package net.sf.saxon.query;

import net.sf.saxon.Configuration;
import net.sf.saxon.Controller;
import net.sf.saxon.event.*;
import net.sf.saxon.evpull.ComplexContentProcessor;
import net.sf.saxon.evpull.EventIterator;
import net.sf.saxon.evpull.EventIteratorToReceiver;
import net.sf.saxon.expr.*;
import net.sf.saxon.instruct.Executable;
import net.sf.saxon.instruct.GlobalVariable;
import net.sf.saxon.instruct.SlotManager;
import net.sf.saxon.om.*;
import net.sf.saxon.pull.PullFromIterator;
import net.sf.saxon.pull.PullNamespaceReducer;
import net.sf.saxon.pull.PullProvider;
import net.sf.saxon.pull.PullPushCopier;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trace.TraceListener;
import net.sf.saxon.trans.UncheckedXPathException;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.Type;
import net.sf.saxon.value.DateTimeValue;
import net.sf.saxon.value.Value;

import javax.xml.transform.ErrorListener;
import javax.xml.transform.Result;
import javax.xml.transform.TransformerException;
import javax.xml.transform.stream.StreamResult;
import java.io.OutputStream;
import java.util.*;

/**
 * XQueryExpression represents a compiled query. This object is immutable and thread-safe,
 * the same compiled query may be executed many times in series or in parallel. The object
 * can be created only by using the compileQuery method of the QueryProcessor class.
 * <p/>
 * <p>Various methods are provided for evaluating the query, with different options for
 * delivery of the results.</p>
 */
public class XQueryExpression implements Container {

    private Expression expression;
    private SlotManager stackFrameMap;
    private Executable executable;
    private QueryModule staticContext;
    private PathMap pathMap;
    private boolean allowDocumentProjection;
    private boolean isUpdating;

    /**
     * The constructor is protected, to ensure that instances can only be
     * created using the compileQuery() methods of StaticQueryContext
     *
     * @param exp        an expression to be wrapped as an XQueryExpression
     * @param exec       the executable
     * @param mainModule the static context of the main module
     * @param config     the configuration
     * @throws XPathException if an error occurs
     */

    protected XQueryExpression(Expression exp, Executable exec, QueryModule mainModule, Configuration config)
            throws XPathException {
        stackFrameMap = config.makeSlotManager();
        executable = exec;
        exp.setContainer(this);
        try {
            ExpressionVisitor visitor = ExpressionVisitor.make(mainModule);
            visitor.setExecutable(exec);
            exp = visitor.simplify(exp);
            exp.checkForUpdatingSubexpressions();
            exp = visitor.typeCheck(exp, mainModule.getUserQueryContext().getRequiredContextItemType());
//            ExpressionPresenter presenter = new ExpressionPresenter(config,
//                    ExpressionPresenter.defaultDestination(config, new FileOutputStream("c:/projects/montreal/before50.xml")));
//            exp.explain(presenter);
//            presenter.close();
            exp = exp.optimize(visitor, Type.ITEM_TYPE);
        } catch (XPathException err) {
            //err.printStackTrace();
            mainModule.reportFatalError(err);
            throw err;
        }
        ExpressionTool.allocateSlots(exp, 0, stackFrameMap);

        expression = exp;
        executable.setConfiguration(config);
        executable.setDefaultCollationName(mainModule.getDefaultCollationName());
        executable.setCollationTable(mainModule.getUserQueryContext().getAllCollations());
        staticContext = mainModule;
        isUpdating = exp.isUpdatingExpression();
    }

    /**
     * Get the expression wrapped in this XQueryExpression object
     *
     * @return the underlying expression
     */

    public Expression getExpression() {
        return expression;
    }

    /**
     * Ask whether this query uses the context item
     *
     * @return true if the context item is referenced either in the query body or in the initializer
     *         of any global variable
     */

    public boolean usesContextItem() {
        if ((expression.getDependencies() & StaticProperty.DEPENDS_ON_FOCUS) != 0) {
            return true;
        }
        HashMap map = executable.getCompiledGlobalVariables();
        if (map != null) {
            Iterator iter = map.values().iterator();
            while (iter.hasNext()) {
                GlobalVariable var = (GlobalVariable)iter.next();
                Expression select = var.getSelectExpression();
                if (select != null && (select.getDependencies() & StaticProperty.DEPENDS_ON_FOCUS) != 0) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Ask whether this is an update query
     *
     * @return true if the body of the query is an updating expression
     *         (as defined by the XQuery Update specification). Note that a query can use Update syntax
     *         (notably the copy-modify syntax) without being an updating expression.
     */

