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    • com.github.jknack.handlebars.internal.Transformer Maven / Gradle / Ivy

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    /**
 * Copyright (c) 2012-2013 Edgar Espina
 *
 * This file is part of Handlebars.java.
 *
 * 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.github.jknack.handlebars.internal;

import java.util.Arrays;
import java.util.EnumSet;
import java.util.List;

/**
 * Transform a value and produce a new value if applies. For example, arrays are
 * converted to list in order to iterate over them using the Iterable interface.
 *
 * @author edgar.espina
 * @since 0.1.0
 */
enum Transformer {
  /**
   * No transformation at all.
   */
  NONE,

  /**
   * Convert arrays into list.
   */
  ARRAY {
    @Override
    boolean apply(final Object candidate) {
      return candidate != null && candidate.getClass().isArray();
    }

    @Override
    public Object doTransform(final Object candidate) {
      List list = Arrays.asList((Object[]) candidate);
      return list;
    }
  };

  /**
   * All the transformer are here except {@link #NONE}.
   */
  private static final EnumSet transformers = EnumSet
      .allOf(Transformer.class);;

  static {
    transformers.remove(NONE);
  }

  /**
   * Return true if the strategy applies for the candidate value.
   *
   * @param candidate The candidate value may be null.
   * @return True if the strategy applies for the candidate value.
   */
  boolean apply(final Object candidate) {
    return false;
  }

  /**
   * Transform the given value into something different or leave it as it is.
   *
   * @param candidate The candidate value, may be null.
   * @return A new value or the original value.
   */
  Object doTransform(final Object candidate) {
    return candidate;
  }

  /**
   * Transform the given value into something different or leave it as it is.
   *
   * @param canidate The candidate value. May be null.
   * @return A transformed value or the original value.
   */
  public static Object transform(final Object canidate) {
    return get(canidate).doTransform(canidate);
  }

  /**
   * Find the best transformer for the given value.
   *
   * @param candidate The candidate value.
   * @return The best transformer for the given value. Not null.
   */
  private static Transformer get(final Object candidate) {
    for (Transformer transformer : transformers) {
      if (transformer.apply(candidate)) {
        return transformer;
      }
    }
    return NONE;
  }
}
    
    
    
    

    




    
    
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