/*

  * #%L

  * JsonSerializationVisitor.java - mongodb-async-driver - Allanbank Consulting, Inc.

  * %%

  * Copyright (C) 2011 - 2014 Allanbank Consulting, Inc.

  * %%

  * 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.

  * #L%

  */

 package com.allanbank.mongodb.bson.element;

 import java.io.IOException;

 import java.io.Writer;

 import java.text.SimpleDateFormat;

 import java.util.Date;

 import java.util.List;

 import java.util.TimeZone;

 import java.util.regex.Pattern;

 import com.allanbank.mongodb.bson.Document;

 import com.allanbank.mongodb.bson.Element;

 import com.allanbank.mongodb.bson.Visitor;

 import com.allanbank.mongodb.error.JsonException;

 import com.allanbank.mongodb.util.IOUtils;

 /**

  * JsonSerializationVisitor provides a BSON Visitor that generates a JSON

  * document.

  * 

  * @api.no This class is <b>NOT</b> part of the drivers API. This class may be

  *         mutated in incompatible ways between any two releases of the driver.

  * @copyright 2012-2013, Allanbank Conublic sulting, Inc., All Rights Reserved

  */

 public class JsonSerializationVisitor implements Visitor {

     /** The platforms new line string. */

     public static final String NL = System.getProperty("line.separator", "\n");

     /** A pattern to detect valid "symbol" names. */

     public static final Pattern SYMBOL_PATTERN = Pattern

             .compile("\\p{Alpha}\\p{Alnum}*");

     /** The default time zone. */

     public static final TimeZone UTC = TimeZone.getTimeZone("UTC");

     /** The current indent level. */

     private int myIndentLevel = 0;

     /** If true then the visitor will write the document to 1 line. */

     private final boolean myOneLine;

     /** The Writer to write to. */

     private final Writer mySink;

     /**

      * If true then the names of the elements should be suppressed because we

      * are in an array.

      */

     private boolean mySuppressNames = false;

     /**

      * Creates a new JsonSerializationVisitor.

      * 

      * @param sink

      *            The Writer to write to.

      * @param oneLine

      *            If true then the visitor will write the document to 1 line,

      *            otherwise the visitor will write the document accross multiple

      *            lines with indenting.

      */

     public JsonSerializationVisitor(final Writer sink, final boolean oneLine) {

         mySink = sink;

         myOneLine = oneLine;

         myIndentLevel = 0;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to create a JSON representation of the document's elements to

      * the writer provided when this object was created.

      * </p>

      */

     @Override

     public void visit(final List<Element> elements) {

         try {

             if (elements.isEmpty()) {

                 mySink.write("{}");

             }

             else if ((elements.size() == 1)

                     && !(elements.get(0) instanceof DocumentElement)

                     && !(elements.get(0) instanceof ArrayElement)) {

                 mySink.write("{ ");

                 final boolean oldSuppress = mySuppressNames;

                 mySuppressNames = false;

                 elements.get(0).accept(this);

                 mySuppressNames = oldSuppress;

                 mySink.write(" }");

             }

             else {

                 mySink.write('{');

                 myIndentLevel += 1;

                 final boolean oldSuppress = mySuppressNames;

                 mySuppressNames = false;

                 boolean first = true;

                 for (final Element element : elements) {

                     if (!first) {

                         mySink.write(",");

                     }

                     nl();

                     element.accept(this);

                     first = false;

                 }

                 mySuppressNames = oldSuppress;

                 myIndentLevel -= 1;

                 nl();

                 mySink.write('}');

             }

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the array's elements to the

      * writer provided when this object was created.

      * </p>

      */

     @Override

     public void visitArray(final String name, final List<Element> elements) {

         try {

             writeName(name);

             if (elements.isEmpty()) {

                 mySink.write("[]");

             }

             else if ((elements.size() == 1)

                     && !(elements.get(0) instanceof DocumentElement)

                     && !(elements.get(0) instanceof ArrayElement)) {

                 mySink.write("[ ");

                 final boolean oldSuppress = mySuppressNames;

                 mySuppressNames = true;

                 elements.get(0).accept(this);

                 mySuppressNames = oldSuppress;

                 mySink.write(" ]");

             }

             else {

                 mySink.write("[");

                 myIndentLevel += 1;

                 final boolean oldSuppress = mySuppressNames;

                 mySuppressNames = true;

                 boolean first = true;

                 for (final Element element : elements) {

                     if (!first) {

                         mySink.write(", ");

                     }

                     nl();

                     element.accept(this);

                     first = false;

                 }

                 mySuppressNames = oldSuppress;

                 myIndentLevel -= 1;

                 nl();

                 mySink.append(']');

             }

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the binary element to the

      * writer provided when this object was created. This method generates the

      * MongoDB standard BinData(...) JSON extension.

