/*******************************************************************************
 *Copyright (c) 2008 Standards for Technology in Automotive Retail and others.
 *All rights reserved. This program and the accompanying materials
 *are made available under the terms of the Eclipse Public License v1.0
 *which accompanies this distribution, and is available at
 *http://www.eclipse.org/legal/epl-v10.html
 *
 *Contributors:
 *    David Carver (STAR) - bug 240170 - initial API and implementation
 *******************************************************************************/
package org.eclipse.wst.xsl.ui.internal.contentassist;

import java.util.ArrayList;
import java.util.List;

import javax.xml.transform.TransformerException;

import org.eclipse.jface.text.ITextViewer;
import org.eclipse.jface.text.contentassist.ICompletionProposal;
import org.eclipse.wst.sse.core.internal.provisional.text.IStructuredDocumentRegion;
import org.eclipse.wst.sse.core.internal.provisional.text.ITextRegion;
import org.eclipse.wst.xsl.ui.internal.contentassist.CustomCompletionProposal;
import org.eclipse.wst.xml.core.internal.provisional.document.IDOMAttr;
import org.eclipse.wst.xml.core.internal.provisional.document.IDOMElement;
import org.eclipse.wst.xml.xpath.core.internal.parser.XPathParser;
import org.eclipse.wst.xml.xpath.core.util.XSLTXPathHelper;
import org.eclipse.wst.xml.xpath.ui.internal.contentassist.XPathTemplateCompletionProcessor;
import org.eclipse.wst.xml.xpath.ui.internal.templates.TemplateContextTypeIdsXPath;
import org.eclipse.wst.xsl.ui.internal.XSLUIPlugin;
import org.eclipse.wst.xsl.ui.internal.util.XSLPluginImageHelper;
import org.eclipse.wst.xsl.ui.internal.util.XSLPluginImages;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;


/**
 * This class provides content assistance for the XSL select attribute.
 * 
 * @author dcarver
 *
 */
public class SelectAttributeContentAssist extends AbstractXSLContentAssistRequest {
	
	private static final String XPATH_GLOBAL_VARIABLES = "/xsl:stylesheet/xsl:variable"; //$NON-NLS-1$

	/**
	 * Retrieve all global parameters in the stylesheet.
	 */
	private static final String XPATH_GLOBAL_PARAMS = "/xsl:stylesheet/xsl:param"; //$NON-NLS-1$

	/**
	 * Limit selection of variables to those that are in the local scope.
	 */
	private static final String XPATH_LOCAL_VARIABLES = "ancestor::xsl:template/descendant::xsl:variable"; //$NON-NLS-1$

	/**
	 * Limit selection of params to those that are in the local scope.
	 */
	private static final String XPATH_LOCAL_PARAMS = "ancestor::xsl:template/descendant::xsl:param"; //$NON-NLS-1$

	private XPathTemplateCompletionProcessor fTemplateProcessor = null;
	private List<String> fTemplateContexts = new ArrayList<String>();
	private static final byte[] XPATH_LOCK = new byte[0];

	/**
	 * Handles Content Assistance requests for Select Attributes.  This is called an instantiated
	 * through the use of the computeProposals method from the XSLContentAssistProcessor.  It will
	 * calculate the available proposals that are available for the XSL select attribute.
	 * 
	 * @param node
	 * @param documentRegion
	 * @param completionRegion
	 * @param begin
	 * @param length
	 * @param filter
	 * @param textViewer
	 */
	public SelectAttributeContentAssist(Node node,
			IStructuredDocumentRegion documentRegion,
			ITextRegion completionRegion, int begin, int length, String filter,
			ITextViewer textViewer) {
		super(node, documentRegion, completionRegion, begin, length, filter, textViewer);
		// TODO Auto-generated constructor stub
	}

	
	/** 
	 * (non-Javadoc)
	 * @see org.eclipse.wst.xml.ui.internal.contentassist.ContentAssistRequest#getCompletionProposals()
	 */
	@Override
	public ArrayList<ICompletionProposal> getCompletionProposals() {
		proposals.clear();
		
		adjustXPathStart();
		
		int offset = getReplacementBeginPosition();
		IDOMAttr attrNode = (IDOMAttr)((IDOMElement)getNode()).getAttributeNode("select");
		
		this.matchString = extractXPathMatchString(attrNode, getRegion(), getReplacementBeginPosition());
		
	    addSelectProposals((Element)getNode().getParentNode(), offset);

		return  getAllCompletionProposals();
    }
	
	
	/**
	 *  This needs to setup the content assistance correctly. Here is what needs to happen:
	 *  1. Adjust the matchString (This should have been calculated earlier) 
	 *  2. Get the current tokens offset position..this will be the starting offset.
	 *  3. Get the replacement length...this is the difference between the token offset and the next token or end of the string
	 */
	protected void adjustXPathStart() {
	    IDOMElement elem = (IDOMElement)getNode();
	    IDOMAttr xpathNode = (IDOMAttr)elem.getAttributeNode("select");
		
