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/*

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 *  matiec - a compiler for the programming languages defined in IEC 61131-3

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 *

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 *  Copyright (C) 2014  Mario de Sousa (msousa@fe.up.pt)

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 *

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 *  This program is free software: you can redistribute it and/or modify

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 *  it under the terms of the GNU General Public License as published by

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 *  the Free Software Foundation, either version 3 of the License, or

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 *  (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,

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 *  but WITHOUT ANY WARRANTY; without even the implied warranty of

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 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

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 *  GNU General Public License for more details.

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 *

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 *  You should have received a copy of the GNU General Public License

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 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.

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 *

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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 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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/*

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 * Re-oder the POUs in te library so that no forward references occur.

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 * 

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 * Since stage1_2 now suppport POUs that contain references to POUS that are only declared later,

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 * (e.g. a variable of FB1_t is declared, before the FB1_T function block is itself declared!)

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 * we may need to re-order all the POUs in the library so that these forward references do not occur.

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 * 

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 * This utility function will do just that. However, it does not destroy the original abstract syntax 

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 * tree (AST). It instead creates a new re-ordered AST, by instantiating a new library_c object.

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 * This new library_c object will however point to the *same* objects of the original AST, just in 

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 * a new order. 

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 * This means that the new and original AST share all the object instances, and only use a distinct

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 * library_c object!

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 */

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#include "remove_forward_dependencies.hh"

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#include "../main.hh" // required for ERROR() and ERROR_MSG() macros.

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#include "../absyntax_utils/absyntax_utils.hh"

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#define FIRST_(symbol1, symbol2) (((symbol1)->first_order < (symbol2)->first_order)   ? (symbol1) : (symbol2))

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#define  LAST_(symbol1, symbol2) (((symbol1)->last_order  > (symbol2)->last_order)    ? (symbol1) : (symbol2))

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#define FIRST_(symbol1, symbol2) (((symbol1)->first_order < (symbol2)->first_order)   ? (symbol1) : (symbol2))

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#define  LAST_(symbol1, symbol2) (((symbol1)->last_order  > (symbol2)->last_order)    ? (symbol1) : (symbol2))

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#define STAGE3_ERROR(error_level, symbol1, symbol2, ...) {                                                                  \

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  if (current_display_error_level >= error_level) {                                                                         \

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    fprintf(stderr, "%s:%d-%d..%d-%d: error: ",                                                                             \

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            FIRST_(symbol1,symbol2)->first_file, FIRST_(symbol1,symbol2)->first_line, FIRST_(symbol1,symbol2)->first_column,\

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                                                 LAST_(symbol1,symbol2) ->last_line,  LAST_(symbol1,symbol2) ->last_column);\

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    fprintf(stderr, __VA_ARGS__);                                                                                           \

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    fprintf(stderr, "\n");                                                                                                  \

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    error_count++;                                                                                                     \

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  }                                                                                                                         \

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}

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#define STAGE3_WARNING(symbol1, symbol2, ...) {                                                                             \

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    fprintf(stderr, "%s:%d-%d..%d-%d: warning: ",                                                                           \

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            FIRST_(symbol1,symbol2)->first_file, FIRST_(symbol1,symbol2)->first_line, FIRST_(symbol1,symbol2)->first_column,\

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                                                 LAST_(symbol1,symbol2) ->last_line,  LAST_(symbol1,symbol2) ->last_column);\

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    fprintf(stderr, __VA_ARGS__);                                                                                           \

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    fprintf(stderr, "\n");                                                                                                  \

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    warning_found = true;                                                                                                   \

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}

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/* NOTE: We create an independent visitor for this task instead of having this done by the remove_forward_dependencies_c

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 *       because we do not want to handle the ***_pragma_c classes while doing this search.

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 *      (remove_forward_dependencies_c needs to visit those classes when handling all the possible entries in

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 *       library_c, and must have those visitors)

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 * 

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 * NOTE:

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 *      This class could have been written by visiting all the AST objects that could _reference_ a

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 *          - FB type

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 *          - Program type

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 *          - Function type

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 *      and by checking whether those references are in the declared_identifiers list.

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 *      However, one of those objects, the ref_spec_c, may reference an FB type, or any other datatype, so we must have a way

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 *      of knowing what is being referenced in this case. I have opted to introduce a new object type in the AST, the

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 *      poutype_identifier_c, that will be used anywhere in the AST that references either a PROGRAM name or a FB type name

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 *      or a FUNCTION name (previously a simple identifier_c was used!).

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 *      This means that we merely need to visit the new poutype_identifier_c object in this visitor.

