/*
    * 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.logging.log4j.core.config.plugins.util;
  
  import java.lang.annotation.Annotation;
  import java.lang.reflect.AccessibleObject;
  import java.lang.reflect.Field;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.lang.reflect.Modifier;
  import java.util.Collection;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.config.Configuration;
  import org.apache.logging.log4j.core.config.ConfigurationException;
  import org.apache.logging.log4j.core.config.Node;
  import org.apache.logging.log4j.core.config.plugins.PluginAliases;
  import org.apache.logging.log4j.core.config.plugins.PluginBuilderFactory;
  import org.apache.logging.log4j.core.config.plugins.PluginFactory;
  import org.apache.logging.log4j.core.config.plugins.validation.ConstraintValidator;
  import org.apache.logging.log4j.core.config.plugins.validation.ConstraintValidators;
  import org.apache.logging.log4j.core.config.plugins.visitors.PluginVisitor;
  import org.apache.logging.log4j.core.config.plugins.visitors.PluginVisitors;
  import org.apache.logging.log4j.core.util.Builder;
  import org.apache.logging.log4j.core.util.ReflectionUtil;
  import org.apache.logging.log4j.core.util.TypeUtil;
  import org.apache.logging.log4j.status.StatusLogger;
  import org.apache.logging.log4j.util.StringBuilders;
  
  /**
   * Builder class to instantiate and configure a Plugin object using a PluginFactory method or PluginBuilderFactory
   * builder class.
   */
  public class PluginBuilder implements Builder<Object> {
  
      private static final Logger LOGGER = StatusLogger.getLogger();
  
      private final PluginType<?> pluginType;
      private final Class<?> clazz;
  
      private Configuration configuration;
      private Node node;
      private LogEvent event;
  
      /**
       * Constructs a PluginBuilder for a given PluginType.
       *
       * @param pluginType type of plugin to configure
       */
      public PluginBuilder(final PluginType<?> pluginType) {
          this.pluginType = pluginType;
          this.clazz = pluginType.getPluginClass();
      }
  
      /**
       * Specifies the Configuration to use for constructing the plugin instance.
       *
       * @param configuration the configuration to use.
       * @return {@code this}
       */
      public PluginBuilder withConfiguration(final Configuration configuration) {
          this.configuration = configuration;
          return this;
      }
  
      /**
       * Specifies the Node corresponding to the plugin object that will be created.
       *
       * @param node the plugin configuration node to use.
       * @return {@code this}
       */
      public PluginBuilder withConfigurationNode(final Node node) {
          this.node = node;
          return this;
      }
  
      /**
       * Specifies the LogEvent that may be used to provide extra context for string substitutions.
       *
       * @param event the event to use for extra information.
      * @return {@code this}
      */
     public PluginBuilder forLogEvent(final LogEvent event) {
         this.event = event;
         return this;
     }
 
     /**
      * Builds the plugin object.
      *
      * @return the plugin object or {@code null} if there was a problem creating it.
      */
     @Override
     public Object build() {
         verify();
         // first try to use a builder class if one is available
         try {
             LOGGER.debug("Building Plugin[name={}, class={}]. Searching for builder factory method...", pluginType.getElementName(),
                     pluginType.getPluginClass().getName());
             final Builder<?> builder = createBuilder(this.clazz);
             if (builder != null) {
                 injectFields(builder);
                 final Object result = builder.build();
                 LOGGER.debug("Built Plugin[name={}] OK from builder factory method.", pluginType.getElementName());
                 return result;
             }
         } catch (final Exception e) {
             LOGGER.error("Unable to inject fields into builder class for plugin type {}, element {}.", this.clazz,
                 node.getName(), e);
         }
         // or fall back to factory method if no builder class is available
         try {
             LOGGER.debug("Still building Plugin[name={}, class={}]. Searching for factory method...",
                     pluginType.getElementName(), pluginType.getPluginClass().getName());
             final Method factory = findFactoryMethod(this.clazz);
             final Object[] params = generateParameters(factory);
             final Object plugin = factory.invoke(null, params);
             LOGGER.debug("Built Plugin[name={}] OK from factory method.", pluginType.getElementName());
             return plugin;
         } catch (final Exception e) {
             LOGGER.error("Unable to invoke factory method in class {} for element {}.", this.clazz, this.node.getName(),
                 e);
             return null;
         }
     }
 
     private void verify() {
         Objects.requireNonNull(this.configuration, "No Configuration object was set.");
         Objects.requireNonNull(this.node, "No Node object was set.");
     }
 
     private static Builder<?> createBuilder(final Class<?> clazz)
         throws InvocationTargetException, IllegalAccessException {
         for (final Method method : clazz.getDeclaredMethods()) {
             if (method.isAnnotationPresent(PluginBuilderFactory.class) &&
                 Modifier.isStatic(method.getModifiers()) &&
                 TypeUtil.isAssignable(Builder.class, method.getGenericReturnType())) {
                 ReflectionUtil.makeAccessible(method);
                 @SuppressWarnings("unchecked")
                 final Builder<?> builder = (Builder<?>) method.invoke(null);
                 LOGGER.debug("Found builder factory method [{}]: {}.", method.getName(), method);
                 return builder;
             }
         }
         LOGGER.debug("No builder factory method found in class {}. Going to try finding a factory method instead.",
             clazz.getName());
         return null;
     }
 
