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package au.id.zancanaro.javacheck;
import java.io.IOException;
import java.io.Writer;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;
import java.util.stream.IntStream;
import java.util.stream.Stream;
@SuppressWarnings("unused")
public class ShrinkTree<T> {
private final T value;
private final Supplier<Stream<ShrinkTree<T>>> children;
private ShrinkTree(T value, Supplier<Stream<ShrinkTree<T>>> children) {
this.value = value;
this.children = children;
}
public T getValue() {
return value;
}
public Stream<ShrinkTree<T>> getChildren() {
return children.get();
}
@SuppressWarnings("Convert2MethodRef")
public static <T> ShrinkTree<T> pure(T value) {
// Converting the () -> Stream.empty() into Stream::empty actually
// breaks Java's generic type inference. Who would have thought?
return new ShrinkTree<>(value, () -> Stream.empty());
}
public static <T> ShrinkTree<T> join(ShrinkTree<ShrinkTree<T>> tree) {
return new ShrinkTree<>(
tree.getValue().getValue(),
() -> Stream.concat(
tree.getChildren().map(ShrinkTree::join),
tree.getValue().getChildren()));
}
private static <T> List<T> makeHeadList(ShrinkTree<T>[] trees) {
List<T> heads = new ArrayList<>(trees.length);
for (ShrinkTree<T> tree : trees) {
heads.add(tree.getValue());
}
return heads;
}
@SuppressWarnings({"unchecked", "SuspiciousUninitializedArray"})
public static <T> Stream<ShrinkTree<T>[]> promoteChildren(ShrinkTree<? super T>[] trees) {
return IntStream.range(0, trees.length)
.mapToObj(index -> trees[index].getChildren().map(child ->
IntStream.range(0, trees.length)
.mapToObj(i -> (i == index ? child : trees[i]))
.toArray(ShrinkTree<?>[]::new)))
.flatMap(x -> x)
.map(x -> (ShrinkTree<T>[]) x);
}
@SuppressWarnings("unchecked")
public static <T> Stream<ShrinkTree<T>[]> removeChildren(ShrinkTree<? super T>[] trees) {
return IntStream.range(0, trees.length)
.mapToObj(index ->
IntStream.range(0, trees.length)
.filter(i -> i != index)
.mapToObj(i -> trees[i])
.toArray(ShrinkTree<?>[]::new))
.map(x -> (ShrinkTree<T>[]) x);
}
public static <T> Stream<ShrinkTree<T>[]> removeAndPromoteChildren(ShrinkTree<? super T>[] trees) {
return Stream.concat(removeChildren(trees), promoteChildren(trees));
}
public static <T> ShrinkTree<List<T>> combine(
ShrinkTree<T>[] trees,
Function<ShrinkTree<T>[], Stream<ShrinkTree<T>[]>> processChildren) {
return new ShrinkTree<>(
makeHeadList(trees),
() -> processChildren.apply(trees)
.map(shrinks -> combine(shrinks, processChildren)));
}
public <R> ShrinkTree<R> map(Function<? super T, ? extends R> f) {
return new ShrinkTree<>(
f.apply(this.value),
() -> this.getChildren().map(tree -> tree.map(f)));
}
public <R> ShrinkTree<R> flatMap(Function<? super T, ? extends ShrinkTree<R>> f) {
return ShrinkTree.join(this.map(f));
}
public ShrinkTree<T> filter(Predicate<? super T> predicate) {
T value = this.getValue();
if (predicate.test(value)) {
return new ShrinkTree<>(
value,
() -> this.getChildren()
.filter(tree -> predicate.test(tree.getValue()))
.map(tree -> tree.filter(predicate)));
} else {
throw new IllegalArgumentException("Current value doesn't match predicate: whoops!");
}
}
public ShrinkTree<T> withShrinkStrategy(ShrinkStrategy<T> strategy) {
return new ShrinkTree<>(this.getValue(), () -> strategyStream(this.getValue(), strategy));
}
private static <T> Stream<ShrinkTree<T>> strategyStream(final T value, final ShrinkStrategy<T> strategy) {
return strategy.shrink(value)
.map(v -> new ShrinkTree<>(v, () -> strategyStream(v, strategy)));
}
public void print(Writer output) throws IOException {
print(output, Object::toString);
}
public void print(Writer output, Function<? super T, ? extends String> toString) throws IOException {
output.write(toString.apply(this.getValue()));
output.write('[');
Iterator<ShrinkTree<T>> iterator = children.get().iterator();
while (iterator.hasNext()) {
iterator.next().print(output, toString);
if (iterator.hasNext()) {
output.write(' ');
}
}
output.write(']');
output.flush();
}
}
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