    public boolean isUpdateQuery() {
        return isUpdating;
    }

    /**
     * Get the stack frame map used for the outermost level of this query
     *
     * @return the stack frame map
     */

    public SlotManager getStackFrameMap() {
        return stackFrameMap;
    }

    /**
     * Replace one subexpression by a replacement subexpression. For internal use only
     *
     * @param original    the original subexpression
     * @param replacement the replacement subexpression
     * @return true if the original subexpression is found
     */

    public boolean replaceSubExpression(Expression original, Expression replacement) {
        boolean found = false;
        if (expression == original) {
            expression = replacement;
            found = true;
        }
        return found;
    }


    /**
     * Get the static context in which this expression was compiled. This is essentially an internal
     * copy of the original user-created StaticQueryContext object, augmented with information obtained
     * from the query prolog of the main query module, and with information about functions and variables
     * imported from other library modules. The user-created StaticQueryContext object is not modified
     * by Saxon, whereas the QueryModule object includes additional information found in the query prolog.
     *
     * @return the QueryModule object representing the static context of the main module of the query.
     *         This is available for inspection, but must not be modified or reused by the application.
     */
    public QueryModule getStaticContext() {
        return staticContext;
    }

    /**
     * Get a list containing the names of the external variables in the query.
     * <p/>
     * <p><i>Changed in Saxon 9.0 to return an array of StructuredQName objects rather than
     * integer fingerprints.</i></p>
     *
     * @return an array of StructuredQName objects, representing the names of external variables defined
     *         in the query
     */

    public StructuredQName[] getExternalVariableNames() {
        List list = stackFrameMap.getVariableMap();
        StructuredQName[] names = new StructuredQName[stackFrameMap.getNumberOfVariables()];
        for (int i = 0; i < names.length; i++) {
            names[i] = (StructuredQName)list.get(i);
        }
        return names;
    }

    /**
     * Execute a the compiled Query, returning the results as a List.
     *
     * @param env Provides the dynamic query evaluation context
     * @return The results of the expression, as a List. The List represents the sequence
     *         of items returned by the expression. Each item in the list will either be an
     *         object representing a node, or an object representing an atomic value.
     *         For the types of Java object that may be returned, see the description of the
     *         {@link net.sf.saxon.xpath.XPathEvaluator#evaluate evaluate} method
     *         of class XPathProcessor
     */

    public List evaluate(DynamicQueryContext env) throws XPathException {
        if (isUpdating) {
            throw new XPathException("Cannot call evaluate() on an updating query");
        }
        SequenceIterator iterator = iterator(env);
        ArrayList list = new ArrayList(100);
        while (true) {
            Item item = iterator.next();
            if (item == null) {
                return list;
            }
            list.add(Value.convertToJava(item));
        }
    }

    /**
     * Execute the compiled Query, returning the first item in the result.
     * This is useful where it is known that the expression will only return
     * a singleton value (for example, a single node, or a boolean).
     *
     * @param env Provides the dynamic query evaluation context
     * @return The first item in the sequence returned by the expression. If the expression
     *         returns an empty sequence, this method returns null. Otherwise, it returns the first
     *         item in the result sequence, represented as a Java object using the same mapping as for
     *         the {@link XQueryExpression#evaluate evaluate} method
     */

    public Object evaluateSingle(DynamicQueryContext env) throws XPathException {
        if (isUpdating) {
            throw new XPathException("Cannot call evaluateSingle() on an updating query");
        }
        SequenceIterator iterator = iterator(env);
        Item item = iterator.next();
        if (item == null) {
            return null;
        }
        return Value.convertToJava(item);
    }

