1 files changed, 137 insertions, 0 deletions
diff --git a/src/main/java/bjc/data/internals/BoundLazy.java b/src/main/java/bjc/data/internals/BoundLazy.java
new file mode 100644
index 0000000..728af8e
--- /dev/null
+++ b/src/main/java/bjc/data/internals/BoundLazy.java
@@ -0,0 +1,137 @@
+package bjc.data.internals;
+
+import java.util.function.Function;
+import java.util.function.Supplier;
+import java.util.function.UnaryOperator;
+
+import bjc.data.IHolder;
+import bjc.data.Lazy;
+import bjc.funcdata.FunctionalList;
+import bjc.funcdata.IList;
+
+/**
+ * Implements a lazy holder that has been bound.
+ *
+ * @author Ben Culkin
+ */
+@SuppressWarnings("javadoc")
+public class BoundLazy<OldType, BoundContainedType> implements IHolder<BoundContainedType> {
+	/* The old value. */
+	private final Supplier<IHolder<OldType>> oldSupplier;
+
+	/* The function to use to transform the old value into a new value. */
+	private final Function<OldType, IHolder<BoundContainedType>> binder;
+
+	/* The bound value being held. */
+	private IHolder<BoundContainedType> boundHolder;
+
+	/* Whether the bound value has been actualized or not. */
+	private boolean holderBound;
+
+	/* Transformations currently pending on the bound value. */
+	private final IList<UnaryOperator<BoundContainedType>> actions = new FunctionalList<>();
+
+	/**
+	 * Create a new bound lazy value.
+	 *
+	 * @param supp
+	 *        The supplier of the old value.
+	 *
+	 * @param binder
+	 *        The function to use to bind the old value to the new one.
+	 */
+	public BoundLazy(final Supplier<IHolder<OldType>> supp,
+			final Function<OldType, IHolder<BoundContainedType>> binder) {
+		oldSupplier = supp;
+		this.binder = binder;
+	}
+
+	@Override
+	public <BoundType> IHolder<BoundType> bind(final Function<BoundContainedType, IHolder<BoundType>> bindr) {
+		if(bindr == null) throw new NullPointerException("Binder must not be null");
+
+		/* Prepare a list of pending actions. */
+		final IList<UnaryOperator<BoundContainedType>> pendingActions = new FunctionalList<>();
+		actions.forEach(pendingActions::add);
+
+		/* Create the new supplier of a value. */
+		final Supplier<IHolder<BoundContainedType>> typeSupplier = () -> {
+			IHolder<BoundContainedType> oldHolder = boundHolder;
+
+			/* Bind the value if it hasn't been bound before. */
+			if(!holderBound) {
+				oldHolder = oldSupplier.get().unwrap(binder);
+			}
+
+			/* Apply all the pending actions. */
+			return pendingActions.reduceAux(oldHolder, (action, state) -> {
+				return state.transform(action);
+			}, (value) -> value);
+		};
+
+		return new BoundLazy<>(typeSupplier, bindr);
+	}
+
+	@Override
+	public <NewType> Function<BoundContainedType, IHolder<NewType>> lift(
+			final Function<BoundContainedType, NewType> func) {
+		if(func == null) throw new NullPointerException("Function to lift must not be null");
+
+		return (val) -> {
+			return new Lazy<>(func.apply(val));
+		};
+	}
+
+	@Override
+	public <MappedType> IHolder<MappedType> map(final Function<BoundContainedType, MappedType> mapper) {
+		if(mapper == null) throw new NullPointerException("Mapper must not be null");
+
+		/* Prepare a list of pending actions. */
+		final IList<UnaryOperator<BoundContainedType>> pendingActions = new FunctionalList<>();
+		actions.forEach(pendingActions::add);
+
+		/* Prepare the new supplier. */
+		final Supplier<MappedType> typeSupplier = () -> {
+			IHolder<BoundContainedType> oldHolder = boundHolder;
+
+			/* Bound the value if it hasn't been bound. */
+			if(!holderBound) {
+				oldHolder = oldSupplier.get().unwrap(binder);
+			}
+
+			/* Apply pending actions. */
+			return pendingActions.reduceAux(oldHolder.getValue(), (action, state) -> {
+				return action.apply(state);
+			}, (value) -> mapper.apply(value));
+		};
+
+		return new Lazy<>(typeSupplier);
+	}
+
+	@Override
+	public String toString() {
+		if(holderBound) return boundHolder.toString();
+
+		return "(unmaterialized)";
+	}
+
+	@Override
+	public IHolder<BoundContainedType> transform(final UnaryOperator<BoundContainedType> transformer) {
+		if(transformer == null) throw new NullPointerException("Transformer must not be null");
+
+		actions.add(transformer);
+
+		return this;
+	}
+
+	@Override
+	public <UnwrappedType> UnwrappedType unwrap(final Function<BoundContainedType, UnwrappedType> unwrapper) {
+		if(unwrapper == null) throw new NullPointerException("Unwrapper must not be null");
+
+		if(!holderBound) {
+			boundHolder = oldSupplier.get().unwrap(binder::apply);
+		}
+
+		return boundHolder.unwrap(unwrapper);
+	}
+}