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package javax.faces.component;

import java.io.Serializable;

import javax.faces.component.StateHolder;
import javax.faces.context.FacesContext;
import javax.faces.el.EvaluationException;
import javax.faces.el.MethodBinding;

import javax.el.MethodExpression;
import javax.el.MethodInfo;
import javax.el.ELException;
import javax.el.ELContext;
import javax.el.ExpressionFactory;
import javax.el.ValueExpression;

import java.util.Arrays;
import java.lang.reflect.Method;

/**
 * <p>Wrap a MethodExpression instance and expose it as a MethodBinding</p>
 *
 */
 class MethodBindingMethodExpressionAdapter extends MethodBinding implements StateHolder, 
    Serializable {

    private static final long serialVersionUID = 7334926223014401689L;

    private MethodExpression methodExpression= null;
    private boolean tranzient;

    public MethodBindingMethodExpressionAdapter() {} // for StateHolder
    
     MethodBindingMethodExpressionAdapter(MethodExpression methodExpression) {
        this.methodExpression = methodExpression;    
    }

    public Object invoke(FacesContext context, Object params[])
        throws javax.faces.el.EvaluationException, javax.faces.el.MethodNotFoundException {
	assert(null != methodExpression);
        if ( context == null ) {
            throw new NullPointerException("FacesConext -> null");
        }
        
	Object result = null;
	try {
	    result = methodExpression.invoke(context.getELContext(),
					     params);
	}
	catch (javax.el.MethodNotFoundException e) {
	    throw new javax.faces.el.MethodNotFoundException(e);
	}
	catch (javax.el.PropertyNotFoundException e) {
	    throw new EvaluationException(e);
	}
	catch (ELException e) {
            Throwable cause = e.getCause();
            if (cause == null) {
                cause = e;
            }
            throw new EvaluationException(cause);
	} catch (NullPointerException e) {
	    throw new javax.faces.el.MethodNotFoundException(e);
	}
	return result;
    }

    public Class getType(FacesContext context) throws javax.faces.el.MethodNotFoundException {
	assert(null != methodExpression);
	if (context == null) {
	        throw new NullPointerException("FacesConext -> null");
    }
	Class result = null;
        if ( context == null ) {
            throw new NullPointerException();
        }
        
	try {
	    MethodInfo mi = 
		methodExpression.getMethodInfo(context.getELContext());
	    result = mi.getReturnType();
	}
	catch (javax.el.PropertyNotFoundException e) {
	    throw new javax.faces.el.MethodNotFoundException(e);
	}
	catch (javax.el.MethodNotFoundException e) {
	    throw new javax.faces.el.MethodNotFoundException(e);
	}
	catch (ELException e) {
	    throw new javax.faces.el.MethodNotFoundException(e);
	}
	return result;
    }
    
   
    public String getExpressionString() {
	assert(null != methodExpression);
        return methodExpression.getExpressionString();
    }

    public boolean equals(Object other) {
        if (this == other) {
            return true;       
        }
        if (other instanceof MethodBindingMethodExpressionAdapter) {
            return methodExpression.equals(((MethodBindingMethodExpressionAdapter) other).getWrapped());                        
        } else if (other instanceof MethodBinding) {
            MethodBinding binding = (MethodBinding) other;
            
            // We'll need to do a little leg work to determine
            // if the MethodBinding is equivalent to the 
            // wrapped MethodExpression
            String expr = binding.getExpressionString();
            int idx = expr.indexOf('.');
            String target = expr.substring(0, idx).substring(2);
            String t = expr.substring(idx + 1);
            String method = t.substring(0, (t.length() - 1));
            
            FacesContext context = FacesContext.getCurrentInstance();
            ELContext elContext = context.getELContext();
            MethodInfo controlInfo = methodExpression.getMethodInfo(elContext);
            
            // ensure the method names are the same
            if (!controlInfo.getName().equals(method)) {
                return false;
            }
            
            // Using the target, create an expression and evaluate
            // it.           
            ExpressionFactory factory = context.getApplication().getExpressionFactory();
            ValueExpression ve = factory.createValueExpression(elContext,
                                                               "#{" + target + '}',
                                                               Object.class);
            if (ve == null) {
                return false;                                                               
            }
            
            Object result = ve.getValue(elContext);
            
            if (result == null) {
                return false;
            }
            
            // Get all of the methods with the matching name and try
            // to find a match based on controlInfo's return and parameter
            // types
            Class type = binding.getType(context);
            Method[] methods = result.getClass().getMethods();
            for (Method meth : methods) {
                if (meth.getName().equals(method)
                     && type.equals(controlInfo.getReturnType())
                     && Arrays.equals(meth.getParameterTypes(), 
                                      controlInfo.getParamTypes())) {
                    return true;                      
                }
            }
        }
        
        return false;
        
    }

    public int hashCode() {
	assert(null != methodExpression);

	return methodExpression.hashCode();
    }


    public boolean isTransient() {
        return this.tranzient;
    }
    
    public void setTransient(boolean tranzient) {
        this.tranzient = tranzient;
    }
    
    public Object saveState(FacesContext context){
        if (context == null) {
            throw new NullPointerException();
        }
	Object result = null;
	if (!tranzient) {
	    if (methodExpression instanceof StateHolder) {
		Object [] stateStruct = new Object[2];
		
		// save the actual state of our wrapped methodExpression
		stateStruct[0] = ((StateHolder)methodExpression).saveState(context);
		// save the class name of the methodExpression impl
		stateStruct[1] = methodExpression.getClass().getName();

		result = stateStruct;
	    }
	    else {
		result = methodExpression;
	    }
	}

	return result;
	
    }

    public void restoreState(FacesContext context, Object state) {
        if (context == null) {
            throw new NullPointerException();
        }
	// if we have state
	if (null == state) {
	    return;
	}
	
	if (!(state instanceof MethodExpression)) {
	    Object [] stateStruct = (Object []) state;
	    Object savedState = stateStruct[0];
	    String className = stateStruct[1].toString();
	    MethodExpression result = null;
	    
	    Class toRestoreClass = null;
	    if (null != className) {
		try {
		    toRestoreClass = loadClass(className, this);
		}
		catch (ClassNotFoundException e) {
		    throw new IllegalStateException(e.getMessage());
		}
		
		if (null != toRestoreClass) {
		    try {
			result = 
			    (MethodExpression) toRestoreClass.newInstance();
		    }
		    catch (InstantiationException e) {
			throw new IllegalStateException(e.getMessage());
		    }
		    catch (IllegalAccessException a) {
			throw new IllegalStateException(a.getMessage());
		    }
		}
		
		if (null != result && null != savedState) {
		    // don't need to check transient, since that was
		    // done on the saving side.
		    ((StateHolder)result).restoreState(context, savedState);
		}
		methodExpression = result;
	    }
	}
	else {
	    methodExpression = (MethodExpression) state;
	}
    }
    
    public MethodExpression getWrapped() {
        return methodExpression;
    }

    //
    // Helper methods for StateHolder
    //

    private static Class loadClass(String name, 
            Object fallbackClass) throws ClassNotFoundException {
        ClassLoader loader =
            Thread.currentThread().getContextClassLoader();
        if (loader == null) {
            loader = fallbackClass.getClass().getClassLoader();
        }
        return Class.forName(name, true, loader);
    }
 


}
