//
//  ========================================================================
//  Copyright (c) 1995-2020 Mort Bay Consulting Pty Ltd and others.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.util.ajax;

import java.io.Externalizable;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.eclipse.jetty.util.IO;
import org.eclipse.jetty.util.Loader;
import org.eclipse.jetty.util.TypeUtil;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;

/**
 * JSON Parser and Generator.
 * <p>
 * This class provides some static methods to convert POJOs to and from JSON
 * notation. The mapping from JSON to java is:
 *
 * <pre>
 *   object --&gt; Map
 *   array  --&gt; Object[]
 *   number --&gt; Double or Long
 *   string --&gt; String
 *   null   --&gt; null
 *   bool   --&gt; Boolean
 * </pre>
 *
 * The java to JSON mapping is:
 *
 * <pre>
 *   String --&gt; string
 *   Number --&gt; number
 *   Map    --&gt; object
 *   List   --&gt; array
 *   Array  --&gt; array
 *   null   --&gt; null
 *   Boolean--&gt; boolean
 *   Object --&gt; string (dubious!)
 * </pre>
 *
 * The interface {@link JSON.Convertible} may be implemented by classes that
 * wish to externalize and initialize specific fields to and from JSON objects.
 * Only directed acyclic graphs of objects are supported.
 * <p>
 * The interface {@link JSON.Generator} may be implemented by classes that know
 * how to render themselves as JSON and the {@link #toString(Object)} method
 * will use {@link JSON.Generator#addJSON(Appendable)} to generate the JSON.
 * The class {@link JSON.Literal} may be used to hold pre-generated JSON object.
 * <p>
 * The interface {@link JSON.Convertor} may be implemented to provide static
 * converters for objects that may be registered with
 * {@link #registerConvertor(Class, Convertor)}.
 * These converters are looked up by class, interface and super class by
 * {@link #getConvertor(Class)}.
 * <p>
 * If a JSON object has a "class" field, then a java class for that name is
 * loaded and the method {@link #convertTo(Class, Map)} is used to find a
 * {@link JSON.Convertor} for that class.
 * <p>
 * If a JSON object has a "x-class" field then a direct lookup for a
 * {@link JSON.Convertor} for that class name is done (without loading the class).
 */
public class JSON
{
    static final Logger LOG = Log.getLogger(JSON.class);
    public static final JSON DEFAULT = new JSON();

    private Map<String, Convertor> _convertors = new ConcurrentHashMap<String, Convertor>();
    private int _stringBufferSize = 1024;

    public JSON()
    {
    }

    /**
     * Reset the default JSON behaviors to default
     */
    public static void reset()
    {
        DEFAULT._convertors.clear();
        DEFAULT._stringBufferSize = 1024;
    }

    /**
     * @return the initial stringBuffer size to use when creating JSON strings
     * (default 1024)
     */
    public int getStringBufferSize()
    {
        return _stringBufferSize;
    }

    /**
     * @param stringBufferSize the initial stringBuffer size to use when creating JSON
     * strings (default 1024)
     */
    public void setStringBufferSize(int stringBufferSize)
    {
        _stringBufferSize = stringBufferSize;
    }

    /**
     * Register a {@link Convertor} for a class or interface.
     *
     * @param forClass The class or interface that the convertor applies to
     * @param convertor the convertor
     */
    public static void registerConvertor(Class forClass, Convertor convertor)
    {
        DEFAULT.addConvertor(forClass, convertor);
    }

    public static JSON getDefault()
    {
        return DEFAULT;
    }

    @Deprecated
    public static void setDefault(JSON json)
    {
    }

    public static String toString(Object object)
    {
        StringBuilder buffer = new StringBuilder(DEFAULT.getStringBufferSize());
        DEFAULT.append(buffer, object);
        return buffer.toString();
    }

    public static String toString(Map object)
    {
        StringBuilder buffer = new StringBuilder(DEFAULT.getStringBufferSize());
        DEFAULT.appendMap(buffer, object);
        return buffer.toString();
    }

    public static String toString(Object[] array)
    {
        StringBuilder buffer = new StringBuilder(DEFAULT.getStringBufferSize());
        DEFAULT.appendArray(buffer, array);
        return buffer.toString();
    }

    /**
     * @param s String containing JSON object or array.
     * @return A Map, Object array or primitive array parsed from the JSON.
     */
    public static Object parse(String s)
    {
        return DEFAULT.parse(new StringSource(s), false);
    }

