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package bjc.utils.data.lazy;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Supplier;
import bjc.utils.data.GenHolder;
import bjc.utils.data.IPair;
import bjc.utils.funcdata.FunctionalList;
import bjc.utils.funcdata.IFunctionalList;
/**
* New implementation of lazy pair not delegating to {@link LazyHolder}
*
* @author ben
* @param <L>
* The type on the left side of the pair
* @param <R>
* The type on the right side of the pair
*
*/
public class NewLazyPair<L, R> implements IPair<L, R>, ILazy {
private static class BoundLazyPair<OldL, OldR, NewL, NewR>
implements IPair<NewL, NewR> {
private Supplier<OldL> oldLeftSupplier;
private Supplier<OldR> oldRightSupplier;
private BiFunction<OldL, OldR, IPair<NewL, NewR>> newPairSupplier;
private IPair<NewL, NewR> newPair;
private boolean newPairMaterialized;
public BoundLazyPair(Supplier<OldL> leftSup,
Supplier<OldR> rightSup,
BiFunction<OldL, OldR, IPair<NewL, NewR>> binder) {
oldLeftSupplier = leftSup;
oldRightSupplier = rightSup;
newPairSupplier = binder;
}
@Override
public <L2, R2> IPair<L2, R2> bind(
BiFunction<NewL, NewR, IPair<L2, R2>> binder) {
// TODO Auto-generated method stub
return null;
}
@Override
public void doWith(BiConsumer<NewL, NewR> action) {
// TODO Auto-generated method stub
}
@Override
public <E> E merge(BiFunction<NewL, NewR, E> merger) {
if (!newPairMaterialized) {
newPair = newPairSupplier.apply(oldLeftSupplier.get(),
oldRightSupplier.get());
}
return newPair.merge(merger);
}
}
private L leftValue;
private R rightValue;
private Supplier<R> rightValueSupplier;
private Supplier<L> leftValueSupplier;
private boolean rightMaterialized;
private boolean leftMaterialized;
private IFunctionalList<BiConsumer<L, R>> actions;
/**
* Create a new lazy pair
*
* @param leftVal
* The left value in the pair
* @param rightVal
* The right value in the pair
*/
public NewLazyPair(L leftVal, R rightVal) {
leftValueSupplier = () -> leftVal;
rightValueSupplier = () -> rightVal;
}
/**
* Create a new lazy pair
*
* @param leftSupplier
* The supplier for the left value in the pair
* @param rightSupplier
* The supplier for the right value in the pair
*/
public NewLazyPair(Supplier<L> leftSupplier,
Supplier<R> rightSupplier) {
leftValueSupplier = leftSupplier;
rightValueSupplier = rightSupplier;
}
@Override
public void applyPendingActions() {
if (!isMaterialized()) {
throw new UnsupportedOperationException(
"Can only apply actions to materialized values");
}
actions.forEach((action) -> {
action.accept(leftValue, rightValue);
});
actions = new FunctionalList<>();
}
private void applyPossiblyPendingActions(GenHolder<Boolean> hasActions,
IFunctionalList<BiConsumer<L, R>> pendingActions) {
if (hasActions.unwrap((val) -> val) == true) {
pendingActions.forEach((action) -> {
action.accept(leftValue, rightValue);
});
hasActions.transform((val) -> false);
}
}
@Override
public <L2, R2> IPair<L2, R2> bind(
BiFunction<L, R, IPair<L2, R2>> binder) {
GenHolder<Boolean> hasActions = new GenHolder<>(true);
IFunctionalList<BiConsumer<L, R>> pendingActions = new FunctionalList<>();
actions.forEach(pendingActions::add);
return new BoundLazyPair<>(() -> {
applyPossiblyPendingActions(hasActions, pendingActions);
return leftValue;
}, () -> {
applyPossiblyPendingActions(hasActions, pendingActions);
return rightValue;
}, binder);
}
@Override
public void doWith(BiConsumer<L, R> action) {
actions.add(action);
}
@Override
public boolean hasPendingActions() {
return !actions.isEmpty();
}
@Override
public boolean isMaterialized() {
if (leftValueSupplier == null) {
if (rightValueSupplier == null) {
return true;
}
return rightMaterialized;
}
if (rightValueSupplier == null) {
return leftMaterialized;
}
return leftMaterialized && rightMaterialized;
}
@Override
public void materialize() {
if (isMaterialized()) {
throw new UnsupportedOperationException(
"Cannot materialize lazy object twice");
}
if (leftValueSupplier != null) {
leftValue = leftValueSupplier.get();
}
if (rightValueSupplier != null) {
rightValue = rightValueSupplier.get();
}
}
@Override
public <E> E merge(BiFunction<L, R, E> merger) {
if (!isMaterialized()) {
materialize();
}
applyPendingActions();
return merger.apply(leftValue, rightValue);
}
}
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