/*
 * Copyright (c) 2007 The Akuma Project
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 * $Id: rule-check.c 133 2007-05-29 14:32:04Z asmodai $
 */
/*
    		 Crown Copyright (c) 1997

    This TenDRA(r) Computer Program is subject to Copyright
    owned by the United Kingdom Secretary of State for Defence
    acting through the Defence Evaluation and Research Agency
    (DERA).  It is made available to Recipients with a
    royalty-free licence for its use, reproduction, transfer
    to other parties and amendment for any purpose not excluding
    product development provided that any such use et cetera
    shall be deemed to be acceptance of the following conditions:-

        (1) Its Recipients shall ensure that this Notice is
        reproduced upon any copies or amended versions of it;

        (2) Any amended version of it shall be clearly marked to
        show both the nature of and the organisation responsible
        for the relevant amendment or amendments;

        (3) Its onward transfer from a recipient to another
        party shall be deemed to be that party's acceptance of
        these conditions;

        (4) DERA gives no warranty or assurance as to its
        quality or suitability for any purpose and DERA accepts
        no liability whatsoever in relation to any use to which
        it may be put.
*/


/*** rule-check.c --- Checks for grammar validity.
 *
 ** Author: Steve Folkes <smf@hermes.mod.uk>
 *
 *** Commentary:
 *
 * This file implements the routines that check to see if the grammar is
 * valid.  There are for checks that are made:
 *
 *	- The first sets of all alternatives in a rule are checked to ensure
 *	that they are disjoint (this includes the predicate first sets).  This
 *	also includes checking that there is only one see through alternative.
 *
 *	- The follow set of each rule is computed, and checked to ensure that
 *	if the rule is see through, its follow set does not intersect with its
 *	first set (this includes predicate follow and first sets).
 *
 *	- If there is a see through alternative, this is computed.
 *
 *	- The first set of each alternative is computed.
 *
 *** Change Log:
 * $Log: rule-check.c,v $
 * Revision 1.1.1.1  1998/01/17  15:57:46  release
 * First version to be checked into rolling release.
 *
 * Revision 1.3  1994/12/15  09:58:35  smf
 * Brought into line with OSSG C Coding Standards Document, as per
 * "CR94_178.sid+tld-update".
 *
 * Revision 1.2  1994/08/22  09:37:22  smf
 * Fixed bug DR114:ids-too-long.
 *
 * Revision 1.1.1.1  1994/07/25  16:04:38  smf
 * Initial import of SID 1.8 non shared files.
 *
**/

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

#include "rule.h"
#include "basic.h"
#include "bitvec.h"
#include "gen-errors.h"

/*--------------------------------------------------------------------------*/

static void
rule_check_first_set_1(RuleP rule, GrammarP grammar)
{
    BoolT         is_empty            = rule_has_empty_alt(rule);
    BoolT         is_empty_mesg_shown = FALSE;
    BitVecT       test;
    EntryListT    predicate_list;
    AltP          alt;
    BasicClosureT closure;

    closure.grammar = grammar;
    bitvec_init(&test);
    entry_list_init(&predicate_list);
    for (alt = rule_alt_head(rule); alt; alt = alt_next(alt)) {
	ItemP item        = alt_item_head(alt);
	ItemP initial     = item;
	BoolT see_through = TRUE;

	for (; see_through && item; item = item_next(item)) {
	    EntryP entry = item_entry(item);

	    switch (item_type(item))EXHAUSTIVE {
	      case ET_PREDICATE:
		ASSERT(item == initial);
		if (entry_list_contains(&predicate_list, entry)) {
		    E_predicate_collision(rule, entry_key(entry));
		} else {
		    entry_list_add(&predicate_list, entry);
		}
		see_through = FALSE;
		break;
	      case ET_ACTION:
	      case ET_RENAME:
		break;
	      case ET_BASIC: {
		  unsigned terminal = basic_terminal(entry_get_basic(entry));

		  see_through = FALSE;
		  if (bitvec_is_set(&test, terminal)) {
		      BitVecT tmp;

		      bitvec_init(&tmp);
		      bitvec_set(&tmp, terminal);
		      bitvec_and(&tmp, &test);
		      closure.bitvec = &tmp;
		      E_first_set_collision(rule, &closure);
		      bitvec_destroy(&tmp);
		  } else {
		      bitvec_set(&test, terminal);
		  }
	      }
		break;
	      case ET_RULE: {
		  RuleP      item_rule  = entry_get_rule(entry);
		  EntryListP item_preds = rule_predicate_first(item_rule);
		  EntryListT tmp_list;
		  BitVecP    bitvec;

		  entry_list_intersection(&tmp_list, &predicate_list,
					  item_preds);
		  if (!entry_list_is_empty(&tmp_list)) {
		      E_predicate_list_collision(rule, &tmp_list);
		  }
		  entry_list_destroy(&tmp_list);
		  entry_list_append(&predicate_list, item_preds);
		  bitvec      = rule_first_set(item_rule);
		  see_through = rule_is_see_through(item_rule);
		  if (bitvec_intersects(&test, bitvec)) {
		      BitVecT tmp;

