package de.intevation.flys.artifacts.datacage.templating;

import java.util.List;
import java.util.Collection;
import java.util.Map;
import java.util.ArrayList;

import javax.xml.xpath.XPathFunctionResolver;
import javax.xml.xpath.XPathFunction;
import javax.xml.xpath.XPathFunctionException;

import javax.xml.namespace.QName;

import org.apache.log4j.Logger;


/** Resolves functions (e.g. dc:contains) in Datacage/Meta-Data system. */
public class FunctionResolver
implements   XPathFunctionResolver
{
    /** Home logger. */
    private static Logger log = Logger.getLogger(FunctionResolver.class);

    public static final String FUNCTION_NAMESPACE_URI = "dc";

    public static final class Entry {

        String        name;
        XPathFunction function;
        int           arity;

        public Entry() {
        }

        public Entry(String name, XPathFunction function, int arity) {
            this.name     = name;
            this.function = function;
            this.arity    = arity;
        }
    } // class Entry

    public static final FunctionResolver FUNCTIONS = new FunctionResolver();

    static {
        /** Implementation of case-ignoring dc:contains. */
        FUNCTIONS.addFunction("contains", 2, new XPathFunction() {
            @Override
            public Object evaluate(List args) throws XPathFunctionException {
                Object haystack = args.get(0);
                Object needle   = args.get(1);

                if (needle instanceof String) {
                    needle = ((String)needle).toUpperCase();
                }

                try {
                    if (haystack instanceof Collection) {
                        return Boolean.valueOf(
                            ((Collection)haystack).contains(needle));
                    }

                    if (haystack instanceof Map) {
                        return Boolean.valueOf(
                            ((Map)haystack).containsKey(needle));
                    }

                    if (haystack instanceof Object []) {
                        for (Object straw: (Object [])haystack) {
                            if (straw.equals(needle)) {
                                return Boolean.TRUE;
                            }
                        }
                    }

                    return Boolean.FALSE;
                }
                catch (Exception e) {
                    log.error(e);
                    throw new XPathFunctionException(e);
                }
            }
        });
    }

    /** List of functions. */
    protected List<Entry> functions;

    public FunctionResolver() {
        functions = new ArrayList<Entry>();
    }

    /**
     * Create a new function.
     * @param name  Name of the function.
     * @param arity Number of arguments for function.
     * @param function the function itself.
     */
    public void addFunction(String name, int arity, XPathFunction function) {
        functions.add(new Entry(name, function, arity));
    }

    @Override
    public XPathFunction resolveFunction(QName functionName, int arity) {

        if (!functionName.getNamespaceURI().equals(FUNCTION_NAMESPACE_URI)) {
            return null;
        }

        String name = functionName.getLocalPart();
        for (Entry entry: functions) {
            if (entry.arity == arity && entry.name.equals(name)) {
                return entry.function;
            }
        }

        return null;
    }
}
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