1 files changed, 228 insertions, 0 deletions
diff --git a/src/main/java/bjc/data/internals/BoundLazyPair.java b/src/main/java/bjc/data/internals/BoundLazyPair.java
new file mode 100644
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--- /dev/null
+++ b/src/main/java/bjc/data/internals/BoundLazyPair.java
@@ -0,0 +1,228 @@
+package bjc.data.internals;
+
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+import bjc.data.IHolder;
+import bjc.data.IPair;
+import bjc.data.Identity;
+import bjc.data.LazyPair;
+
+/**
+ * Implements a lazy pair that has been bound.
+ *
+ * @author Ben Culkin
+ */
+@SuppressWarnings("javadoc")
+public class BoundLazyPair<OldLeft, OldRight, NewLeft, NewRight> implements IPair<NewLeft, NewRight> {
+	/* The supplier of the left value. */
+	private final Supplier<OldLeft> leftSupplier;
+	/* The supplier of the right value. */
+	private final Supplier<OldRight> rightSupplier;
+
+	/* The binder to transform values. */
+	private final BiFunction<OldLeft, OldRight, IPair<NewLeft, NewRight>> binder;
+
+	/* The bound pair. */
+	private IPair<NewLeft, NewRight> boundPair;
+
+	/* Whether the pair has been bound yet. */
+	private boolean pairBound;
+
+	/**
+	 * Create a new bound lazy pair.
+	 *
+	 * @param leftSupp
+	 *        The supplier for the left value.
+	 *
+	 * @param rightSupp
+	 *        The supplier for the right value.
+	 *
+	 * @param bindr
+	 *        The function to use to bind the left and right into a new
+	 *        pair.
+	 */
+	public BoundLazyPair(final Supplier<OldLeft> leftSupp, final Supplier<OldRight> rightSupp,
+			final BiFunction<OldLeft, OldRight, IPair<NewLeft, NewRight>> bindr) {
+		leftSupplier = leftSupp;
+		rightSupplier = rightSupp;
+		binder = bindr;
+	}
+
+	@Override
+	public <BoundLeft, BoundRight> IPair<BoundLeft, BoundRight> bind(
+			final BiFunction<NewLeft, NewRight, IPair<BoundLeft, BoundRight>> bindr) {
+		if(bindr == null) throw new NullPointerException("Binder must not be null");
+
+		final IHolder<IPair<NewLeft, NewRight>> newPair = new Identity<>(boundPair);
+		final IHolder<Boolean> newPairMade = new Identity<>(pairBound);
+
+		final Supplier<NewLeft> leftSupp = () -> {
+			if(!newPairMade.getValue()) {
+				/*
+				 * If the pair hasn't been bound before, bind
+				 * it.
+				 */
+				newPair.replace(binder.apply(leftSupplier.get(), rightSupplier.get()));
+
+				newPairMade.replace(true);
+			}
+
+			return newPair.unwrap((pair) -> pair.getLeft());
+		};
+
+		final Supplier<NewRight> rightSupp = () -> {
+			if(!newPairMade.getValue()) {
+				/*
+				 * If the pair hasn't been bound before, bind
+				 * it.
+				 */
+				newPair.replace(binder.apply(leftSupplier.get(), rightSupplier.get()));
+
+				newPairMade.replace(true);
+			}
+
+			return newPair.unwrap((pair) -> pair.getRight());
+		};
+
+		return new BoundLazyPair<>(leftSupp, rightSupp, bindr);
+	}
+
+	@Override
+	public <BoundLeft> IPair<BoundLeft, NewRight> bindLeft(
+			final Function<NewLeft, IPair<BoundLeft, NewRight>> leftBinder) {
+		if(leftBinder == null) throw new NullPointerException("Left binder must not be null");
+
+		final Supplier<NewLeft> leftSupp = () -> {
+			IPair<NewLeft, NewRight> newPair = boundPair;
+
+			if(!pairBound) {
+				/*
+				 * If the pair hasn't been bound before, bind
+				 * it.
