package org.eclipse.jst.pagedesigner.itemcreation;

import org.eclipse.jst.jsf.core.internal.tld.ITLDConstants;
import org.eclipse.jst.pagedesigner.dom.IDOMPosition;
import org.eclipse.wst.xml.core.internal.provisional.document.IDOMElement;
import org.w3c.dom.Element;

/**
 * The abstract class from which all client ITagCreator instances
 * should be derived.
 * 
 * The createTag method enforces a set of steps required by the framework
 * to create a new tag.  However, it allows you to configure some of the steps
 * by providing an ITagCreationAdvisor through the doSelectCreationAdvisor.
 *
 * <p><b>Provisional API - subject to change</b></p>
 *
 * @author cbateman
 *
 */
public abstract class AbstractTagCreator implements ITagCreator 
{
    /* (non-Javadoc)
     * @see org.eclipse.jst.pagedesigner.itemcreation.ITagCreator#createTag(org.eclipse.jst.pagedesigner.editors.palette.TagToolPaletteEntry, org.eclipse.wst.xml.core.internal.provisional.document.IDOMModel, org.eclipse.jst.pagedesigner.dom.IDOMPosition)
     */
    public final Element createTag(final CreationData creationData) 
    {
        final ITagCreationAdvisor  advisor = selectCreationAdvisor(creationData);
        
        // adjust the creation position to accommodate required containers
        final IDOMPosition position = 
            advisor.checkAndApplyNecessaryContainers(creationData.getModel(), creationData.getDomPosition());
        
        if (position == null) return null;//throw exception?

        creationData.setAdjustedPosition(position);
        
        // create the element
        final Element ele =  createElement(creationData);
        if (ele == null) return null;//throw exception?

        // apply tag customization
        advisor.applyCustomization(creationData.getModel(), ele);

        // ensure that any attributes required by the tag's definition
        // is initialized.
        // TODO: a drawback of this approach is that it leaves the tag in
        // a state where there are no error flags to tell the user something is
        // missing, but may initialize the tag with an (empty) invalid value
        //ensureRequiredAttrs(ele, creationData);

        addTagToContainer(position, ele);

        return ele;
    }

    private ITagCreationAdvisor selectCreationAdvisor(CreationData creationData)
    {
        ITagCreationAdvisor advisor  = doSelectCreationAdvisor(creationData);

        // enforce that the advisor must be an AbstractTagCreationAdvisor to 
        // avoid using the default (not this case also covers advisor == null)
        if (! (advisor instanceof AbstractTagCreationAdvisor))
        {
            advisor = new DefaultTagCreationAdvisor(creationData);
        }

        return advisor;
    }
    
    /**
     * @param creationData
     * @return a tag creation advisor or null to indicate the use of the system default
     */
    protected abstract ITagCreationAdvisor doSelectCreationAdvisor(CreationData creationData);

    /**
     * @param creationData 
     * @return {@link Element}
     */
    protected final Element createElement(final CreationData creationData)
    {
        Element ele =  creationData.getModel().getDocument().createElement(creationData.getTagName());
        if (ele == null) return null;

        //ugly... fix me
        
        // TODO: move this into an ensure method?
        // XXX: we are using "startsWith("directive.")" to test whether
        // should setJSPTag, this
        // maybe is not the best way. Need check whether SSE have special
        // API for it.
        if (ITLDConstants.URI_JSP.equals(creationData.getUri())
                && (ele.getLocalName().startsWith("directive.")
                        || "declaration".equals(ele.getLocalName())
                        || "expression".equals(ele.getLocalName()) || "scriptlet"
                        .equals(ele.getLocalName()))) {
            // it is a jsp tag
            ((IDOMElement) ele).setJSPTag(true);
        }

        if (creationData.getPrefix() != null)
        {
            ele.setPrefix(creationData.getPrefix());
        }

        return ele;
    }

    /**
     * @param position
     * @param tagElement
     */
    private void addTagToContainer(final IDOMPosition position, final Element tagElement) {
        if (position == null || position.getContainerNode() == null) {
            return;
        }

        if (position.getNextSiblingNode() == null) {
            position.getContainerNode().appendChild(tagElement);
        } else {
            position.getContainerNode().insertBefore(tagElement,
                    position.getNextSiblingNode());
        }
    }
}