1 files changed, 147 insertions, 0 deletions
diff --git a/base/src/main/java/bjc/utils/parserutils/pattern/PatternPart.java b/base/src/main/java/bjc/utils/parserutils/pattern/PatternPart.java
new file mode 100644
index 0000000..6661072
--- /dev/null
+++ b/base/src/main/java/bjc/utils/parserutils/pattern/PatternPart.java
@@ -0,0 +1,147 @@
+package bjc.utils.parserutils.pattern;
+
+import java.util.StringJoiner;
+import java.util.function.Supplier;
+import java.util.regex.*;
+
+/**
+ * Builder interface for regex patterns.
+ * 
+ * @author bjculkin
+ *
+ */
+public interface PatternPart {
+	/**
+	 * Convert this pattern part into a regex.
+	 * 
+	 * @return The regex this part represents.
+	 */
+	public String toRegex();
+	
+	public boolean canOptimize();
+	
+	static PatternPart part(boolean canOptimize, Supplier<String> func) {
+		return new PatternPart() {
+			
+			@Override
+			public String toRegex() {
+				return func.get();
+			}
+			
+			@Override
+			public boolean canOptimize() {
+				return canOptimize;
+			}
+		};
+	}
+	
+	static PatternPart var(Supplier<String> source) {
+		return part(false, source);
+	}
+	/**
+	 * Create a 'raw' pattern part, which just echoes the given string.
+	 * 
+	 * @param str The regex to include
+	 * 
+	 * @return A pattern part which converts to the given string.
+	 */
+	static PatternPart raw(String str) {
+		return part(true, () -> str);
+	}
+	
+	static PatternPart joining(String joiner, PatternPart... parts) {
+		return new PatternPart() {
+			
+			@Override
+			public String toRegex() {
+				StringJoiner sj = new StringJoiner(joiner);
+				for (PatternPart part : parts) sj.add(part.toRegex());
+				return sj.toString();
+			}
+			
+			@Override
+			public boolean canOptimize() {
+				for (PatternPart part : parts)
+					if (!part.canOptimize()) return false;
+				
+				return true;
+			}
+		};
+	}
+	/**
+	 * Create a pattern part which matches the given string.
+	 * 
+	 * @param str The string to match
+	 * 
+	 * @return A pattern which matches the given string.
+	 */
+	static PatternPart literal(String str) {
+		return part(true, () -> Pattern.quote(str));
+	}
+	
+	/**
+	 * Create a pattern part which matches a single digit.
+	 * 
+	 * @return A pattern that matches a digit.
+	 */
+	static PatternPart digit() {
+		return raw("\\d");
+	}
+	
+	static PatternPart cclass(char... chars) {
+		return part(true, () -> {
+			StringBuilder sb = new StringBuilder("[");
+			for (char ch : chars) sb.append(ch);
+			sb.append("]");
+			return sb.toString();
+		});
+	}
+	
+	static PatternPart notCClass(char... chars) {
+		return part(true, () -> {
+			StringBuilder sb = new StringBuilder("[^");
+			for (char ch : chars) sb.append(ch);
+			sb.append("]");
+			return sb.toString();
+		});
+	}
+	
+	static PatternPart nonspace() {
+		return raw("\\S");
+	}
+	
+	static PatternPart concat(PatternPart... parts) {
+		return joining(" ", parts);
+	}
+	
+	static PatternPart alternate(PatternPart... parts) {
+		return joining("|", parts);
+	}
+	
+	static PatternPart repeat(PatternPart part) {
+		return part(part.canOptimize(), () -> part.toRegex() + "*");
+	}
+	
+	static PatternPart optional(PatternPart part) {
+		return part(part.canOptimize(), () -> part.toRegex() + "?");
+	}
+	
+	static PatternPart repeatAtLeastOnce(PatternPart part) {
+		return part(part.canOptimize(), () -> part.toRegex() + "*");
+	}
+	
+	static PatternPart surround(String lhs, String rhs, PatternPart part) {
+		return part(part.canOptimize(), () -> lhs + part.toRegex() + rhs);
+	}
+	static PatternPart group(PatternPart part) {
+		return surround("(", ")", part);
+	}
+
+	static PatternPart namedGroup(String groupName, PatternPart part) {
+		return surround("(<" + groupName + ">", ")", part);
+	}
+	
+	static PatternPart nonCaptureGroup(PatternPart part) {
+		return surround("(?:", ")", part);
+	}
+}