package net.sf.saxon.dom;

import net.sf.saxon.Configuration;
import net.sf.saxon.event.PipelineConfiguration;
import net.sf.saxon.event.Receiver;
import net.sf.saxon.expr.JPConverter;
import net.sf.saxon.expr.PJConverter;
import net.sf.saxon.expr.StaticProperty;
import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.om.*;
import net.sf.saxon.pattern.AnyNodeTest;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.value.SequenceExtent;
import net.sf.saxon.value.Value;
import org.w3c.dom.Document;
import org.w3c.dom.DocumentFragment;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.dom.DOMResult;
import javax.xml.transform.dom.DOMSource;
import javax.xml.xpath.XPathConstants;
import java.io.Serializable;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;

/**
 * This interface must be implemented by any third-party object model that can
 * be wrapped with a wrapper that implements the Saxon Object Model (the NodeInfo interface).
 * This implementation of the interface supports wrapping of DOM Documents.
 */

public class DOMObjectModel implements ExternalObjectModel, Serializable {

    private static DOMObjectModel THE_INSTANCE = new DOMObjectModel();

    /**
     * Get a reusable instance instance of this class.
     * <p>Note, this is not actually a singleton instance; the class also has a public constructor,
     * which is needed to support the automatic loading of object models into the Configuration.</p>
     * @return the singleton instance
     */

    public static DOMObjectModel getInstance() {
        return THE_INSTANCE;
    }

    /**
     * In JDK 1.5, the DOMResult object has a nextSibling property
     */

    private static Method nextSiblingMethod;
    private static boolean nextSiblingMethodUnavailable = false;

    static {
        try {
            //noinspection RedundantArrayCreation
            nextSiblingMethod = DOMResult.class.getMethod("getNextSibling", new Class[]{});
        } catch (NoSuchMethodException err) {
            nextSiblingMethodUnavailable = true;
        }
    }

    /**
     * Create an instance of the DOMObjectModel class.
     * <p>When possible, use the getInstance() method in preference, as the instance is then reusable.</p>
     */

    public DOMObjectModel() {}

    /**
     * Get the URI of the external object model as used in the JAXP factory interfaces for obtaining
     * an XPath implementation
     */

    public String getIdentifyingURI() {
        return XPathConstants.DOM_OBJECT_MODEL;
    }

    /**
     * Get a converter from XPath values to values in the external object model
     * @param targetClass the required class of the result of the conversion. If this class represents
     * a node or list of nodes in the external object model, the method should return a converter that takes
     * a native node or sequence of nodes as input and returns a node or sequence of nodes in the
     * external object model representation. Otherwise, it should return null.
     * @return a converter, if the targetClass is recognized as belonging to this object model;
     * otherwise null
     */

    public PJConverter getPJConverter(Class targetClass) {
        if (Node.class.isAssignableFrom(targetClass) && !(NodeOverNodeInfo.class.isAssignableFrom(targetClass))) {
            return new PJConverter() {
                public Object convert(ValueRepresentation value, Class targetClass, XPathContext context) throws XPathException {
                    return convertXPathValueToObject(Value.asValue(value), targetClass, context);
                }
            };
        } else if (NodeList.class == targetClass) {
            return new PJConverter() {
                public Object convert(ValueRepresentation value, Class targetClass, XPathContext context) throws XPathException {
                    return convertXPathValueToObject(Value.asValue(value), targetClass, context);
                }
            };
        } else {
            return null;
        }
    }


    public JPConverter getJPConverter(Class targetClass) {
        if (Node.class.isAssignableFrom(targetClass) && !(NodeOverNodeInfo.class.isAssignableFrom(targetClass))) {
            return new JPConverter() {
                public ValueRepresentation convert(Object obj, XPathContext context) throws XPathException {
                    return wrapOrUnwrapNode((Node)obj, context.getConfiguration());
                }
                public ItemType getItemType() {
                    return AnyNodeTest.getInstance();
                }
            };
        } else if (NodeList.class == targetClass) {
            return new JPConverter() {
                public ValueRepresentation convert(Object obj, XPathContext context) throws XPathException {
                    Configuration config = context.getConfiguration();
                    NodeList list = ((NodeList)obj);
                    final int len = list.getLength();
                    NodeInfo[] nodes = new NodeInfo[len];
                    for (int i=0; i<len; i++) {
                        nodes[i] = wrapOrUnwrapNode(list.item(i), config);
                    }
                    return new SequenceExtent(nodes);
                }
                public ItemType getItemType() {
                    return AnyNodeTest.getInstance();
                }
                public int getCardinality() {
                    return StaticProperty.ALLOWS_ZERO_OR_MORE;
                }
            };
        } else {
            return null;
        }
    }

