sf.util.TemplatingUtility Maven / Gradle / Ivy

/*
========================================================================
SchemaCrawler
http://www.schemacrawler.com
Copyright (c) 2000-2016, Sualeh Fatehi .
All rights reserved.
------------------------------------------------------------------------

SchemaCrawler is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

SchemaCrawler and the accompanying materials are made available under
the terms of the Eclipse Public License v1.0, GNU General Public License
v3 or GNU Lesser General Public License v3.

You may elect to redistribute this code under any of these licenses.

The Eclipse Public License is available at:
http://www.eclipse.org/legal/epl-v10.html

The GNU General Public License v3 and the GNU Lesser General Public
License v3 are available at:
http://www.gnu.org/licenses/

========================================================================
*/

package sf.util;


import static sf.util.Utility.isBlank;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Properties;
import java.util.Set;

/**
 * Configuration properties.
 *
 * @author Sualeh Fatehi
 */
public final class TemplatingUtility
{

  private static final String DELIMITER_START = "${";

  private static final String DELIMITER_END = "}";

  /**
   * Expands a template using system properties. Variables in the
   * template are in the form of ${variable}.
   *
   * @param template
   *        Template to expand.
   * @return Expanded template
   */
  public static String expandTemplate(final String template)
  {
    return expandTemplate(template, propertiesMap(System.getProperties()));
  }

  /**
   * Expands a template using variable values in the provided map.
   * Variables in the template are in the form of ${variable}.
   *
   * @param template
   *        Template to expand.
   * @param variablesMap
   *        Variables and values.
   * @return Expanded template
   */
  public static String expandTemplate(final String template,
                                      final Map variablesMap)
  {
    if (isBlank(template) || variablesMap == null)
    {
      return template;
    }

    final StringBuilder buffer = new StringBuilder(template.length());
    int currentPosition = 0;
    int delimiterStartPosition;
    int delimiterEndPosition;

    while (true)
    {
      delimiterStartPosition = template.indexOf(DELIMITER_START,
                                                currentPosition);
      if (delimiterStartPosition == -1)
      {
        if (currentPosition == 0)
        {
          // No substitutions required at all
          return template;
        }
        else
        {
          // No more substitutions
          buffer.append(template.substring(currentPosition, template.length()));
          return buffer.toString();
        }
      }
      else
      {
        buffer
          .append(template.substring(currentPosition, delimiterStartPosition));
        delimiterEndPosition = template.indexOf(DELIMITER_END,
                                                delimiterStartPosition);
        if (delimiterEndPosition > -1)
        {
          delimiterStartPosition = delimiterStartPosition
                                   + DELIMITER_START.length();
          final String key = template.substring(delimiterStartPosition,
                                                delimiterEndPosition);
          final String value = variablesMap.get(key);
          if (value != null)
          {
            buffer.append(value);
          }
          else
          {
            // Do not substitute
            buffer.append(DELIMITER_START).append(key).append(DELIMITER_END);
          }
          // Advance current position
          currentPosition = delimiterEndPosition + DELIMITER_END.length();
        }
        else
        {
          // End brace not found, so advance current position
          buffer.append(DELIMITER_START);
          currentPosition = delimiterStartPosition + DELIMITER_START.length();
        }
      }
    }
  }

  /**
   * Extracts variables from the template. Variables are in the form of
   * ${variable}.
   *
   * @param template
   *        Template to extract variables from.
   * @return Extracted variables
   */
  public static Set extractTemplateVariables(final String template)
  {

    if (isBlank(template))
    {
      return new HashSet<>();
    }

    String shrunkTemplate = template;
    final Set keys = new HashSet<>();
    for (int left; (left = shrunkTemplate.indexOf(DELIMITER_START)) >= 0;)
    {
      final int right = shrunkTemplate.indexOf(DELIMITER_END, left + 2);
      if (right >= 0)
      {
        final String propertyKey = shrunkTemplate.substring(left + 2, right);
        keys.add(propertyKey);
        // Destroy key, so we can find the next one
        shrunkTemplate = shrunkTemplate.substring(0, left)
                         + shrunkTemplate.substring(right + 1);
      }
      else
      {
        // No ending baracket found
        break;
      }
    }

    return keys;
  }

  /**
   * Does one pass over the values in the map, and expands each as a
   * template, using the rest of the values in the same map. Variables
   * in the template are in the form of ${variable}.
   *
   * @param variablesMap
   *        Map to expand.
   */
  public static void substituteVariables(final Map variablesMap)
  {
    if (variablesMap != null && !variablesMap.isEmpty())
    {
      for (final Map.Entry entry: variablesMap.entrySet())
      {
        variablesMap.put(entry.getKey(),
                         expandTemplate(entry.getValue(), variablesMap));
      }
    }
  }

  /**
   * Copies properties into a map.
   *
   * @param properties
   *        Properties to copy
   * @return Map of properties and values
   */
  private static Map propertiesMap(final Properties properties)
  {
    final Map propertiesMap = new HashMap<>();
    if (properties != null)
    {
      final Set> entries = properties.entrySet();
      for (final Entry entry: entries)
      {
        propertiesMap.put((String) entry.getKey(), (String) entry.getValue());
      }
    }
    return propertiesMap;
  }

  private TemplatingUtility()
  {
  }

}