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/* ReferenceImpl.java

	Purpose:
		
	Description:
		
	History:
		Jan 12, 2012 9:11:03 AM, Created by henrichen

Copyright (C) 2012 Potix Corporation. All Rights Reserved.
*/

package org.zkoss.bind.impl;

import java.util.Set;

import org.zkoss.bind.BindContext;
import org.zkoss.bind.Binder;
import org.zkoss.bind.Property;
import org.zkoss.bind.sys.BinderCtrl;
import org.zkoss.bind.sys.ReferenceBinding;
import org.zkoss.bind.sys.debugger.BindingExecutionInfoCollector;
import org.zkoss.bind.sys.debugger.impl.info.LoadInfo;
import org.zkoss.bind.sys.debugger.impl.info.SaveInfo;
import org.zkoss.bind.xel.zel.BindELContext;
import org.zkoss.xel.ExpressionX;
import org.zkoss.xel.ValueReference;
import org.zkoss.zk.ui.Component;

/**
 * Implementation of {@link ReferenceBinding}.
 * @author henrichen
 * @since 6.0.0
 */
public class ReferenceBindingImpl extends BindingImpl implements ReferenceBinding {
	private static final long serialVersionUID = 20120204122151L;
	private static final Object NULL_VALUE = new Object();

	// make lazy init
	private ExpressionX _exprX;
	private final String _expression;
	private transient Object _cacheValue; //null means invalid
	private final String _attr;

	public ReferenceBindingImpl(Binder binder, Component comp, String attr, String expression) {
		super(binder, comp, null);
		_expression = expression;
		_attr = attr;
	}

	// make lazy init
	private ExpressionX initExpressionX() {
		if (_exprX == null) {
			final BindContext ctx = newBindContext();
			_exprX = getBinder().getEvaluatorX().parseExpressionX(ctx, _expression, Object.class);
		}

		return _exprX;
	}

	public Object getValue(BindELContext ctx) {
		load(null);
		return _cacheValue == NULL_VALUE ? null : _cacheValue;
	}

	public void setValue(BindELContext ctx, Object val) {
		invalidateCache();
		final BindContext bctx = newBindContext();
		getBinder().getEvaluatorX().setValue(bctx, getComponent(), initExpressionX(), val);

		final BindingExecutionInfoCollector collector = ((BinderCtrl) getBinder()).getBindingExecutionInfoCollector();
		if (collector != null) {
			collector.addInfo(new SaveInfo(SaveInfo.REFERENCE, getComponent(), null, _attr, getPropertyString(), val,
					null, null));
		}

		//copy notifies back
		final Set notifies = BindELContext.getNotifys(bctx);
		if (notifies != null) {
			BindELContext.addNotifys(notifies, ctx.getBindContext());
		}
	}

	private BindContext newBindContext() {
		return BindContextUtil.newBindContext(getBinder(), this, false, null, getComponent(), null);
	}

	public void load(BindContext ctx) {
		if (_cacheValue == null) {
			final BindContext bctx = newBindContext();
			final Object val = getBinder().getEvaluatorX().getValue(bctx, getComponent(), initExpressionX());
			_cacheValue = val == null ? NULL_VALUE : val;

			final BindingExecutionInfoCollector collector = ((BinderCtrl) getBinder())
					.getBindingExecutionInfoCollector();
			if (collector != null) {
				collector.addInfo(new LoadInfo(LoadInfo.REFERENCE, getComponent(), null, getPropertyString(), _attr,
						_cacheValue, null, null));
			}
		}
	}

	public String getPropertyString() {
		return BindEvaluatorXUtil.getExpressionString(initExpressionX());
	}

	public void invalidateCache() {
		_cacheValue = null;
	}

	public String toString() {
		return new StringBuilder().append(getClass().getSimpleName()).append("@")
				.append(Integer.toHexString(hashCode())).append(",component:").append(getComponent()).toString();
	}

	/*package*/ ValueReference getValueReference() {
		final BindContext bctx = newBindContext();
		return getBinder().getEvaluatorX().getValueReference(bctx, getComponent(), initExpressionX());
	}
}