/*
    * 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.commons.weaver.privilizer;
  
  import java.lang.annotation.ElementType;
  import java.util.LinkedHashSet;
  import java.util.Set;
  
  import org.apache.commons.lang3.Validate;
  import org.apache.commons.weaver.model.ScanRequest;
  import org.apache.commons.weaver.model.Scanner;
  import org.apache.commons.weaver.model.WeavableClass;
  import org.apache.commons.weaver.model.WeaveEnvironment;
  import org.apache.commons.weaver.model.WeaveInterest;
  import org.apache.commons.weaver.spi.Weaver;
  
  /**
   * Privilizer {@link Weaver} implementation.
   */
  public class PrivilizerWeaver implements Weaver {
      @Override
      public boolean process(final WeaveEnvironment weaveEnvironment, final Scanner scanner) {
          final Privilizer privilizer = new Privilizer(weaveEnvironment);
  
          final Set<Class<?>> privilizedTypes = new LinkedHashSet<>();
  
          // handle blueprints:
          for (final WeavableClass<?> type : scanner.scan(
              new ScanRequest().add(WeaveInterest.of(Privilizing.class, ElementType.TYPE))).getClasses()) {
  
              final Class<?> target = type.getTarget();
              if (privilizedTypes.add(target) && validateRequest(privilizer, type)) {
                  privilizer.blueprint(target, type.getAnnotation(Privilizing.class));
              }
          }
  
          // handle remaining classes declaring @Privileged methods:
  
          for (final WeavableClass<?> type : scanner.scan(
              new ScanRequest().add(WeaveInterest.of(Privileged.class, ElementType.METHOD))).getClasses()) {
              final Class<?> target = type.getTarget();
              if (privilizedTypes.add(target) && validateRequest(privilizer, type)) {
                  privilizer.privilize(target);
              }
          }
          return !privilizedTypes.isEmpty();
      }
  
      /**
       * Validate a weaving request for a given target type.
       * @param privilizer whose configuration to consult
       * @param type target
       * @return whether weaving should proceed
       * @throws IllegalStateException if class has already been woven with some other policy
       */
      private boolean validateRequest(final Privilizer privilizer, final WeavableClass<?> type) {
          final Privilized marker = type.getAnnotation(Privilized.class);
          if (marker == null) {
              return privilizer.policy != Policy.NEVER;
          }
          Validate.validState(privilizer.policy.name().equals(marker.value()), "%s already privilized with policy %s",
              type.getTarget().getName(), marker.value());
  
          return false;
      }
  }