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Set of utilities and auxiliary classes to make development easier.
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/*
 * Copyright 2015 Igor Maznitsa.
 *
 * 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.igormaznitsa.meta.common.utils;

import static com.igormaznitsa.meta.common.utils.Assertions.assertFalse;
import static com.igormaznitsa.meta.common.utils.Assertions.assertNotNull;

import com.igormaznitsa.meta.annotation.Constraint;
import com.igormaznitsa.meta.annotation.Weight;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.ThreadSafe;

/**
 * Auxiliary methods to get values.
 *
 * @since 1.0
 */
@ThreadSafe
@Weight(Weight.Unit.LIGHT)
public final class GetUtils {

  private GetUtils() {
  }

  /**
   * Get value and ensure that the value is not null
   *
   * @param           type of value
   * @param value        the value
   * @param defaultValue the default value to be returned if the value is null
   * @return not null value
   * @throws AssertionError if both the value and the default value are null
   * @since 1.0
   */
  @Nonnull
  public static  T ensureNonNull(@Nullable final T value, @Nonnull final T defaultValue) {
    return value == null ? Assertions.assertNotNull(defaultValue) : value;
  }

  /**
   * Get value if it is not null.
   *
   * @param    type of value
   * @param value the value
   * @return the value if it is not null
   * @throws AssertionError if the value is null
   * @since 1.0
   */
  @Nonnull
  public static  T ensureNonNull(@Nonnull final T value) {
    return Assertions.assertNotNull(value);
  }

  /**
   * Find the first non-null value in an array and return that.
   *
   * @param      type of value
   * @param objects array to find value
   * @return the first non-null value from the array
   * @throws AssertionError if the array is null, or it doesn't contain a
   *                        non-null value
   * @since 1.0
   */
  @SafeVarargs
  @Nonnull
  public static  T findFirstNonNull(@Nonnull final T... objects) {
    for (final T obj : ensureNonNull(objects)) {
      if (obj != null) {
        return obj;
      }
    }
    throw Assertions.fail("Can't find non-null item in array");
  }

  /**
   * Get non-null non-empty string.
   *
   * @param value        a base string
   * @param defaultValue default string to be provided if value is null or empty
   * @return non-nullable non-empty string
   * @since 1.1.1
   */
  @Nonnull
  public static String ensureNonNullAndNonEmpty(@Nullable final String value,
                                                @Nonnull @Constraint("notEmpty(X)")
                                                final String defaultValue) {
    String result = value;
    if (result == null || result.isEmpty()) {
      assertFalse("Default value must not be empty",
          assertNotNull("Default value must not be null", defaultValue).isEmpty());
      result = defaultValue;
    }
    return result;
  }

  /**
   * Ensure that a string will not be null.
   *
   * @param value value to be checked
   * @return the value if it is not null or empty string if the value is null
   * @since 1.1.1
   */
  @Nonnull
  public static String ensureNonNullStr(@Nullable final String value) {
    return value == null ? "" : value;
  }
}