    /**
     * Get a converter that converts a sequence of XPath nodes to this model's representation
     * of a node list.
     * @param node an example of the kind of node used in this model
     * @return if the model does not recognize this node as one of its own, return null. Otherwise
     *         return a PJConverter that takes a list of XPath nodes (represented as NodeInfo objects) and
     *         returns a collection of nodes in this object model
     */

    public PJConverter getNodeListCreator(Object node) {
        return new PJConverter() {
            public Object convert(ValueRepresentation value, Class targetClass, XPathContext context) throws XPathException {
                return convertXPathValueToObject(Value.asValue(value), NodeList.class, context);
            }
        };
    }

    /**
     * Test whether this object model recognizes a given node as one of its own
     */

//    private boolean isRecognizedNode(Object object) {
//         return object instanceof Node && !(object instanceof NodeOverNodeInfo);
//    }

    /**
     * Test whether this object model recognizes a given class as representing a
     * node in that object model. This method will generally be called at compile time.
     *
     * @param nodeClass A class that possibly represents nodes
     * @return true if the class is used to represent nodes in this object model
     */

//    private boolean isRecognizedNodeClass(Class nodeClass) {
//        return Node.class.isAssignableFrom(nodeClass) && !(NodeOverNodeInfo.class.isAssignableFrom(nodeClass));
//    }

    /**
     * Test whether this object model recognizes a given class as representing a
     * list of nodes in that object model. This method will generally be called at compile time.
     *
     * @param nodeClass A class that possibly represents nodes
     * @return true if the class is used to represent nodes in this object model
     */

//    private boolean isRecognizedNodeListClass(Class nodeClass) {
//        return NodeList.class.isAssignableFrom(nodeClass);
//    }

    /**
     * Test whether this object model recognizes a particular kind of JAXP Result object,
     * and if it does, return a Receiver that builds an instance of this data model from
     * a sequence of events. If the Result is not recognised, return null.
     */

    public Receiver getDocumentBuilder(Result result) throws XPathException {
        if (result instanceof DOMResult) {
            DOMWriter emitter = new DOMWriter();
            Node root = ((DOMResult)result).getNode();
            // JDK 1.5 adds a nextSibling() property to identify the insertion point among the siblings
            Node nextSibling = null;
            if (!nextSiblingMethodUnavailable) {
                try {
                    nextSibling = (Node)nextSiblingMethod.invoke(result, new Object[]{});
                } catch (IllegalAccessException err) {
                    //
                } catch (InvocationTargetException err) {
                    //
                }
            }
            if (root == null) {
                try {
                    DocumentBuilderFactory dfactory = DocumentBuilderFactory.newInstance();
                    DocumentBuilder docBuilder = dfactory.newDocumentBuilder();
                    Document out = docBuilder.newDocument();
                    ((DOMResult)result).setNode(out);
                    emitter.setNode(out);
                } catch (ParserConfigurationException e) {
                    throw new XPathException(e);
                }
            } else {
                emitter.setNode(root);
                emitter.setNextSibling(nextSibling);
            }
            return emitter;
        }
        return null;
    }

    /**
     * Test whether this object model recognizes a particular kind of JAXP Source object,
     * and if it does, send the contents of the document to a supplied Receiver, and return true.
     * Otherwise, return false
     */

    public boolean sendSource(Source source, Receiver receiver, PipelineConfiguration pipe) throws XPathException {
        if (source instanceof DOMSource) {
            Node startNode = ((DOMSource)source).getNode();
            DOMSender driver = new DOMSender();
            driver.setStartNode(startNode);
            driver.setReceiver(receiver);
            driver.setPipelineConfiguration(pipe);
            driver.setSystemId(source.getSystemId());
            driver.send();
            return true;
        }
        return false;
    }

    /**
     * Wrap or unwrap a node using this object model to return the corresponding Saxon node. If the supplied
     * source does not belong to this object model, return null
     */

    public NodeInfo unravel(Source source, Configuration config) {

        if (source instanceof DOMSource) {
            Node dsnode = ((DOMSource)source).getNode();
            if (!(dsnode instanceof NodeOverNodeInfo)) {
                // Supplied source is an ordinary DOM Node: wrap it
                Document dom;
                if (dsnode.getNodeType() == Node.DOCUMENT_NODE) {
                    dom = (Document)dsnode;
                } else {
                    dom = dsnode.getOwnerDocument();
                }
                DocumentWrapper docWrapper = new DocumentWrapper(dom, source.getSystemId(), config);
                return docWrapper.wrap(dsnode);
            }
        }
        return null;
    }