    /**
     * @param s String containing JSON object or array.
     * @param stripOuterComment If true, an outer comment around the JSON is ignored.
     * @return A Map, Object array or primitive array parsed from the JSON.
     */
    public static Object parse(String s, boolean stripOuterComment)
    {
        return DEFAULT.parse(new StringSource(s), stripOuterComment);
    }

    /**
     * @param in Reader containing JSON object or array.
     * @return A Map, Object array or primitive array parsed from the JSON.
     * @throws IOException if unable to parse
     */
    public static Object parse(Reader in) throws IOException
    {
        return DEFAULT.parse(new ReaderSource(in), false);
    }

    /**
     * @param in Reader containing JSON object or array.
     * @param stripOuterComment If true, an outer comment around the JSON is ignored.
     * @return A Map, Object array or primitive array parsed from the JSON.
     * @throws IOException if unable to parse
     */
    public static Object parse(Reader in, boolean stripOuterComment) throws IOException
    {
        return DEFAULT.parse(new ReaderSource(in), stripOuterComment);
    }

    /**
     * @param in Reader containing JSON object or array.
     * @return A Map, Object array or primitive array parsed from the JSON.
     * @throws IOException if unable to parse
     * @deprecated use {@link #parse(Reader)}
     */
    @Deprecated
    public static Object parse(InputStream in) throws IOException
    {
        return DEFAULT.parse(new StringSource(IO.toString(in)), false);
    }

    /**
     * @param in Stream containing JSON object or array.
     * @param stripOuterComment If true, an outer comment around the JSON is ignored.
     * @return A Map, Object array or primitive array parsed from the JSON.
     * @throws IOException if unable to parse
     * @deprecated use {@link #parse(Reader, boolean)}
     */
    @Deprecated
    public static Object parse(InputStream in, boolean stripOuterComment) throws IOException
    {
        return DEFAULT.parse(new StringSource(IO.toString(in)), stripOuterComment);
    }

    private void quotedEscape(Appendable buffer, String input)
    {
        try
        {
            buffer.append('"');
            if (input != null && !input.isEmpty())
            {
                escapeString(buffer, input);
            }
            buffer.append('"');
        }
        catch (IOException e)
        {
            throw new RuntimeException(e);
        }
    }

    public void escapeString(Appendable buffer, String input) throws IOException
    {
        // default escaping here.

        for (int i = 0; i < input.length(); ++i)
        {
            char c = input.charAt(i);

            // ASCII printable range
            if ((c >= 0x20) && (c <= 0x7E))
            {
                // Special cases for quotation-mark, reverse-solidus, and solidus
                if ((c == '"') || (c == '\\')
                  /* solidus is optional - per Carsten Bormann (IETF)
                     || (c == '/') */)
                {
                    buffer.append('\\').append(c);
                }
                else
                {
                    // ASCII printable (that isn't escaped above)
                    buffer.append(c);
                }
            }
            else
            {
                // All other characters are escaped (in some way)

                // First we deal with the special short-form escaping
                if (c == '\b') // backspace
                    buffer.append("\\b");
                else if (c == '\f') // form-feed
                    buffer.append("\\f");
                else if (c == '\n') // line feed
                    buffer.append("\\n");
                else if (c == '\r') // carriage return
                    buffer.append("\\r");
                else if (c == '\t') // tab
                    buffer.append("\\t");
                else if (c < 0x20 || c == 0x7F) // all control characters
                {
                    // default behavior is to encode
                    buffer.append(String.format("\\u%04x", (short)c));
                }
                else
                {
                    // optional behavior in JSON spec
                    escapeUnicode(buffer, c);
                }
            }
        }
    }

    /**
     * Per spec, unicode characters are by default NOT escaped.
     * This overridable allows for alternate behavior to escape those with your choice
     * of encoding.
     *
     * <code>
     * protected void escapeUnicode(Appendable buffer, char c) throws IOException
     * {
     * // Unicode is slash-u escaped
     * buffer.append(String.format("\\u%04x", (int)c));
     * }
     * </code>
     */
    protected void escapeUnicode(Appendable buffer, char c) throws IOException
    {
        buffer.append(c);
    }

    /**
     * Convert Object to JSON
     *
     * @param object The object to convert
     * @return The JSON String
     */
    public String toJSON(Object object)
    {
        StringBuilder buffer = new StringBuilder(getStringBufferSize());
        append(buffer, object);
        return buffer.toString();
    }

    /**
     * Convert JSON to Object
     *
     * @param json The json to convert
     * @return The object
     */
    public Object fromJSON(String json)
    {
        Source source = new StringSource(json);
        return parse(source);
    }

    @Deprecated
    public void append(StringBuffer buffer, Object object)
    {
        append((Appendable)buffer, object);
    }

