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package org.javimmutable.collections.util;

import org.javimmutable.collections.GenericCollector;
import org.javimmutable.collections.JImmutableList;
import org.javimmutable.collections.JImmutableListMap;
import org.javimmutable.collections.JImmutableRandomAccessList;
import org.javimmutable.collections.JImmutableSet;

import javax.annotation.Nonnull;
import java.util.Comparator;
import java.util.function.Function;
import java.util.stream.Collector;

/**
 * Utility class providing static methods for collecting various immutable collections using streams.
 */
public final class JImmutableCollectors
{
    private JImmutableCollectors()
    {
    }

    /**
     * Collects values into a JImmutableList.
     */
    @Deprecated
    @Nonnull
    public static  Collector> toList()
    {
        return JImmutables.list().listCollector();
    }

    /**
     * Collects values into a JImmutableRandomAccessList.
     */
    @Deprecated
    @Nonnull
    public static  Collector> toRalist()
    {
        return JImmutables.ralist().ralistCollector();
    }

    /**
     * Collects values into a hashed JImmutableSet.
     */
    @Deprecated
    @Nonnull
    public static  Collector> toSet()
    {
        return JImmutables.set().setCollector();
    }

    /**
     * Collects values into a sorted JImmutableSet using natural sort order of elements.
     */
    @Deprecated
    @Nonnull
    public static > Collector> toSortedSet()
    {
        return JImmutables.sortedSet().setCollector();
    }

    /**
     * Collects values into a sorted JImmutableSet using specified Comparator.
     */
    @Deprecated
    @Nonnull
    public static  Collector> toSortedSet(@Nonnull Comparator comparator)
    {
        return JImmutables.sortedSet(comparator).setCollector();
    }

    /**
     * Collects values into a hashed JImmutableListMap using the specified classifier function
     * to generate keys from the encountered elements.
     */
    @Nonnull
    public static  Collector> groupingBy(@Nonnull Function classifier)
    {
        return GenericCollector.ordered(JImmutables.listMap(),
                                        JImmutables.listMap(),
                                        a -> a.isEmpty(),
                                        (a, v) -> a.insert(classifier.apply(v), v),
                                        (a, b) -> a.insertAll(b.entries()));
    }
}