      * </p>

      */

     @Override

     public void visitBinary(final String name, final byte subType,

             final byte[] data) {

         try {

             writeName(name);

             mySink.write("BinData( ");

             mySink.write(Integer.toString(subType));

             mySink.write(", '");

             mySink.write(IOUtils.toBase64(data));

             mySink.write("' )");

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the boolean element to the

      * writer provided when this object was created.

      * </p>

      */

     @Override

     public void visitBoolean(final String name, final boolean value) {

         try {

             writeName(name);

             mySink.write(Boolean.toString(value));

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the DBPointer element to

      * the writer provided when this object was created. This method generates

      * the non-standard DBPointer(...) JSON extension.

      * </p>

      */

     @Override

     public void visitDBPointer(final String name, final String databaseName,

             final String collectionName, final ObjectId id) {

         try {

             writeName(name);

             mySink.write("DBPointer( ");

             writeQuotedString(databaseName);

             mySink.write(", ");

             writeQuotedString(collectionName);

             mySink.write(", ");

             writeObjectId(id);

             mySink.write(" )");

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the sub-document element to

      * the writer provided when this object was created.

      * </p>

      */

     @Override

     public void visitDocument(final String name, final List<Element> elements) {

         try {

             writeName(name);

             visit(elements);

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the double element to the

      * writer provided when this object was created.

      * </p>

      */

     @Override

     public void visitDouble(final String name, final double value) {

         try {

             writeName(name);

             mySink.write(Double.toString(value));

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the integer element to the

      * writer provided when this object was created.

      * </p>

      */

     @Override

     public void visitInteger(final String name, final int value) {

         try {

             writeName(name);

             mySink.write(Integer.toString(value));

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the JavaScript element to

      * the writer provided when this object was created. This method writes the

      * elements as a <code>{ $code : &lt;code&gt; }</code> sub-document.

      * </p>

      */

     @Override

     public void visitJavaScript(final String name, final String code) {

         try {

             writeName(name);

             mySink.write("{ $code : ");

             writeQuotedString(code);

             mySink.write(" }");

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the JavaScript element to

      * the writer provided when this object was created. This method writes the

      * elements as a

      * <code>{ $code : &lt;code&gt;, $scope : &lt;scope&gt; }</code>

      * sub-document.

      * </p>

      */

     @Override

     public void visitJavaScript(final String name, final String code,

             final Document scope) {

         try {

             writeName(name);

             mySink.write("{ $code : ");

             writeQuotedString(code);

             mySink.write(", $scope : ");

             scope.accept(this);

             mySink.write(" }");

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the binary element to the

      * writer provided when this object was created. This method generates the

      * MongoDB standard NumberLong(...) JSON extension.

      * </p>

      */

     @Override

     public void visitLong(final String name, final long value) {

         try {

             writeName(name);

             mySink.write("NumberLong('");

             mySink.write(Long.toString(value));

             mySink.write("')");

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the DBPointer element to

      * the writer provided when this object was created. This method generates

      * the non-standard MaxKey() JSON extension.

      * </p>

      */

     @Override

     public void visitMaxKey(final String name) {

         try {

             writeName(name);

             mySink.write("MaxKey()");

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the DBPointer element to

      * the writer provided when this object was created. This method generates

      * the non-standard MinKey() JSON extension.

      * </p>

      */

     @Override

     public void visitMinKey(final String name) {

         try {

             writeName(name);

             mySink.write("MinKey()");

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the binary element to the

      * writer provided when this object was created. This method generates the

      * MongoDB standard Timestamp(...) JSON extension.

      * </p>

      */

     @Override

     public void visitMongoTimestamp(final String name, final long value) {

         try {

             final long time = (value >> Integer.SIZE) & 0xFFFFFFFFL;

             final long increment = value & 0xFFFFFFFFL;

             writeName(name);

             mySink.write("Timestamp(");

             mySink.write(Long.toString(time * 1000));

             mySink.write(", ");

             mySink.write(Long.toString(increment));

             mySink.write(')');

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the null element to the

      * writer provided when this object was created.

      * </p>

      */

     @Override

     public void visitNull(final String name) {

         try {

             writeName(name);

             mySink.write("null");

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the binary element to the

      * writer provided when this object was created. This method generates the

      * MongoDB standard ObjectId(...) JSON extension.

