/* $Id$ */

/*
 * Copyright (C) 2006 Richard Braun
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifndef _MTXLANGUAGE_H
#define _MTXLANGUAGE_H

#include <string>
#include <vector>

#include "mtx.h"
#include "mtxsymbol.h"

/**
 * \def MTXLANGUAGE_VALUES_INDEX
 * \brief Index of the lexical group of values in lexical groups array.
 */
#define MTXLANGUAGE_VALUES_INDEX 0

/**
 * \def MTXLANGUAGE_OPERATORS_INDEX
 * \brief Index of the lexical group of operators in lexical groups array.
 */
#define MTXLANGUAGE_OPERATORS_INDEX 1

/**
 * \def MTXLANGUAGE_OPERATORS_MAX_LENGTH
 * \brief Maximum length of the string representation of an operator.
 */
#define MTXLANGUAGE_OPERATORS_MAX_LENGTH 2

/**
 * \def MTXLANGUAGE_ANS_VARIABLE
 * \brief name of the automatic variable \a ans
 */
#define MTXLANGUAGE_ANS_VARIABLE "ans"

/**
 * Main language object used as interface between user and engine.
 */
class MtxLanguage
{
  private:
    /**
     * Vector of known variables.
     * 
     * @see getSymbols()
     */
    std::vector<MtxSymbol> symbols;

    /**
     * Return the lexical group of the given character.
     * 
     * Throw an exception if the character isn't registered.
     */
    size_t findGroup(char c) const;

    /**
     * Check a lexical element.
     * 
     * Throw an exception if the lexical element is invalid.
     */
    void checkLexicalElement(const std::string &lexical_element) const;

    /**
     * Lexical analysis.
     * 
     * Return a vector of the lexical elements of the given expression. An
     * exception is thrown if an invalid character is present.
     */
    mtx_expression_t parseLexicalElements(const std::string &expression) const;

    /**
     * Compile a set of lexical elements into expressions.
     * 
     * Parse the given lexical elements and compile them in a vector of
     * expressions. An MtxException exception is thrown if an error occurs.
     */
    std::vector<MtxSymbol *>
    parseExpressions(const mtx_expression_t &lexical_elements);

    /**
     * Release the memory referenced by the pointers in the given vector.
     */
    void freeExpressions(std::vector<MtxSymbol *> &expressions);

    /**
     * Array of groups of lexical elements. E.g. + and = are in the same
     * group.
     */
    static const char *lexical_groups[];

  public:
    /**
     * Default constructor.
     */
    MtxLanguage();

    /**
     * Parse the given expression into a set of results.
     * 
     * This is the main interface between the user and the engine.
     * The caller should catch MtxException exceptions.
     */
    std::vector<MtxSymbol> parse(const std::string &expression);

    /**
     * Set a named variable.
     */
    void setSymbol(const MtxSymbol &symbol);

    /**
     * Get a variable from its name.
     */
    MtxSymbol getSymbol(const std::string &name) const;

    /**
     * Return a copy of the vector of symbols.
     * 
     * Mainly used to list all registered variables.
     * 
     * @see symbols.
     */
    std::vector<MtxSymbol> getSymbols() const;
};

#endif /* _MTXLANGUAGE_H */