/*
 * 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.el.mvel.datatype;

import org.mule.mvel2.compiler.CompiledExpression;
import org.mule.runtime.api.metadata.DataType;
import org.mule.runtime.core.api.Event;

import java.io.Serializable;
import java.util.LinkedList;
import java.util.List;

/**
 * Resolves expression's data type using {@link ExpressionDataTypeResolver}
 */
public class MvelDataTypeResolver {


  private final List<ExpressionDataTypeResolver> resolvers;

  public MvelDataTypeResolver() {
    this(getDefaultDataTypeResolvers());
  }

  public MvelDataTypeResolver(List<ExpressionDataTypeResolver> resolvers) {
    this.resolvers = new LinkedList<>(resolvers);
  }

  private static List<ExpressionDataTypeResolver> getDefaultDataTypeResolvers() {
    List<ExpressionDataTypeResolver> resolvers;
    resolvers = new LinkedList<>();
    resolvers.add(new PayloadExpressionDataTypeResolver());
    resolvers.add(new PropertyExpressionDataTypeResolver());
    resolvers.add(new FlowVarExpressionDataTypeResolver());
    resolvers.add(new SessionVarExpressionDataTypeResolver());

    return resolvers;
  }

  /**
   * Resolves expression data type
   *
   * @param value result of evaluating the expression on the given message
   * @param event event under evaluation
   * @param serializedExpression expression
   * @return the data type corresponding to the given expression if there is an expression resolver able to resolved it. A default
   *         data type for the value if the expression was not resolved.
   */
  public DataType resolve(Object value, Event event, Serializable serializedExpression) {
    DataType result = null;

    if (serializedExpression instanceof CompiledExpression) {
      CompiledExpression compiledExpression = (CompiledExpression) serializedExpression;

      for (ExpressionDataTypeResolver resolver : resolvers) {
        result = resolver.resolve(event, compiledExpression);

        if (result != null) {
          break;
        }
      }
    }

    if (result == null) {
      Class<?> type = value == null ? Object.class : value.getClass();
      result = DataType.fromType(type);
    }

    return result;
  }
}