//
// LexicalHandler.h
//
// Library: XML
// Package: SAX
// Module:  SAX
//
// SAX2-ext LexicalHandler Interface.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier:	BSL-1.0
//


#ifndef SAX_LexicalHandler_INCLUDED
#define SAX_LexicalHandler_INCLUDED


#include "Poco/XML/XML.h"
#include "Poco/XML/XMLString.h"


namespace Poco
{
namespace XML
{


    class XML_API LexicalHandler
    /// This is an optional extension handler for SAX2 to provide lexical information
    /// about an XML document, such as comments and CDATA section boundaries.
    /// XML readers are not required to recognize this handler, and it is not part of
    /// core-only SAX2 distributions.
    ///
    /// The events in the lexical handler apply to the entire document, not just to the
    /// document element, and all lexical handler events must appear between the content
    /// handler's startDocument and endDocument events.
    ///
    /// To set the LexicalHandler for an XML reader, use the setProperty method with the
    /// property name http://xml.org/sax/properties/lexical-handler and an object implementing
    /// this interface (or null) as the value. If the reader does not report lexical events,
    /// it will throw a SAXNotRecognizedException when you attempt to register the handler.
    {
    public:
        virtual void startDTD(const XMLString & name, const XMLString & publicId, const XMLString & systemId) = 0;
        /// Report the start of DTD declarations, if any.
        ///
        /// This method is intended to report the beginning of the DOCTYPE declaration;
        /// if the document has no DOCTYPE declaration, this method will not be invoked.
        ///
        /// All declarations reported through DTDHandler or DeclHandler events must appear
        /// between the startDTD and endDTD events. Declarations are assumed to belong to
        /// the internal DTD subset unless they appear between startEntity and endEntity
        /// events. Comments and processing instructions from the DTD should also be reported
        /// between the startDTD and endDTD events, in their original order of (logical) occurrence;
        /// they are not required to appear in their correct locations relative to DTDHandler or
        /// DeclHandler events, however.
        ///
        /// Note that the start/endDTD events will appear within the start/endDocument events from
        /// ContentHandler and before the first startElement event.

        virtual void endDTD() = 0;
        /// Report the end of DTD declarations.
        ///
        /// This method is intended to report the end of the DOCTYPE declaration; if the document
        /// has no DOCTYPE declaration, this method will not be invoked.

        virtual void startEntity(const XMLString & name) = 0;
        /// Report the beginning of some internal and external XML entities.
        ///
        /// The reporting of parameter entities (including the external DTD subset) is optional,
        /// and SAX2 drivers that report LexicalHandler events may not implement it; you can use the
        /// http://xml.org/sax/features/lexical-handler/parameter-entities feature to query or control
        /// the reporting of parameter entities.
        ///
        /// General entities are reported with their regular names, parameter entities have '%'
        /// prepended to their names, and the external DTD subset has the pseudo-entity name "[dtd]".
        ///
        /// When a SAX2 driver is providing these events, all other events must be properly nested
        /// within start/end entity events. There is no additional requirement that events from
        /// DeclHandler or DTDHandler be properly ordered.
        ///
        /// Note that skipped entities will be reported through the skippedEntity event, which is part of
        /// the ContentHandler interface.
        ///
        /// Because of the streaming event model that SAX uses, some entity boundaries cannot be reported under
        /// any circumstances:
        ///
        ///     * general entities within attribute values
        ///     * parameter entities within declarations
        ///
        /// These will be silently expanded, with no indication of where the original entity boundaries were.
        ///
        /// Note also that the boundaries of character references (which are not really entities anyway) are not reported.
        ///
        /// All start/endEntity events must be properly nested.

        virtual void endEntity(const XMLString & name) = 0;
        /// Report the end of an entity.

        virtual void startCDATA() = 0;
        /// Report the start of a CDATA section.
        ///
        /// The contents of the CDATA section will be reported through the regular characters event;
        /// this event is intended only to report the boundary.

        virtual void endCDATA() = 0;
        /// Report the end of a CDATA section.

        virtual void comment(const XMLChar ch[], int start, int length) = 0;
        /// Report an XML comment anywhere in the document.
        ///
        /// This callback will be used for comments inside or outside the document element,
        /// including comments in the external DTD subset (if read). Comments in the DTD must
        /// be properly nested inside start/endDTD and start/endEntity events (if used).

    protected:
        virtual ~LexicalHandler();
    };


}
} // namespace Poco::XML


#endif // SAX_LexicalHandler_INCLUDED