/*

Copyright 2010, Google Inc.
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modification, are permitted provided that the following conditions are
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    * Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following disclaimer
in the documentation and/or other materials provided with the
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    * Neither the name of Google Inc. nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.

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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,           
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY           
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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*/

package com.google.refine.importers;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PushbackInputStream;
import java.io.Serializable;
import java.util.List;

import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;

import org.json.JSONArray;
import org.json.JSONObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.refine.ProjectMetadata;
import com.google.refine.importers.tree.ImportColumnGroup;
import com.google.refine.importers.tree.TreeImportingParserBase;
import com.google.refine.importers.tree.TreeReader;
import com.google.refine.importers.tree.TreeReaderException;
import com.google.refine.importing.ImportingJob;
import com.google.refine.importing.ImportingUtilities;
import com.google.refine.model.Project;
import com.google.refine.util.JSONUtilities;

public class XmlImporter extends TreeImportingParserBase {
    static final Logger logger = LoggerFactory.getLogger(XmlImporter.class);
    
    public XmlImporter() {
        super(true);
    }
    
    static private class PreviewParsingState {
        int tokenCount;
    }
    
    final static private int PREVIEW_PARSING_LIMIT = 1000;
    
    @Override
    public JSONObject createParserUIInitializationData(
            ImportingJob job, List<JSONObject> fileRecords, String format) {
        JSONObject options = super.createParserUIInitializationData(job, fileRecords, format);
        try {
            if (fileRecords.size() > 0) {
                JSONObject firstFileRecord = fileRecords.get(0);
                File file = ImportingUtilities.getFile(job, firstFileRecord);
                InputStream is = new FileInputStream(file);
                
                try {
                    XMLStreamReader parser = createXMLStreamReader(is);
                    PreviewParsingState state = new PreviewParsingState();

                    while (parser.hasNext() && state.tokenCount < PREVIEW_PARSING_LIMIT) {
                        int tokenType = parser.next();
                        state.tokenCount++;
                        if (tokenType == XMLStreamConstants.START_ELEMENT) {
                            JSONObject rootElement = descendElement(parser, state);
                            if (rootElement != null) {
                                JSONUtilities.safePut(options, "dom", rootElement);
                                break;
                            }
                        } else {
                            // ignore everything else
                        }
                    }
                } catch (XMLStreamException e) {
                    logger.warn("Error generating parser UI initialization data for XML file", e);
                } finally {
                    is.close();
                }
            }
        } catch (IOException e) {
            logger.error("Error generating parser UI initialization data for XML file", e);
        }

        return options;
    }
    
    final static private JSONObject descendElement(XMLStreamReader parser, PreviewParsingState state) {
        JSONObject result = new JSONObject();
        {
            String name = parser.getLocalName();
            JSONUtilities.safePut(result, "n", name);
            
            String prefix = parser.getPrefix();
            if (prefix != null) {
                JSONUtilities.safePut(result, "p", prefix);
            }
            String nsUri = parser.getNamespaceURI();
            if (nsUri != null) {
                JSONUtilities.safePut(result, "uri", nsUri);
            }
        }
        
        int namespaceCount = parser.getNamespaceCount();
        if (namespaceCount > 0) {
            JSONArray namespaces = new JSONArray();
            JSONUtilities.safePut(result, "ns", namespaces);
            
            for (int i = 0; i < namespaceCount; i++) {
                JSONObject namespace = new JSONObject();
                JSONUtilities.append(namespaces, namespace);
                JSONUtilities.safePut(namespace, "p", parser.getNamespacePrefix(i));
                JSONUtilities.safePut(namespace, "uri", parser.getNamespaceURI(i));
            }
        }
        
        int attributeCount = parser.getAttributeCount();
        if (attributeCount > 0) {
            JSONArray attributes = new JSONArray();
            JSONUtilities.safePut(result, "a", attributes);
            
            for (int i = 0; i < attributeCount; i++) {
                JSONObject attribute = new JSONObject();
                JSONUtilities.append(attributes, attribute);
                JSONUtilities.safePut(attribute, "n", parser.getAttributeLocalName(i));
                JSONUtilities.safePut(attribute, "v", parser.getAttributeValue(i));
                String prefix = parser.getAttributePrefix(i);
                if (prefix != null) {
                    JSONUtilities.safePut(attribute, "p", prefix);
                }
            }
        }
        
        JSONArray children = new JSONArray();
        try {
            while (parser.hasNext() && state.tokenCount < PREVIEW_PARSING_LIMIT) {
                int tokenType = parser.next();
                state.tokenCount++;
                if (tokenType == XMLStreamConstants.END_ELEMENT) {
                    break;
                } else if (tokenType == XMLStreamConstants.START_ELEMENT) {
                    JSONObject childElement = descendElement(parser, state);
                    if (childElement != null) {
                        JSONUtilities.append(children, childElement);
                    }
                } else if (tokenType == XMLStreamConstants.CHARACTERS ||
                           tokenType == XMLStreamConstants.CDATA ||
                           tokenType == XMLStreamConstants.SPACE) {
                    JSONObject childElement = new JSONObject();
                    JSONUtilities.safePut(childElement, "t", parser.getText());
                    JSONUtilities.append(children, childElement);
                } else {
                    // ignore everything else
                }
            }
        } catch (XMLStreamException e) {
            logger.error("Error generating parser UI initialization data for XML file", e);
        }
        
        if (children.length() > 0) {
            JSONUtilities.safePut(result, "c", children);
        }
        return result;
    }
    
