/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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 org.apache.myfaces.tobago.security;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import javax.annotation.security.DenyAll;
  import javax.annotation.security.PermitAll;
  import javax.annotation.security.RolesAllowed;
  import javax.faces.context.FacesContext;
  import java.lang.annotation.Annotation;
  import java.lang.reflect.AnnotatedElement;
  import java.lang.reflect.Method;
  import java.util.Arrays;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  
  public class AuthorizationUtils {
    private static final Logger LOG = LoggerFactory.getLogger(AuthorizationUtils.class);
  
    private static final Object NULL_VALUE = new Object();
    private static final Map<String, Object> AUTHORISATION_CACHE = new ConcurrentHashMap<String, Object>();
  
    public static boolean isAuthorized(FacesContext facesContext, String expression) {
  
      Annotation securityAnnotation = getSecurityAnnotation(facesContext, expression);
      if (securityAnnotation == null) {
        return true;
      }
  
      if (securityAnnotation instanceof DenyAll) {
        if (LOG.isDebugEnabled()) {
          LOG.debug("DenyAll");
        }
        return false;
      }
      if (securityAnnotation instanceof RolesAllowed) {
        String [] roles = ((RolesAllowed) securityAnnotation).value();
        if (LOG.isDebugEnabled()) {
          LOG.debug("RolesAllowed " + Arrays.asList(((RolesAllowed) securityAnnotation).value()));
        }
        for (String role : roles) {
          boolean authorised = facesContext.getExternalContext().isUserInRole(role);
          if (authorised) {
            return true;
          }
        }
        return false;
      }
      if (securityAnnotation instanceof PermitAll) {
        if (LOG.isDebugEnabled()) {
          LOG.debug("PermitAll");
        }
        return true;
      }
      return true;
    }
  
    private static Annotation getSecurityAnnotations(AnnotatedElement annotatedElement) {
      Annotation annotation = annotatedElement.getAnnotation(RolesAllowed.class);
      if (annotation != null) {
        return annotation;
      }
      annotation = annotatedElement.getAnnotation(DenyAll.class);
      if (annotation != null) {
        return annotation;
      }
      annotation = annotatedElement.getAnnotation(PermitAll.class);
      if (annotation != null) {
        return annotation;
      }
      return null;
    }
  
    private static Annotation getSecurityAnnotation(FacesContext facesContext, String expression) {
      if (AUTHORISATION_CACHE.containsKey(expression)) {
        Object obj = AUTHORISATION_CACHE.get(expression);
        if (obj instanceof Annotation) {
          return (Annotation) obj;
        }
        return null;
     } else {
       Annotation securityAnnotation = null;
       if (expression.startsWith("#{") && expression.endsWith("}")) {
         expression = expression.substring(2, expression.length()-1);
         int index = expression.lastIndexOf('.');
         if (index != -1) {
           String methodExpression = expression.substring(index+1, expression.length());
           String beanExpression = expression.substring(0, index);
           // TODO find a better way
           Object bean =
               facesContext.getApplication().getVariableResolver().resolveVariable(facesContext, beanExpression);
           if (bean != null) {
             try {
               Method method = bean.getClass().getMethod(methodExpression);
               securityAnnotation = getSecurityAnnotations(method);
               if (securityAnnotation == null) {
                 securityAnnotation = getSecurityAnnotations(bean.getClass());
               }
             } catch (NoSuchMethodException e) {
               LOG.error("No Method " + methodExpression + " in class " + bean.getClass(), e);
             }
           }
         }
       }
       if (securityAnnotation != null) {
         AUTHORISATION_CACHE.put(expression, securityAnnotation);
       } else {
         AUTHORISATION_CACHE.put(expression, NULL_VALUE);
       }
       return securityAnnotation;
     }
   }
 }