		if (xpathNode != null) {
			XPathParser parser = new XPathParser(xpathNode.getValue());
			int startOffset = xpathNode.getValueRegionStartOffset() + parser.getTokenStartOffset(1, getReplacementBeginPosition() - xpathNode.getValueRegionStartOffset()) - 1;
			replacementLength = getReplacementBeginPosition() - startOffset;
		}
	}
		
	protected String extractXPathMatchString(IDOMAttr node, ITextRegion aRegion, int offset) {
		if (node == null || node.getValue().length() == 0)	return "";
		
		if (matchString.length() == 1) {
			return matchString;
		}
		
		int column = offset - node.getValueRegionStartOffset() - 1;
		String nodeValue = node.getValue();
		XPathParser parser = new XPathParser(nodeValue);
		int tokenStart = parser.getTokenStartOffset(1, column);
		
		if (tokenStart >= column) {
			return "";
		}
		
		return node.getValue().substring(tokenStart - 1, column);
	}


	protected void addSelectProposals(Element rootElement, int offset) {
			addGlobalProposals(rootElement, offset);
			addLocalProposals(getNode(), offset);
			addTemplates(TemplateContextTypeIdsXPath.AXIS, offset);
			addTemplates(TemplateContextTypeIdsXPath.XPATH, offset);
			addTemplates(TemplateContextTypeIdsXPath.CUSTOM, offset);
			addTemplates(TemplateContextTypeIdsXPath.OPERATOR, offset);
	}
	
	/**
	 * Adds XPath related templates to the list of proposals
	 * 
	 * @param contentAssistRequest
	 * @param context
	 * @param startOffset
	 */
	protected void addTemplates(String context, int startOffset) {

		if (!fTemplateContexts.contains(context)) {
			fTemplateContexts.add(context);
			
			if (getTemplateCompletionProcessor() != null) {
				getTemplateCompletionProcessor().setContextType(context);
				ICompletionProposal[] proposals = getTemplateCompletionProcessor()
						.computeCompletionProposals(textViewer, startOffset);
				for (int i = 0; i < proposals.length; ++i) {
					ICompletionProposal proposal = proposals[i];
					if (matchString.length() > 0) {
						if (proposal.getDisplayString().startsWith(matchString) ) {
							addProposal(proposals[i]);
						}
					} else {
						addProposal(proposals[i]);
					}
				}
			}
		}
	}
	

	private void addLocalProposals(Node xpathnode, int offset) {
		addVariablesProposals(XPATH_LOCAL_VARIABLES, xpathnode, offset);
		addVariablesProposals(XPATH_LOCAL_PARAMS, xpathnode, offset);
	}

	private void addGlobalProposals(Node xpathnode, int offset) {
		addVariablesProposals(XPATH_GLOBAL_VARIABLES, xpathnode, offset);
		addVariablesProposals(XPATH_GLOBAL_PARAMS, xpathnode, offset);
	}

	/**
	 * Adds Parameter and Variables as proposals. This
	 * information is selected based on the XPath statement that is sent to it
	 * and the input Node passed. It uses a custom composer to XSL Variable
	 * proposal.
	 * 
	 * @param xpath
	 * @param xpathnode
	 * @param contentAssistRequest
	 * @param offset
	 */
	private void addVariablesProposals(String xpath, Node xpathnode, int offset) {
		synchronized (XPATH_LOCK) {
			try {
				NodeList nodes = XSLTXPathHelper.selectNodeList(xpathnode, xpath);
				int startLength = getCursorPosition() - offset;

				if (hasNodes(nodes)) {
					for (int nodecnt = 0; nodecnt < nodes.getLength(); nodecnt++) {
						Node node = nodes.item(nodecnt);
						
						String variableName = "$" + node.getAttributes().getNamedItem("name").getNodeValue(); //$NON-NLS-1$ //$NON-NLS-2$
						CustomCompletionProposal proposal = new CustomCompletionProposal(
								variableName, offset, 0, startLength + variableName.length(),
								XSLPluginImageHelper.getInstance().getImage(XSLPluginImages.IMG_VARIABLES),
								variableName, null, null, 0);
						
						if (matchString.length() > 0) {
							if (proposal.getDisplayString().startsWith(matchString)) {
								addProposal(proposal);
							}
						} else {
							addProposal(proposal);
						}
					}
				}

			} catch (TransformerException ex) {
				XSLUIPlugin.log(ex);
			}
		}
	}

	private XPathTemplateCompletionProcessor getTemplateCompletionProcessor() {
		if (fTemplateProcessor == null) {
			fTemplateProcessor = new XPathTemplateCompletionProcessor();
		}
		return fTemplateProcessor;
	}
}