      * </p>

      */

     @Override

     public void visitObjectId(final String name, final ObjectId id) {

         try {

             writeName(name);

             writeObjectId(id);

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the JavaScript element to

      * the writer provided when this object was created. This method writes the

      * elements as a

      * <code>{ $regex : &lt;pattern&gt;, $options : &lt;options&gt; }</code>

      * sub-document.

      * </p>

      */

     @Override

     public void visitRegularExpression(final String name, final String pattern,

             final String options) {

         try {

             writeName(name);

             mySink.write("{ $regex : '");

             mySink.write(pattern);

             if (options.isEmpty()) {

                 mySink.write("' }");

             }

             else {

                 mySink.write("', $options : '");

                 mySink.write(options);

                 mySink.write("' }");

             }

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the string element to the

      * writer provided when this object was created.

      * </p>

      */

     @Override

     public void visitString(final String name, final String value) {

         try {

             writeName(name);

             writeQuotedString(value);

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the symbol element to the

      * writer provided when this object was created.

      * </p>

      */

     @Override

     public void visitSymbol(final String name, final String symbol) {

         try {

             writeName(name);

             if (SYMBOL_PATTERN.matcher(symbol).matches()) {

                 mySink.write(symbol);

             }

             else {

                 writeQuotedString(symbol);

             }

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to append a JSON representation of the binary element to the

      * writer provided when this object was created. This method generates the

      * MongoDB standard ISODate(...) JSON extension.

      * </p>

      */

     @Override

     public void visitTimestamp(final String name, final long timestamp) {

         final SimpleDateFormat sdf = new SimpleDateFormat(

                 "yyyy-MM-dd'T'HH:mm:ss.SSSZ");

         sdf.setTimeZone(UTC);

         try {

             writeName(name);

             mySink.write("ISODate('");

             mySink.write(sdf.format(new Date(timestamp)));

             mySink.write("')");

             mySink.flush();

         }

         catch (final IOException ioe) {

             throw new JsonException(ioe);

         }

     }

     /**

      * Returns if the visitor is currently suppressing the names of elements.

      * This is true when serializing an array.

      * 

      * @return If the visitor is currently suppressing the names of elements.

      *         This is true when serializing an array.

      */

     protected boolean isSuppressNames() {

         return mySuppressNames;

     }

     /**

      * Writes a new line if {@link #myOneLine} is false and indents to the

      * {@link #myIndentLevel}.

      * 

      * @throws IOException

      *             On a failure to write the new line.

      */

     protected void nl() throws IOException {

         if (!myOneLine) {

             mySink.write(NL);

             for (int i = 0; i < myIndentLevel; ++i) {

                 mySink.write("  ");

             }

         }

         else {

             mySink.write(' ');

         }

     }

     /**

      * Sets the value for if the visitor is currently suppressing the names of

      * elements. This is true, for example, when serializing an array.

      * 

      * @param suppressNames

      *            The new value for if names should be suppressed.

      */

     protected void setSuppressNames(final boolean suppressNames) {

         mySuppressNames = suppressNames;

     }

     /**

      * Writes the name if {@link #mySuppressNames} is false.

      * 

      * @param name

      *            The name to write, if not suppressed.

      * @throws IOException

      *             On a failure to write the new line.

      */

     protected void writeName(final String name) throws IOException {

         if (!mySuppressNames) {

             if (SYMBOL_PATTERN.matcher(name).matches()) {

                 mySink.write(name);

             }

             else {

                 writeQuotedString(name);

             }

             mySink.write(" : ");

         }

     }

     /**

      * Writes the {@link ObjectId}.

      * 

      * @param id

      *            The {@link ObjectId} to write.

      * @throws IOException

      *             On a failure writing to the sink.

      */

     protected void writeObjectId(final ObjectId id) throws IOException {

         mySink.write("ObjectId('");

         String hex = Integer.toHexString(id.getTimestamp());

         mySink.write("00000000".substring(hex.length()));

         mySink.write(hex);

         hex = Long.toHexString(id.getMachineId());

         mySink.write("0000000000000000".substring(hex.length()));

         mySink.write(hex);

         mySink.write("')");

     }

     /**

      * Writes the {@code string} as a quoted string.

      * 

      * @param string

      *            The String to write.

      * @throws IOException

      *             On a failure writing the String.

      */

     protected void writeQuotedString(final String string) throws IOException {

         if (string.indexOf('\'') < 0) {

             mySink.write('\'');

             mySink.write(string);

             mySink.write('\'');

         }

         else if (string.indexOf('"') < 0) {

             mySink.write('"');

             mySink.write(string);

             mySink.write('"');

         }

         else {

             mySink.write('\'');

             // Escape any embedded single quotes.

             mySink.write(string.replaceAll("'", "\\\\'"));

             mySink.write('\'');

         }

     }

 }