/**
 * \file json.h
 * 
 * \author Eeli Reilin <eeli@nilier.org>,
 *         Mikko Ahonen <mikko.j.ahonen@jyu.fi>
 * \version 0.1
 * \date 8/25/2010
 */

#ifndef JSON_H
#define JSON_H

#include <QVariant>
#include <QString>

/**
 * \enum JsonToken
 */
enum JsonToken
{
    JsonTokenNone = 0,
    JsonTokenCurlyOpen = 1,
    JsonTokenCurlyClose = 2,
    JsonTokenSquaredOpen = 3,
    JsonTokenSquaredClose = 4,
    JsonTokenColon = 5,
    JsonTokenComma = 6,
    JsonTokenString = 7,
    JsonTokenNumber = 8,
    JsonTokenTrue = 9,
    JsonTokenFalse = 10,
    JsonTokenNull = 11
};

/**
 * \class Json
 * \brief A JSON data parser
 *
 * Json parses a JSON data into a QVariant hierarchy.
 */
class Json
{
    public:
        /**
         * Parse a JSON string
         *
         * \param json The JSON data
         */
        static QVariant parse(const QString &json);

        /**
         * Parse a JSON string
         *
         * \param json The JSON data
         * \param success The success of the parsing
         */
        static QVariant parse(const QString &json, bool &success);

    private:
        /**
         * Parses a value starting from index
         *
         * \param json The JSON data
         * \param index The start index
         * \param success The success of the parse process
         *
         * \return QVariant The parsed value
         */
        static QVariant parseValue(const QString &json, int &index,
                                   bool &success);

        /**
         * Parses an object starting from index
         *
         * \param json The JSON data
         * \param index The start index
         * \param success The success of the object parse
         *
         * \return QVariant The parsed object map
         */
        static QVariant parseObject(const QString &json, int &index,
                                       bool &success);

        /**
         * Parses an array starting from index
         *
         * \param json The JSON data
         * \param index The starting index
         * \param success The success of the array parse
         *
         * \return QVariant The parsed variant array
         */
        static QVariant parseArray(const QString &json, int &index,
                                       bool &success);

        /**
         * Parses a string starting from index
         *
         * \param json The JSON data
         * \param index The starting index
         * \param success The success of the string parse
         *
         * \return QVariant The parsed string
         */
        static QVariant parseString(const QString &json, int &index,
                                    bool &success);

        /**
         * Parses a number starting from index
         *
         * \param json The JSON data
         * \param index The starting index
         *
         * \return QVariant The parsed number
         */
        static QVariant parseNumber(const QString &json, int &index);

        /**
         * Get the last index of a number starting from index
         *
         * \param json The JSON data
         * \param index The starting index
         *
         * \return The last index of the number
         */
        static int lastIndexOfNumber(const QString &json, int index);

        /**
         * Skip unwanted whitespace symbols starting from index
         *
         * \param json The JSON data
         * \param index The start index
         */
        static void eatWhitespace(const QString &json, int &index);

        /**
         * Check what token lies ahead
         *
         * \param json The JSON data
         * \param index The starting index
         *
         * \return int The upcoming token
         */
        static int lookAhead(const QString &json, int index);

        /**
         * Get the next JSON token
         *
         * \param json The JSON data
         * \param index The starting index
         *
         * \return int The next JSON token
         */
        static int nextToken(const QString &json, int &index);
};

#endif //JSON_H

/**
 * \file json.h
 * 
 * \author Eeli Reilin <eeli@nilier.org>,
 *         Mikko Ahonen <mikko.j.ahonen@jyu.fi>
 * \version 0.1
 * \date 8/25/2010
 */

#include <QDebug>
 
#include "json.h"

/**
 * parse
 */
QVariant Json::parse(const QString &json)
{
    bool success = true;
    return Json::parse(json, success);
}

/**
 * parse
 */
QVariant Json::parse(const QString &json, bool &success)
{
    success = true;