    @Override
    public void parseOneFile(Project project, ProjectMetadata metadata,
            ImportingJob job, String fileSource, InputStream inputStream,
            ImportColumnGroup rootColumnGroup, int limit, JSONObject options,
            List<Exception> exceptions) {
        
        try {
            parseOneFile(project, metadata, job, fileSource,
                new XmlParser(inputStream), rootColumnGroup, limit, options, exceptions);
        } catch (XMLStreamException e) {
            exceptions.add(e);
        } catch (IOException e) {
            exceptions.add(e);
        }
    }
    
    static public class XmlParser implements TreeReader {
        final protected XMLStreamReader parser;
        
        public XmlParser(InputStream inputStream) throws XMLStreamException, IOException {
            parser = createXMLStreamReader(inputStream);
        }
        
        @Override
        public Token next() throws TreeReaderException {
            try {
                if (!parser.hasNext()) {
                    throw new TreeReaderException("End of XML stream");
                }
            } catch (XMLStreamException e) {
                throw new TreeReaderException(e);
            }
            
            int currentToken = -1;
            try {
                currentToken = parser.next();
            } catch (XMLStreamException e) {
                throw new TreeReaderException(e);
            }
            
            return mapToToken(currentToken);
        }
        
        protected Token mapToToken(int token) {
            switch(token){
                case XMLStreamConstants.START_ELEMENT: return Token.StartEntity;
                case XMLStreamConstants.END_ELEMENT: return Token.EndEntity;
                case XMLStreamConstants.CHARACTERS: return Token.Value;
                case XMLStreamConstants.START_DOCUMENT: return Token.Ignorable;
                case XMLStreamConstants.END_DOCUMENT: return Token.Ignorable;
                case XMLStreamConstants.SPACE: return Token.Value;
                case XMLStreamConstants.PROCESSING_INSTRUCTION: return Token.Ignorable;
                case XMLStreamConstants.NOTATION_DECLARATION: return Token.Ignorable;
                case XMLStreamConstants.NAMESPACE: return Token.Ignorable;
                case XMLStreamConstants.ENTITY_REFERENCE: return Token.Ignorable;
                case XMLStreamConstants.DTD: return Token.Ignorable;
                case XMLStreamConstants.COMMENT: return Token.Ignorable;
                case XMLStreamConstants.CDATA: return Token.Ignorable;
                case XMLStreamConstants.ATTRIBUTE: return Token.Ignorable;
                default:
                    return Token.Ignorable;
            }
        }
        
        @Override
        public Token current() throws TreeReaderException {
            return this.mapToToken(parser.getEventType());
        }
        
        @Override
        public boolean hasNext() throws TreeReaderException {
            try {
                return parser.hasNext();
            } catch (XMLStreamException e) {
                throw new TreeReaderException(e);
            }
        }
        
        @Override
        public String getFieldName() throws TreeReaderException {
            try {
                return parser.getLocalName();
            } catch (IllegalStateException e) {
                return null;
            }
        }
        
        @Override
        public String getPrefix(){
            return parser.getPrefix();
        }
        
        @Override
        public String getFieldValue(){
            return parser.getText();
        }
    
        @Override
        public Serializable getValue() {
            // XML parser only does string types
            return getFieldValue();
        }

        @Override
        public int getAttributeCount(){
            return parser.getAttributeCount();
        }
        
        @Override
        public String getAttributeValue(int index){
            return parser.getAttributeValue(index);
        }
        
        @Override
        public String getAttributePrefix(int index){
            return parser.getAttributePrefix(index);
        }
        
        @Override
        public String getAttributeLocalName(int index){
            return parser.getAttributeLocalName(index);
        }
    }
    
    final static private XMLStreamReader createXMLStreamReader(InputStream inputStream) throws XMLStreamException, IOException {
        XMLInputFactory factory = XMLInputFactory.newInstance();
        factory.setProperty(XMLInputFactory.IS_COALESCING, true);
        factory.setProperty(XMLInputFactory.IS_REPLACING_ENTITY_REFERENCES, true);
        
        return factory.createXMLStreamReader(wrapPrefixRemovingInputStream(inputStream));
    }
    
    final static private InputStream wrapPrefixRemovingInputStream(InputStream inputStream)
            throws XMLStreamException, IOException {
        PushbackInputStream pis = new PushbackInputStream(inputStream);
        int b;
        int count = 0;
        while (count < 100 && (b = pis.read()) >= 0) {
            if (++count > 100) {
                throw new XMLStreamException(
                    "File starts with too much non-XML content to skip over");
            } else if (b == '<') {
                pis.unread(b);
                break;
            }
        }
        return pis;
    }
}