/**

  * Copyright (c) 2012-2014, jcabi.com

  * All rights reserved.

  *

  * Redistribution and use in source and binary forms, with or without

  * modification, are permitted provided that the following conditions

  * are met: 1) Redistributions of source code must retain the above

  * copyright notice, this list of conditions and the following

  * disclaimer. 2) Redistributions in binary form must reproduce the above

  * copyright notice, this list of conditions and the following

  * disclaimer in the documentation and/or other materials provided

  * with the distribution. 3) Neither the name of the jcabi.com nor

  * the names of its contributors may be used to endorse or promote

  * products derived from this software without specific prior written

  * permission.

  *

  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT

  * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND

  * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL

  * THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,

  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED

  * OF THE POSSIBILITY OF SUCH DAMAGE.

  */

 package com.jcabi.velocity;

 import java.io.PrintWriter;

 import java.io.StringWriter;

 import java.util.Map;

 import javax.validation.constraints.NotNull;

 import org.apache.velocity.Template;

 import org.apache.velocity.VelocityContext;

 import org.apache.velocity.app.VelocityEngine;

 import org.apache.velocity.runtime.RuntimeConstants;

 import org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader;

 /**

  * Velocity page, builder/wrapper around Apache Velocity template.

  *

  * <p>The template should be in classpath:

  *

  * <pre> String text = new VelocityPage("com/foo/my-template.vm")

  *   .set("name", "John Doe")

  *   .toString();</pre>

  *

  * <p>At the moment all logging is forwarded to LOG4J. In Velocity 2.0 there

  * will be an adapter for SLF4J and we'll use it: {@code Slf4jLogChute}.

  *

  * <p>The class is mutable and thread-safe.

  *

  * @author Yegor Bugayenko (yegor@tpc2.com)

  * @version $Id$

  * @since 0.1.6

  * @see <a href="http://velocity.apache.org/engine/releases/velocity-1.7/user-guide.html">Velocity User Guide</a>

  * @see <a href="http://velocity.apache.org/engine/releases/velocity-1.7/developer-guide.html">Velocity Developer Guide</a>

  * @see <a href="http://velocity.apache.org/engine/devel/apidocs/org/apache/velocity/slf4j/Slf4jLogChute.html">Slf4jLogChute</a>

  */

 public final class VelocityPage {

     /**

      * The engine to use.

      */

     private static final VelocityEngine ENGINE = VelocityPage.init();

     /**

      * Name of resource.

      */

     private final transient String name;

     /**

      * The context.

      */

     private final transient VelocityContext context = new VelocityContext();

     /**

      * Public ctor, with absolute resource name in classpath.

      * @param res Name of resource with template (absolute resource name in

      *  classpath)

      */

     public VelocityPage(@NotNull final String res) {

         this.name = res;

     }

     /**

      * Set the name to the value specified.

      * @param prop Name of the property to set

      * @param value The value to use

      * @return This object

      */

     public VelocityPage set(@NotNull final String prop, final Object value) {

         synchronized (this.context) {

             this.context.put(prop, value);

         }

         return this;

     }

     /**

      * Set all names in one go.

      * @param args Map of arguments

      * @return This object

      * @since 0.8

      */

     public VelocityPage set(@NotNull final Map<String, Object> args) {

         synchronized (this.context) {

             for (final Map.Entry<String, Object> entry : args.entrySet()) {

                 this.context.put(entry.getKey(), entry.getValue());

             }

         }

         return this;

     }

     /**

      * {@inheritDoc}

      */

     @Override

     public String toString() {

         final Template template =

             VelocityPage.ENGINE.getTemplate(this.name, "UTF-8");

         final StringWriter writer = new StringWriter();

         template.merge(this.context, new PrintWriter(writer));

         return writer.toString();

     }

     /**

      * Create and initialize Velocity engine.

      * @return The engine to use

      */

     private static VelocityEngine init() {

         final VelocityEngine engine = new VelocityEngine();

         engine.setProperty("resource.loader", "cp");

         engine.setProperty(

             "cp.resource.loader.class",

             ClasspathResourceLoader.class.getName()

         );

         engine.setProperty(

             RuntimeConstants.RUNTIME_LOG_LOGSYSTEM_CLASS,

             "org.apache.velocity.runtime.log.Log4JLogChute"

         );

         engine.setProperty(

             "runtime.log.logsystem.log4j.logger",

             "org.apache.velocity"

         );

         engine.init();

         return engine;

     }

 }