    /**
     * Wrap a DOM Node as a NodeInfo, unless it already wraps a NodeInfo, inwhich case unwrap it
     * @param node the node to be wrapped
     * @param config the Saxon Configuration. This must be the same Configuration, or one that is compatible with,
     * the Configuration used to compile and execute the query or stylesheet.
     * @return the new wrapper node
     */

    private NodeInfo wrapOrUnwrapNode(Node node, Configuration config) throws XPathException {
        if (node instanceof NodeOverNodeInfo) {
            return ((NodeOverNodeInfo)node).getUnderlyingNodeInfo();
        } else {
            DocumentInfo doc = wrapDocument(node, "", config);
            return wrapNode(doc, node);
        }        
    }

    /**
     * Convert a Java object to an XPath value. If the supplied object is recognized as a representation
     * of a value using this object model, the object model should convert the value to an XPath value
     * and return this as the result. If not, it should return null. If the object is recognized but cannot
     * be converted, an exception should be thrown
     */

//    private Value convertObjectToXPathValue(Object object, Configuration config) throws XPathException {
//        if (object instanceof NodeList && !(object instanceof Node)) {
//            // We're interested in a NodeList here. There's a class in Xerces that implements both
//            // Node and NodeList, and we want to treat it as a Node: hence the strange test above.
//            NodeList list = ((NodeList)object);
//            final int len = list.getLength();
//            NodeInfo[] nodes = new NodeInfo[len];
//            for (int i=0; i<len; i++) {
//                if (list.item(i) instanceof NodeOverNodeInfo) {
//                    nodes[i] = ((NodeOverNodeInfo)list.item(i)).getUnderlyingNodeInfo();
//                } else {
//                    DocumentInfo doc = wrapDocument(list.item(i), "", config);
//                    NodeInfo node = wrapNode(doc, list.item(i));
//                    nodes[i] = node;
//                }
//            }
//            return new SequenceExtent(nodes);
//
//            // Note, we accept the nodes in the order returned by the function; there
//            // is no requirement that this should be document order.
//        } else if (object instanceof Node) {
//            return new SingletonNode(wrapOrUnwrapNode((Node)object, config));
//        } else {
//            return null;
//        }
//    }

    /**
     * Convert an XPath value to an object in this object model. If the supplied value can be converted
     * to an object in this model, of the specified class, then the conversion should be done and the
     * resulting object returned. If the value cannot be converted, the method should return null. Note
     * that the supplied class might be a List, in which case the method should inspect the contents of the
     * Value to see whether they belong to this object model.
     * @throws XPathException if the target class is explicitly associated with this object model, but the
     * supplied value cannot be converted to the appropriate class
     */

    private Object convertXPathValueToObject(Value value, Object targetClass, XPathContext context) throws XPathException {
        // We accept the object if (a) the target class is Node, Node[], or NodeList,
        // or (b) the supplied object is a node, or sequence of nodes, that wrap DOM nodes,
        // provided that the target class is Object or a collection class
        Class target = (Class)targetClass;
        boolean requireDOM =
                (Node.class.isAssignableFrom(target) || (target == NodeList.class) ||
                (target.isArray() && Node.class.isAssignableFrom(target.getComponentType())));

        // Note: we allow the declared type of the method argument to be a subclass of Node. If the actual
        // node supplied is the wrong kind of node, this will result in a Java exception.

        boolean allowDOM =
                (target == Object.class || target.isAssignableFrom(ArrayList.class) ||
                target.isAssignableFrom(HashSet.class) ||
                (target.isArray() && target.getComponentType() == Object.class));
        if (!(requireDOM || allowDOM)) {
            return null;
        }
        List nodes = new ArrayList(20);

