1 files changed, 136 insertions, 0 deletions
diff --git a/BJC-Utils2/src/main/java/bjc/utils/data/Lazy.java b/BJC-Utils2/src/main/java/bjc/utils/data/Lazy.java
new file mode 100644
index 0000000..f4bc24a
--- /dev/null
+++ b/BJC-Utils2/src/main/java/bjc/utils/data/Lazy.java
@@ -0,0 +1,136 @@
+package bjc.utils.data;
+
+import java.util.function.Function;
+import java.util.function.Supplier;
+import java.util.function.UnaryOperator;
+
+import bjc.utils.funcdata.FunctionalList;
+import bjc.utils.funcdata.IFunctionalList;
+
+/**
+ * A holder that holds a means to create a value, but doesn't actually
+ * compute the value until it's needed
+ * 
+ * @author ben
+ *
+ * @param <ContainedType>
+ */
+public class Lazy<ContainedType> implements IHolder<ContainedType> {
+	private Supplier<ContainedType>							valueSupplier;
+
+	private IFunctionalList<UnaryOperator<ContainedType>>	actions	= new FunctionalList<>();
+
+	private boolean											valueMaterialized;
+
+	private ContainedType									heldValue;
+
+	/**
+	 * Create a new lazy value from the specified seed value
+	 * 
+	 * @param value
+	 *            The seed value to use
+	 */
+	public Lazy(ContainedType value) {
+		heldValue = value;
+
+		valueMaterialized = true;
+	}
+
+	/**
+	 * Create a new lazy value from the specified value source
+	 * 
+	 * @param supp
+	 *            The source of a value to use
+	 */
+	public Lazy(Supplier<ContainedType> supp) {
+		valueSupplier = supp;
+
+		valueMaterialized = false;
+	}
+
+	private Lazy(Supplier<ContainedType> supp,
+			IFunctionalList<UnaryOperator<ContainedType>> pendingActions) {
+		valueSupplier = supp;
+
+		actions = pendingActions;
+	}
+
+	@Override
+	public <BoundType> IHolder<BoundType> bind(
+			Function<ContainedType, IHolder<BoundType>> binder) {
+		IFunctionalList<UnaryOperator<ContainedType>> pendingActions = new FunctionalList<>();
+
+		actions.forEach(pendingActions::add);
+
+		Supplier<ContainedType> supplier = () -> {
+			if (valueMaterialized) {
+				return heldValue;
+			}
+
+			return valueSupplier.get();
+		};
+
+		return new BoundLazy<>(() -> {
+			return new Lazy<>(supplier, pendingActions);
+		}, binder);
+	}
+
+	@Override
+	public <MappedType> IHolder<MappedType> map(
+			Function<ContainedType, MappedType> mapper) {
+		IFunctionalList<UnaryOperator<ContainedType>> pendingActions = new FunctionalList<>();
+
+		actions.forEach(pendingActions::add);
+
+		return new Lazy<>(() -> {
+			ContainedType currVal = heldValue;
+
+			if (!valueMaterialized) {
+				currVal = valueSupplier.get();
+			}
+
+			return pendingActions.reduceAux(currVal,
+					UnaryOperator<ContainedType>::apply,
+					(value) -> mapper.apply(value));
+		});
+	}
+
+	@Override
+	public IHolder<ContainedType> transform(
+			UnaryOperator<ContainedType> transformer) {
+		actions.add(transformer);
+
+		return this;
+	}
+
+	@Override
+	public <UnwrappedType> UnwrappedType unwrap(
+			Function<ContainedType, UnwrappedType> unwrapper) {
+		if (!valueMaterialized) {
+			heldValue = valueSupplier.get();
+
+			valueMaterialized = true;
+		}
+
+		actions.forEach((action) -> {
+			heldValue = action.apply(heldValue);
+		});
+
+		actions = new FunctionalList<>();
+
+		return unwrapper.apply(heldValue);
+	}
+
+	@Override
+	public String toString() {
+		if (valueMaterialized) {
+			if (actions.isEmpty()) {
+				return "value[v='" + heldValue + "']";
+			}
+
+			return "value[v='" + heldValue + "'] (has pending transforms)";
+		}
+
+		return "(unmaterialized)";
+	}
+}