    /**
     * Append object as JSON to string buffer.
     *
     * @param buffer the buffer to append to
     * @param object the object to append
     */
    public void append(Appendable buffer, Object object)
    {
        try
        {
            if (object == null)
            {
                buffer.append("null");
            }
            // Most likely first
            else if (object instanceof Map)
            {
                appendMap(buffer, (Map)object);
            }
            else if (object instanceof String)
            {
                appendString(buffer, (String)object);
            }
            else if (object instanceof Number)
            {
                appendNumber(buffer, (Number)object);
            }
            else if (object instanceof Boolean)
            {
                appendBoolean(buffer, (Boolean)object);
            }
            else if (object.getClass().isArray())
            {
                appendArray(buffer, object);
            }
            else if (object instanceof Character)
            {
                appendString(buffer, object.toString());
            }
            else if (object instanceof Convertible)
            {
                appendJSON(buffer, (Convertible)object);
            }
            else if (object instanceof Generator)
            {
                appendJSON(buffer, (Generator)object);
            }
            else
            {
                // Check Convertor before Collection to support JSONCollectionConvertor
                Convertor convertor = getConvertor(object.getClass());
                if (convertor != null)
                {
                    appendJSON(buffer, convertor, object);
                }
                else if (object instanceof Collection)
                {
                    appendArray(buffer, (Collection)object);
                }
                else
                {
                    appendString(buffer, object.toString());
                }
            }
        }
        catch (IOException e)
        {
            throw new RuntimeException(e);
        }
    }

    @Deprecated
    public void appendNull(StringBuffer buffer)
    {
        appendNull((Appendable)buffer);
    }

    public void appendNull(Appendable buffer)
    {
        try
        {
            buffer.append("null");
        }
        catch (IOException e)
        {
            throw new RuntimeException(e);
        }
    }

    @Deprecated
    public void appendJSON(final StringBuffer buffer, final Convertor convertor, final Object object)
    {
        appendJSON((Appendable)buffer, convertor, object);
    }

    public void appendJSON(final Appendable buffer, final Convertor convertor, final Object object)
    {
        appendJSON(buffer, new Convertible()
        {
            @Override
            public void fromJSON(Map object)
            {
            }

            @Override
            public void toJSON(Output out)
            {
                convertor.toJSON(object, out);
            }
        });
    }

    @Deprecated
    public void appendJSON(final StringBuffer buffer, Convertible converter)
    {
        appendJSON((Appendable)buffer, converter);
    }

    public void appendJSON(final Appendable buffer, Convertible converter)
    {
        ConvertableOutput out = new ConvertableOutput(buffer);
        converter.toJSON(out);
        out.complete();
    }

    @Deprecated
    public void appendJSON(StringBuffer buffer, Generator generator)
    {
        generator.addJSON(buffer);
    }

    public void appendJSON(Appendable buffer, Generator generator)
    {
        generator.addJSON(buffer);
    }

    @Deprecated
    public void appendMap(StringBuffer buffer, Map<?, ?> map)
    {
        appendMap((Appendable)buffer, map);
    }

    public void appendMap(Appendable buffer, Map<?, ?> map)
    {
        try
        {
            if (map == null)
            {
                appendNull(buffer);
                return;
            }

            buffer.append('{');
            Iterator<?> iter = map.entrySet().iterator();
            while (iter.hasNext())
            {
                Map.Entry<?, ?> entry = (Map.Entry<?, ?>)iter.next();
                quotedEscape(buffer, entry.getKey().toString());
                buffer.append(':');
                append(buffer, entry.getValue());
                if (iter.hasNext())
                    buffer.append(',');
            }

            buffer.append('}');
        }
        catch (IOException e)
        {
            throw new RuntimeException(e);
        }
    }

    @Deprecated
    public void appendArray(StringBuffer buffer, Collection collection)
    {
        appendArray((Appendable)buffer, collection);
    }

    public void appendArray(Appendable buffer, Collection collection)
    {
        try
        {
            if (collection == null)
            {
                appendNull(buffer);
                return;
            }

            buffer.append('[');
            Iterator iter = collection.iterator();
            boolean first = true;
            while (iter.hasNext())
            {
                if (!first)
                    buffer.append(',');

                first = false;
                append(buffer, iter.next());
            }

            buffer.append(']');
        }
        catch (IOException e)
        {
            throw new RuntimeException(e);
        }
    }