        SequenceIterator iter = value.iterate();
        while (true) {
            Item item = iter.next();
            if (item == null) {
                break;
            }
            if (item instanceof VirtualNode) {
                Object o = ((VirtualNode)item).getUnderlyingNode();
                if (o instanceof Node) {
                    nodes.add(o);
                } else {
                    if (requireDOM) {
                        XPathException err = new XPathException("Extension function required class " + target.getName() +
                                "; supplied value of class " + item.getClass().getName() +
                                " could not be converted");
                        err.setXPathContext(context);
                        throw err;
                    }
                }
            } else if (requireDOM) {
                if (item instanceof NodeInfo) {
                    nodes.add(NodeOverNodeInfo.wrap((NodeInfo)item));
                } else {
                    XPathException err = new XPathException("Extension function required class " + target.getName() +
                            "; supplied value of class " + item.getClass().getName() +
                            " could not be converted");
                    err.setXPathContext(context);
                    throw err;
                }
            } else {
                return null;    // DOM Nodes are not actually required; let someone else try the conversion
            }
        }

        if (nodes.isEmpty() && !requireDOM) {
            return null;  // empty sequence supplied - try a different mapping
        }
        if (Node.class.isAssignableFrom(target)) {
            if (nodes.size() != 1) {
                XPathException err = new XPathException("Extension function requires a single DOM Node" +
                        "; supplied value contains " + nodes.size() + " nodes");
                err.setXPathContext(context);
                throw err;
            }
            return nodes.get(0);
            // could fail if the node is of the wrong kind
        } else if (target == NodeList.class) {
            return new DOMNodeList(nodes);
        } else if (target.isArray() && target.getComponentType() == Node.class) {
            Node[] array = new Node[nodes.size()];
            nodes.toArray(array);
            return array;
        } else if (target.isAssignableFrom(ArrayList.class)) {
            return nodes;
        } else if (target.isAssignableFrom(HashSet.class)) {
            return new HashSet(nodes);
        } else {
            // after all this work, give up
            return null;
        }
    }

    /**
     * Wrap a document node in the external object model in a document wrapper that implements
     * the Saxon DocumentInfo interface. (However, if the supplied object is a wrapper for a Saxon
     * NodeInfo object, then we <i>unwrap</i> it.
     * @param node    a node (any node) in the third party document
     * @param baseURI the base URI of the node (supply "" if unknown)
     * @param config the Saxon configuration (which among other things provides access to the NamePool)
     * @return the wrapper, which must implement DocumentInfo
     */

    private DocumentInfo wrapDocument(Object node, String baseURI, Configuration config) {
        if (node instanceof DocumentOverNodeInfo) {
            return (DocumentInfo)((DocumentOverNodeInfo)node).getUnderlyingNodeInfo();
        }
        if (node instanceof NodeOverNodeInfo) {
            return ((NodeOverNodeInfo)node).getUnderlyingNodeInfo().getDocumentRoot();
        }
        if (node instanceof org.w3c.dom.Node) {
            if (((Node)node).getNodeType() == Node.DOCUMENT_NODE) {
                Document doc = (org.w3c.dom.Document)node;
                return new DocumentWrapper(doc, baseURI, config);
            } else if (((Node)node).getNodeType() == Node.DOCUMENT_FRAGMENT_NODE) {
                DocumentFragment doc = (org.w3c.dom.DocumentFragment)node;
                return new DocumentWrapper(doc, baseURI, config);
            } else {
                Document doc = ((org.w3c.dom.Node)node).getOwnerDocument();
                return new DocumentWrapper(doc, baseURI, config);
            }
        }
        throw new IllegalArgumentException("Unknown node class " + node.getClass());
    }

    /**
     * Wrap a node within the external object model in a node wrapper that implements the Saxon
     * VirtualNode interface (which is an extension of NodeInfo)
     * @param document the document wrapper, as a DocumentInfo object
     * @param node the node to be wrapped. This must be a node within the document wrapped by the
     * DocumentInfo provided in the first argument
     * @return the wrapper for the node, as an instance of VirtualNode
     */

    private NodeInfo wrapNode(DocumentInfo document, Object node) {
        return ((DocumentWrapper)document).wrap((Node)node);
    }


}


//
// The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
// you may not use this file except in compliance with the License. You may obtain a copy of the
// License at http://www.mozilla.org/MPL/
//
// Software distributed under the License is distributed on an "AS IS" basis,
// WITHOUT WARRANTY OF ANY KIND, either express or implied.
// See the License for the specific language governing rights and limitations under the License.
//
// The Original Code is: all this file.
//
// The Initial Developer of the Original Code is Michael H. Kay.
//
// Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
//
// Contributor(s): Gunther Schadow (changes to allow access to public fields; also wrapping
// of extensions and mapping of null to empty sequence).
//
