
+	 */
+	public String guard;
+
+	/**
 	 * The string to look for.
 	 */
 	public String find;
@@ -448,6 +453,10 @@ public class ReplPair implements Comparable<ReplPair>, UnaryOperator<String> {
 
 	@Override
 	public String apply(String inp) {
+		if (guard != null) {
+			if (!inp.matches(guard)) return inp;
+		}
+
 		return inp.replaceAll(find, replace);
 	}
 
@@ -521,6 +530,28 @@ public class ReplPair implements Comparable<ReplPair>, UnaryOperator<String> {
 							rp.name = cont.get(0);
 						}
 						break;
+					case "GUARD":
+					case "G":
+						if (cont.count() != 1) {
+							String errMsg = String.format("One guard argument was expected (got %d)",
+									cont.count());
+
+							errs.add(new ReplError(lno, pno, errMsg, nam));
+						} else {
+							String pat = cont.get(0);
+
+							try {
+								Pattern.compile(pat);
+							} catch (PatternSyntaxException psex) {
+								String errMsg = String.format("Guard argument '%s' is not a valid regex (%s)",
+										pat, psex.getMessage());
+
+								errs.add(new ReplError(lno, pno, errMsg, nam));
+							}
+
+							rp.guard = cont.get(0);
+						}
+						break;
 					case "PRIORITY":
 					case "PRIOR":
 					case "P":
@@ -796,8 +827,7 @@ public class ReplPair implements Comparable<ReplPair>, UnaryOperator<String> {
 	}
 	
 	private static ControlledString getControls(String lne, List<ReplError> errs,
-			ReplOpts ropts, IntHolder lno, IntHolder pno, String type) 
-	{
+			ReplOpts ropts, IntHolder lno, IntHolder pno, String type) {
 		try {
 			return ControlledString.parse(lne, new ParseStrings("//", ";", "/", "|"));
 		} catch (IllegalArgumentException iaex) {
diff --git a/src/test/java/bjc/everge/ReplPairTest.java b/src/test/java/bjc/everge/ReplPairTest.java
index 8edb42e..e098605 100644
--- a/src/test/java/bjc/everge/ReplPairTest.java
+++ b/src/test/java/bjc/everge/ReplPairTest.java
@@ -86,4 +86,9 @@ public class ReplPairTest {
 	public void testGlobals() {
 		assertMultiReplace("data/test/test8.rp", "b1d\n1d\n1b1", "acca");
 	}
+
+	@Test
+	public void testGuards() {
+		assertMultiReplace("data/test/test10.rp", "a", "a", "bbb", "aaa");
+	}
 }