    @Deprecated
    public void appendArray(StringBuffer buffer, Object array)
    {
        appendArray((Appendable)buffer, array);
    }

    public void appendArray(Appendable buffer, Object array)
    {
        try
        {
            if (array == null)
            {
                appendNull(buffer);
                return;
            }

            buffer.append('[');
            int length = Array.getLength(array);

            for (int i = 0; i < length; i++)
            {
                if (i != 0)
                    buffer.append(',');
                append(buffer, Array.get(array, i));
            }

            buffer.append(']');
        }
        catch (IOException e)
        {
            throw new RuntimeException(e);
        }
    }

    @Deprecated
    public void appendBoolean(StringBuffer buffer, Boolean b)
    {
        appendBoolean((Appendable)buffer, b);
    }

    public void appendBoolean(Appendable buffer, Boolean b)
    {
        try
        {
            if (b == null)
            {
                appendNull(buffer);
                return;
            }
            buffer.append(b ? "true" : "false");
        }
        catch (IOException e)
        {
            throw new RuntimeException(e);
        }
    }

    @Deprecated
    public void appendNumber(StringBuffer buffer, Number number)
    {
        appendNumber((Appendable)buffer, number);
    }

    public void appendNumber(Appendable buffer, Number number)
    {
        try
        {
            if (number == null)
            {
                appendNull(buffer);
                return;
            }
            buffer.append(String.valueOf(number));
        }
        catch (IOException e)
        {
            throw new RuntimeException(e);
        }
    }

    @Deprecated
    public void appendString(StringBuffer buffer, String string)
    {
        appendString((Appendable)buffer, string);
    }

    public void appendString(Appendable buffer, String string)
    {
        if (string == null)
        {
            appendNull(buffer);
            return;
        }

        quotedEscape(buffer, string);
    }

    // Parsing utilities

    protected String toString(char[] buffer, int offset, int length)
    {
        return new String(buffer, offset, length);
    }

    protected Map<String, Object> newMap()
    {
        return new HashMap<String, Object>();
    }

    protected Object[] newArray(int size)
    {
        return new Object[size];
    }

    protected JSON contextForArray()
    {
        return this;
    }

    protected JSON contextFor(String field)
    {
        return this;
    }

    protected Object convertTo(Class type, Map map)
    {
        if (type != null && Convertible.class.isAssignableFrom(type))
        {
            try
            {
                Convertible conv = (Convertible)type.getDeclaredConstructor().newInstance();
                conv.fromJSON(map);
                return conv;
            }
            catch (Exception e)
            {
                throw new RuntimeException(e);
            }
        }

        Convertor convertor = getConvertor(type);
        if (convertor != null)
        {
            return convertor.fromJSON(map);
        }
        return map;
    }

    /**
     * Register a {@link Convertor} for a class or interface.
     *
     * @param forClass The class or interface that the convertor applies to
     * @param convertor the convertor
     */
    public void addConvertor(Class forClass, Convertor convertor)
    {
        _convertors.put(forClass.getName(), convertor);
    }

    /**
     * Lookup a convertor for a class.
     * <p>
     * If no match is found for the class, then the interfaces for the class are
     * tried. If still no match is found, then the super class and it's
     * interfaces are tried recursively.
     *
     * @param forClass The class
     * @return a {@link JSON.Convertor} or null if none were found.
     */
    protected Convertor getConvertor(Class forClass)
    {
        Class cls = forClass;
        Convertor convertor = _convertors.get(cls.getName());
        if (convertor == null && this != DEFAULT)
            convertor = DEFAULT.getConvertor(cls);

        while (convertor == null && cls != Object.class)
        {
            Class[] ifs = cls.getInterfaces();
            int i = 0;
            while (convertor == null && ifs != null && i < ifs.length)
            {
                convertor = _convertors.get(ifs[i++].getName());
            }
            if (convertor == null)
            {
                cls = cls.getSuperclass();
                convertor = _convertors.get(cls.getName());
            }
        }
        return convertor;
    }

    /**
     * Register a {@link JSON.Convertor} for a named class or interface.
     *
     * @param name name of a class or an interface that the convertor applies to
     * @param convertor the convertor
     */
    public void addConvertorFor(String name, Convertor convertor)
    {
        _convertors.put(name, convertor);
    }

    /**
     * Lookup a convertor for a named class.
     *
     * @param name name of the class
     * @return a {@link JSON.Convertor} or null if none were found.
     */
    public Convertor getConvertorFor(String name)
    {
        Convertor convertor = _convertors.get(name);
        if (convertor == null && this != DEFAULT)
            convertor = DEFAULT.getConvertorFor(name);
        return convertor;
    }

    public Object parse(Source source, boolean stripOuterComment)
    {
        int commentState = 0; // 0=no comment, 1="/", 2="/*", 3="/* *" -1="//"
        if (!stripOuterComment)
            return parse(source);

        int stripState = 1; // 0=no strip, 1=wait for /*, 2= wait for */

        Object o = null;
        while (source.hasNext())
        {
            char c = source.peek();

