package org.opendaylight.controller.sal.streams.listeners;

import io.netty.channel.Channel;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.util.internal.ConcurrentSet;

import java.io.ByteArrayOutputStream;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.text.SimpleDateFormat;
import java.util.Collection;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Random;
import java.util.Set;
import java.util.concurrent.Executors;

import javax.activation.UnsupportedDataTypeException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.opendaylight.controller.md.sal.common.api.data.DataChangeEvent;
import org.opendaylight.controller.sal.core.api.data.DataChangeListener;
import org.opendaylight.controller.sal.rest.impl.XmlMapper;
import org.opendaylight.controller.sal.restconf.impl.ControllerContext;
import org.opendaylight.yangtools.concepts.ListenerRegistration;
import org.opendaylight.yangtools.yang.common.QName;
import org.opendaylight.yangtools.yang.data.api.CompositeNode;
import org.opendaylight.yangtools.yang.data.api.InstanceIdentifier;
import org.opendaylight.yangtools.yang.data.api.InstanceIdentifier.NodeIdentifierWithPredicates;
import org.opendaylight.yangtools.yang.data.api.InstanceIdentifier.NodeWithValue;
import org.opendaylight.yangtools.yang.data.api.InstanceIdentifier.PathArgument;
import org.opendaylight.yangtools.yang.model.api.DataNodeContainer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;

import com.google.common.base.Preconditions;
import com.google.common.eventbus.AsyncEventBus;
import com.google.common.eventbus.EventBus;
import com.google.common.eventbus.Subscribe;

public class ListenerAdapter implements DataChangeListener {

    private static final Logger logger = LoggerFactory.getLogger(ListenerAdapter.class);
    private final XmlMapper xmlMapper = new XmlMapper();
    private final SimpleDateFormat rfc3339 = new SimpleDateFormat("yyyy-MM-dd'T'hh:mm:ssZ");

    private final InstanceIdentifier path;
    private ListenerRegistration<DataChangeListener> registration;
    private final String streamName;
    private Set<Channel> subscribers = new ConcurrentSet<>();
    private final EventBus eventBus;
    private final EventBusChangeRecorder eventBusChangeRecorder;

    ListenerAdapter(InstanceIdentifier path, String streamName) {
        Preconditions.checkNotNull(path);
        Preconditions.checkArgument(streamName != null && !streamName.isEmpty());
        this.path = path;
        this.streamName = streamName;
        eventBus = new AsyncEventBus(Executors.newSingleThreadExecutor());
        eventBusChangeRecorder = new EventBusChangeRecorder();
        eventBus.register(eventBusChangeRecorder);
    }

    @Override
    public void onDataChanged(DataChangeEvent<InstanceIdentifier, CompositeNode> change) {
        if (!change.getCreatedConfigurationData().isEmpty() || !change.getCreatedOperationalData().isEmpty()
                || !change.getUpdatedConfigurationData().isEmpty() || !change.getUpdatedOperationalData().isEmpty()
                || !change.getRemovedConfigurationData().isEmpty() || !change.getRemovedOperationalData().isEmpty()) {
            String xml = prepareXmlFrom(change);
            Event event = new Event(EventType.NOTIFY);
            event.setData(xml);
            eventBus.post(event);
        }
    }

    private final class EventBusChangeRecorder {
        @Subscribe public void recordCustomerChange(Event event) {
            if (event.getType() == EventType.REGISTER) {
                Channel subscriber = event.getSubscriber();
                if (!subscribers.contains(subscriber)) {
                    subscribers.add(subscriber);
                }
            } else if (event.getType() == EventType.DEREGISTER) {
                subscribers.remove(event.getSubscriber());
                Notificator.removeListenerIfNoSubscriberExists(ListenerAdapter.this);
            } else if (event.getType() == EventType.NOTIFY) {
                for (Channel subscriber : subscribers) {
                    if (subscriber.isActive()) {
                        logger.debug("Data are sent to subscriber {}:", subscriber.remoteAddress());
                        subscriber.writeAndFlush(new TextWebSocketFrame(event.getData()));
                    } else {
                        logger.debug("Subscriber {} is removed - channel is not active yet.", subscriber.remoteAddress());
                        subscribers.remove(subscriber);
                    }
                }
            }
        }
    }

    private final class Event {
        private final EventType type;
        private Channel subscriber;
        private String data;

        public Event(EventType type) {
            this.type = type;
        }

        public Channel getSubscriber() {
            return subscriber;
        }

        public void setSubscriber(Channel subscriber) {
            this.subscriber = subscriber;
        }

        public String getData() {
            return data;
        }

        public void setData(String data) {
            this.data = data;
        }

        public EventType getType() {
            return type;
        }
    }

    private enum EventType {
        REGISTER,
        DEREGISTER,
        NOTIFY;
    }

    private String prepareXmlFrom(DataChangeEvent<InstanceIdentifier, CompositeNode> change) {
        Document doc = createDocument();
        Element notificationElement = doc.createElementNS("urn:ietf:params:xml:ns:netconf:notification:1.0",
                "notification");
        doc.appendChild(notificationElement);

