/*
 * Copyright (c) MuleSoft, Inc.  All rights reserved.  http://www.mulesoft.com
 * The software in this package is published under the terms of the CPAL v1.0
 * license, a copy of which has been included with this distribution in the
 * LICENSE.txt file.
 */
package org.mule.runtime.core.expression.transformers;

import static org.mule.runtime.core.util.ClassUtils.withContextClassLoader;
import org.mule.runtime.api.metadata.DataType;
import org.mule.runtime.core.api.Event;
import org.mule.runtime.core.api.MuleContext;
import org.mule.runtime.core.api.context.MuleContextAware;
import org.mule.runtime.core.api.expression.ExpressionRuntimeException;
import org.mule.runtime.core.api.transformer.Transformer;
import org.mule.runtime.core.api.transformer.TransformerException;
import org.mule.runtime.core.config.i18n.CoreMessages;
import org.mule.runtime.core.expression.ExpressionConfig;

/**
 * TODO
 */
public class ExpressionArgument implements MuleContextAware {

  private ExpressionConfig expressionConfig = new ExpressionConfig();
  private String name;
  private boolean optional;
  private Class<?> returnClass;
  protected ClassLoader expressionEvaluationClassLoader = ExpressionArgument.class.getClassLoader();
  private MuleContext muleContext;

  public ExpressionArgument() {
    super();
  }

  public ExpressionArgument(String name, ExpressionConfig expressionConfig, boolean optional) {
    this(name, expressionConfig, optional, null);
  }

  public ExpressionArgument(String name, ExpressionConfig expressionConfig, boolean optional, Class<?> returnClass) {
    this.expressionConfig = expressionConfig;
    this.name = name;
    this.optional = optional;
    this.returnClass = returnClass;
  }

  @Override
  public void setMuleContext(MuleContext context) {
    this.muleContext = context;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public ExpressionConfig getExpressionConfig() {
    return expressionConfig;
  }

  public void setExpressionConfig(ExpressionConfig expressionConfig) {
    this.expressionConfig = expressionConfig;
  }

  public boolean isOptional() {
    return optional;
  }

  public void setOptional(boolean optional) {
    this.optional = optional;
  }

  protected String getFullExpression() {
    return expressionConfig.getFullExpression();
  }

  protected void validate() {
    expressionConfig.validate();
  }

  /**
   * Evaluates this Expression against the passed in Message. If a returnClass is set on this Expression Argument it will be
   * checked to ensure the Argument returns the correct class type.
   * 
   * @param event the event to execute the expression on
   * @return the result of the expression
   * @throws ExpressionRuntimeException if the wrong return type is returned from the expression.
   */
  public Object evaluate(Event event) throws ExpressionRuntimeException {

    // MULE-4797 Because there is no way to specify the class-loader that script
    // engines use and because scripts when used for expressions are compiled in
    // runtime rather than at initialization the only way to ensure the correct
    // class-loader to used is to switch it out here. We may want to consider
    // passing the class-loader to the MuleExpressionLanguage and only doing this for
    // certain ExpressionEvaluators further in.
    Object result =
        withContextClassLoader(expressionEvaluationClassLoader,
                               () -> muleContext.getExpressionManager().evaluate(getExpression(), event).getValue());

    if (getReturnClass() != null && result != null) {
      if (!getReturnClass().isInstance(result)) {
        // If the return type does not match, lets attempt to transform it before throwing an error
        try {
          Transformer t =
              muleContext.getRegistry().lookupTransformer(DataType.fromObject(result), DataType.fromType(getReturnClass()));
          result = t.transform(result);
        } catch (TransformerException e) {
          throw new ExpressionRuntimeException(CoreMessages.transformUnexpectedType(result.getClass(), getReturnClass()), e);
        }

      }
      // if(result instanceof Collection && ((Collection)result).size()==0 && !isOptional())
      // {
      // throw new ExpressionRuntimeException(CoreMessages.expressionEvaluatorReturnedNull(this.getEvaluator(),
      // this.getExpression()));
      // }
    }
    return result;
  }

  public String getExpression() {
    return expressionConfig.getExpression();
  }

  public void setExpression(String expression) {
    expressionConfig.setExpression(expression);
  }

  public Class<?> getReturnClass() {
    return returnClass;
  }

  public void setReturnDataType(Class<?> returnClass) {
    this.returnClass = returnClass;
  }

  public void setExpressionEvaluationClassLoader(ClassLoader expressionEvaluationClassLoader) {
    this.expressionEvaluationClassLoader = expressionEvaluationClassLoader;
  }

}