# SimpleXMLEventReader.java

    /*
     * Copyright 2011, 2012 Odysseus Software GmbH
     *
     * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */
    package org.apache.synapse.commons.staxon.core.event;

    import javax.xml.stream.XMLEventReader;
    import javax.xml.stream.XMLStreamConstants;
    import javax.xml.stream.XMLStreamException;
    import javax.xml.stream.XMLStreamReader;
    import javax.xml.stream.events.XMLEvent;
    import javax.xml.stream.util.XMLEventAllocator;

    /**
     * Simple implementation of {@link XMLEventReader}.
     */
    public class SimpleXMLEventReader implements XMLEventReader {
        private final XMLEventAllocator allocator;
        private final XMLStreamReader delegate;

        private int currentEventType = -1;
        private XMLEvent peekedEvent = null;

        public SimpleXMLEventReader(XMLStreamReader delegate) {
            this(delegate, new SimpleXMLEventAllocator());
        }

        public SimpleXMLEventReader(XMLStreamReader delegate, XMLEventAllocator allocator) {
            this.delegate = delegate;
            this.allocator = allocator;
        }

        protected XMLEvent allocate() throws XMLStreamException {
            return allocator.allocate(delegate);
        }

        @Override
        public void close() throws XMLStreamException {
            delegate.close();
        }

        @Override
        public String getElementText() throws XMLStreamException {
            if (currentEventType != XMLStreamConstants.START_ELEMENT) {
                throw new XMLStreamException("Expected start element event");
            }

            if (peekedEvent == null) {
                String result = delegate.getElementText();
                currentEventType = delegate.getEventType();
                if (currentEventType != XMLStreamConstants.END_ELEMENT) {
                    throw new XMLStreamException("Expected end element event");
                }
                return result;
            }

            currentEventType = peekedEvent.getEventType();
            assert currentEventType == delegate.getEventType();
            peekedEvent = null;

            String leadText = null;
            switch (currentEventType) {
                case XMLStreamConstants.CDATA:
                case XMLStreamConstants.CHARACTERS:
                case XMLStreamConstants.ENTITY_REFERENCE:
                    leadText = delegate.getText();
                    break;
                case XMLStreamConstants.COMMENT:
                case XMLStreamConstants.PROCESSING_INSTRUCTION:
                case XMLStreamConstants.SPACE:
                    break;
                case XMLStreamConstants.END_ELEMENT:
                    return "";
                default:
                    throw new XMLStreamException("Unexpected event type " + currentEventType, delegate.getLocation());
            }

            StringBuilder builder = null;
            while (true) {
                currentEventType = delegate.next();
                switch (currentEventType) {
                    case XMLStreamConstants.CDATA:
                    case XMLStreamConstants.CHARACTERS:
                    case XMLStreamConstants.ENTITY_REFERENCE:
                        if (leadText == null) { // first event?
                            leadText = delegate.getText();
                        } else {
                            if (builder == null) { // second event?
                                builder = new StringBuilder(leadText);
                            }
                            builder.append(delegate.getText());
                        }
                        break;
                    case XMLStreamConstants.COMMENT:
                    case XMLStreamConstants.PROCESSING_INSTRUCTION:
                    case XMLStreamConstants.SPACE:
                        break;
                    case XMLStreamConstants.END_ELEMENT:
                        return builder == null ? (leadText == null ? "" : leadText) : builder.toString();
                    default:
                        throw new XMLStreamException("Unexpected event type " + currentEventType, delegate.getLocation());
                }
            }
        }

        @Override
        public Object getProperty(String name) {
            return delegate.getProperty(name);
        }

        @Override
        public boolean hasNext() {
            try {
                return peek() != null;
            } catch (XMLStreamException e) {
                throw new RuntimeException("Cannot determine next state", e);
            }
        }

        @Override
        public XMLEvent nextEvent() throws XMLStreamException {
            XMLEvent currentEvent = peek();
            if (currentEvent == null) {
                throw new XMLStreamException("no more events");
            }
            currentEventType = currentEvent.getEventType();
            peekedEvent = null;
            return currentEvent;
        }

        @Override
        public Object next() {
            try {
                return nextEvent();
            } catch (XMLStreamException e) {
                throw new RuntimeException(e);
            }
        }

        @Override
        public XMLEvent nextTag() throws XMLStreamException {
            if (peekedEvent == null) {
                currentEventType = delegate.nextTag();
                if (currentEventType != XMLStreamConstants.START_ELEMENT && currentEventType != XMLStreamConstants.END_ELEMENT) {
                    throw new XMLStreamException("Expected start element event or end element event");

                }
                return allocate();
            }

            currentEventType = peekedEvent.getEventType();
            assert currentEventType == delegate.getEventType();
            XMLEvent event = peekedEvent;
            peekedEvent = null;

            switch (event.getEventType()) {
                case XMLStreamConstants.START_DOCUMENT:
                    break;
                case XMLStreamConstants.COMMENT:
                case XMLStreamConstants.PROCESSING_INSTRUCTION:
                case XMLStreamConstants.SPACE:
                    break;
                case XMLStreamConstants.CDATA:
                case XMLStreamConstants.CHARACTERS:
                    if (!event.asCharacters().isWhiteSpace()) {
                        throw new XMLStreamException("Encountered non-whitespace text");
                    }
                    break;
                case XMLStreamConstants.START_ELEMENT:
                case XMLStreamConstants.END_ELEMENT:
                    return event;
                default:
                    throw new XMLStreamException("Encountered unexpected event: " + event.getEventType());
            }

            while (true) {
                currentEventType = delegate.next();
                switch (currentEventType) {
                    case XMLStreamConstants.COMMENT:
                    case XMLStreamConstants.PROCESSING_INSTRUCTION:
                    case XMLStreamConstants.SPACE:
                        continue;
                    case XMLStreamConstants.CDATA:
                    case XMLStreamConstants.CHARACTERS:
                        if (!delegate.isWhiteSpace()) {
                            throw new XMLStreamException("Encountered non-whitespace text");
                        }
                        continue;
                    case XMLStreamConstants.START_ELEMENT:
                    case XMLStreamConstants.END_ELEMENT:
                        return allocate();
                    default:
                        throw new XMLStreamException("Encountered unexpected event: " + delegate.getEventType());
                }
            }
        }

        @Override
        public XMLEvent peek() throws XMLStreamException {
            if (peekedEvent == null) {
                if (currentEventType < 0) { // first event
                    peekedEvent = allocate();
                } else if (delegate.hasNext()) {
                    delegate.next();
                    peekedEvent = allocate();
                }
            }
            return peekedEvent;
        }

        @Override
        public void remove() {
            throw new UnsupportedOperationException("Cannot remove events");
        }
    }