        Element eventTimeElement = doc.createElement("eventTime");
        eventTimeElement.setTextContent(toRFC3339(new Date()));
        notificationElement.appendChild(eventTimeElement);

        Element dataChangedNotificationEventElement = doc.createElementNS(
                "urn:opendaylight:params:xml:ns:yang:controller:md:sal:remote", "data-changed-notification");
        addValuesToDataChangedNotificationEventElement(doc, dataChangedNotificationEventElement, change);
        notificationElement.appendChild(dataChangedNotificationEventElement);

        try {
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            TransformerFactory tf = TransformerFactory.newInstance();
            Transformer transformer = tf.newTransformer();
            transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");
            transformer.setOutputProperty(OutputKeys.METHOD, "xml");
            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
            transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
            transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");
            transformer.transform(new DOMSource(doc), new StreamResult(new OutputStreamWriter(out, "UTF-8")));
            byte[] charData = out.toByteArray();
            return new String(charData, "UTF-8");
        } catch (TransformerException | UnsupportedEncodingException e) {
            String msg = "Error during transformation of Document into String";
            logger.error(msg, e);
            return msg;
        }
    }

    private String toRFC3339(Date d) {
        return rfc3339.format(d).replaceAll("(\\d\\d)(\\d\\d)$", "$1:$2");
    }

    private Document createDocument() {
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        Document doc = null;
        try {
            DocumentBuilder bob = dbf.newDocumentBuilder();
            doc = bob.newDocument();
        } catch (ParserConfigurationException e) {
            return null;
        }
        return doc;
    }

    private void addValuesToDataChangedNotificationEventElement(Document doc,
            Element dataChangedNotificationEventElement, DataChangeEvent<InstanceIdentifier, CompositeNode> change) {
        addValuesFromDataToElement(doc, change.getCreatedConfigurationData(), dataChangedNotificationEventElement, Store.CONFIG, Operation.CREATED);
        addValuesFromDataToElement(doc, change.getCreatedOperationalData(), dataChangedNotificationEventElement, Store.OPERATION, Operation.CREATED);
        if (change.getCreatedConfigurationData().isEmpty()) {
            addValuesFromDataToElement(doc, change.getUpdatedConfigurationData(), dataChangedNotificationEventElement, Store.CONFIG, Operation.UPDATED);
        }
        if (change.getCreatedOperationalData().isEmpty()) {
            addValuesFromDataToElement(doc, change.getUpdatedOperationalData(), dataChangedNotificationEventElement, Store.OPERATION, Operation.UPDATED);
        }
        addValuesFromDataToElement(doc, change.getRemovedConfigurationData(), dataChangedNotificationEventElement, Store.CONFIG, Operation.DELETED);
        addValuesFromDataToElement(doc, change.getRemovedOperationalData(), dataChangedNotificationEventElement, Store.OPERATION, Operation.DELETED);
    }

    private void addValuesFromDataToElement(Document doc, Set<InstanceIdentifier> data, Element element, Store store,
            Operation operation) {
        if (data == null || data.isEmpty()) {
            return;
        }
        for (InstanceIdentifier path : data) {
            Node node = createDataChangeEventElement(doc, path, null, store, operation);
            element.appendChild(node);
        }
    }

    private void addValuesFromDataToElement(Document doc, Map<InstanceIdentifier, CompositeNode> data, Element element, Store store,
            Operation operation) {
        if (data == null || data.isEmpty()) {
            return;
        }
        for (Entry<InstanceIdentifier, CompositeNode> entry : data.entrySet()) {
            Node node = createDataChangeEventElement(doc, entry.getKey(), entry.getValue(), store, operation);
            element.appendChild(node);
        }
    }

    private Node createDataChangeEventElement(Document doc, InstanceIdentifier path, CompositeNode data, Store store,
            Operation operation) {
        Element dataChangeEventElement = doc.createElement("data-change-event");

        Element pathElement = doc.createElement("path");
        addPathAsValueToElement(path, pathElement);
        dataChangeEventElement.appendChild(pathElement);

        Element storeElement = doc.createElement("store");
        storeElement.setTextContent(store.value);
        dataChangeEventElement.appendChild(storeElement);

