/*
    * #%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.IOException;
  
  import javax.servlet.Servlet;
  import javax.servlet.ServletConfig;
  import javax.servlet.ServletException;
  import javax.servlet.ServletRequest;
  import javax.servlet.ServletResponse;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.apache.commons.lang3.CharEncoding;
  import org.apache.commons.lang3.StringUtils;
  import org.apache.felix.scr.annotations.Activate;
  import org.apache.felix.scr.annotations.Component;
  import org.apache.felix.scr.annotations.Deactivate;
  import org.apache.felix.scr.annotations.Reference;
  import org.apache.felix.scr.annotations.Service;
  import org.osgi.framework.Bundle;
  import org.osgi.service.component.ComponentContext;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import io.wcm.caravan.hal.docs.impl.model.LinkRelation;
  import io.wcm.caravan.hal.docs.impl.reader.ServiceModelReader;
  
  /**
   * Serves HAL documentation pages generated from JSON service documentation models with handlebars.
   */
  @Component(factory = HalDocsServlet.FACTORY)
  @Service(Servlet.class)
  public class HalDocsServlet extends HttpServlet {
  
    private static final long serialVersionUID = 1L;
  
    static final String FACTORY = "caravan.haldocs.servlet.factory";
    static final String PROPERTY_BUNDLE = "caravan.haldocs.relatedBundle";
  
    private io.wcm.caravan.hal.docs.impl.model.Service serviceModel;
  
    @Reference
    private TemplateRenderer templateRenderer;
  
    private static final Logger log = LoggerFactory.getLogger(HalDocsServlet.class);
  
    @Activate
    void activate(ComponentContext componentContext) {
      // bundle which contains the JAX-RS services
      Bundle bundle = (Bundle)componentContext.getProperties().get(PROPERTY_BUNDLE);
      serviceModel = ServiceModelReader.read(bundle);
    }
  
    @Deactivate
    void deactivate(ComponentContext componentContext) {
      serviceModel = null;
    }
  
    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
      HttpServletRequest request = (HttpServletRequest)servletRequest;
      HttpServletResponse response = (HttpServletResponse)servletResponse;
  
      if (serviceModel != null) {
        try {
          String uri = StringUtils.defaultString(request.getPathInfo());
          if (StringUtils.equals(uri, "/")) {
            sendMarkup(templateRenderer.renderServiceHtml(serviceModel), response);
            return;
          }
          else {
            String rel = StringUtils.substringAfter(uri, "/");
            LinkRelation linkRelation = serviceModel.getLinkRelations().stream()
                .filter(item -> StringUtils.equals(item.getRel(), rel))
                .findFirst().orElse(null);
            if (linkRelation != null) {
              sendMarkup(templateRenderer.renderLinkRelationHtml(serviceModel, linkRelation), response);
              return;
            }
         }
       }
       catch (Throwable ex) {
         log.error("Error rendering HAL docs for " + serviceModel.getServiceId() + ": " + request.getPathInfo(), ex);
         response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex.getMessage());
       }
     }
 
     response.sendError(HttpServletResponse.SC_NOT_FOUND);
   }
 
   private void sendMarkup(String markup, HttpServletResponse response) throws IOException {
     byte[] data = markup.getBytes(CharEncoding.UTF_8);
     response.setContentType(HttpContextWrapper.MIMETYPE_HTML);
     response.setContentLength(data.length);
     response.getOutputStream().write(data);
   }
 
   @Override
   public void init() throws ServletException {
     // nothing to do
   }
 
   @Override
   public void init(ServletConfig config) throws ServletException {
     // nothing to do
   }
 
   @Override
   public void destroy() {
     // nothing to do
   }
 
 }