    /**
     * Get an iterator over the results of the expression. This returns results without
     * any conversion of the returned items to "native" Java classes. The iterator will
     * deliver a sequence of Item objects, each item being either a NodeInfo (representing
     * a node) or an AtomicValue (representing an atomic value).
     * <p/>
     * <p>To get the results of the query in the form of an XML document in which each
     * item is wrapped by an element indicating its type, use:</p>
     * <p/>
     * <p><code>QueryResult.wrap(iterator(env))</code></p>
     * <p/>
     * <p>To serialize the results to a file, use the QueryResult.serialize() method.</p>
     *
     * @param env Provides the dynamic query evaluation context
     * @return an iterator over the results of the query. The class SequenceIterator
     *         is modeled on the standard Java Iterator class, but has extra functionality
     *         and can throw exceptions when errors occur.
     * @throws XPathException if a dynamic error occurs in evaluating the query. Some
     *                        dynamic errors will not be reported by this method, but will only be reported
     *                        when the individual items of the result are accessed using the returned iterator.
     */

    public SequenceIterator iterator(DynamicQueryContext env) throws XPathException {
        if (isUpdating) {
            throw new XPathException("Cannot call iterator() on an updating query");
        }
        Controller controller = newController();
        initializeController(env, controller);

        try {
            Item contextItem = env.getContextItem();

            //Bindery bindery = controller.getBindery();
            //bindery.openStackFrame();
            controller.defineGlobalParameters();
            XPathContextMajor context = controller.newXPathContext();

            if (contextItem != null) {
                if (!staticContext.getUserQueryContext().getRequiredContextItemType().matchesItem(
                        contextItem, false, env.getConfiguration())) {
                    throw new XPathException("The supplied context item does not match the required context item type");
                }
                UnfailingIterator single = SingletonIterator.makeIterator(contextItem);
                single.next();
                context.setCurrentIterator(single);
                controller.setInitialContextItem(contextItem);
            }

            // In tracing/debugging mode, evaluate all the global variables first
            if (controller.getTraceListener() != null) {
                controller.preEvaluateGlobals(context);
            }

            context.openStackFrame(stackFrameMap);

            SequenceIterator iterator = expression.iterate(context);
            return new ErrorReportingIterator(iterator, controller.getErrorListener());
        } catch (XPathException err) {
            TransformerException terr = err;
            while (terr.getException() instanceof TransformerException) {
                terr = (TransformerException)terr.getException();
            }
            XPathException de = XPathException.makeXPathException(terr);
            controller.reportFatalError(de);
            throw de;
        }
    }

    private void initializeController(DynamicQueryContext env, Controller controller) {
        HashMap parameters = env.getParameters();
        if (parameters != null) {
            Iterator iter = parameters.keySet().iterator();
            while (iter.hasNext()) {
                String paramName = (String)iter.next();
                Object paramValue = parameters.get(paramName);
                controller.setParameter(paramName, paramValue);
            }
        }

        controller.setURIResolver(env.getURIResolver());
        controller.setErrorListener(env.getErrorListener());
        controller.addTraceListener(env.getTraceListener());
        controller.setTraceFunctionDestination(env.getTraceFunctionDestination());
        DateTimeValue currentDateTime = env.getCurrentDateTime();
        if (currentDateTime != null) {
            try {
                controller.setCurrentDateTime(currentDateTime);
            } catch (XPathException e) {
                throw new AssertionError(e);    // the value should already have been checked
            }
        }
    }

    /**
     * Run the query, sending the results directly to a JAXP Result object. This way of executing
     * the query is most efficient in the case of queries that produce a single document (or parentless
     * element) as their output, because it avoids constructing the result tree in memory: instead,
     * it is piped straight to the serializer.
     *
     * @param env              the dynamic query context
     * @param result           the destination for the results of the query. The query is effectively wrapped
     *                         in a document{} constructor, so that the items in the result are concatenated to form a single
     *                         document; this is then written to the requested Result destination, which may be (for example)
     *                         a DOMResult, a SAXResult, or a StreamResult
     * @param outputProperties Supplies serialization properties, in JAXP format, if the result is to
     *                         be serialized. This parameter can be defaulted to null.
     * @throws XPathException if the query fails.
     */

    public void run(DynamicQueryContext env, Result result, Properties outputProperties) throws XPathException {
        if (isUpdating) {
            throw new XPathException("Cannot call run() on an updating query");
        }
        Controller controller = newController();
        initializeController(env, controller);

        if (allowDocumentProjection) {
            controller.setUseDocumentProjection(getPathMap());
        }
        Properties actualProperties = validateOutputProperties(controller, outputProperties);

        controller.defineGlobalParameters();

