/**
    * 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.
   */
  package org.apache.creadur.tentacles;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.Reader;
  import java.io.StringWriter;
  import java.io.Writer;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  
  import org.apache.velocity.VelocityContext;
  import org.apache.velocity.app.VelocityEngine;
  
  public class TemplateBuilder {
      private static final String LOG_TAG_NAME = TemplateBuilder.class.getName();
  
      private final TentaclesResources tentaclesResources;
      private final VelocityEngine engine;
      private final IOSystem ioSystem;
      private final String templateName;
      private final Map<String, Object> templateContextMap =
              new ConcurrentHashMap<String, Object>();
  
      public TemplateBuilder(final String template, final IOSystem ioSystem,
              final VelocityEngine engine,
              final TentaclesResources tentaclesResources) {
          this.templateName = template;
          this.ioSystem = ioSystem;
          this.engine = engine;
          this.tentaclesResources = tentaclesResources;
      }
  
      public TemplateBuilder add(final String key, final Object value) {
          this.templateContextMap.put(key, value);
          return this;
      }
  
      public TemplateBuilder addAll(final Map<String, Object> map) {
          this.templateContextMap.putAll(map);
          return this;
      }
  
      public String apply() {
          final StringWriter writer = new StringWriter();
  
          evaluate(writer);
  
          return writer.toString();
      }
  
      public File write(final File file) throws IOException {
          this.ioSystem.writeString(file, apply());
          return file;
      }
  
      private void evaluate(final Writer writer) {
          try {
              final Reader templateReader =
                      this.tentaclesResources.read(this.templateName);
  
              final VelocityContext context =
                      new VelocityContext(this.templateContextMap);
              this.engine.evaluate(context, writer, LOG_TAG_NAME, templateReader);
  
          } catch (final IOException ioe) {
              throw new RuntimeException("can't apply template "
                      + this.templateName, ioe);
          }
      }
  
  }