package org.eclipse.jst.jsf.ui.internal.jspeditor;

import org.eclipse.core.runtime.IStatus;
import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.Region;
import org.eclipse.jst.jsf.context.resolver.structureddocument.IStructuredDocumentContextResolverFactory;
import org.eclipse.jst.jsf.context.resolver.structureddocument.internal.ITextRegionContextResolver;
import org.eclipse.jst.jsf.context.structureddocument.IStructuredDocumentContext;
import org.eclipse.jst.jsf.core.internal.contentassist.el.ContentAssistParser;
import org.eclipse.jst.jsf.core.internal.contentassist.el.SymbolInfo;
import org.eclipse.jst.jsf.designtime.DTAppManagerUtil;
import org.eclipse.jst.jsf.designtime.internal.view.XMLViewDefnAdapter;
import org.eclipse.jst.jsf.designtime.internal.view.IDTViewHandler.ViewHandlerException;
import org.eclipse.jst.jsf.designtime.internal.view.XMLViewDefnAdapter.DTELExpression;
import org.eclipse.jst.jsf.ui.internal.JSFUiPlugin;
import org.eclipse.wst.xml.core.internal.regions.DOMRegionContext;

/**
 * Utility class to access EL symbols in jsp file.
 */
public final class JSPSourceUtil
{

    private JSPSourceUtil()
    {
        // utility class, no instances.
    }

    /**
     * Find the Region
     * 
     * @param context -
     *            the IStructuredDocumentContext
     * @return region of el expression, null if context doesn't point to an el
     *         expression
     */
    public static Region findELRegion(final IStructuredDocumentContext context)
    {
        if (context != null)
        {
            final XMLViewDefnAdapter adapter =
                    DTAppManagerUtil.getXMLViewDefnAdapter(context);
            if (adapter != null)
            {
                DTELExpression expression;
                try
                {
                    expression = adapter.getELExpression(context);
                }
                catch (ViewHandlerException e)
                {
                    JSFUiPlugin.log(IStatus.ERROR, "", e);
                    expression = null;
                }

                if (expression != null)
                {
                    final ITextRegionContextResolver resolver =
                            IStructuredDocumentContextResolverFactory.INSTANCE
                                    .getTextRegionResolver(expression
                                            .getDocumentContext());

                    if (resolver != null)
                    {
                        final String regionType = resolver.getRegionType();

                        if (regionType != null
                                && resolver.matchesRelative(new String[]
                                { DOMRegionContext.XML_TAG_ATTRIBUTE_VALUE }))
                        {
                            return new Region(resolver.getStartOffset(),
                                    resolver.getLength());
                        }
                    }
                }
            }
        }
        return null;
    }

    /**
     * Determines symbol and symbol region at a given document position
     * 
     * @param context -
     *            the IStructuredDocumentContext
     * @param elRegion -
     *            the region of the el expression to consider
     * @param documentPosition -
     *            the document position to get the symbol for
     * @return SymbolInfo
     */
    public static SymbolInfo determineSymbolInfo(
            final IStructuredDocumentContext context, final Region elRegion,
            final int documentPosition)
    {
        if (context != null && elRegion != null)
        {
            try
            {
                String elText;
                elText =
                        context.getStructuredDocument().get(
                                elRegion.getOffset(), elRegion.getLength());
                final SymbolInfo symbolInfo =
                        ContentAssistParser.getSymbolInfo(context,
                                documentPosition - elRegion.getOffset() + 1,
                                elText);
                return symbolInfo;
            }
            catch (final BadLocationException e)
            {
                // well, so we simply have no symbol, no reason to worry (or
                // log...)
                return null;
            }
        }
        return null;
    }
}