        XPathContextMajor context = initialContext(env, controller);

        // In tracing/debugging mode, evaluate all the global variables first
        TraceListener tracer = controller.getTraceListener();
        if (tracer != null) {
            controller.preEvaluateGlobals(context);
            tracer.open();
        }

        context.openStackFrame(stackFrameMap);

        boolean mustClose = (result instanceof StreamResult &&
                ((StreamResult)result).getOutputStream() == null);
        context.changeOutputDestination(actualProperties, result, true,
                Configuration.XQUERY, Validation.PRESERVE, null);
        context.getReceiver().open();

        // Run the query
        try {
            expression.process(context);
        } catch (XPathException err) {
            controller.reportFatalError(err);
            throw err;
        }

        if (tracer != null) {
            tracer.close();
        }

        context.getReceiver().close();
        if (mustClose) {
            OutputStream os = ((StreamResult)result).getOutputStream();
            if (os != null) {
                try {
                    os.close();
                } catch (java.io.IOException err) {
                    throw new XPathException(err);
                }
            }
        }
    }

    private Properties validateOutputProperties(Controller controller, Properties outputProperties) throws XPathException {
        // Validate the serialization properties requested

        Properties baseProperties = controller.getOutputProperties();
        if (outputProperties != null) {
            Enumeration iter = outputProperties.propertyNames();
            while (iter.hasMoreElements()) {
                String key = (String)iter.nextElement();
                String value = outputProperties.getProperty(key);
                try {
                    SaxonOutputKeys.checkOutputProperty(key, value, controller.getConfiguration().getNameChecker());
                    baseProperties.setProperty(key, value);
                } catch (XPathException dynamicError) {
                    try {
                        outputProperties.remove(key);
                        controller.getErrorListener().warning(dynamicError);
                    } catch (TransformerException err2) {
                        throw XPathException.makeXPathException(err2);
                    }
                }
            }
        }
        if (baseProperties.getProperty("method") == null) {
            // XQuery forces the default method to XML, unlike XSLT where it depends on the contents of the result tree
            baseProperties.setProperty("method", "xml");
        }
        return baseProperties;
    }

    /**
     * Run the query in pull mode.
     * <p/>
     * <p>For maximum effect this method should be used when lazyConstructionMode has been set in the Configuration.</p>
     * <p/>
     * <p><b>Note: this method usually has very similar performance to the
     * {@link #run(DynamicQueryContext,javax.xml.transform.Result,java.util.Properties)} method (which does
     * the same thing), but sometimes it is significantly slower. Therefore, the run() method is preferred.</b></p>
     *
     * @param dynamicEnv       the dynamic context for query evaluation
     * @param destination      the destination of the query results
     * @param outputProperties the serialization parameters
     * @see Configuration#setLazyConstructionMode(boolean)
     */

    public void pullOLD(DynamicQueryContext dynamicEnv, Result destination, Properties outputProperties) throws XPathException {
        try {
            SequenceIterator iter = iterator(dynamicEnv);
            PullProvider pull = new PullFromIterator(iter);
            pull = new PullNamespaceReducer(pull);
            final Configuration config = executable.getConfiguration();
            pull.setPipelineConfiguration(config.makePipelineConfiguration());

            SerializerFactory sf = config.getSerializerFactory();
            Receiver receiver = sf.getReceiver(destination,
                    pull.getPipelineConfiguration(),
                    outputProperties);

//            NamespaceReducer reducer = new NamespaceReducer();
//            PipelineConfiguration pipe = pull.getPipelineConfiguration();
//            reducer.setPipelineConfiguration(pipe);
//            reducer.setUnderlyingReceiver(receiver);
//            ComplexContentOutputter outputter = new ComplexContentOutputter();
//            outputter.setReceiver(reducer);
//            outputter.setPipelineConfiguration(pipe);
            Receiver outputter = receiver;
            if ("yes".equals(outputProperties.getProperty(SaxonOutputKeys.WRAP))) {
                receiver = new SequenceWrapper(outputter);
            } else {
                //receiver = new TreeReceiver(outputter);
            }
            new PullPushCopier(pull, receiver).copy();
        } catch (UncheckedXPathException e) {
            throw e.getXPathException();
        }
    }

