/*

  * Licensed to the Apache Software Foundation (ASF) under one or more

  * contributor license agreements.  See the NOTICE file distributed with

  * this work for additional information regarding copyright ownership.

  * The ASF licenses this file to You 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.any23.writer;

 import org.apache.any23.extractor.ExtractionContext;

 import org.openrdf.model.BNode;

 import org.openrdf.model.Literal;

 import org.openrdf.model.Resource;

 import org.openrdf.model.URI;

 import org.openrdf.model.Value;

 import java.io.BufferedOutputStream;

 import java.io.OutputStream;

 import java.io.PrintStream;

 /**

  * Implementation of <i>JSON</i> format writer.

  *

  * @author Michele Mostarda (mostarda@fbk.eu)

  */

 @Writer(identifier = "json", mimeType = "text/json" )

 public class JSONWriter implements FormatWriter {

     private final PrintStream ps;

     private boolean documentStarted = false;

     private boolean firstArrayElemWritten = false;

     private boolean firstObjectWritten    = false;

     public JSONWriter(OutputStream os) {

         if(os == null) {

             throw new NullPointerException("Output stream cannot be null.");

         }

         this.ps = new PrintStream(new BufferedOutputStream(os));

     }

     public void startDocument(URI documentURI) throws TripleHandlerException {

         if(documentStarted) {

             throw new IllegalStateException("Document already started.");

         }

         documentStarted = true;

         firstArrayElemWritten = false;

         ps.print("{ \"quads\" : [");

     }

     public void openContext(ExtractionContext context) throws TripleHandlerException {

         // Empty.

     }

     public void receiveTriple(Resource s, URI p, Value o, URI g, ExtractionContext context)

     throws TripleHandlerException {

         validateDocumentStarted();

         if(firstArrayElemWritten) {

             ps.print(", ");

         } else {

             firstArrayElemWritten = true;

         }

         firstObjectWritten    = false;

         ps.print('[');

         if(s instanceof URI) {

             printExplicitURI(s.stringValue(), ps);

         } else {

             printBNode(s.stringValue(), ps);

         }

         printURI(p.stringValue(), ps);

          if(o instanceof URI) {

             printExplicitURI(o.stringValue(), ps);

         } else if(o instanceof BNode) {

             printBNode(o.stringValue(), ps);

         } else {

             printLiteral((Literal) o, ps);

         }

         printURI(g == null ? null : g.stringValue(), ps);

         ps.print(']');

     }

     public void receiveNamespace(String prefix, String uri, ExtractionContext context)

     throws TripleHandlerException {

         // Empty.

     }

     public void closeContext(ExtractionContext context) throws TripleHandlerException {

         // Empty.

     }

     public void endDocument(URI documentURI) throws TripleHandlerException {

         validateDocumentStarted();

         ps.print("]}");

         documentStarted = false;

     }

     public void setContentLength(long contentLength) {

         // Empty.

     }

     public void close() throws TripleHandlerException {

         ps.close();

     }

     private void validateDocumentStarted() {

        if(!documentStarted) {

             throw new IllegalStateException("Document didn't start.");

         }

     }

     private void printURI(String uri, PrintStream ps) {

         printValue(uri, ps);

     }

     private void printExplicitURI(String uri, PrintStream ps) {

         printValue("uri", uri, ps);

     }

     private void printBNode(String bnode, PrintStream ps) {

         printValue("bnode", bnode, ps);

     }

     private void printCommaIfNeeded(PrintStream ps) {

         if(firstObjectWritten) {

             ps.print(", ");

         } else {

             firstObjectWritten = true;

         }

     }

     private void printLiteral(Literal literal, PrintStream ps) {

         printCommaIfNeeded(ps);

         ps.print('{');

         ps.print("\"type\" : \"literal\"");

         ps.print(", ");

         ps.print("\"value\" : ");

         ps.print('"');

         ps.print(literal.stringValue());

         ps.print('"');

         ps.print(", ");

         ps.print("\"lang\" : ");

         final String language = literal.getLanguage();

         if (language != null) {

             ps.print('"');

             ps.print(literal.getLanguage());

             ps.print('"');

         } else {

             ps.print("null");

         }

         ps.print(", ");

         ps.print("\"datatype\" : ");

         final URI datatype = literal.getDatatype();

         if(datatype != null) {

         ps.print('"');

         ps.print(datatype.stringValue());

         ps.print('"');

         } else {

             ps.print("null");

         }

         ps.print('}');

     }

     private void printValue(String type, String value, PrintStream ps) {

         printCommaIfNeeded(ps);

         ps.print("{ \"type\" : \"");

         ps.print(type);

         ps.print("\", \"value\" : ");

         if (value != null) {

             ps.print('"');

             ps.print(value);

             ps.print('"');

         } else {

             ps.print("null");

         }

         ps.print('}');

     }

     private void printValue(String value, PrintStream ps) {

         printCommaIfNeeded(ps);

         if (value != null) {

             ps.print('"');

             ps.print(value);

             ps.print('"');

         } else {

             ps.print("null");

         }

     }

     @Override

     public boolean isAnnotated() {

         return false; // TODO: add annotation support.

     }

     @Override

     public void setAnnotated(boolean f) {

         // Empty.

     }

 }