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/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * Copyright (C) 2007 The Guava Authors
 */
package com.facebook.presto.spi.predicate;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

import static java.util.Objects.requireNonNull;

/**
 * Contains static utility methods pertaining to primitive types and their
 * corresponding wrapper types.
 *
 * @author Kevin Bourrillion
 * @since 1.0
 */
final class Primitives
{
    private Primitives() {}

    /**
     * A map from primitive types to their corresponding wrapper types.
     */
    private static final Map, Class> PRIMITIVE_TO_WRAPPER_TYPE;

    /**
     * A map from wrapper types to their corresponding primitive types.
     */
    private static final Map, Class> WRAPPER_TO_PRIMITIVE_TYPE;

    // Sad that we can't use a BiMap. :(

    static {
        Map, Class> primToWrap = new HashMap<>(16);
        Map, Class> wrapToPrim = new HashMap<>(16);

        add(primToWrap, wrapToPrim, boolean.class, Boolean.class);
        add(primToWrap, wrapToPrim, byte.class, Byte.class);
        add(primToWrap, wrapToPrim, char.class, Character.class);
        add(primToWrap, wrapToPrim, double.class, Double.class);
        add(primToWrap, wrapToPrim, float.class, Float.class);
        add(primToWrap, wrapToPrim, int.class, Integer.class);
        add(primToWrap, wrapToPrim, long.class, Long.class);
        add(primToWrap, wrapToPrim, short.class, Short.class);

        PRIMITIVE_TO_WRAPPER_TYPE = Collections.unmodifiableMap(primToWrap);
        WRAPPER_TO_PRIMITIVE_TYPE = Collections.unmodifiableMap(wrapToPrim);
    }

    private static void add(Map, Class> forward,
            Map, Class> backward, Class key, Class value)
    {
        forward.put(key, value);
        backward.put(value, key);
    }

    /**
     * Returns an immutable set of all nine primitive types (including {@code
     * void}). Note that a simpler way to test whether a {@code Class} instance
     * is a member of this set is to call {@link Class#isPrimitive}.
     *
     * @since 3.0
     */
    public static Set> allPrimitiveTypes()
    {
        return PRIMITIVE_TO_WRAPPER_TYPE.keySet();
    }

    /**
     * Returns an immutable set of all eight primitive-wrapper types
     *
     * @since 3.0
     */
    public static Set> allWrapperTypes()
    {
        return WRAPPER_TO_PRIMITIVE_TYPE.keySet();
    }

    /**
     * Returns {@code true} if {@code type} is one of the nine
     * primitive-wrapper types, such as {@link Integer}.
     *
     * @see Class#isPrimitive
     */
    public static boolean isWrapperType(Class type)
    {
        return WRAPPER_TO_PRIMITIVE_TYPE.containsKey(requireNonNull(type));
    }

    /**
     * Returns the corresponding wrapper type of {@code type} if it is a primitive
     * type; otherwise returns {@code type} itself. Idempotent.
     *      *     wrap(int.class) == Integer.class
     *     wrap(Integer.class) == Integer.class
     *     wrap(String.class) == String.class
     * 
     */
    public static  Class wrap(Class type)
    {
        requireNonNull(type);

        // cast is safe: long.class and Long.class are both of type Class
        @SuppressWarnings("unchecked")
        Class wrapped = (Class) PRIMITIVE_TO_WRAPPER_TYPE.get(type);
        return (wrapped == null) ? type : wrapped;
    }

    /**
     * Returns the corresponding primitive type of {@code type} if it is a
     * wrapper type; otherwise returns {@code type} itself. Idempotent.
     *      *     unwrap(Integer.class) == int.class
     *     unwrap(int.class) == int.class
     *     unwrap(String.class) == String.class
     * 
     */
    public static  Class unwrap(Class type)
    {
        requireNonNull(type);

        // cast is safe: long.class and Long.class are both of type Class
        @SuppressWarnings("unchecked")
        Class unwrapped = (Class) WRAPPER_TO_PRIMITIVE_TYPE.get(type);
        return (unwrapped == null) ? type : unwrapped;
    }
}