    /**
     * Run the query in pull mode.
     * <p/>
     * <p>For maximum effect this method should be used when lazyConstructionMode has been set in the Configuration.</p>
     * <p/>
     * <p><b>Note: this method usually has very similar performance to the
     * {@link #run(DynamicQueryContext,javax.xml.transform.Result,java.util.Properties)} method (which does
     * the same thing), but sometimes it is significantly slower. Therefore, the run() method is preferred.</b></p>
     *
     * @param dynamicEnv       the dynamic context for query evaluation
     * @param destination      the destination of the query results
     * @param outputProperties the serialization parameters
     * @see Configuration#setLazyConstructionMode(boolean)
     */

    public void pull(DynamicQueryContext dynamicEnv, Result destination, Properties outputProperties) throws XPathException {
        if (isUpdating) {
            throw new XPathException("Cannot call pull() on an updating query");
        }
        Configuration config = dynamicEnv.getConfiguration();
        try {
            Controller controller = newController();
            //initializeController(dynamicEnv, controller);
            EventIterator iter = iterateEvents(controller, dynamicEnv);
            //iter = new Decomposer(iter, config);

            Properties actualProperties = validateOutputProperties(controller, outputProperties);
            SerializerFactory sf = config.getSerializerFactory();
            PipelineConfiguration pipe = config.makePipelineConfiguration();
            pipe.setSerializing(true);
            Receiver receiver = sf.getReceiver(destination, pipe, actualProperties);

            receiver = new NamespaceReducer(receiver);
            if ("yes".equals(actualProperties.getProperty(SaxonOutputKeys.WRAP))) {
                receiver = new SequenceWrapper(receiver);
                //receiver = new TracingFilter(receiver);
            } else {
                receiver = new TreeReceiver(receiver);
            }
            EventIteratorToReceiver.copy(iter, (SequenceReceiver)receiver);
        } catch (XPathException err) {
            config.reportFatalError(err);
            throw err;
        }

    }

    /**
     * Run the query returning the results as an EventIterator
     *
     * @param controller The Controller used to run the query
     * @param dynamicEnv the XQuery dynamic context for evaluating the query
     * @return an EventIterator representing the results of the query as a sequence of events
     */

    public EventIterator iterateEvents(Controller controller, DynamicQueryContext dynamicEnv) throws XPathException {
        if (isUpdating) {
            throw new XPathException("Cannot call iterateEvents() on an updating query");
        }
        initializeController(dynamicEnv, controller);

        XPathContextMajor context = initialContext(dynamicEnv, controller);

        // In tracing/debugging mode, evaluate all the global variables first
        if (controller.getTraceListener() != null) {
            controller.preEvaluateGlobals(context);
        }

        context.openStackFrame(stackFrameMap);

        final Configuration config = executable.getConfiguration();

        EventIterator ei = expression.iterateEvents(context);
        //ei = new TracingEventIterator(EventStackIterator.flatten(ei));
        return new ComplexContentProcessor(config, ei);
    }

    /**
     * Run an updating query
     *
     * @param dynamicEnv the dynamic context for query execution
     * @return a set of nodes representing the roots of trees that have been modified as a result
     *         of executing the update. Note that this method will never modify persistent data on disk; it returns
     *         the root nodes of the affected documents (which will often be document nodes whose document-uri can
     *         be ascertained), and it is the caller's responsibility to decide what to do with them.
     *         <p>On completion of this method it is generally unsafe to rely on the contents or relationships
     *         of NodeInfo objects that were obtained before the updating query was run. Such objects may or may not
     *         reflect the results of the update operations. This is especially true in the case of nodes that
     *         are part of a subtree that has been deleted (detached from its parent). Instead, the new updated
     *         tree should be accessed by navigation from the root nodes returned by this method.</p>
     * @throws XPathException if evaluation of the update query fails, or it this is not an updating query
     */

    public Set runUpdate(DynamicQueryContext dynamicEnv) throws XPathException {
        if (!isUpdating) {
            throw new XPathException("Calling runUpdate() on a non-updating query");
        }