+				 */
+				newPair = binder.apply(leftSupplier.get(), rightSupplier.get());
+			}
+
+			return newPair.getLeft();
+		};
+
+		return new HalfBoundLazyPair<>(leftSupp, leftBinder);
+	}
+
+	@Override
+	public <BoundRight> IPair<NewLeft, BoundRight> bindRight(
+			final Function<NewRight, IPair<NewLeft, BoundRight>> rightBinder) {
+		if(rightBinder == null) throw new NullPointerException("Right binder must not be null");
+
+		final Supplier<NewRight> rightSupp = () -> {
+			IPair<NewLeft, NewRight> newPair = boundPair;
+
+			if(!pairBound) {
+				/*
+				 * If the pair hasn't been bound before, bind
+				 * it.
+				 */
+				newPair = binder.apply(leftSupplier.get(), rightSupplier.get());
+			}
+
+			return newPair.getRight();
+		};
+
+		return new HalfBoundLazyPair<>(rightSupp, rightBinder);
+	}
+
+	@Override
+	public <OtherLeft, OtherRight, CombinedLeft, CombinedRight> IPair<CombinedLeft, CombinedRight> combine(
+			final IPair<OtherLeft, OtherRight> otherPair,
+			final BiFunction<NewLeft, OtherLeft, CombinedLeft> leftCombiner,
+			final BiFunction<NewRight, OtherRight, CombinedRight> rightCombiner) {
+		if(otherPair == null) {
+			throw new NullPointerException("Other pair must not be null");
+		} else if(leftCombiner == null) {
+			throw new NullPointerException("Left combiner must not be null");
+		} else if(rightCombiner == null) {
+			throw new NullPointerException("Right combiner must not be null");
+		}
+
+		return otherPair.bind((otherLeft, otherRight) -> {
+			return bind((leftVal, rightVal) -> {
+				CombinedLeft cLeft = leftCombiner.apply(leftVal, otherLeft);
+				CombinedRight cRight = rightCombiner.apply(rightVal, otherRight);
+
+				return new LazyPair<>(cLeft, cRight);
+			});
+		});
+	}
+
+	@Override
+	public <NewLeftType> IPair<NewLeftType, NewRight> mapLeft(final Function<NewLeft, NewLeftType> mapper) {
+		if(mapper == null) throw new NullPointerException("Mapper must not be null");
+
+		final Supplier<NewLeftType> leftSupp = () -> {
+			if(!pairBound) {
+				final NewLeft leftVal = binder.apply(leftSupplier.get(), rightSupplier.get()).getLeft();
+
+				return mapper.apply(leftVal);
+			}
+
+			return mapper.apply(boundPair.getLeft());
+		};
+
+		final Supplier<NewRight> rightSupp = () -> {
+			if(!pairBound) return binder.apply(leftSupplier.get(), rightSupplier.get()).getRight();
+
+			return boundPair.getRight();
+		};
+
+		return new LazyPair<>(leftSupp, rightSupp);
+	}
+
+	@Override
+	public <NewRightType> IPair<NewLeft, NewRightType> mapRight(final Function<NewRight, NewRightType> mapper) {
+		if(mapper == null) throw new NullPointerException("Mapper must not be null");
+
+		final Supplier<NewLeft> leftSupp = () -> {
+			if(!pairBound) return binder.apply(leftSupplier.get(), rightSupplier.get()).getLeft();
+
+			return boundPair.getLeft();
+		};
+
+		final Supplier<NewRightType> rightSupp = () -> {
+			if(!pairBound) {
+				final NewRight rightVal = binder.apply(leftSupplier.get(), rightSupplier.get())
+						.getRight();
+
+				return mapper.apply(rightVal);
+			}
+
+			return mapper.apply(boundPair.getRight());
+		};
+
+		return new LazyPair<>(leftSupp, rightSupp);
+	}
+
+	@Override
+	public <MergedType> MergedType merge(final BiFunction<NewLeft, NewRight, MergedType> merger) {
+		if(merger == null) throw new NullPointerException("Merger must not be null");
+
+		if(!pairBound) {
+			/*
+			 * If the pair isn't bound yet, bind it.
+			 */
+			boundPair = binder.apply(leftSupplier.get(), rightSupplier.get());
+
+			pairBound = true;
+		}
+
+		return boundPair.merge(merger);
+	}
+
+	@Override
+	public String toString() {
+		if(pairBound) return boundPair.toString();
+
+		return "(un-materialized)";
+	}
+}