package org.openslx.dnbd3;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;

import org.jdom2.Attribute;
import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.JDOMException;
import org.jdom2.filter.Filters;
import org.jdom2.input.SAXBuilder;
import org.jdom2.output.Format;
import org.jdom2.output.XMLOutputter;
import org.jdom2.xpath.XPathExpression;
import org.jdom2.xpath.XPathFactory;

public class DNBD3Server {

    private static final int CMDSTOP = 0;
    private static final int CMDRELOAD = 1;
    private static final int CMDINFO = 2;
    private static final int CMDCONFIG = 3;

    private static final String HOST = "127.0.0.1";
    private static final int PORT = 5004;

    public void doReload() throws IOException, DNBD3Exception {
        Socket sock = new Socket(HOST, PORT);
        sendHeader(sock, new DNBD3Header(CMDRELOAD, 0, 0));
        receiveHeader(sock);
        sock.close();
    }

    public void doShutdown() throws IOException, DNBD3Exception {
        Socket sock = new Socket(HOST, PORT);
        sendHeader(sock, new DNBD3Header(CMDSTOP, 0, 0));
        receiveHeader(sock);
        sock.close();
    }

    public void addImage(DNBD3Image image) throws IOException, DNBD3Exception {

        Element rootNode = new Element("dnbd3-server");
        Element imageNode = new Element("image");
        imageNode.setAttribute(new Attribute("group", image.getGroup()));
        imageNode.setAttribute(new Attribute("atime", image.getAtime()));
        imageNode.setAttribute(new Attribute("vid", String.valueOf(image.getVid())));
        imageNode.setAttribute(new Attribute("rid", String.valueOf(image.getRid())));
        imageNode.setAttribute(new Attribute("file", image.getPath()));
        imageNode.setAttribute(new Attribute("servers", image.getServers()));
        imageNode.setAttribute(new Attribute("cache_file", image.getCache()));
        rootNode.addContent(imageNode);
        Document doc = new Document(rootNode);
        Socket sock = new Socket(HOST, PORT);
        OutputStream os = sock.getOutputStream();
        XMLOutputter outputter = new XMLOutputter(Format.getPrettyFormat());
        sendHeader(sock, new DNBD3Header(CMDCONFIG, outputter.outputString(doc).length(), 0));
        outputter.output(doc, os);
        receiveHeader(sock);
        sock.close();
    }

    public List<DNBD3Image> getImages() throws IOException, DNBD3Exception {
        List<DNBD3Image> images = new ArrayList<DNBD3Image>();
        Socket sock = new Socket(HOST, PORT);
        sendHeader(sock, new DNBD3Header(CMDINFO, 0, 0));
        receiveHeader(sock);

        try {
            String group, atime, path, servers, cache;
            int vid, rid;
            InputStream is = sock.getInputStream();
            SAXBuilder builder = new SAXBuilder();
            Document document = (Document) builder.build(is);
            XPathFactory xpfac = XPathFactory.instance();
            XPathExpression<Element> xp;
            xp = xpfac.compile("//dnbd3-server/images/image", Filters.element());
            for (Element e : xp.evaluate(document)) {
                group = e.getAttributeValue("group");
                atime = e.getAttributeValue("atime");
                vid = Integer.parseInt(e.getAttributeValue("vid"));
                rid = Integer.parseInt(e.getAttributeValue("rid"));
                path = e.getAttributeValue("file");
                servers = e.getAttributeValue("servers");
                cache = e.getAttributeValue("cache_file");
                images.add(new DNBD3Image(group, atime, vid, rid, path, servers, cache));
            }

        } catch (JDOMException ex) {
            ex.printStackTrace();
        }

        sock.close();
        return images;
    }

    public List<DNBD3Client> getClients() throws IOException, DNBD3Exception {
        List<DNBD3Client> clients = new ArrayList<DNBD3Client>();
        Socket sock = new Socket(HOST, PORT);
        sendHeader(sock, new DNBD3Header(CMDINFO, 0, 0));
        receiveHeader(sock);

        try {
            String ip, image;
            InputStream is = sock.getInputStream();
            SAXBuilder builder = new SAXBuilder();
            Document document = (Document) builder.build(is);
            XPathFactory xpfac = XPathFactory.instance();
            XPathExpression<Element> xp;
            xp = xpfac.compile("//dnbd3-server/clients/client", Filters.element());
            for (Element e : xp.evaluate(document)) {
                ip = e.getAttributeValue("ip");
                image = e.getAttributeValue("file");
                clients.add(new DNBD3Client(ip, image));
            }

        } catch (JDOMException ex) {
            ex.printStackTrace();
        }

        sock.close();
        return clients;
    }

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

    private void sendHeader(Socket sock, DNBD3Header header) throws IOException {
        OutputStream os = sock.getOutputStream();
        os.write(header.toByteArray());
    }

    private DNBD3Header receiveHeader(Socket sock) throws IOException, DNBD3Exception {
        DNBD3Header header = new DNBD3Header();
        InputStream is = sock.getInputStream();
        byte[] bytes = ByteBuffer.allocate(12).array();
        is.read(bytes, 0, 12);
        header.fromByteArray(bytes);

        switch (header.getError()) {

        case 0:
            return header;

        case DNBD3Header.ERROR_IMAGE_NOT_FOUND:
            throw new DNBD3Exception(DNBD3Header.ERROR_IMAGE_NOT_FOUND,
                    "Image file does not exist or is not readable");

        case DNBD3Header.ERROR_IMAGE_ALREADY_EXISTS:
            throw new DNBD3Exception(DNBD3Header.ERROR_IMAGE_ALREADY_EXISTS,
                    "Image with given vid and rid already exists");

        case DNBD3Header.ERROR_CONFIG_FILE_PERMISSIONS:
            throw new DNBD3Exception(DNBD3Header.ERROR_CONFIG_FILE_PERMISSIONS,
                    "Config file is not writable");

        default:
            throw new DNBD3Exception(DNBD3Header.ERROR_UNKNOWN,
                    "Unknown error, something went horribly wrong...");
        }
    }

}