/*
 * (c) 2003 Mario de Sousa
 *
 * Offered to the public 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.
 *
 * This code is made available on the understanding that it will not be
 * used in safety-critical situations without a full and competent review.
 */

/*
 * An IEC 61131-3 IL and ST compiler.
 *
 * Based on the
 * FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10)
 *
 */


/* Decomposes a variable instance name into its constituents,
 * example:
 *    window.points[1].coordinate.x
 *
 *  will succesfully return
 *        - window
 *        - points
 *        - coordinate
 *        - x
 * on succesive calls to decompose_var_instance_name_c::next_part()
 */
class decompose_var_instance_name_c: null_visitor_c {

  private:
    symbol_c *variable_name;
    symbol_c *next_variable_name;
    symbol_c *current_recursive_variable_name;
    symbol_c *previously_returned_variable_name;

  public:
    decompose_var_instance_name_c(symbol_c *variable_instance_name) {
      variable_name = variable_instance_name;
      next_variable_name = NULL;
      current_recursive_variable_name = NULL;
      previously_returned_variable_name = NULL;
    }

  public:
    symbol_c *next_part(void) {
      /* We must always start from the top!
       * See note in the structured_variable_c visitor
       * to understand why...
       */
      symbol_c *res = (symbol_c *)variable_name->accept(*this);
      next_variable_name = current_recursive_variable_name;

      if (previously_returned_variable_name == res)
        return NULL;
      previously_returned_variable_name = res;
      return res;
    }

  public:
/*********************/
/* B 1.4 - Variables */
/*********************/
    void *visit(symbolic_variable_c *symbol) {return (void *)(symbol->var_name);}

/********************************************/
/* B.1.4.1   Directly Represented Variables */
/********************************************/
    void *visit(direct_variable_c *symbol) {return (void *)symbol;}

/*************************************/
/* B.1.4.2   Multi-element Variables */
/*************************************/
/*  subscripted_variable '[' subscript_list ']' */
// SYM_REF2(array_variable_c, subscripted_variable, subscript_list)
    void *visit(array_variable_c *symbol) {
      /* NOTE: the subscripted_variable may itself be a structure!,
       * so we must recursevily visit!
       */
      return symbol->subscripted_variable->accept(*this);
    }

/*  record_variable '.' field_selector */
/*  WARNING: input and/or output variables of function blocks
 *           may be accessed as fields of a tructured variable!
 *           Code handling a structured_variable_c must take
 *           this into account!
 */
//SYM_REF2(structured_variable_c, record_variable, field_selector)
    void *visit(structured_variable_c *symbol) {
      /* NOTE: The following code will not work, as structured_variable_c
       *       are grouped on the left, and not on the right!
       *
       *       example: window.origin.x
       *       will result in
       *       s1 = structured_variable_c("window, "origin");
       *       s2 = structured_variable_c(s1, "x");
       *       AND NOT
       *       s1 = structured_variable_c("origin", "x");
       *       s2 = structured_variable_c("window", s1);
       *
       *       as the following code assumes!!
       *
      current_variable_name = symbol->field_selector;
      return symbol->record_variable->accept(*this);
       */

      /* The correct code, is therefore more complex... */
      if (next_variable_name == symbol) {
        /* NOTE: field_selector is always an identifier_c,
	 * so we do not have to recursevily visit it again...
	 * return (void *)symbol->field_selector->accept(*this);  -> NOT REQUIRED!!
	 */
	return (void *)symbol->field_selector;
      }

      current_recursive_variable_name = symbol;
      return symbol->record_variable->accept(*this);
    }
};