package util;

// Java imports
import java.io.*;
import java.util.*;
import javax.xml.parsers.*;
import org.w3c.dom.*;

// Utility methods for managing XML documents
public class XML {

    // This class cannot be instantiated
    private XML() { }



    ///////////////////////////////////////////////////////////////////////////
    //                               Constants                               //
    ///////////////////////////////////////////////////////////////////////////

    // Parsing instance
    private static final DocumentBuilder XML_PARSER;

    // Static initializer
    static {
        DocumentBuilder parser = null;
        try { parser =
            DocumentBuilderFactory.newInstance().newDocumentBuilder();
        } catch (Exception e) { }
        XML_PARSER = parser;
    }



    ///////////////////////////////////////////////////////////////////////////
    //                            Static Methods                             //
    ///////////////////////////////////////////////////////////////////////////

    // Retrieve an attribute value from an XML element
    public static String attribute(Element element, String attribute) {
        return element.hasAttribute(attribute) ?
            element.getAttribute(attribute) : null;
    }

    // Retrieve the child elements of an XML node
    public static Element[] children(Node node) {
        var nodes = node.getChildNodes();
        int count = nodes.getLength();
        var ret   = new ArrayList<Element>();
        for (int x = 0; x < count; x++) {
            node = nodes.item(x);
            if (node.getNodeType() == Node.ELEMENT_NODE)
                ret.add((Element) node);
        }
        return ret.toArray(new Element[ret.size()]);
    }

    // Retrieve the first node matching the given hierarchy
    public static Element element(Node node, String hierarchy) {

        // Error checking
        if (node == null || hierarchy == null)
            return null;

        // Propagate down the hierarchy
        outer: for (String name : hierarchy.split("\\.")) {
            var nodes = node.getChildNodes();
            int count = nodes.getLength();
            for (int x = 0; x < count; x++) {
                node = nodes.item(x);
                if (
                    node.getNodeType() == Node.ELEMENT_NODE &&
                    node.getNodeName().equals(name)
                ) continue outer;
            }
            return null;
        }

        return (Element) node;
    }

    // Retrieve all nodes matching the endpoint of a given hierarchy
    public static Element[] elements(Node node, String hierarchy) {

        // Find the first matching node
        node = element(node, hierarchy);
        if (node == null)
            return new Element[0];

        // Working variables
        var    names = hierarchy.split("\\.");
        String name  = names[names.length - 1];
        var    ret   = new ArrayList<Element>();

        // Include all siblings with the same tag name
        ret.add((Element) node);
        for (;;) {
            node = node.getNextSibling();
            if (node == null)
                break;
            if (
                node.getNodeType() == Node.ELEMENT_NODE &&
                node.getNodeName().equals(name)
            ) ret.add((Element) node);
        }

        return ret.toArray(new Element[ret.size()]);
    }

    // Read and parse an XML file
    public static Node read(String filename) {
        try { return XML_PARSER.parse(
            new ByteArrayInputStream(Util.fileRead(filename)));
        } catch (Exception e) { return null; }
    }

    // Retrieve the text content of an element
    public static String text(Node node) {

        // Error checking
        if (node == null)
            return null;

        // Find the child node called #text
        var nodes = node.getChildNodes();
        int count = nodes.getLength();
        for (int x = 0; x < count; x++) {
            node = nodes.item(x);
            if (node.getNodeType() != Node.TEXT_NODE)
                continue;
            String text = node.getNodeValue();
            return text == null ? "" : text.trim();
        }
        return "";
    }

}