helix-core/src/main/java/org/apache/helix/util/StringTemplate.java

package org.apache.helix.util;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class StringTemplate {
  private static Logger LOG = LoggerFactory.getLogger(StringTemplate.class);

  Map<Enum, Map<Integer, String>> templateMap = new HashMap<Enum, Map<Integer, String>>();
  static Pattern pattern = Pattern.compile("(\\{.+?\\})");

  public void addEntry(Enum type, int numKeys, String template) {
    if (!templateMap.containsKey(type)) {
      templateMap.put(type, new HashMap<Integer, String>());
    }
    LOG.trace("Add template for type: " + type.name() + ", arguments: " + numKeys + ", template: "
        + template);
    templateMap.get(type).put(numKeys, template);
  }

  public String instantiate(Enum type, String... keys) {
    if (keys == null) {
      keys = new String[] {};
    }

    String template = null;
    if (templateMap.containsKey(type)) {
      template = templateMap.get(type).get(keys.length);
    }

    String result = null;

    if (template != null) {
      result = template;
      Matcher matcher = pattern.matcher(template);
      int count = 0;
      while (matcher.find()) {
        String var = matcher.group();
        result = result.replace(var, keys[count]);
        count++;
      }
    }

    if (result == null || result.indexOf('{') > -1 || result.indexOf('}') > -1) {
      String errMsg =
          "Unable to instantiate template: " + template + " using keys: " + Arrays.toString(keys);
      LOG.error(errMsg);
      throw new IllegalArgumentException(errMsg);
    }

    return result;
  }

}