		      bitvec_copy(&tmp, bitvec);
		      bitvec_and(&tmp, &test);
		      closure.bitvec = &tmp;
		      E_first_set_collision(rule, &closure);
		      bitvec_destroy(&tmp);
		  } else {
		      bitvec_or(&test, bitvec);
		  }
	      }
		break;
	      case ET_NON_LOCAL:
	      case ET_TYPE:
	      case ET_NAME:
		UNREACHED;
	    }
	}
	if (see_through) {
	    if (is_empty) {
		if (!is_empty_mesg_shown) {
		    E_multiple_see_through_alts(rule);
		    is_empty_mesg_shown = TRUE;
		}
	    } else {
		is_empty = TRUE;
	    }
	}
    }
    bitvec_destroy(&test);
}

static void rule_compute_follow_set_1(RuleP, GrammarP, BitVecP, EntryListP,
				      ClashListP);

static void
rule_compute_follow_set_3(GrammarP grammar, ItemP item, BitVecP context,
			  EntryListP pred_context, ClashListP clashes)
{
    if (item != NIL(ItemP)) {
	EntryP entry;

	rule_compute_follow_set_3(grammar, item_next(item), context,
				  pred_context, clashes);
	entry = item_entry(item);
	switch (item_type(item))EXHAUSTIVE {
	  case ET_PREDICATE:
	    entry_list_destroy(pred_context);
	    entry_list_init(pred_context);
	    entry_list_add(pred_context, entry);
	    clashes->next = NIL(ClashListP);
	    break;
	  case ET_ACTION:
	  case ET_RENAME:
	    break;
	  case ET_RULE: {
	      RuleP rule = entry_get_rule(entry);

	      clashes->item = item;
	      rule_compute_follow_set_1(rule, grammar, context, pred_context,
					clashes);
	      if (rule_is_see_through(rule)) {
		  bitvec_or(context, rule_first_set(rule));
		  entry_list_append(pred_context, rule_predicate_first(rule));
	      } else {
		  bitvec_replace(context, rule_first_set(rule));
		  entry_list_destroy(pred_context);
		  entry_list_init(pred_context);
		  entry_list_append(pred_context, rule_predicate_first(rule));
		  clashes->next = NIL(ClashListP);
	      }
	  }
	    break;
	  case ET_BASIC: {
	      BasicP basic = entry_get_basic(entry);

	      bitvec_empty(context);
	      bitvec_set(context, basic_terminal(basic));
	      clashes->next = NIL(ClashListP);
	  }
	    break;
	  case ET_NON_LOCAL:
	  case ET_NAME:
	  case ET_TYPE:
	    UNREACHED;
	}
    }
}

static void
rule_compute_follow_set_2(RuleP rule, GrammarP grammar, AltP alt,
			  BitVecP context, EntryListP pred_context,
			  ClashListP clashes)
{
    BitVecT    tmp;
    EntryListT tmp_list;
    ClashListT clash;

    clash.next = clashes;
    clash.rule = rule;
    clash.alt  = alt;
    bitvec_copy(&tmp, context);
    entry_list_copy(&tmp_list, pred_context);
    rule_compute_follow_set_3(grammar, alt_item_head(alt), &tmp, &tmp_list,
			      &clash);
    bitvec_destroy(&tmp);
    entry_list_destroy(&tmp_list);
}

static void
rule_compute_follow_set_1(RuleP rule, GrammarP grammar, BitVecP context,
			  EntryListP pred_context, ClashListP clashes)
{
    BitVecP       follow      = rule_follow_set(rule);
    EntryListP    pred_follow = rule_predicate_follow(rule);
    BitVecP       first       = rule_first_set(rule);
    EntryListP    pred_first  = rule_predicate_first(rule);
    BitVecT       test;
    AltP          alt;
    BasicClosureT closure;

    if (rule_has_started_follows(rule)) {
	bitvec_copy(&test, follow);
	bitvec_or(follow, context);
	if (bitvec_equal(&test, follow) &&
	    entry_list_includes(pred_follow, pred_context)) {
	    bitvec_destroy(&test);
	    return;
	}
	entry_list_append(pred_follow, pred_context);
	bitvec_destroy(&test);
    } else {
	bitvec_replace(follow, context);
	entry_list_append(pred_follow, pred_context);
	rule_started_follows(rule);
    }
    closure.grammar = grammar;
    if (rule_is_see_through(rule)) {
	EntryListT tmp_list;