            // handle // or /* comment
            if (commentState == 1)
            {
                switch (c)
                {
                    case '/':
                        commentState = -1;
                        break;
                    case '*':
                        commentState = 2;
                        if (stripState == 1)
                        {
                            commentState = 0;
                            stripState = 2;
                        }
                }
            }
            // handle  comment
            else if (commentState > 1)
            {
                switch (c)
                {
                    case '*':
                        commentState = 3;
                        break;
                    case '/':
                        if (commentState == 3)
                        {
                            commentState = 0;
                            if (stripState == 2)
                                return o;
                        }
                        else
                            commentState = 2;
                        break;
                    default:
                        commentState = 2;
                }
            }
            // handle // comment
            else if (commentState < 0)
            {
                switch (c)
                {
                    case '\r':
                    case '\n':
                        commentState = 0;
                        break;
                    default:
                        break;
                }
            }
            // handle unknown
            else
            {
                if (!Character.isWhitespace(c))
                {
                    if (c == '/')
                        commentState = 1;
                    else if (c == '*')
                        commentState = 3;
                    else if (o == null)
                    {
                        o = parse(source);
                        continue;
                    }
                }
            }

            source.next();
        }

        return o;
    }

    public Object parse(Source source)
    {
        int commentState = 0; // 0=no comment, 1="/", 2="/*", 3="/* *" -1="//"

        while (source.hasNext())
        {
            char c = source.peek();

            // handle // or /* comment
            if (commentState == 1)
            {
                switch (c)
                {
                    case '/':
                        commentState = -1;
                        break;
                    case '*':
                        commentState = 2;
                }
            }
            // handle  comment
            else if (commentState > 1)
            {
                switch (c)
                {
                    case '*':
                        commentState = 3;
                        break;
                    case '/':
                        if (commentState == 3)
                            commentState = 0;
                        else
                            commentState = 2;
                        break;
                    default:
                        commentState = 2;
                }
            }
            // handle // comment
            else if (commentState < 0)
            {
                switch (c)
                {
                    case '\r':
                    case '\n':
                        commentState = 0;
                        break;
                    default:
                        break;
                }
            }
            // handle unknown
            else
            {
                switch (c)
                {
                    case '{':
                        return parseObject(source);
                    case '[':
                        return parseArray(source);
                    case '"':
                        return parseString(source);
                    case '-':
                        return parseNumber(source);

                    case 'n':
                        complete("null", source);
                        return null;
                    case 't':
                        complete("true", source);
                        return Boolean.TRUE;
                    case 'f':
                        complete("false", source);
                        return Boolean.FALSE;
                    case 'u':
                        complete("undefined", source);
                        return null;
                    case 'N':
                        complete("NaN", source);
                        return null;

                    case '/':
                        commentState = 1;
                        break;

                    default:
                        if (Character.isDigit(c))
                            return parseNumber(source);
                        else if (Character.isWhitespace(c))
                            break;
                        return handleUnknown(source, c);
                }
            }
            source.next();
        }

        return null;
    }

    protected Object handleUnknown(Source source, char c)
    {
        throw new IllegalStateException("unknown char '" + c + "'(" + (int)c + ") in " + source);
    }

    protected Object parseObject(Source source)
    {
        if (source.next() != '{')
            throw new IllegalStateException();
        Map<String, Object> map = newMap();

        char next = seekTo("\"}", source);

        while (source.hasNext())
        {
            if (next == '}')
            {
                source.next();
                break;
            }

            String name = parseString(source);
            seekTo(':', source);
            source.next();

            Object value = contextFor(name).parse(source);
            map.put(name, value);

            seekTo(",}", source);
            next = source.next();
            if (next == '}')
                break;
            else
                next = seekTo("\"}", source);
        }

        String xclassname = (String)map.get("x-class");
        if (xclassname != null)
        {
            Convertor c = getConvertorFor(xclassname);
            if (c != null)
                return c.fromJSON(map);
            LOG.warn("No Convertor for x-class '{}'", xclassname);
        }