     private void injectFields(final Builder<?> builder) throws IllegalAccessException {
         final Field[] fields = builder.getClass().getDeclaredFields();
         AccessibleObject.setAccessible(fields, true);
         final StringBuilder log = new StringBuilder();
         boolean invalid = false;
         for (final Field field : fields) {
             log.append(log.length() == 0 ? "with params(" : ", ");
             final Annotation[] annotations = field.getDeclaredAnnotations();
             final String[] aliases = extractPluginAliases(annotations);
             for (final Annotation a : annotations) {
                 if (a instanceof PluginAliases) {
                     continue; // already processed
                 }
                 final PluginVisitor<? extends Annotation> visitor =
                     PluginVisitors.findVisitor(a.annotationType());
                 if (visitor != null) {
                     final Object value = visitor.setAliases(aliases)
                         .setAnnotation(a)
                         .setConversionType(field.getType())
                         .setStrSubstitutor(configuration.getStrSubstitutor())
                         .setMember(field)
                         .visit(configuration, node, event, log);
                     // don't overwrite default values if the visitor gives us no value to inject
                     if (value != null) {
                         field.set(builder, value);
                     }
                 }
             }
             final Collection<ConstraintValidator<?>> validators =
                 ConstraintValidators.findValidators(annotations);
             final Object value = field.get(builder);
             for (final ConstraintValidator<?> validator : validators) {
                 if (!validator.isValid(value)) {
                     invalid = true;
                 }
             }
         }
         if (log.length() > 0) {
             log.append(')');
         }
         LOGGER.debug("Calling build() on class {} for element {} {}", builder.getClass(), node.getName(),
             log.toString());
         if (invalid) {
             throw new ConfigurationException("Arguments given for element " + node.getName() + " are invalid");
         }
         checkForRemainingAttributes();
         verifyNodeChildrenUsed();
     }
 
     private static Method findFactoryMethod(final Class<?> clazz) {
         for (final Method method : clazz.getDeclaredMethods()) {
             if (method.isAnnotationPresent(PluginFactory.class) &&
                 Modifier.isStatic(method.getModifiers())) {
                 LOGGER.debug("Found factory method [{}]: {}.", method.getName(), method);
                 ReflectionUtil.makeAccessible(method);
                 return method;
             }
         }
         throw new IllegalStateException("No factory method found for class " + clazz.getName());
     }
 
     private Object[] generateParameters(final Method factory) {
         final StringBuilder log = new StringBuilder();
         final Class<?>[] types = factory.getParameterTypes();
         final Annotation[][] annotations = factory.getParameterAnnotations();
         final Object[] args = new Object[annotations.length];
         boolean invalid = false;
         for (int i = 0; i < annotations.length; i++) {
             log.append(log.length() == 0 ? "with params(" : ", ");
             final String[] aliases = extractPluginAliases(annotations[i]);
             for (final Annotation a : annotations[i]) {
                 if (a instanceof PluginAliases) {
                     continue; // already processed
                 }
                 final PluginVisitor<? extends Annotation> visitor = PluginVisitors.findVisitor(
                     a.annotationType());
                 if (visitor != null) {
                     final Object value = visitor.setAliases(aliases)
                         .setAnnotation(a)
                         .setConversionType(types[i])
                         .setStrSubstitutor(configuration.getStrSubstitutor())
                         .setMember(factory)
                         .visit(configuration, node, event, log);
                     // don't overwrite existing values if the visitor gives us no value to inject
                     if (value != null) {
                         args[i] = value;
                     }
                 }
             }
             final Collection<ConstraintValidator<?>> validators =
                 ConstraintValidators.findValidators(annotations[i]);
             final Object value = args[i];
             for (final ConstraintValidator<?> validator : validators) {
                 if (!validator.isValid(value)) {
                     invalid = true;
                 }
             }
         }
         if (log.length() > 0) {
             log.append(')');
         }
         checkForRemainingAttributes();
         verifyNodeChildrenUsed();
         LOGGER.debug("Calling {} on class {} for element {} {}", factory.getName(), clazz.getName(), node.getName(),
             log.toString());
         if (invalid) {
             throw new ConfigurationException("Arguments given for element " + node.getName() + " are invalid");
         }
         return args;
     }
 
     private static String[] extractPluginAliases(final Annotation... parmTypes) {
         String[] aliases = null;
         for (final Annotation a : parmTypes) {
             if (a instanceof PluginAliases) {
                 aliases = ((PluginAliases) a).value();
             }
         }
         return aliases;
     }
 
     private void checkForRemainingAttributes() {
         final Map<String, String> attrs = node.getAttributes();
         if (!attrs.isEmpty()) {
             final StringBuilder sb = new StringBuilder();
             for (final String key : attrs.keySet()) {
                 if (sb.length() == 0) {
                     sb.append(node.getName());
                     sb.append(" contains ");
                     if (attrs.size() == 1) {
                         sb.append("an invalid element or attribute ");
                     } else {
                         sb.append("invalid attributes ");
                     }
                 } else {
                     sb.append(", ");
                 }
                 StringBuilders.appendDqValue(sb, key);
             }
             LOGGER.error(sb.toString());
         }
     }
 
     private void verifyNodeChildrenUsed() {
         final List<Node> children = node.getChildren();
         if (!(pluginType.isDeferChildren() || children.isEmpty())) {
             for (final Node child : children) {
                 final String nodeType = node.getType().getElementName();
                 final String start = nodeType.equals(node.getName()) ? node.getName() : nodeType + ' ' + node.getName();
                 LOGGER.error("{} has no parameter that matches element {}", start, child.getName());
             }
         }
     }
 }