/*
    *    Copyright 2018-2022 the original author or authors.
    *
    *    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
    *
    *       https://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.mybatis.scripting.thymeleaf;
  
  import java.lang.reflect.Proxy;
  import java.util.Map;
  
  import org.thymeleaf.IEngineConfiguration;
  import org.thymeleaf.context.IContext;
  import org.thymeleaf.context.IEngineContext;
  import org.thymeleaf.context.IEngineContextFactory;
  import org.thymeleaf.engine.TemplateData;
  
  /**
   * The implementation of {@link IEngineContextFactory} for integrating with MyBatis.
   *
   * @author Kazuki Shimizu
   *
   * @version 1.0.0
   */
  public class MyBatisIntegratingEngineContextFactory implements IEngineContextFactory {
    private final IEngineContextFactory delegate;
    private final ClassLoader classLoader = getClass().getClassLoader();
  
    /**
     * Constructor.
     *
     * @param delegate
     *          A target context factory for delegating
     */
    public MyBatisIntegratingEngineContextFactory(IEngineContextFactory delegate) {
      this.delegate = delegate;
    }
  
    /**
     * {@inheritDoc}
     */
    @Override
    public IEngineContext createEngineContext(IEngineConfiguration configuration, TemplateData templateData,
        Map<String, Object> templateResolutionAttributes, IContext context) {
      IEngineContext engineContext = delegate.createEngineContext(configuration, templateData,
          templateResolutionAttributes, context);
      return (IEngineContext) Proxy.newProxyInstance(classLoader, new Class[] { IEngineContext.class },
          (proxy, method, args) -> {
            if (method.getName().equals("getVariable")) {
              String name = (String) args[0];
              Object value;
              MyBatisBindingContext bindingContext = MyBatisBindingContext.load(engineContext);
              if (bindingContext.isFallbackParameterObject()) {
                value = engineContext.containsVariable(name) ? engineContext.getVariable(name)
                    : engineContext.getVariable(SqlGenerator.ContextKeys.PARAMETER_OBJECT);
              } else {
                value = engineContext.getVariable(name);
              }
              return value;
            }
            return method.invoke(engineContext, args);
          });
    }
  
  }