        String classname = (String)map.get("class");
        if (classname != null)
        {
            try
            {
                Class c = Loader.loadClass(classname);
                return convertTo(c, map);
            }
            catch (ClassNotFoundException e)
            {
                LOG.warn("No Class for '{}'", classname);
            }
        }

        return map;
    }

    protected Object parseArray(Source source)
    {
        if (source.next() != '[')
            throw new IllegalStateException();

        int size = 0;
        ArrayList list = null;
        Object item = null;
        boolean coma = true;

        while (source.hasNext())
        {
            char c = source.peek();
            switch (c)
            {
                case ']':
                    source.next();
                    switch (size)
                    {
                        case 0:
                            return newArray(0);
                        case 1:
                            Object array = newArray(1);
                            Array.set(array, 0, item);
                            return array;
                        default:
                            return list.toArray(newArray(list.size()));
                    }

                case ',':
                    if (coma)
                        throw new IllegalStateException();
                    coma = true;
                    source.next();
                    break;

                default:
                    if (Character.isWhitespace(c))
                        source.next();
                    else
                    {
                        coma = false;
                        if (size++ == 0)
                            item = contextForArray().parse(source);
                        else if (list == null)
                        {
                            list = new ArrayList();
                            list.add(item);
                            item = contextForArray().parse(source);
                            list.add(item);
                            item = null;
                        }
                        else
                        {
                            item = contextForArray().parse(source);
                            list.add(item);
                            item = null;
                        }
                    }
            }
        }

        throw new IllegalStateException("unexpected end of array");
    }

    protected String parseString(Source source)
    {
        if (source.next() != '"')
            throw new IllegalStateException();

        boolean escape = false;

        StringBuilder b = null;
        final char[] scratch = source.scratchBuffer();

        if (scratch != null)
        {
            int i = 0;
            while (source.hasNext())
            {
                if (i >= scratch.length)
                {
                    // we have filled the scratch buffer, so we must
                    // use the StringBuffer for a large string
                    b = new StringBuilder(scratch.length * 2);
                    b.append(scratch, 0, i);
                    break;
                }

                char c = source.next();

                if (escape)
                {
                    escape = false;
                    switch (c)
                    {
                        case '"':
                            scratch[i++] = '"';
                            break;
                        case '\\':
                            scratch[i++] = '\\';
                            break;
                        case '/':
                            scratch[i++] = '/';
                            break;
                        case 'b':
                            scratch[i++] = '\b';
                            break;
                        case 'f':
                            scratch[i++] = '\f';
                            break;
                        case 'n':
                            scratch[i++] = '\n';
                            break;
                        case 'r':
                            scratch[i++] = '\r';
                            break;
                        case 't':
                            scratch[i++] = '\t';
                            break;
                        case 'u':
                            char uc = (char)((TypeUtil.convertHexDigit((byte)source.next()) << 12) + (TypeUtil.convertHexDigit((byte)source.next()) << 8) +
                                (TypeUtil.convertHexDigit((byte)source.next()) << 4) + (TypeUtil.convertHexDigit((byte)source.next())));
                            scratch[i++] = uc;
                            break;
                        default:
                            scratch[i++] = c;
                    }
                }
                else if (c == '\\')
                {
                    escape = true;
                }
                else if (c == '\"')
                {
                    // Return string that fits within scratch buffer
                    return toString(scratch, 0, i);
                }
                else
                {
                    scratch[i++] = c;
                }
            }

            // Missing end quote, but return string anyway ?
            if (b == null)
                return toString(scratch, 0, i);
        }
        else
            b = new StringBuilder(getStringBufferSize());

        // parse large string into string buffer
        final StringBuilder builder = b;
        while (source.hasNext())
        {
            char c = source.next();

            if (escape)
            {
                escape = false;
                switch (c)
                {
                    case '"':
                        builder.append('"');
                        break;
                    case '\\':
                        builder.append('\\');
                        break;
                    case '/':
                        builder.append('/');
                        break;
                    case 'b':
                        builder.append('\b');
                        break;
                    case 'f':
                        builder.append('\f');
                        break;
                    case 'n':
                        builder.append('\n');
                        break;
                    case 'r':
                        builder.append('\r');
                        break;
                    case 't':
                        builder.append('\t');
                        break;
                    case 'u':
                        char uc = (char)((TypeUtil.convertHexDigit((byte)source.next()) << 12) + (TypeUtil.convertHexDigit((byte)source.next()) << 8) +
                            (TypeUtil.convertHexDigit((byte)source.next()) << 4) + (TypeUtil.convertHexDigit((byte)source.next())));
                        builder.append(uc);
                        break;
                    default:
                        builder.append(c);
                }
            }
            else if (c == '\\')
            {
                escape = true;
            }
            else if (c == '\"')
            {
                break;
            }
            else
            {
                builder.append(c);
            }
        }
        return builder.toString();
    }