        Configuration config = executable.getConfiguration();
        Controller controller = newController();
        initializeController(dynamicEnv, controller);
        XPathContextMajor context = initialContext(dynamicEnv, controller);
        try {
            PendingUpdateList pul = config.newPendingUpdateList();
            context.openStackFrame(stackFrameMap);
            expression.evaluatePendingUpdates(context, pul);
            pul.apply(context, staticContext.getRevalidationMode());
            // Only mark a document for rewriting to disk if it is in the document pool,
            // that is, if it was supplied using doc() or similar functions.
            Set rewrittenTrees = new HashSet();
            for (Iterator iter = pul.getAffectedTrees().iterator(); iter.hasNext();) {
                NodeInfo node = (NodeInfo)iter.next();
                if (node.isSameNodeInfo(controller.getDocumentPool().find(node.getSystemId()))) {
                     rewrittenTrees.add(node);
                }
            }
            return rewrittenTrees;
        } catch (XPathException e) {
            if (!e.hasBeenReported()) {
                try {
                    controller.getErrorListener().fatalError(e);
                } catch (TransformerException e2) {
                    // ignore secondary error
                }
            }
            throw e;
        }
    }

    private XPathContextMajor initialContext(DynamicQueryContext dynamicEnv, Controller controller) throws XPathException {
        Item contextItem = dynamicEnv.getContextItem();
        controller.defineGlobalParameters();
        XPathContextMajor context = controller.newXPathContext();

        if (contextItem != null) {
            if (!staticContext.getUserQueryContext().getRequiredContextItemType().matchesItem(
                    contextItem, false, dynamicEnv.getConfiguration())) {
                throw new XPathException("The supplied context item does not match the required context item type");
            }
            UnfailingIterator single = SingletonIterator.makeIterator(contextItem);
            single.next();
            context.setCurrentIterator(single);
            controller.setInitialContextItem(contextItem);
        }
        return context;
    }

    /**
     * Get a controller that can be used to execute functions in this compiled query.
     * Functions in the query module can be found using {@link QueryModule#getUserDefinedFunction}.
     * They can then be called directly from the Java application using {@link net.sf.saxon.instruct.UserFunction#call}
     * The same Controller can be used for a series of function calls. Note that the Controller should only be used
     * in a single thread.
     *
     * @return a newly constructed Controller
     */

    public Controller newController() {
        Controller controller = new Controller(executable.getConfiguration(), executable);
        executable.initializeBindery(controller.getBindery());
        if (isUpdating && controller.getTreeModel() == Builder.TINY_TREE) {
            controller.setTreeModel(Builder.LINKED_TREE);
        }
        return controller;
    }

    /**
     * Deprecated synonym for {@link #newController}
     *
     * @return a newly constructed Controller
     * @deprecated since 8.5.1 - use newController()
     */

    public Controller getController() {
        return newController();
    }

    /**
     * Diagnostic method: display a representation of the compiled query on the
     * selected output stream.
     *
     * @param out an ExpressionPresenter to which the XML representation of the compiled query
     *            will be sent
     */

    public void explain(ExpressionPresenter out) {
        out.startElement("query");
        staticContext.getExecutable().getKeyManager().explainKeys(out);
        staticContext.getExecutable().explainGlobalVariables(out);
        staticContext.explainGlobalFunctions(out);
        out.startElement("body");
        expression.explain(out);
        out.endElement();
        out.endElement();
        out.close();
    }

    /**
     * Get the Executable (representing a complete stylesheet or query) of which this Container forms part
     */

    public Executable getExecutable() {
        return executable;
    }

    /**
     * Get the path map for the query expression
     *
     * @return the path map (which is constructed if this has not already been done)
     */

    public PathMap getPathMap() {
        if (pathMap == null) {
            pathMap = new PathMap(expression);
        }
        HashMap map = executable.getCompiledGlobalVariables();
        if (map != null) {
            Iterator iter = map.values().iterator();
            while (iter.hasNext()) {
                GlobalVariable var = (GlobalVariable)iter.next();
                Expression select = var.getSelectExpression();
                select.addToPathMap(pathMap, null);
            }
        }
        return pathMap;
    }

    /**
     * Get the LocationProvider allowing location identifiers to be resolved.
     */

    public LocationProvider getLocationProvider() {
        return executable.getLocationMap();
    }

