1 files changed, 134 insertions, 0 deletions
diff --git a/BJC-Utils2/src/main/java/bjc/utils/data/LazyPair.java b/BJC-Utils2/src/main/java/bjc/utils/data/LazyPair.java
new file mode 100644
index 0000000..fd432c1
--- /dev/null
+++ b/BJC-Utils2/src/main/java/bjc/utils/data/LazyPair.java
@@ -0,0 +1,134 @@
+package bjc.utils.data;
+
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+/**
+ * A lazy implementation of a pair
+ * 
+ * @author ben
+ *
+ * @param <LeftType>
+ *            The type on the left side of the pair
+ * @param <RightType>
+ *            The type on the right side of the pair
+ */
+public class LazyPair<LeftType, RightType>
+		implements IPair<LeftType, RightType> {
+	private LeftType			leftValue;
+	private RightType			rightValue;
+
+	private Supplier<LeftType>	leftSupplier;
+	private Supplier<RightType>	rightSupplier;
+
+	private boolean				leftMaterialized;
+	private boolean				rightMaterialized;
+
+	/**
+	 * Create a new lazy pair, using the set value s
+	 * 
+	 * @param leftVal
+	 *            The value for the left side of the pair
+	 * @param rightVal
+	 *            The value for the right side of the pair
+	 */
+	public LazyPair(LeftType leftVal, RightType rightVal) {
+		leftValue = leftVal;
+		rightValue = rightVal;
+
+		leftMaterialized = true;
+		rightMaterialized = true;
+	}
+
+	/**
+	 * Create a new lazy pair from the given value sources
+	 * 
+	 * @param leftSupp
+	 *            The source for a value on the left side of the pair
+	 * @param rightSupp
+	 *            The source for a value on the right side of the pair
+	 */
+	public LazyPair(Supplier<LeftType> leftSupp,
+			Supplier<RightType> rightSupp) {
+		leftSupplier = leftSupp;
+		rightSupplier = rightSupp;
+
+		leftMaterialized = false;
+		rightMaterialized = false;
+	}
+
+	@Override
+	public <BoundLeft> IPair<BoundLeft, RightType> bindLeft(
+			Function<LeftType, IPair<BoundLeft, RightType>> leftBinder) {
+		Supplier<LeftType> leftSupp = () -> {
+			if (leftMaterialized) {
+				return leftValue;
+			}
+
+			return leftSupplier.get();
+		};
+
+		return new HalfBoundLazyPair<>(leftSupp, leftBinder);
+	}
+
+	@Override
+	public <BoundRight> IPair<LeftType, BoundRight> bindRight(
+			Function<RightType, IPair<LeftType, BoundRight>> rightBinder) {
+		Supplier<RightType> rightSupp = () -> {
+			if (rightMaterialized) {
+				return rightValue;
+			}
+
+			return rightSupplier.get();
+		};
+
+		return new HalfBoundLazyPair<>(rightSupp, rightBinder);
+	}
+
+	@Override
+	public <BoundLeft, BoundRight> IPair<BoundLeft, BoundRight> bind(
+			BiFunction<LeftType, RightType, IPair<BoundLeft, BoundRight>> binder) {
+		return new BoundLazyPair<>(leftSupplier, rightSupplier, binder);
+	}
+
+	@Override
+	public <MergedType> MergedType merge(
+			BiFunction<LeftType, RightType, MergedType> merger) {
+		if (!leftMaterialized) {
+			leftValue = leftSupplier.get();
+
+			leftMaterialized = true;
+		}
+
+		if (!rightMaterialized) {
+			rightValue = rightSupplier.get();
+
+			rightMaterialized = true;
+		}
+
+		return merger.apply(leftValue, rightValue);
+	}
+
+	@Override
+	public LeftType getLeft() {
+		if (!leftMaterialized) {
+			leftValue = leftSupplier.get();
+
+			leftMaterialized = true;
+		}
+
+		return leftValue;
+	}
+
+	@Override
+	public RightType getRight() {
+		if (!rightMaterialized) {
+			rightValue = rightSupplier.get();
+
+			rightMaterialized = true;
+		}
+
+		return rightValue;
+	}
+}