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Wrangler API Libaray.
There is a newer version: 3.2.2
/*
 * Copyright © 2017 Cask Data, Inc.
 *
 * 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 co.cask.wrangler.api;

import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * This class {@link DirectiveConfig} defines the configuration for the Wrangler.
 * It specifies the directive exclusions -- meaning directives that should
 * not be accessible to the users and as well as directive aliases.
 *
 * {
 *   "exclusions" : [
 *      "parse-as-csv",
 *      "parse-as-excel",
 *      "set",
 *      "invoke-http"
 *    ],
 *  "aliases" : {
 *      "json-parser" : "parse-as-json",
 *      "js-parser" : "parse-as-json"
 *   }
 *  }
 */
public final class DirectiveConfig {
  // RecipeParser to be excluded or made non-accessible.
  private Set exclusions = new HashSet<>();

  // RecipeParser to be aliased.
  private Map aliases = new HashMap<>();


  /**
   * Checks if a directive is aliased.
   *
   * @param directive to checked for alias.
   * @return
   */
  public boolean hasAlias(String directive) {
    if (aliases != null && aliases.containsKey(directive)) {
      return true;
    }
    return false;
  }

  /**
   * Dereferences an alias if defined, else returns the directive itself.
   *
   * @param directive to be dereferenced.
   * @return dereferenced directive or null.
   */
  public String getAliasName(String directive) {
    return aliases.get(directive);
  }

  public Map> getReverseAlias() {
    Map> reverse = new HashMap<>();
    if (aliases == null) {
      return reverse;
    }
    for(Map.Entry alias : aliases.entrySet()) {
      List list;
      if(reverse.containsKey(alias.getValue())) {
        list = reverse.get(alias.getValue());
      } else {
        list = new ArrayList<>();
      }
      list.add(alias.getKey());
      reverse.put(alias.getValue(), list);
    }
    return reverse;
  }

  /**
   * Checks if the directive should be excluded.
   *
   * @param directive to checked if it has to be excluded.
   * @return true if directive is excluded, false otherwise.
   */
  public boolean isExcluded(String directive) {
    if (exclusions != null && exclusions.contains(directive)) {
      return true;
    }
    return false;
  }

  /**
   * Converts this object into a {@link JsonElement}.
   *
   * @return {@link JsonElement} representation of this object.
   */
  public JsonElement toJson() {
    Gson gson = new Gson();
    JsonObject object = new JsonObject();
    object.add("exclusions", gson.toJsonTree(exclusions));
    object.add("aliases", gson.toJsonTree(aliases));
    return object;
  }
}