    //Return an empty QVariant if the JSON data is either null or empty
    if(!json.isNull() || !json.isEmpty())
    {
        QString data = json;
        //We'll start from index 0
        int index = 0;

        //Parse the first value
        QVariant value = Json::parseValue(data, index, success);

        //Return the parsed value
        return value;
    }
    else
    {
        //Return the empty QVariant
        return QVariant();
    }
}

/**
 * parseValue
 */
QVariant Json::parseValue(const QString &json, int &index, bool &success)
{
    //Determine what kind of data we should parse by
    //checking out the upcoming token
    switch(Json::lookAhead(json, index))
    {
        case JsonTokenString:
            return Json::parseString(json, index, success);
        case JsonTokenNumber:
            return Json::parseNumber(json, index);
        case JsonTokenCurlyOpen:
            return Json::parseObject(json, index, success);
        case JsonTokenSquaredOpen:
            return Json::parseArray(json, index, success);
        case JsonTokenTrue:
            Json::nextToken(json, index);
            return QVariant(true);
        case JsonTokenFalse:
            Json::nextToken(json, index);
            return QVariant(false);
        case JsonTokenNull:
            Json::nextToken(json, index);
            return QVariant();
        case JsonTokenNone:
            break;
    }

    //If there were no tokens, flag the failure and return an empty QVariant
    success = false;
    return QVariant();
}

/**
 * parseObject
 */
QVariant Json::parseObject(const QString &json, int &index, bool &success)
{
    QVariantMap map;
    int token;

    //Get rid of the whitespace and increment index
    Json::nextToken(json, index);

    //Loop through all of the key/value pairs of the object
    bool done = false;
    while(!done)
    {
        //Get the upcoming token
        token = Json::lookAhead(json, index);

        if(token == JsonTokenNone)
        {
             success = false;
             return QVariantMap();
        }
        else if(token == JsonTokenComma)
        {
            Json::nextToken(json, index);
        }
        else if(token == JsonTokenCurlyClose)
        {
            Json::nextToken(json, index);
            return map;
        }
        else
        {
            //Parse the key/value pair's name
            QString name = Json::parseString(json, index, success).toString();

            if(!success)
            {
                return QVariantMap();
            }

            //Get the next token
            token = Json::nextToken(json, index);

            //If the next token is not a colon, flag the failure
            //return an empty QVariant
            if(token != JsonTokenColon)
            {
                success = false;
                return QVariant(QVariantMap());
            }

            //Parse the key/value pair's value
            QVariant value = Json::parseValue(json, index, success);

            if(!success)
            {
                return QVariantMap();
            }

            //Assign the value to the key in the map
            map[name] = value;
        }
    }

    //Return the map successfully
    return QVariant(map);
}

/**
 * parseArray
 */
QVariant Json::parseArray(const QString &json, int &index, bool &success)
{
    QVariantList list;

    Json::nextToken(json, index);

    bool done = false;
    while(!done)
    {
        int token = Json::lookAhead(json, index);

                if(token == JsonTokenNone)
        {
            success = false;
            return QVariantList();
        }
        else if(token == JsonTokenComma)
        {
            Json::nextToken(json, index);
        }
        else if(token == JsonTokenSquaredClose)
        {
            Json::nextToken(json, index);
            break;
        }
        else
        {
            QVariant value = Json::parseValue(json, index, success);

            if(!success)
            {
                return QVariantList();
            }

            list.push_back(value);
                          }
            }

    return QVariant(list);
}

/**
 * parseString
 */
QVariant Json::parseString(const QString &json, int &index, bool &success)
{
    QString s;
    QChar c;

