net.codestory.http.templating.HandlebarsCompiler Maven / Gradle / Ivy

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/**
 * Copyright (C) 2013 [email protected]
 *
 * 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 net.codestory.http.templating;

import java.io.*;
import java.util.*;

import net.codestory.http.templating.helpers.*;

import com.github.jknack.handlebars.*;
import com.github.jknack.handlebars.cache.*;
import com.github.jknack.handlebars.context.*;
import com.github.jknack.handlebars.helper.*;
import com.github.jknack.handlebars.io.*;

public class HandlebarsCompiler {
  public String compile(String template, Map variables) throws IOException {
    return handlebars(variables)
        .compileInline(template)
        .apply(context(variables));
  }

  private static Handlebars handlebars(Map variables) {
    Handlebars hb = new Handlebars();

    hb.startDelimiter("[[");
    hb.endDelimiter("]]");
    hb.registerHelpers(new EachReverseHelperSource());
    hb.registerHelpers(new EachValueHelperSource());
    hb.registerHelpers(StringHelpers.class);
    hb.with(new ConcurrentMapTemplateCache());
    hb.with(new AbstractTemplateLoader() {
      @Override
      public TemplateSource sourceAt(String location) {
        return new StringTemplateSource(location, new Template("_includes", location).render(variables).content());
      }
    });

    if (isThereACustomHandleBarHelperToLoad()) {
      hb.registerHelpers(findHandleBarHelpers());
    }

    return hb;
  }

  private static boolean isThereACustomHandleBarHelperToLoad() {
    return null != Site.get().get("handleBarHelper");
  }


  private static Class findHandleBarHelpers() {
    String helperClassName = (String) Site.get().get("handleBarHelper");
    try {
      return Class.forName(helperClassName);
    } catch (Exception e) {
      throw new IllegalStateException("Unable to register " + helperClassName);
    }
  }

  private static Context context(Map variables) {
    return Context.newBuilder(null)
        .resolver(
            MapValueResolver.INSTANCE,
            JavaBeanValueResolver.INSTANCE,
            FieldValueResolver.INSTANCE,
            MethodValueResolver.INSTANCE,
            Site.SiteValueResolver.INSTANCE)
        .combine("site", Site.get())
        .combine(variables)
        .build();
  }

  private static class NopRegister {
  }
}