/* $Id$ */

/*
 * 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 _MTXEXPRESSION_H
#define _MTXEXPRESSION_H

#include <string>
#include <vector>

#include "mtx.h"
#include "mtxvalue.h"
#include "mtxsymbol.h"
#include "mtxlanguage.h"

#define MTXEXPRESSION_OPERATOR_NULL \
  {NULL, MTXEXPRESSION_FUNCTION_NULL, MTXEXPRESSION_ASSOCIATIVITY_NULL}

/**
 * \enum mtx_function_id
 * \brief ID of a function/operator. E.g. assignment, addition.
 */
enum mtx_function_id
{
  MTXEXPRESSION_FUNCTION_NULL,
  MTXEXPRESSION_FUNCTION_ASSIGNMENT,
  MTXEXPRESSION_FUNCTION_ADDITION,
  MTXEXPRESSION_FUNCTION_ADD_ASSIGN,
  MTXEXPRESSION_FUNCTION_SUBTRACTION,
  MTXEXPRESSION_FUNCTION_SUBTRACT_ASSIGN,
  MTXEXPRESSION_FUNCTION_MULTIPLY,
  MTXEXPRESSION_FUNCTION_MULTIPLY_ASSIGN,
  MTXEXPRESSION_FUNCTION_DIVIDE,
  MTXEXPRESSION_FUNCTION_DIVIDE_ASSIGN,
  MTXEXPRESSION_FUNCTION_DETERMINANT,
  MTXEXPRESSION_FUNCTION_INVERSE,
  MTXEXPRESSION_FUNCTION_TRANSPOSE,
  MTXEXPRESSION_FUNCTION_AUGMENT,
  MTXEXPRESSION_FUNCTION_LUDECOMPOSITION
};

/**
 * \enum mtx_operator_associativity
 * \brief Associativity of an operator.
 */
enum mtx_operator_associativity
{
  MTXEXPRESSION_ASSOCIATIVITY_NULL,
  MTXEXPRESSION_RIGHT_TO_LEFT,
  MTXEXPRESSION_LEFT_TO_RIGHT
};

/**
 * A function.
 */
struct mtx_function
{
  /**
   * Function string as entered by the user.
   */
  const char *str;

  /**
   * ID of the function.
   */
  enum mtx_function_id id;

  /**
   * Number of arguments.
   */
  size_t argc;
};

/**
 * An operator.
 * 
 * XXX Inheritence from struct mtx_function seems to cause trouble. Why ?
 */
struct mtx_operator
{
  /**
   * Operator string as entered by the user.
   */
  const char *str;

  /**
   * ID of the operator.
   */
  enum mtx_function_id id;

  /**
   * Associativity of the operator.
   */
  enum mtx_operator_associativity associativity;
};

/**
 * An expression.
 * 
 * All language expressions that are not atomic symbols (e.g. "a" or "2")
 * are expressions which consist of a function/operator and one or more
 * arguments. These arguments are in turn MtxExpression or MtxSymbol
 * objects. MtxExpression objects are always nodes in the tree of symbols,
 * whereas MtxSymbol objects are always leaves.
 */
class MtxExpression: public MtxSymbol
{
  private:
    /**
     * Function/operator compiled in this expression.
     */
    enum mtx_function_id function;

    /**
     * Vector of arguments.
     */
    std::vector<MtxSymbol *> expressions;

    /**
     * True if silent.
     * 
     * A silent expression is an expression ended with the ';' character.
     * Engine users should not display silent expressions. This property
     * is propagated to underlying expressions and symbols.
     * 
     * @see isSilent()
     */
    bool silent;

    /**
     * Find an operator in the vector of lexical elements.
     * 
     * This method uses the \a operators array to look for operators by
     * order of precedence.
     * 
     * @param lexical_elements vector of strings in which to look for an
     *                         operator
     * @param str operator string as entered by the user to look for
     * @see operators
     * @see rfindOperator()
     */
    mtx_expression_t::iterator
    findOperator(mtx_expression_t &lexical_elements, const char *str);

    /**
     * Find an operator in the vector of lexical elements in reverse order.
     * 
     * @see findOperator().
     */
    mtx_expression_t::reverse_iterator
    rfindOperator(mtx_expression_t &lexical_elements, const char *str);

    /**
     * Free the pointers stored in the given vector of symbols.
     * 
     * Mainly used after parsing a matrix or function arguments is done or
     * failed.
     */
    void freeSymbols(std::vector<MtxSymbol *> &symbols) const;

    /**
     * Parse the given lexical elements and extract symbols and expressions
     * from it to create the list of elements that will be used to create a
     * matrix. An exception is thrown if the syntax doesn't comply with
     * the matrix creation syntax.
     * 
     * @param lexical_elements vector of strings to parse
     * @param symbols vector of symbols/expressions updated by this method
     * @param rows number of rows found
     * @param columns number of columns found
     */
    void parseMatrix(const mtx_expression_t &lexical_elements,
                     std::vector<MtxSymbol *> &symbols,
                     size_t &rows, size_t &columns) const;

    /**
     * Parse the given lexical elements and extract symbols and expressions
     * from it to create the list of arguments of a function. An exception is
     * thrown if the syntax is invalid.
     * 
     * @param lexical_elements vector of strings to parse
     * @param symbols vector of symbols/expressions updated by this method
     */
    void parseArguments(const mtx_expression_t &lexical_elements,
                        std::vector<MtxSymbol *> &symbols) const;

    /**
     * Array of builtin functions.
     */
    static struct mtx_function functions[];

    /**
     * Multidimensional array of supported operators.
     * 
     * Each line of the array indicates a level of precedence. Lines must
     * be ordered in reverse order of precedence, e.g. = has low precedence,
     * so it is placed in first line. Operators of same precedence must have
     * the same associativity (this is never checked).
     * 
     * XXX There are at most 5 operators for the same precedence (+ a null
     * entry to indicate end of list), so the second dimension is 6.
     * 
     * @see isOperator()
     */
    static struct mtx_operator operators[][6];

    /**
     * Return true if the given string matches an operator.
     * 
     * @see operators()
     */
    static bool isOperator(const std::string &str);

    /**
     * Return true if the given string is a valid variable name.
     * 
     * A valid variable name consist of [a-zA-Z0-9_] characters only,
     * and cannot begin with a digit.
     */
    static bool isVariableName(const std::string &str);

  public:
    /**
     * Create an expression from a set of lexical elements.
     * 
     * @param language address of the MtxLanguage object used to get/set
     *                 variables
     * @param lexical_elements vector of lexical elements
     * @param silent see silent
     * @see silent
     */
    MtxExpression(MtxLanguage *language, mtx_expression_t &lexical_elements,
                  bool silent = false);

    virtual ~MtxExpression();
    virtual MtxSymbol getSymbol(bool create = false,
                                bool fail_if_special = true) const;
    virtual std::string getName() const;
    virtual MtxValue * getValue() const;
    virtual std::string toString() const;

    /**
     * Return the silent member.
     * 
     * As MtxExpression objects are always nodes, and there is always a node
     * on top of a leaf, it is not necessary to propagate the silent property
     * to underlying objects. When the engine calls isSilent(), it always get
     * a return value from the first node it is calling the function on.
     * That's why MtxSymbol objects don't have a silent property.
     */
    virtual bool isSilent() const;
};

#endif /* _MTXEXPRESSION_H */