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 */

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class find_forward_dependencies_c: public search_visitor_c {

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  private:

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    identifiers_symbtable_t *declared_identifiers; // list of identifiers already declared by the symbols in the new tree

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  public:

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    find_forward_dependencies_c(identifiers_symbtable_t *declared_identifiers_) {declared_identifiers = declared_identifiers_;}

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

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  /* B 1.1 - Letters, digits and identifiers */

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

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  // return NULL if the symbol is already in the declared_identifiers symbol table, otherwise return the missing symbol!

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  void *visit(            poutype_identifier_c *symbol)

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    {if (declared_identifiers->find(symbol) != declared_identifiers->end()) return NULL; else return symbol;}

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};   /* class find_forward_dependencies_c */

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/* A class to count the number of POUs (Function, FBs Programs and Configurations) in a library.

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 * This will be used to make sure whether we have copied all the POUs from the original AST (abstract

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 * syntax tree) to the new AST.

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 * Note that we can't simply use the number of 'elements' in the AST, as it may contain unknown/unsupported pragmas.

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 */

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class pou_count_c: public search_visitor_c {

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  private:

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    static pou_count_c *singleton;

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    long long int count;

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  public:

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    static long long int get_count(library_c *library) {

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      if (NULL == singleton) singleton = new pou_count_c;

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      if (NULL == singleton) ERROR;

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      singleton->count = 0;

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      library->accept(*singleton);

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      return singleton->count;

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    }

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

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    /* B.1.5 - Program organization units */

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

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    void *visit(      function_declaration_c *symbol) {count++; return NULL;}

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    void *visit(function_block_declaration_c *symbol) {count++; return NULL;} 

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    void *visit(       program_declaration_c *symbol) {count++; return NULL;} 

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    void *visit( configuration_declaration_c *symbol) {count++; return NULL;} 

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};   /* class pou_count_c */

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pou_count_c *pou_count_c::singleton = NULL;

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symbol_c remove_forward_dependencies_c_null_symbol;

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

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

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/******   The main class: Remove Forward Depencies    *******/

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

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

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// constructor & destructor

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remove_forward_dependencies_c:: remove_forward_dependencies_c(void) {

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  find_forward_dependencies      = new find_forward_dependencies_c(&declared_identifiers);

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  current_display_error_level = error_level_default;

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  error_count = 0;

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}

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remove_forward_dependencies_c::~remove_forward_dependencies_c(void) {

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  delete find_forward_dependencies;

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}

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int remove_forward_dependencies_c::get_error_count(void) {

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  return error_count;

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}

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library_c *remove_forward_dependencies_c::create_new_tree(symbol_c *tree) {

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  library_c *old_tree = dynamic_cast<library_c *>(tree);

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  if (NULL == old_tree) ERROR;

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  new_tree = new library_c;

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  *((symbol_c *)new_tree) = *((symbol_c *)tree); // copy any annotations from tree to new_tree;

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  new_tree->clear(); // remove all elements from list.

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  tree->accept(*this);

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  return new_tree;

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}

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void *remove_forward_dependencies_c::handle_library_symbol(symbol_c *symbol, symbol_c *name, symbol_c *search1, symbol_c *search2, symbol_c *search3) {

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  if (inserted_symbols.find(symbol) != inserted_symbols.end())                 return NULL; // already previously inserted into new_tree and declared_identifiers. Do not handle again!

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  if ((search1 != NULL) && (search1->accept(*find_forward_dependencies) != NULL)) return NULL; // A forward depency has not yet been satisfied. Wait for a later iteration to try again! 

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  if ((search2 != NULL) && (search2->accept(*find_forward_dependencies) != NULL)) return NULL; // A forward depency has not yet been satisfied. Wait for a later iteration to try again!

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  if ((search3 != NULL) && (search3->accept(*find_forward_dependencies) != NULL)) return NULL; // A forward depency has not yet been satisfied. Wait for a later iteration to try again!

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  /* no forward dependencies found => insert into new AST, and add to the 'defined identifiers' and 'inserted symbol' lists */

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  if (declared_identifiers.find(name) == declared_identifiers.end())

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      declared_identifiers.insert(name, NULL);  // only add if not yet in the symbol table (an overloaded version of this same POU could have been inderted previously!)

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  inserted_symbols.insert(symbol);

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  new_tree->add_element(current_code_generation_pragma);  

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  new_tree->add_element(symbol);  

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  return NULL;

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}

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/* Tell the user that the source code contains a circular dependency */

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void remove_forward_dependencies_c::print_circ_error(library_c *symbol) {

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  /* Note that we only print Functions and FBs, as Programs and Configurations cannot contain circular references due to syntax rules */

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  /* Note too that circular references in derived datatypes is also not possible due to sytax!                                        */

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  int initial_error_count = error_count;

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  for (int i = 0; i < symbol->n; i++) 

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  if (error_count == initial_error_count) ERROR; // We were unable to determine which POUs contain the circular references!!