    public Number parseNumber(Source source)
    {
        boolean minus = false;
        long number = 0;
        StringBuilder buffer = null;

        longLoop:
        while (source.hasNext())
        {
            char c = source.peek();
            switch (c)
            {
                case '0':
                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                    number = number * 10 + (c - '0');
                    source.next();
                    break;

                case '-':
                case '+':
                    if (number != 0)
                        throw new IllegalStateException("bad number");
                    minus = true;
                    source.next();
                    break;

                case '.':
                case 'e':
                case 'E':
                    buffer = new StringBuilder(16);
                    if (minus)
                        buffer.append('-');
                    buffer.append(number);
                    buffer.append(c);
                    source.next();
                    break longLoop;

                default:
                    break longLoop;
            }
        }

        if (buffer == null)
            return minus ? -1 * number : number;

        doubleLoop:
        while (source.hasNext())
        {
            char c = source.peek();
            switch (c)
            {
                case '0':
                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                case '-':
                case '.':
                case '+':
                case 'e':
                case 'E':
                    buffer.append(c);
                    source.next();
                    break;

                default:
                    break doubleLoop;
            }
        }
        return new Double(buffer.toString());
    }

    protected void seekTo(char seek, Source source)
    {
        while (source.hasNext())
        {
            char c = source.peek();
            if (c == seek)
                return;

            if (!Character.isWhitespace(c))
                throw new IllegalStateException("Unexpected '" + c + " while seeking '" + seek + "'");
            source.next();
        }

        throw new IllegalStateException("Expected '" + seek + "'");
    }

    protected char seekTo(String seek, Source source)
    {
        while (source.hasNext())
        {
            char c = source.peek();
            if (seek.indexOf(c) >= 0)
            {
                return c;
            }

            if (!Character.isWhitespace(c))
                throw new IllegalStateException("Unexpected '" + c + "' while seeking one of '" + seek + "'");
            source.next();
        }

        throw new IllegalStateException("Expected one of '" + seek + "'");
    }

    protected static void complete(String seek, Source source)
    {
        int i = 0;
        while (source.hasNext() && i < seek.length())
        {
            char c = source.next();
            if (c != seek.charAt(i++))
                throw new IllegalStateException("Unexpected '" + c + " while seeking  \"" + seek + "\"");
        }

        if (i < seek.length())
            throw new IllegalStateException("Expected \"" + seek + "\"");
    }

    private final class ConvertableOutput implements Output
    {
        private final Appendable _buffer;
        char c = '{';

        private ConvertableOutput(Appendable buffer)
        {
            _buffer = buffer;
        }

        public void complete()
        {
            try
            {
                if (c == '{')
                    _buffer.append("{}");
                else if (c != 0)
                    _buffer.append("}");
            }
            catch (IOException e)
            {
                throw new RuntimeException(e);
            }
        }

        @Override
        public void add(Object obj)
        {
            if (c == 0)
                throw new IllegalStateException();
            append(_buffer, obj);
            c = 0;
        }

        @Override
        public void addClass(Class type)
        {
            try
            {
                if (c == 0)
                    throw new IllegalStateException();
                _buffer.append(c);
                _buffer.append("\"class\":");
                append(_buffer, type.getName());
                c = ',';
            }
            catch (IOException e)
            {
                throw new RuntimeException(e);
            }
        }

        @Override
        public void add(String name, Object value)
        {
            try
            {
                if (c == 0)
                    throw new IllegalStateException();
                _buffer.append(c);
                quotedEscape(_buffer, name);
                _buffer.append(':');
                append(_buffer, value);
                c = ',';
            }
            catch (IOException e)
            {
                throw new RuntimeException(e);
            }
        }

        @Override
        public void add(String name, double value)
        {
            try
            {
                if (c == 0)
                    throw new IllegalStateException();
                _buffer.append(c);
                quotedEscape(_buffer, name);
                _buffer.append(':');
                appendNumber(_buffer, value);
                c = ',';
            }
            catch (IOException e)
            {
                throw new RuntimeException(e);
            }
        }

        @Override
        public void add(String name, long value)
        {
            try
            {
                if (c == 0)
                    throw new IllegalStateException();
                _buffer.append(c);
                quotedEscape(_buffer, name);
                _buffer.append(':');
                appendNumber(_buffer, value);
                c = ',';
            }
            catch (IOException e)
            {
                throw new RuntimeException(e);
            }
        }

