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Java SDK to connect to the Onegini platform

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/*
 * Copyright 2013-2020 Onegini b.v.
 *
 * 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.
 */

package com.onegini.sdk.util;

import java.lang.reflect.InvocationTargetException;
import java.util.EnumSet;
import java.util.Map;


/**
 * Encodes Enums to their bit value based on the {@link StableOrdinal} of the Enum. We use bit shifting to append all
 * enums in an EnumSet to represent the entire {@link EnumSet} as a single long which means we can only encode enums
 * which contain 64 or less enum values as we otherwise would go over the {@link Long#MAX_VALUE}
 * This solution is inspired by a Stackoverflow article.
 *
 * @see Stackoverflow article
 */
public final class EnumEncoder {

  private EnumEncoder() {
    throw new UnsupportedOperationException();
  }

  public static  & StableOrdinal> long encode(final EnumSet set) {
    long ret = 0;

    for (final E val : set) {
      ret |= (1 << val.getStableOrdinal());
    }

    return ret;
  }

  @SuppressWarnings("unchecked")
  public static  & StableOrdinal> EnumSet decode(final long code, final Class enumType) {
    long c = code;
    final EnumSet result = EnumSet.noneOf(enumType);
    final Map values;

    try {
      values = (Map) enumType.getMethod("valuesWithStableOrdinal").invoke(null);
    } catch (IllegalAccessException | NoSuchMethodException | InvocationTargetException ex) {
      throw new RuntimeException("Cannot decode EnumSet", ex);
    }

    while (c != 0) {
      final int stableOrdinal = Long.numberOfTrailingZeros(c);
      c ^= Long.lowestOneBit(c);
      result.add(values.get(stableOrdinal));
    }
    return result;
  }
}