/**
 * (The MIT License)
 *
 * Copyright (c) 2008 - 2011:
 *
 * * {Aaron Patterson}[http://tenderlovemaking.com]
 * * {Mike Dalessio}[http://mike.daless.io]
 * * {Charles Nutter}[http://blog.headius.com]
 * * {Sergio Arbeo}[http://www.serabe.com]
 * * {Patrick Mahoney}[http://polycrystal.org]
 * * {Yoko Harada}[http://yokolet.blogspot.com]
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * 'Software'), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 * 
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package nokogiri.internals;

import java.util.List;

import javax.xml.xpath.XPathFunction;
import javax.xml.xpath.XPathFunctionException;
import javax.xml.namespace.QName;

import org.jruby.Ruby;
import org.jruby.RubyArray;
import org.jruby.RubyBoolean;
import org.jruby.RubyFixnum;
import org.jruby.RubyFloat;
import org.jruby.RubyInteger;
import org.jruby.RubyString;
import org.jruby.javasupport.JavaUtil;
import org.jruby.runtime.Helpers;
import org.jruby.runtime.ThreadContext;
import org.jruby.runtime.builtin.IRubyObject;
import org.w3c.dom.NodeList;

import nokogiri.XmlNode;
import nokogiri.XmlNodeSet;

import static nokogiri.internals.NokogiriHelpers.nodeListToRubyArray;

/**
 * Xpath function handler.
 * 
 * @author sergio
 * @author Yoko Harada <yokolet@gmail.com>
 */
public class NokogiriXPathFunction implements XPathFunction {

    private final IRubyObject handler;
    private final QName name;
    private final int arity;
    
    public static NokogiriXPathFunction create(IRubyObject handler, QName name, int arity) {
        return new NokogiriXPathFunction(handler, name, arity);
    }

    private NokogiriXPathFunction(IRubyObject handler, QName name, int arity) {
        this.handler = handler;
        this.name = name;
        this.arity = arity;
    }

    public Object evaluate(List args) throws XPathFunctionException {
        if (args.size() != this.arity) {
            throw new XPathFunctionException("arity does not match");
        }
        
        if (name.getNamespaceURI().equals(NokogiriNamespaceContext.NOKOGIRI_BUILTIN_URI)) {
            if (name.getLocalPart().equals("css-class")) {
                return builtinCssClass(args);
            }
        }

        if (this.handler.isNil()) {
            throw new XPathFunctionException("no custom function handler declared for '" + name + "'");
        }

        final Ruby runtime = this.handler.getRuntime();
        ThreadContext context = runtime.getCurrentContext();
        IRubyObject result = Helpers.invoke(context, this.handler, this.name.getLocalPart(),
                                            fromObjectToRubyArgs(runtime, args));
        return fromRubyToObject(runtime, result);
    }

    private static IRubyObject[] fromObjectToRubyArgs(final Ruby runtime, List args) {
        IRubyObject[] newArgs = new IRubyObject[args.size()];
        for(int i = 0; i < args.size(); i++) {
            newArgs[i] = fromObjectToRuby(runtime, args.get(i));
        }
        return newArgs;
    }

    private static IRubyObject fromObjectToRuby(final Ruby runtime, Object obj) {
        // argument object type is one of NodeList, String, Boolean, or Double.
        if (obj instanceof NodeList) {
            IRubyObject[] nodes = nodeListToRubyArray(runtime, (NodeList) obj);
            return XmlNodeSet.newNodeSet(runtime, nodes);
        }
        return JavaUtil.convertJavaToUsableRubyObject(runtime, obj);
    }

    private static Object fromRubyToObject(final Ruby runtime, IRubyObject obj) {
        if (obj instanceof RubyString) return obj.asJavaString();
        if (obj instanceof RubyBoolean) return obj.toJava(Boolean.class);
        if (obj instanceof RubyFloat) return obj.toJava(Double.class);
        if (obj instanceof RubyInteger) {
            if ( obj instanceof RubyFixnum ) return RubyFixnum.fix2long(obj);
            return obj.toJava(java.math.BigInteger.class);
        }
        if (obj instanceof XmlNodeSet) return obj;
        if (obj instanceof RubyArray) {
            return XmlNodeSet.newNodeSet(runtime, ((RubyArray) obj).toJavaArray());
        }
        /*if (o instanceof XmlNode)*/ return ((XmlNode) obj).getNode();
    }

    private static boolean builtinCssClass(List args) throws XPathFunctionException {
        if (args.size() != 2) {
            throw new XPathFunctionException("builtin function nokogiri:css-class takes two arguments");
        }

        String hay = args.get(0).toString();
        String needle = args.get(1).toString();

        if (needle.length() == 0) {
            return true;
        }

        int j = 0;
        int j_lim = hay.length() - needle.length();
        while (j <= j_lim) {
            int k;
            for (k = 0; k < needle.length(); k++) {
                if (needle.charAt(k) != hay.charAt(j+k)) {
                    break;
                }
            }
            if (k == needle.length()) {
                if ((hay.length() == (j+k)) || isWhitespace(hay.charAt(j+k))) {
                    return true ;
                }
            }

            /* advance str to whitespace */
            while (j <= j_lim && !isWhitespace(hay.charAt(j))) {
                j++;
            }

            /* advance str to start of next word or end of string */
            while (j <= j_lim && isWhitespace(hay.charAt(j))) {
                j++;
            }
        }

        return false;
    }

    private static boolean isWhitespace(char subject) {
        // see libxml2's xmlIsBlank_ch()
        return ((subject == 0x09) || (subject == 0x0A) || (subject == 0x0D) || (subject == 0x20));
    }
}