        @Override
        public void add(String name, boolean value)
        {
            try
            {
                if (c == 0)
                    throw new IllegalStateException();
                _buffer.append(c);
                quotedEscape(_buffer, name);
                _buffer.append(':');
                appendBoolean(_buffer, value ? Boolean.TRUE : Boolean.FALSE);
                c = ',';
            }
            catch (IOException e)
            {
                throw new RuntimeException(e);
            }
        }
    }

    public interface Source
    {
        boolean hasNext();

        char next();

        char peek();

        char[] scratchBuffer();
    }

    public static class StringSource implements Source
    {
        private final String string;
        private int index;
        private char[] scratch;

        public StringSource(String s)
        {
            string = s;
        }

        @Override
        public boolean hasNext()
        {
            if (index < string.length())
                return true;
            scratch = null;
            return false;
        }

        @Override
        public char next()
        {
            return string.charAt(index++);
        }

        @Override
        public char peek()
        {
            return string.charAt(index);
        }

        @Override
        public String toString()
        {
            return string.substring(0, index) + "|||" + string.substring(index);
        }

        @Override
        public char[] scratchBuffer()
        {
            if (scratch == null)
                scratch = new char[string.length()];
            return scratch;
        }
    }

    public static class ReaderSource implements Source
    {
        private Reader _reader;
        private int _next = -1;
        private char[] scratch;

        public ReaderSource(Reader r)
        {
            _reader = r;
        }

        public void setReader(Reader reader)
        {
            _reader = reader;
            _next = -1;
        }

        @Override
        public boolean hasNext()
        {
            getNext();
            if (_next < 0)
            {
                scratch = null;
                return false;
            }
            return true;
        }

        @Override
        public char next()
        {
            getNext();
            char c = (char)_next;
            _next = -1;
            return c;
        }

        @Override
        public char peek()
        {
            getNext();
            return (char)_next;
        }

        private void getNext()
        {
            if (_next < 0)
            {
                try
                {
                    _next = _reader.read();
                }
                catch (IOException e)
                {
                    throw new RuntimeException(e);
                }
            }
        }

        @Override
        public char[] scratchBuffer()
        {
            if (scratch == null)
                scratch = new char[1024];
            return scratch;
        }
    }

    /**
     * JSON Output class for use by {@link Convertible}.
     */
    public interface Output
    {
        void addClass(Class c);

        void add(Object obj);

        void add(String name, Object value);

        void add(String name, double value);

        void add(String name, long value);

        void add(String name, boolean value);
    }

    /**
     * JSON Convertible object. Object can implement this interface in a similar
     * way to the {@link Externalizable} interface is used to allow classes to
     * provide their own serialization mechanism.
     * <p>
     * A JSON.Convertible object may be written to a JSONObject or initialized
     * from a Map of field names to values.
     * <p>
     * If the JSON is to be convertible back to an Object, then the method
     * {@link Output#addClass(Class)} must be called from within toJSON()
     */
    public interface Convertible
    {
        void toJSON(Output out);

        void fromJSON(Map object);
    }

    /**
     * Static JSON Convertor.
     * <p>
     * may be implemented to provide static convertors for objects that may be
     * registered with
     * {@link JSON#registerConvertor(Class, org.eclipse.jetty.util.ajax.JSON.Convertor)}
     * . These convertors are looked up by class, interface and super class by
     * {@link JSON#getConvertor(Class)}. Convertors should be used when the
     * classes to be converted cannot implement {@link Convertible} or
     * {@link Generator}.
     */
    public interface Convertor
    {
        void toJSON(Object obj, Output out);

        Object fromJSON(Map object);
    }

    /**
     * JSON Generator. A class that can add it's JSON representation directly to
     * a StringBuffer. This is useful for object instances that are frequently
     * converted and wish to avoid multiple Conversions
     */
    public interface Generator
    {
        void addJSON(Appendable buffer);
    }

    /**
     * A Literal JSON generator A utility instance of {@link JSON.Generator}
     * that holds a pre-generated string on JSON text.
     */
    public static class Literal implements Generator
    {
        private String _json;

        /**
         * Construct a literal JSON instance for use by
         * {@link JSON#toString(Object)}. If {@link Logger#isDebugEnabled()} is
         * true, the JSON will be parsed to check validity
         *
         * @param json A literal JSON string.
         */
        public Literal(String json)
        {
            if (LOG.isDebugEnabled()) // TODO: Make this a configurable option on JSON instead!
                parse(json);
            _json = json;
        }

        @Override
        public String toString()
        {
            return _json;
        }

        @Override
        public void addJSON(Appendable buffer)
        {
            try
            {
                buffer.append(_json);
            }
            catch (IOException e)
            {
                throw new RuntimeException(e);
            }
        }
    }
}
