/*
    * #%L
    * wcm.io
    * %%
    * Copyright (C) 2014 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.wcm.ui.granite.util;
  
  import javax.servlet.http.HttpServletRequest;
  
  import org.apache.commons.lang3.StringUtils;
  import org.apache.commons.lang3.Strings;
  import org.apache.sling.api.SlingHttpServletRequest;
  import org.apache.sling.api.resource.Resource;
  import org.apache.sling.api.resource.ResourceResolver;
  import org.apache.sling.api.resource.ResourceUtil;
  import org.jetbrains.annotations.NotNull;
  import org.jetbrains.annotations.Nullable;
  import org.osgi.annotation.versioning.ProviderType;
  
  import com.adobe.granite.ui.components.Value;
  import com.day.cq.wcm.api.Page;
  import com.day.cq.wcm.api.PageManager;
  
  /**
   * Helper methods for GraniteUI components.
   *
   * <p>
   * It uses some heuristics to get the current content path in context of a GraniteUI component:
   * </p>
   * <ol>
   * <li>Inside create page wizard, try to get content path from referrer header</li>
   * <li>Try to get content path from request suffix</li>
   * <li>Try to get content path from "item" request parameter (inside multifield component)</li>
   * </ol>
   */
  @ProviderType
  public final class GraniteUi {
  
    static final String CREATEPAGEWITZARD_PROPERTIES_URI = "/mnt/overlay/wcm/core/content/sites/createpagewizard/properties.html";
    static final String CREATEPAGEWITZARD_URI = "/mnt/overlay/wcm/core/content/sites/createpagewizard.html";
    static final String HEADER_REFERER = "Referer";
  
    private GraniteUi() {
      // static methods only
    }
  
    /**
     * Current content resource
     * @param request Request
     * @return Current content resource or null
     */
    public static @Nullable Resource getContentResource(@NotNull HttpServletRequest request) {
      String contentPath = getContentPath(request);
      if (contentPath != null) {
        SlingHttpServletRequest slingRequest = (SlingHttpServletRequest)request;
        return slingRequest.getResourceResolver().getResource(contentPath);
      }
      return null;
    }
  
    /**
     * Get current content resource
     * If it does not exist, go up the content path and return the first resource that exists.
     * @param request Request
     * @return Current content resource or the first existing parent/ancestor.
     */
    public static @Nullable Resource getContentResourceOrParent(@NotNull HttpServletRequest request) {
      String contentPath = getContentPath(request);
      return getContentResourceOrParentFromPath((SlingHttpServletRequest)request, contentPath);
    }
  
    /**
     * Current content page. If the current resource does not exist the content page
     * of the next-existing parent resource is returned.
     * @param request Request
     * @return Current content page or null
     */
    public static @Nullable Page getContentPage(@NotNull HttpServletRequest request) {
      SlingHttpServletRequest slingRequest = (SlingHttpServletRequest)request;
      Resource contentResource = getContentResourceOrParent(request);
      if (contentResource != null) {
        PageManager pageManager = slingRequest.getResourceResolver().adaptTo(PageManager.class);
        if (pageManager != null) {
          return pageManager.getContainingPage(contentResource);
        }
     }
     return null;
   }
 
   /**
    * From the list of resource types get the first one that exists.
    * @param resourceResolver Resource resolver
    * @param resourceTypes ResourceTypes
    * @return Existing resource type
    */
   public static @Nullable String getExistingResourceType(@NotNull ResourceResolver resourceResolver, @NotNull String @NotNull... resourceTypes) {
     for (String path : resourceTypes) {
       if (resourceResolver.getResource(path) != null) {
         return path;
       }
     }
     return null;
   }
 
   /**
    * Current content path
    * @param request Request
    * @return Current content path or null
    */
   @SuppressWarnings("deprecation")
   private static @Nullable String getContentPath(@NotNull HttpServletRequest request) {
 
     String contentPath = (String)request.getAttribute(Value.CONTENTPATH_ATTRIBUTE);
 
     // if we are currently in create page wizard try to extract content path from referer,
     // as it is not available via other ways
     if (!isValidContentPath(contentPath) && StringUtils.contains(request.getRequestURI(), CREATEPAGEWITZARD_PROPERTIES_URI)) {
       String referer = request.getHeader(HEADER_REFERER);
       if (referer != null && StringUtils.contains(referer, CREATEPAGEWITZARD_URI)) {
         contentPath = StringUtils.substringAfter(referer, CREATEPAGEWITZARD_URI);
       }
     }
 
     if (!isValidContentPath(contentPath)) {
       // fallback to suffix if CONTENTPATH_ATTRIBUTE is not set
       // (e.g. in inside a /libs/granite/ui/components/foundation/form/multifield component)
       contentPath = ((SlingHttpServletRequest)request).getRequestPathInfo().getSuffix();
     }
 
     if (!isValidContentPath(contentPath)) {
       // fallback to suffix item parameter in query string
       // (e.g. in inside a /libs/granite/ui/components/foundation/form/multifield component)
       contentPath = request.getParameter("item");
     }
 
     if (!isValidContentPath(contentPath)) {
       contentPath = null;
     }
 
     return contentPath;
   }
 
   private static boolean isValidContentPath(@Nullable String path) {
     if (path == null) {
       return false;
     }
     return Strings.CS.startsWith(path, "/");
   }
 
   private static Resource getContentResourceOrParentFromPath(SlingHttpServletRequest slingRequest, String contentPath) {
     if (StringUtils.isNotEmpty(contentPath)) {
       Resource contentResource = slingRequest.getResourceResolver().getResource(contentPath);
       if (contentResource != null) {
         return contentResource;
       }
       else {
         return getContentResourceOrParentFromPath(slingRequest, ResourceUtil.getParent(contentPath));
       }
     }
     return null;
   }
 
 }