1 files changed, 89 insertions, 0 deletions
diff --git a/base/src/main/java/bjc/utils/funcutils/CompoundCollector.java b/base/src/main/java/bjc/utils/funcutils/CompoundCollector.java
new file mode 100644
index 0000000..35695bc
--- /dev/null
+++ b/base/src/main/java/bjc/utils/funcutils/CompoundCollector.java
@@ -0,0 +1,89 @@
+package bjc.utils.funcutils;
+
+import java.util.Set;
+import java.util.function.BiConsumer;
+import java.util.function.BinaryOperator;
+import java.util.function.Function;
+import java.util.function.Supplier;
+import java.util.stream.Collector;
+
+import bjc.utils.data.IHolder;
+import bjc.utils.data.IPair;
+import bjc.utils.data.Identity;
+import bjc.utils.data.Pair;
+
+final class CompoundCollector<InitialType, AuxType1, AuxType2, FinalType1, FinalType2>
+		implements Collector<InitialType, IHolder<IPair<AuxType1, AuxType2>>, IPair<FinalType1, FinalType2>> {
+
+	private final Set<java.util.stream.Collector.Characteristics> characteristicSet;
+
+	private final Collector<InitialType, AuxType1, FinalType1>	first;
+	private final Collector<InitialType, AuxType2, FinalType2>	second;
+
+	public CompoundCollector(final Collector<InitialType, AuxType1, FinalType1> first,
+			final Collector<InitialType, AuxType2, FinalType2> second) {
+		this.first = first;
+		this.second = second;
+
+		characteristicSet = first.characteristics();
+		characteristicSet.addAll(second.characteristics());
+	}
+
+	@Override
+	public BiConsumer<IHolder<IPair<AuxType1, AuxType2>>, InitialType> accumulator() {
+		final BiConsumer<AuxType1, InitialType> firstAccumulator = first.accumulator();
+		final BiConsumer<AuxType2, InitialType> secondAccumulator = second.accumulator();
+
+		return (state, value) -> {
+			state.doWith(statePair -> {
+				statePair.doWith((left, right) -> {
+					firstAccumulator.accept(left, value);
+					secondAccumulator.accept(right, value);
+				});
+			});
+		};
+	}
+
+	@Override
+	public Set<java.util.stream.Collector.Characteristics> characteristics() {
+		return characteristicSet;
+	}
+
+	@Override
+	public BinaryOperator<IHolder<IPair<AuxType1, AuxType2>>> combiner() {
+		final BinaryOperator<AuxType1> firstCombiner = first.combiner();
+		final BinaryOperator<AuxType2> secondCombiner = second.combiner();
+
+		return (leftState, rightState) -> {
+			return leftState.unwrap(leftPair -> {
+				return rightState.transform(rightPair -> {
+					return leftPair.combine(rightPair, firstCombiner, secondCombiner);
+				});
+			});
+		};
+	}
+
+	@Override
+	public Function<IHolder<IPair<AuxType1, AuxType2>>, IPair<FinalType1, FinalType2>> finisher() {
+		return state -> {
+			return state.unwrap(pair -> {
+				return pair.bind((left, right) -> {
+					final FinalType1 finalLeft = first.finisher().apply(left);
+					final FinalType2 finalRight = second.finisher().apply(right);
+
+					return new Pair<>(finalLeft, finalRight);
+				});
+			});
+		};
+	}
+
+	@Override
+	public Supplier<IHolder<IPair<AuxType1, AuxType2>>> supplier() {
+		return () -> {
+			final AuxType1 initialLeft = first.supplier().get();
+			final AuxType2 initialRight = second.supplier().get();
+
+			return new Identity<>(new Pair<>(initialLeft, initialRight));
+		};
+	}
+}