        Element operationElement = doc.createElement("operation");
        operationElement.setTextContent(operation.value);
        dataChangeEventElement.appendChild(operationElement);

        if (data != null) {
            Element dataElement = doc.createElement("data");
            Node dataAnyXml = translateToXml(path, data);
            Node adoptedNode = doc.adoptNode(dataAnyXml);
            dataElement.appendChild(adoptedNode);
            dataChangeEventElement.appendChild(dataElement);
        }

        return dataChangeEventElement;
    }

    private Node translateToXml(InstanceIdentifier path, CompositeNode data) {
        DataNodeContainer schemaNode = ControllerContext.getInstance().getDataNodeContainerFor(path);
        if (schemaNode == null) {
            logger.info("Path '{}' contains node with unsupported type (supported type is Container or List) or some node was not found.", path);
            return null;
        }
        try {
            Document xml = xmlMapper.write(data, schemaNode);
            return xml.getFirstChild();
        } catch (UnsupportedDataTypeException e) {
            logger.error("Error occured during translation of notification to XML.", e);
            return null;
        }
    }

    private void addPathAsValueToElement(InstanceIdentifier path, Element element) {
        // Map< key = namespace, value = prefix>
        Map<String, String> prefixes = new HashMap<>();
        InstanceIdentifier instanceIdentifier = path;
        StringBuilder textContent = new StringBuilder();
        for (PathArgument pathArgument : instanceIdentifier.getPath()) {
            textContent.append("/");
            writeIdentifierWithNamespacePrefix(element, textContent, pathArgument.getNodeType(), prefixes);
            if (pathArgument instanceof NodeIdentifierWithPredicates) {
                Map<QName, Object> predicates = ((NodeIdentifierWithPredicates) pathArgument).getKeyValues();
                for (QName keyValue : predicates.keySet()) {
                    String predicateValue = String.valueOf(predicates.get(keyValue));
                    textContent.append("[");
                    writeIdentifierWithNamespacePrefix(element, textContent, keyValue, prefixes);
                    textContent.append("='");
                    textContent.append(predicateValue);
                    textContent.append("'");
                    textContent.append("]");
                }
            } else if (pathArgument instanceof NodeWithValue) {
                textContent.append("[.='");
                textContent.append(((NodeWithValue)pathArgument).getValue());
                textContent.append("'");
                textContent.append("]");
            }
        }
        element.setTextContent(textContent.toString());
    }

    private static void writeIdentifierWithNamespacePrefix(Element element, StringBuilder textContent, QName qName,
            Map<String, String> prefixes) {
        String namespace = qName.getNamespace().toString();
        String prefix = prefixes.get(namespace);
        if (prefix == null) {
            prefix = qName.getPrefix();
            if (prefix == null || prefix.isEmpty() || prefixes.containsValue(prefix)) {
                prefix = generateNewPrefix(prefixes.values());
            }
        }

        element.setAttribute("xmlns:" + prefix, namespace.toString());
        textContent.append(prefix);
        prefixes.put(namespace, prefix);

        textContent.append(":");
        textContent.append(qName.getLocalName());
    }

    private static String generateNewPrefix(Collection<String> prefixes) {
        StringBuilder result = null;
        Random random = new Random();
        do {
            result = new StringBuilder();
            for (int i = 0; i < 4; i++) {
                int randomNumber = 0x61 + (Math.abs(random.nextInt()) % 26);
                result.append(Character.toChars(randomNumber));
            }
        } while (prefixes.contains(result.toString()));

        return result.toString();
    }

    public InstanceIdentifier getPath() {
        return path;
    }

    public void setRegistration(ListenerRegistration<DataChangeListener> registration) {
        this.registration = registration;
    }

    public String getStreamName() {
        return streamName;
    }

    public void close() throws Exception {
        subscribers = new ConcurrentSet<>();
        registration.close();
        registration = null;
        eventBus.unregister(eventBusChangeRecorder);
    }

    public boolean isListening() {
        return registration == null ? false : true;
    }

    public void addSubscriber(Channel subscriber) {
        if (!subscriber.isActive()) {
            logger.debug("Channel is not active between websocket server and subscriber {}"
                    + subscriber.remoteAddress());
        }
        Event event = new Event(EventType.REGISTER);
        event.setSubscriber(subscriber);
        eventBus.post(event);
    }

    public void removeSubscriber(Channel subscriber) {
        logger.debug("Subscriber {} is removed.", subscriber.remoteAddress());
        Event event = new Event(EventType.DEREGISTER);
        event.setSubscriber(subscriber);
        eventBus.post(event);
    }

    public boolean hasSubscribers() {
        return !subscribers.isEmpty();
    }

    private static enum Store {
        CONFIG("config"),
        OPERATION("operation");

        private final String value;

        private Store(String value) {
            this.value = value;
        }
    }

    private static enum Operation {
        CREATED("created"),
        UPDATED("updated"),
        DELETED("deleted");

        private final String value;

        private Operation(String value) {
            this.value = value;
        }
    }

}