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}

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

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/* B 0 - Programming Model */

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

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/* enumvalue_symtable is filled in by enum_declaration_check_c, during stage3 semantic verification, with a list of all enumerated constants declared inside this POU */

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// SYM_LIST(library_c, enumvalue_symtable_t enumvalue_symtable;)

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void *remove_forward_dependencies_c::visit(library_c *symbol) {

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  /* this method is the expected entry point for this visitor, and implements the main algorithm of the visitor */

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  /* first insert all the derived datatype declarations, in the same order by which they are delcared in the original AST */

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  /* Since IEC 61131-3 does not allow FBs in arrays or structures, it is actually safe to place all the datatypes before all the POUs! */

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  for (int i = 0; i < symbol->n; i++) 

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  /* now do the POUs, in whatever order is necessary to guarantee no forward references. */    

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  long long int old_tree_pou_count = pou_count_c::get_count(symbol);

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    // if no code generation pragma exists before the first entry in the library, the default is to enable code generation.

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  enable_code_generation_pragma_c *default_code_generation_pragma = new enable_code_generation_pragma_c; 

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  int prev_n;

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  cycle_count = 0;

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  do {

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    cycle_count++;

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    prev_n = new_tree->n;

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    current_code_generation_pragma = default_code_generation_pragma;

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  } while (prev_n != new_tree->n); // repeat while new elementns are still being added to the new AST

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  if (old_tree_pou_count != pou_count_c::get_count(new_tree)) 

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    print_circ_error(symbol);

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  return NULL;

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}

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

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/* B.1.5 - Program organization units */

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

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

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/* B 1.5.1 - Functions */

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

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// SYM_REF4(function_declaration_c, derived_function_name, type_name, var_declarations_list, function_body, enumvalue_symtable_t enumvalue_symtable;)

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void *remove_forward_dependencies_c::visit(function_declaration_c *symbol) 

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  {return handle_library_symbol(symbol, symbol->derived_function_name, symbol->type_name, symbol->var_declarations_list, symbol->function_body);}

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

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/* B 1.5.2 - Function Blocks */

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

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/*  FUNCTION_BLOCK derived_function_block_name io_OR_other_var_declarations function_block_body END_FUNCTION_BLOCK */

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// SYM_REF3(function_block_declaration_c, fblock_name, var_declarations, fblock_body, enumvalue_symtable_t enumvalue_symtable;)

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void *remove_forward_dependencies_c::visit(function_block_declaration_c *symbol) 

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  {return handle_library_symbol(symbol, symbol->fblock_name, symbol->var_declarations, symbol->fblock_body);}

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

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/* B 1.5.3 - Programs */

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

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/*  PROGRAM program_type_name program_var_declarations_list function_block_body END_PROGRAM */

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// SYM_REF3(program_declaration_c, program_type_name, var_declarations, function_block_body, enumvalue_symtable_t enumvalue_symtable;)

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void *remove_forward_dependencies_c::visit(program_declaration_c *symbol) 

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  {return handle_library_symbol(symbol, symbol->program_type_name, symbol->var_declarations, symbol->function_block_body);}

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

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/* B 1.7 Configuration elements */

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

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/* CONFIGURATION configuration_name (...) END_CONFIGURATION */

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// SYM_REF5(configuration_declaration_c, configuration_name, global_var_declarations, resource_declarations, access_declarations, instance_specific_initializations, enumvalue_symtable_t enumvalue_symtable;)

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void *remove_forward_dependencies_c::visit(configuration_declaration_c *symbol) 

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  {return handle_library_symbol(symbol, symbol->configuration_name, symbol->global_var_declarations, symbol->resource_declarations, symbol->access_declarations);}

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

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/* 2.1.6 - Pragmas  */

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

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void *remove_forward_dependencies_c::visit(disable_code_generation_pragma_c *symbol) {current_code_generation_pragma = symbol; return NULL;}

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void *remove_forward_dependencies_c::visit( enable_code_generation_pragma_c *symbol) {current_code_generation_pragma = symbol; return NULL;}

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/* I have no ideia what this pragma is. Where should we place it in the re-ordered tree? 

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 * Without knowing the semantics of the pragma, it is not possible to hande it correctly.

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 * We therefore print out an error message, and abort!

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 */

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// TODO: print error message!

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void *remove_forward_dependencies_c::visit(pragma_c *symbol) {

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  if (1 != cycle_count) return NULL; // only handle unknown pragmas in the first cycle!

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  STAGE3_WARNING(symbol, symbol, "Unrecognized pragma. Including the pragma when using the '-p' command line option for 'allow use of forward references' may result in unwanted behaviour.");

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  new_tree->add_element(symbol);

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  return NULL;

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}

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