1 files changed, 83 insertions, 0 deletions
diff --git a/src/main/java/bjc/data/internals/WrappedLazy.java b/src/main/java/bjc/data/internals/WrappedLazy.java
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+++ b/src/main/java/bjc/data/internals/WrappedLazy.java
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+package bjc.data.internals;
+
+import java.util.function.Function;
+import java.util.function.UnaryOperator;
+
+import bjc.data.IHolder;
+import bjc.data.Lazy;
+
+/**
+ * A wrapped lazy value.
+ *
+ * @author Ben Culkin
+ * @param <ContainedType>
+ *        The type of the wrapped value.
+ */
+public class WrappedLazy<ContainedType> implements IHolder<ContainedType> {
+	/* Held value. */
+	private final IHolder<IHolder<ContainedType>> held;
+
+	/**
+	 * Create a new wrapped lazy value.
+	 *
+	 * @param wrappedHolder
+	 *        The holder to make lazy.
+	 */
+	public WrappedLazy(final IHolder<ContainedType> wrappedHolder) {
+		held = new Lazy<>(wrappedHolder);
+	}
+
+	/*
+	 * This has an extra parameter, because otherwise it erases to the same
+	 * as the public one.
+	 *
+	 * This is a case where reified generics would be useful, because then
+	 * the compiler could know which one we meant without the dummy
+	 * parameter.
+	 */
+	private WrappedLazy(final IHolder<IHolder<ContainedType>> wrappedHolder,
+			@SuppressWarnings("unused") final boolean dummy) {
+		held = wrappedHolder;
+	}
+
+	@Override
+	public <BoundType> IHolder<BoundType> bind(final Function<ContainedType, IHolder<BoundType>> binder) {
+		final IHolder<IHolder<BoundType>> newHolder = held.map((containedHolder) -> {
+			return containedHolder.bind(binder);
+		});
+
+		return new WrappedLazy<>(newHolder, false);
+	}
+
+	@Override
+	public <NewType> Function<ContainedType, IHolder<NewType>> lift(final Function<ContainedType, NewType> func) {
+		return (val) -> {
+			return new Lazy<>(func.apply(val));
+		};
+	}
+
+	@Override
+	public <MappedType> IHolder<MappedType> map(final Function<ContainedType, MappedType> mapper) {
+		final IHolder<IHolder<MappedType>> newHolder = held.map((containedHolder) -> {
+			return containedHolder.map(mapper);
+		});
+
+		return new WrappedLazy<>(newHolder, false);
+	}
+
+	@Override
+	public IHolder<ContainedType> transform(final UnaryOperator<ContainedType> transformer) {
+		held.transform((containedHolder) -> {
+			return containedHolder.transform(transformer);
+		});
+
+		return this;
+	}
+
+	@Override
+	public <UnwrappedType> UnwrappedType unwrap(final Function<ContainedType, UnwrappedType> unwrapper) {
+		return held.unwrap((containedHolder) -> {
+			return containedHolder.unwrap(unwrapper);
+		});
+	}
+}