	if (bitvec_intersects(follow, first)) {
	    bitvec_copy(&test, follow);
	    bitvec_and(&test, first);
	    closure.bitvec = &test;
	    E_follow_set_collision(rule, &closure, clashes);
	    bitvec_not(&test);
	    bitvec_and(first, &test);
	    bitvec_destroy(&test);
	}
	entry_list_intersection(&tmp_list, pred_follow, pred_first);
	if (!entry_list_is_empty(&tmp_list)) {
	    E_predicate_follow_set_coll(rule, &tmp_list, clashes);
	    entry_list_unlink_used(pred_first, &tmp_list);
	}
	entry_list_destroy(&tmp_list);
    }
    if ((alt = rule_get_handler(rule)) != NIL(AltP)) {
	rule_compute_follow_set_2(rule, grammar, alt, follow, pred_follow,
				   clashes);
    }
    for (alt = rule_alt_head(rule); alt; alt = alt_next(alt)) {
	rule_compute_follow_set_2(rule, grammar, alt, follow, pred_follow,
				  clashes);
    }
}

static void
rule_compute_see_through_alt_1(RuleP rule)
{
    if (!rule_has_empty_alt(rule)) {
	AltP alt;

	for (alt = rule_alt_head(rule); alt; alt = alt_next(alt)) {
	    ItemP item;

	    for (item = alt_item_head(alt); item; item = item_next(item)) {
		RuleP item_rule;

		if ((!item_is_action(item)) && (!item_is_rename(item)) &&
		    ((!item_is_rule(item)) ||
		     ((item_rule = entry_get_rule(item_entry(item))),
		      (!rule_is_see_through(item_rule))))) {
		    goto next_alt;
		}
	    }
	    rule_set_see_through_alt(rule, alt);
	    return;
	  next_alt:;
	}
    }
}

static void
rule_compute_alt_first_sets_1(RuleP rule)
{
    AltP alt;

    for (alt = rule_alt_head(rule); alt; alt = alt_next(alt)) {
	BitVecP alt_firsts  = alt_first_set(alt);
	ItemP   item        = alt_item_head(alt);
	ItemP   initial     = item;
	BoolT   see_through = TRUE;

	for (; see_through && item; item = item_next(item)) {
	    EntryP entry = item_entry(item);

	    switch (item_type(item))EXHAUSTIVE {
	      case ET_PREDICATE:
		ASSERT(item == initial);
		see_through = FALSE;
		break;
	      case ET_ACTION:
	      case ET_RENAME:
		break;
	      case ET_BASIC:
		see_through = FALSE;
		bitvec_set(alt_firsts, basic_terminal(entry_get_basic(entry)));
		break;
	      case ET_RULE: {
		  RuleP item_rule = entry_get_rule(entry);

		  see_through = rule_is_see_through(item_rule);
		  bitvec_or(alt_firsts, rule_first_set(item_rule));
	      }
		break;
	      case ET_NON_LOCAL:
	      case ET_TYPE:
	      case ET_NAME:
		UNREACHED;
	    }
	}
	if (see_through) {
	    bitvec_or(alt_firsts, rule_follow_set(rule));
	}
    }
}

/*--------------------------------------------------------------------------*/

void
rule_check_first_set(EntryP entry, GenericP gclosure)
{
    GrammarP grammar = (GrammarP)gclosure;

    if (entry_is_rule(entry)) {
	RuleP rule = entry_get_rule(entry);

	rule_check_first_set_1(rule, grammar);
    }
}

void
rule_compute_follow_set(EntryP entry, GenericP gclosure)
{
    GrammarP grammar = (GrammarP)gclosure;

    if (entry_is_rule(entry)) {
	RuleP   rule = entry_get_rule(entry);
	BitVecT    outer;
	EntryListT pred_outer;

	bitvec_init(&outer);
	entry_list_init(&pred_outer);
	rule_compute_follow_set_1(rule, grammar, &outer, &pred_outer,
				  NIL(ClashListP));
	bitvec_destroy(&outer);
	entry_list_destroy(&pred_outer);
    }
}

void
rule_compute_see_through_alt(EntryP entry, GenericP gclosure)
{
    UNUSED(gclosure);
    if (entry_is_rule(entry)) {
	RuleP rule = entry_get_rule(entry);

	rule_compute_see_through_alt_1(rule);
    }
}

void
rule_compute_alt_first_sets(EntryP entry, GenericP gclosure)
{
    UNUSED(gclosure);
    if (entry_is_rule(entry)) {
	RuleP rule = entry_get_rule(entry);

	rule_compute_alt_first_sets_1(rule);
    }
}

void
write_clashes(OStreamP ostream, ClashListP clashes)
{
    write_newline(ostream);
    while (clashes) {
	write_rule_lhs(ostream, clashes->rule);
	write_alt_highlighting(ostream, clashes->alt, clashes->item);
	write_cstring(ostream, "};");
	write_newline(ostream);
	clashes = clashes->next;
    }
}

/*
 * Local variables(smf):
 * eval: (include::add-path-entry "../os-interface" "../library")
 * eval: (include::add-path-entry "../generated")
 * end:
**/