    /**
     * Indicate that document projection is or is not allowed
     *
     * @param allowed true if projection is allowed
     */

    public void setAllowDocumentProjection(boolean allowed) {
        allowDocumentProjection = allowed;
    }

    /**
     * Ask whether document projection is allowed
     *
     * @return true if document projection is allowed
     */

    public boolean isDocumentProjectionAllowed() {
        return allowDocumentProjection;
    }

    /**
     * Return the public identifier for the current document event.
     * <p/>
     * <p>The return value is the public identifier of the document
     * entity or of the external parsed entity in which the markup that
     * triggered the event appears.</p>
     *
     * @return A string containing the public identifier, or
     *         null if none is available.
     * @see #getSystemId
     */
    public String getPublicId() {
        return null;
    }

    /**
     * Return the system identifier for the current document event.
     * <p/>
     * <p>The return value is the system identifier of the document
     * entity or of the external parsed entity in which the markup that
     * triggered the event appears.</p>
     * <p/>
     * <p>If the system identifier is a URL, the parser must resolve it
     * fully before passing it to the application.</p>
     *
     * @return A string containing the system identifier, or null
     *         if none is available.
     * @see #getPublicId
     */
    public String getSystemId() {
        return null;
    }

    /**
     * Return the line number where the current document event ends.
     * <p/>
     * <p><strong>Warning:</strong> The return value from the method
     * is intended only as an approximation for the sake of error
     * reporting; it is not intended to provide sufficient information
     * to edit the character content of the original XML document.</p>
     * <p/>
     * <p>The return value is an approximation of the line number
     * in the document entity or external parsed entity where the
     * markup that triggered the event appears.</p>
     *
     * @return The line number, or -1 if none is available.
     * @see #getColumnNumber
     */
    public int getLineNumber() {
        return -1;
    }

    /**
     * Return the character position where the current document event ends.
     * <p/>
     * <p><strong>Warning:</strong> The return value from the method
     * is intended only as an approximation for the sake of error
     * reporting; it is not intended to provide sufficient information
     * to edit the character content of the original XML document.</p>
     * <p/>
     * <p>The return value is an approximation of the column number
     * in the document entity or external parsed entity where the
     * markup that triggered the event appears.</p>
     *
     * @return The column number, or -1 if none is available.
     * @see #getLineNumber
     */
    public int getColumnNumber() {
        return -1;
    }

    /**
     * Get the host language (XSLT, XQuery, XPath) used to implement the code in this container
     *
     * @return typically {@link net.sf.saxon.Configuration#XSLT} or {@link net.sf.saxon.Configuration#XQUERY}
     */

    public int getHostLanguage() {
        return Configuration.XQUERY;
    }

    /**
     * ErrorReportingIterator is an iterator that wraps a base iterator and reports
     * any exceptions that are raised to the ErrorListener
     */

    private class ErrorReportingIterator implements SequenceIterator {
        private SequenceIterator base;
        private ErrorListener listener;

        public ErrorReportingIterator(SequenceIterator base, ErrorListener listener) {
            this.base = base;
            this.listener = listener;
        }

        public Item next() throws XPathException {
            try {
                return base.next();
            } catch (XPathException e1) {
                e1.maybeSetLocation(expression);
                try {
                    listener.fatalError(e1);
                } catch (TransformerException e2) {
                    //
                }
                e1.setHasBeenReported();
                throw e1;
            }
        }

        public Item current() {
            return base.current();
        }

        public int position() {
            return base.position();
        }

        public void close() {
            base.close();
        }

        public SequenceIterator getAnother() throws XPathException {
            return new ErrorReportingIterator(base.getAnother(), listener);
        }

        /**
         * Get properties of this iterator, as a bit-significant integer.
         *
         * @return the properties of this iterator. This will be some combination of
         *         properties such as {@link #GROUNDED}, {@link #LAST_POSITION_FINDER},
         *         and {@link #LOOKAHEAD}. It is always
         *         acceptable to return the value zero, indicating that there are no known special properties.
         *         It is acceptable for the properties of the iterator to change depending on its state.
         */

        public int getProperties() {
            return 0;
        }
    }

}

//
// 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
//
// Contributor(s):
//