    Json::eatWhitespace(json, index);

    c = json[index++];

    bool complete = false;
    while(!complete)
    {
        if(index == json.size())
        {
            break;
        }

        c = json[index++];

        if(c == '\"')
        {
            complete = true;
            break;
        }
        else if(c == '\\')
        {
            if(index == json.size())
            {
                break;
            }

            c = json[index++];

            if(c == '\"')
            {
                s.append('\"');
            }
            else if(c == '\\')
            {
                s.append('\\');
            }
            else if(c == '/')
            {
                s.append('/');
            }
            else if(c == 'b')
            {
                s.append('\b');
            }
            else if(c == 'f')
            {
                s.append('\f');
            }
            else if(c == 'n')
            {
                s.append('\n');
            }
            else if(c == 'r')
            {
                s.append('\r');
            }
            else if(c == 't')
            {
                s.append('\t');
            }
            else if(c == 'u')
            {
                int remainingLength = json.size() - index;

                if(remainingLength >= 4)
                {
                    QString unicodeStr = json.mid(index, 4);

                    int symbol = unicodeStr.toInt(0, 16);
                    
                    s.append(QChar(symbol));

                    index += 4;
                }
                else
                {
                    break;
                }
            }
        }
        else
        {
            s.append(c);
        }
    }

    if(!complete)
    {
        success = false;
        return QVariant();
    }

    return QVariant(s);
}

/**
 * parseNumber
 */
QVariant Json::parseNumber(const QString &json, int &index)
{
    Json::eatWhitespace(json, index);

    int lastIndex = Json::lastIndexOfNumber(json, index);
    int charLength = (lastIndex - index) + 1;
    QString numberStr;

    numberStr = json.mid(index, charLength);
    
    index = lastIndex + 1;

    return QVariant(numberStr);
}

/**
 * lastIndexOfNumber
 */
int Json::lastIndexOfNumber(const QString &json, int index)
{
    int lastIndex;

    for(lastIndex = index; lastIndex < json.size(); lastIndex++)
    {
        if(QString("0123456789+-.eE").indexOf(json[lastIndex]) == -1)
        {
            break;
        }
    }

    return lastIndex -1;
}

/**
 * eatWhitespace
 */
void Json::eatWhitespace(const QString &json, int &index)
{
    for(; index < json.size(); index++)
    {
        if(QString(" \t\n\r").indexOf(json[index]) == -1)
        {
            break;
        }
    }
}

/**
 * lookAhead
 */
int Json::lookAhead(const QString &json, int index)
{
    int saveIndex = index;
    return Json::nextToken(json, saveIndex);
}

/**
 * nextToken
 */
int Json::nextToken(const QString &json, int &index)
{
    Json::eatWhitespace(json, index);

    if(index == json.size())
    {
        return JsonTokenNone;
    }

    QChar c = json[index];
    index++;
    switch(c.toAscii())
    {
        case '{': return JsonTokenCurlyOpen;
        case '}': return JsonTokenCurlyClose;
        case '[': return JsonTokenSquaredOpen;
        case ']': return JsonTokenSquaredClose;
        case ',': return JsonTokenComma;
        case '"': return JsonTokenString;
        case '0': case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9':
        case '-': return JsonTokenNumber;
        case ':': return JsonTokenColon;
    }

    index--;

    int remainingLength = json.size() - index;

    //True
    if(remainingLength >= 4)
    {
        if (json[index] == 't' && json[index + 1] == 'r' &&
            json[index + 2] == 'u' && json[index + 3] == 'e')
        {
            index += 4;
            return JsonTokenTrue;
        }
    }

    //False
    if (remainingLength >= 5)
    {
        if (json[index] == 'f' && json[index + 1] == 'a' &&
            json[index + 2] == 'l' && json[index + 3] == 's' &&
            json[index + 4] == 'e')
        {
            index += 5;
            return JsonTokenFalse;
        }
    }

    //Null
    if (remainingLength >= 4)
    {
        if (json[index] == 'n' && json[index + 1] == 'u' &&
            json[index + 2] == 'l' && json[index + 3] == 'l')
        {
            index += 4;
            return JsonTokenNull;
        }
    }

    return JsonTokenNone;
}