/*
    * #%L
    * wcm.io
    * %%
    * Copyright (C) 2015 wcm.io
    * %%
    * 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.
   * #L%
   */
  package io.wcm.caravan.hal.docs.impl;
  
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.net.URL;
  import java.util.Map;
  
  import org.apache.felix.scr.annotations.Activate;
  import org.apache.felix.scr.annotations.Component;
  import org.apache.felix.scr.annotations.Service;
  import org.osgi.framework.Bundle;
  import org.osgi.service.component.ComponentContext;
  
  import com.github.jknack.handlebars.Handlebars;
  import com.github.jknack.handlebars.Template;
  import com.github.jknack.handlebars.io.AbstractTemplateLoader;
  import com.github.jknack.handlebars.io.TemplateSource;
  import com.github.jknack.handlebars.io.URLTemplateSource;
  import com.google.common.collect.ImmutableMap;
  
  import io.wcm.caravan.hal.docs.impl.model.LinkRelation;
  
  /**
   * Renders HTML views for HAL documentation.
   */
  @Component(immediate = true)
  @Service(TemplateRenderer.class)
  public class TemplateRenderer {
  
    private static final String CLASSPATH_TEMPLATES = "HALDOCS-TEMPLATE-INF/templates";
  
    private Handlebars handlebars;
    private Template serviceTemplate;
    private Template linkRelationTemplate;
  
    @Activate
    void activate(ComponentContext componentContext) throws IOException {
      Bundle bundle = componentContext.getBundleContext().getBundle();
      this.handlebars = new Handlebars(new BundleTemplateLoader(bundle));
      this.serviceTemplate = handlebars.compile("service.html.hbs");
      this.linkRelationTemplate = handlebars.compile("linkRelation.html.hbs");
    }
  
    /**
     * Generate HTML file for service.
     * @param service Service
     * @return Rendered markup
     * @throws IOException
     */
    public String renderServiceHtml(io.wcm.caravan.hal.docs.impl.model.Service service) throws IOException {
      Map<String, Object> model = ImmutableMap.<String, Object>builder()
          .put("service", service)
          .build();
      return render(service, model, serviceTemplate);
    }
  
    /**
     * Generate HTML file for link relation.
     * @param service Service
     * @param linkRelation Link relation
     * @return Rendered markup
     * @throws IOException
     */
    public String renderLinkRelationHtml(io.wcm.caravan.hal.docs.impl.model.Service service, LinkRelation linkRelation)
        throws IOException {
      Map<String, Object> model = ImmutableMap.<String, Object>builder()
          .put("service", service)
          .put("linkRelation", linkRelation)
          .build();
      return render(service, model, linkRelationTemplate);
    }
  
    /**
     * Generate templated file with handlebars
     * @param model Model
     * @param template Template
     * @return Rendered markup
     */
    private String render(io.wcm.caravan.hal.docs.impl.model.Service service, Map<String, Object> model,
        Template template) throws IOException {
     Map<String, Object> mergedModel = ImmutableMap.<String, Object>builder()
         .putAll(model)
         .put("docsContext", ImmutableMap.<String, Object>builder()
             .put("baseUrl", DocsPath.get(service.getServiceId()) + "/")
             .put("resourcesPath", HalDocsBundleTracker.DOCS_RESOURCES_URI_PREFIX)
             .build())
         .build();
     return template.apply(mergedModel);
   }
 
   /**
    * Loads Handlebars templates from bundle.
    */
   private static class BundleTemplateLoader extends AbstractTemplateLoader {
 
     private final Bundle bundle;
 
     BundleTemplateLoader(Bundle bundle) {
       this.bundle = bundle;
     }
 
     @Override
     public TemplateSource sourceAt(String location) throws IOException {
       URL resource = bundle.getResource(CLASSPATH_TEMPLATES + "/" + location);
       if (resource == null) {
         throw new FileNotFoundException(location);
       }
       return new URLTemplateSource(location, resource);
     }
 
   }
 
 }