package org.exist.xquery.functions.xmldb;

import java.util.List;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.exist.dom.QName;
import org.exist.xquery.BasicFunction;
import org.exist.xquery.FunctionSignature;
import org.exist.xquery.XPathException;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.value.SequenceType;
import org.exist.xquery.value.Type;
import org.exist.xquery.Cardinality;
import org.exist.xquery.XQueryContext;
import org.exist.xquery.value.FunctionParameterSequenceType;
import org.exist.xquery.value.FunctionReturnSequenceType;
import org.exist.xquery.value.ValueSequence;
import org.exist.xquery.value.StringValue;

/**
 *
 * @author Adam Retter <adam@exist-db.org>
 */
public class XMLDBMatchCollection extends BasicFunction {

    protected static final Logger logger = LogManager.getLogger(XMLDBMatchCollection.class);

    public final static FunctionSignature signature = new FunctionSignature(
            new QName("match-collection", XMLDBModule.NAMESPACE_URI, XMLDBModule.PREFIX),
            "Looks for collection names in the collection index that match the provided regexp",
            new SequenceType[]{
                new FunctionParameterSequenceType("regexp", Type.STRING, Cardinality.EXACTLY_ONE, "The expression to use for matching collection names"),
            },
            new FunctionReturnSequenceType(Type.STRING, Cardinality.ZERO_OR_MORE, "The names of the collections that match the expression"));

    
    public XMLDBMatchCollection(XQueryContext context) {
        super(context, signature);
    }
    
    @Override
    public Sequence eval(Sequence[] args, Sequence contextSequence) throws XPathException {
        
        Sequence result = Sequence.EMPTY_SEQUENCE;
        
        final String regexp = args[0].getStringValue();
        
        final List<String> collectionNames = context.getBroker().findCollectionsMatching(regexp);
        if(collectionNames.size() > 0) {
            result = copyListToValueSequence(collectionNames);
        }
        
        return result;
    }

    private Sequence copyListToValueSequence(List<String> collectionNames) {
        final ValueSequence seq = new ValueSequence(collectionNames.size());
        
        for(final String collectionName : collectionNames) {
            seq.add(new StringValue(collectionName));
        }
        
        return seq;
    }
}