/*
 * 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.myfaces.test.el;

import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import javax.el.ELContext;
import javax.el.ELException;
import javax.el.ELResolver;
import javax.el.MethodExpression;
import javax.el.MethodInfo;
import javax.el.MethodNotFoundException;
import javax.faces.context.FacesContext;

/**
 * <p>Mock implementation of <code>MethodExpression</code>.</p>
 * 
 * @since 1.0.0
 */
public class MockMethodExpression extends MethodExpression
{

    // ------------------------------------------------------------ Constructors

    /**
     * Serial version UID.
     */
    private static final long serialVersionUID = 5694105394290316715L;

    /**
     * <p>Construct a new expression for the specified expression string.</p>
     *
     * @param expression Expression string to be evaluated
     * @param signature Parameter signature of the method to be called
     * @param expectedType Expected type of the result
     */
    public MockMethodExpression(String expression, Class[] signature,
            Class expectedType)
    {

        if (expression == null)
        {
            throw new NullPointerException("Expression string cannot be null");
        }
        this.expression = expression;
        this.signature = signature;
        this.expectedType = expectedType;
        parse();

    }

    // ------------------------------------------------------ Instance Variables

    /**
     * <p>The parsed elements of this expression.</p>
     */
    private String[] elements = null;

    /**
     * <p>The expected result type for <code>getValue()</code> calls.</p>
     */
    private Class expectedType = null;

    /**
     * <p>The original expression string used to create this expression.</p>
     */
    private String expression = null;

    /**
     * <p>The method signature of the method to be called.</p>
     */
    private Class[] signature = null;

    // ------------------------------------------------------ Expression Methods

    /**
     * <p>Return <code>true</code> if this expression is equal to the
     * specified expression.</p>
     *
     * @param obj Object to be compared
     */
    public boolean equals(Object obj)
    {

        if ((obj != null) & (obj instanceof MethodExpression))
        {
            return expression.equals(((MethodExpression) obj)
                    .getExpressionString());
        }
        else
        {
            return false;
        }

    }

    /**
     * <p>Return the original String used to create this expression,
     * unmodified.</p>
     */
    public String getExpressionString()
    {

        return this.expression;

    }

    /**
     * <p>Return the hash code for this expression.</p>
     */
    public int hashCode()
    {

        return this.expression.hashCode();

    }

    /**
     * <p>Return <code>true</code> if the expression string for this expression
     * contains only literal text.</p>
     */
    public boolean isLiteralText()
    {

        return (expression.indexOf("${") < 0) && (expression.indexOf("#{") < 0);

    }

    // ------------------------------------------------ MethodExpression Methods

    /**
     * <p>Evaluate the expression relative to the specified context,
     * and return information about the actual implementation method.</p>
     *
     * @param context ELContext for this evaluation
     */
    public MethodInfo getMethodInfo(ELContext context)
    {

        if (context == null)
        {
            throw new NullPointerException();
        }
        return new MethodInfo(elements[elements.length - 1], expectedType,
                signature);

    }

    /**
     * <p>Evaluate the expression relative to the specified ocntext,
     * and return the result after coercion to the expected result type.</p>
     *
     * @param context ELContext for this evaluation
     * @param params Parameters for this method call
     */
    public Object invoke(ELContext context, Object[] params)
    {

        if (context == null)
        {
            throw new NullPointerException();
        }
        if (isLiteralText())
        {
            return expression;
        }

        FacesContext fcontext = (FacesContext) context
                .getContext(FacesContext.class);
        ELResolver resolver = fcontext.getApplication().getELResolver();
        Object base = null;
        for (int i = 0; i < elements.length - 1; i++)
        {
            base = resolver.getValue(context, base, elements[i]);
        }

        try
        {
            Method method = base.getClass().getMethod(
                    elements[elements.length - 1], signature);
            Object result = method.invoke(base, params);
            return fcontext.getApplication().getExpressionFactory()
                    .coerceToType(result, expectedType);
        }
        catch (RuntimeException e)
        {
            throw e;
        }
        catch (NoSuchMethodException e)
        {
            throw new MethodNotFoundException(e);
        }
        catch (Exception e)
        {
            throw new ELException(e);
        }

    }

    // --------------------------------------------------------- Private Methods

    /**
     * <p>Parse the expression string into its constituent elemetns.</p>
     */
    private void parse()
    {

        if (isLiteralText())
        {
            elements = new String[0];
            return;
        }

        if (expression.startsWith("${") || expression.startsWith("#{"))
        {
            if (expression.endsWith("}"))
            {
                String temp = expression.substring(2, expression.length() - 1)
                        .replaceAll(" ", "");
                List names = new ArrayList();
                while (temp.length() > 0)
                {
                    int period = temp.indexOf('.');
                    if (period >= 0)
                    {
                        names.add(temp.substring(0, period));
                        temp = temp.substring(period + 1);
                    }
                    else
                    {
                        names.add(temp);
                        temp = "";
                    }
                }
                elements = (String[]) names.toArray(new String[names.size()]);
            }
            else
            {
                throw new IllegalArgumentException(expression);
            }
        }
        else
        {
            throw new IllegalArgumentException(expression);
        }

    }

}