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/*

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 * (c) 2003 Mario de Sousa

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 *

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 * Offered to the public under the terms of the GNU General Public License

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 * as published by the Free Software Foundation; either version 2 of the

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 * License, or (at your option) any later version.

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 *

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 * This program is distributed in the hope that it will be useful, but

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 * WITHOUT ANY WARRANTY; without even the implied warranty of

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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General

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 * Public License for more details.

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 *

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 * This code is made available on the understanding that it will not be

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 * used in safety-critical situations without a full and competent review.

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 */

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/*

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 * An IEC 61131-3 IL and ST compiler.

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 *

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 * Based on the

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 * FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10)

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 *

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 */

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/* Decomposes a variable instance name into its constituents,

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 * example:

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 *    window.points[1].coordinate.x

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 *

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 *  will succesfully return

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 *        - window

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 *        - points

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 *        - coordinate

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 *        - x

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 * on succesive calls to decompose_var_instance_name_c::next_part()

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 */

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class decompose_var_instance_name_c: null_visitor_c {

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  private:

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    symbol_c *variable_name;

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    symbol_c *next_variable_name;

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    symbol_c *current_recursive_variable_name;

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    symbol_c *previously_returned_variable_name;

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  public:

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    decompose_var_instance_name_c(symbol_c *variable_instance_name) {

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      variable_name = variable_instance_name;

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      next_variable_name = NULL;

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      current_recursive_variable_name = NULL;

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      previously_returned_variable_name = NULL;

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    }

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  public:

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    symbol_c *next_part(void) {

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      /* We must always start from the top!

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       * See note in the structured_variable_c visitor

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       * to understand why...

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       */

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      symbol_c *res = (symbol_c *)variable_name->accept(*this);

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      next_variable_name = current_recursive_variable_name;

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      if (previously_returned_variable_name == res)

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        return NULL;

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      previously_returned_variable_name = res;

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      return res;

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    }

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  public:

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/*********************/

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/* B 1.4 - Variables */

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/*********************/

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    void *visit(symbolic_variable_c *symbol) {return (void *)(symbol->var_name);}

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/********************************************/

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/* B.1.4.1   Directly Represented Variables */

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/********************************************/

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    void *visit(direct_variable_c *symbol) {return (void *)symbol;}

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/*************************************/

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/* B.1.4.2   Multi-element Variables */

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/*************************************/

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/*  subscripted_variable '[' subscript_list ']' */

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// SYM_REF2(array_variable_c, subscripted_variable, subscript_list)

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    void *visit(array_variable_c *symbol) {

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      /* NOTE: the subscripted_variable may itself be a structure!,

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       * so we must recursevily visit!

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       */

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      return symbol->subscripted_variable->accept(*this);

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    }

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/*  record_variable '.' field_selector */

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/*  WARNING: input and/or output variables of function blocks

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 *           may be accessed as fields of a tructured variable!

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 *           Code handling a structured_variable_c must take

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 *           this into account!

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 */

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//SYM_REF2(structured_variable_c, record_variable, field_selector)

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    void *visit(structured_variable_c *symbol) {

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      /* NOTE: The following code will not work, as structured_variable_c

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       *       are grouped on the left, and not on the right!

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       *

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       *       example: window.origin.x

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       *       will result in

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       *       s1 = structured_variable_c("window, "origin");

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       *       s2 = structured_variable_c(s1, "x");

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       *       AND NOT

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       *       s1 = structured_variable_c("origin", "x");

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       *       s2 = structured_variable_c("window", s1);

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       *

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       *       as the following code assumes!!

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       *

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      current_variable_name = symbol->field_selector;

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      return symbol->record_variable->accept(*this);

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       */

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      /* The correct code, is therefore more complex... */

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      if (next_variable_name == symbol) {

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        /* NOTE: field_selector is always an identifier_c,

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	 * so we do not have to recursevily visit it again...

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	 * return (void *)symbol->field_selector->accept(*this);  -> NOT REQUIRED!!

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	 */

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	return (void *)symbol->field_selector;

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      }

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      current_recursive_variable_name = symbol;

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      return symbol->record_variable->accept(*this);

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    }

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};

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