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package com.jsftoolkit.base;

import java.util.Iterator;

import javax.el.ValueExpression;
import javax.faces.component.UIComponent;
import javax.faces.component.UIComponentBase;
import javax.faces.context.FacesContext;

import com.jsftoolkit.utils.Utils;

/**
 * This class may be used as a base class for {@link UIComponent}s, but will
 * typically be used statically, so that components can inherit from other
 * components.
 * 
 * @author noah
 * 
 */
public abstract class ComponentHelp extends UIComponentBase {

	/**
	 * Member version.
	 * 
	 * @see {@link #getAttribute(Object, Object, String, UIComponent, FacesContext)
	 * 
	 * @param 
	 * @param value
	 * @param attribute
	 * @return
	 */
	protected  T getAttribute(T value, String attribute) {
		return getAttribute(value, attribute, this, getFacesContext());
	}

	/**
	 * Member version.
	 * 
	 * @see {@link #getAttribute(Object, Object, String, UIComponent, FacesContext)
	 * 
	 * @param 
	 * @param value
	 * @param defaultValue
	 * @param attribute
	 * @return
	 */
	protected  T getAttribute(T value, T defaultValue, String attribute) {
		return getAttribute(value, defaultValue, attribute, this,
				getFacesContext());
	}

	/**
	 * Get the named attribute, defaulting to null.
	 * 
	 * @see {@link #getAttribute(Object, Object, String, UIComponent, FacesContext)
	 * 
	 * @param 
	 * @param value
	 * @param attribute
	 * @param component
	 * @param context
	 * @return
	 */
	public static  T getAttribute(T value, String attribute,
			UIComponent component, FacesContext context) {
		return getAttribute(value, null, attribute, component, context);
	}

	/**
	 * Helper for component getters. The passed in value should be a component
	 * field that is set by the setter for the property. If value is non-null,
	 * it will always be returned. If it is null, a {@link ValueExpression} for
	 * the attribute will be evaluated. If that value is null, defaultValue is
	 * returned, otherwise the value obtained from the value expression will be
	 * returned.
	 * 
	 * @param 
	 * @param value
	 *            the value of the property field
	 * @param defaultValue
	 *            the default value, if no other value is non-null
	 * @param attribute
	 *            the component attribute being evaluated
	 * @param component
	 *            the component we are getting the attribute value for
	 * @param context
	 *            the faces context
	 * @return value, the result of evaluating the
	 *         {@link ValueExpression} for attribute on
	 *         component, or defaultValue.
	 */
	@SuppressWarnings("unchecked")
	public static  T getAttribute(T value, T defaultValue, String attribute,
			UIComponent component, FacesContext context) {
		if (value != null) {
			return value;
		}

		ValueExpression ve = component.getValueExpression(attribute);
		
		return Utils.getValue((ve == null) ? null : (T) ve.getValue(context
				.getELContext()), defaultValue);
	}

	/**
	 * Convenience method. Creates an iterator that returns the clientId of each
	 * component in components.
	 * 
	 * @param components
	 * @param context
	 * @return
	 */
	public static Iterator getIdIterator(
			final Iterable components, final FacesContext context) {

		return new Iterator() {

			private Iterator it = components.iterator();

			public boolean hasNext() {
				return it.hasNext();
			}

			public String next() {
				return it.next().getClientId(context);
			}

			public void remove() {
				throw new UnsupportedOperationException();
			}

		};
	}
}