/*
symbol.c
Copyright © 2009 William Astle

This file is part of LWASM.

LWASM 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 3 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, see <http://www.gnu.org/licenses/>.
*/

/*
for handling the symbol table
*/

#define __symbol_c_seen__

#include <string.h>

#include "lwasm.h"
#include "util.h"
#include "expr.h"

/*
Note that this function may accept symbols that the expression evaluator doesn't
recognize because the expression evaluator must avoid all ambiguity in order
to achieve predictable results. The checks here are simply a fuzz check.
*/

/*
NOTE: complex symbols always take their value from slot 0 on the expression placeholders
for a line!
*/
int lwasm_register_symbol(asmstate_t *as, lwasm_line_t *l, char *sym, int val, int flags)
{
	lwasm_symbol_ent_t *se, *se2;
	char *p;
	
	int scontext = -1;
	
	// if the symbol is constant, fall back to simple registration!
	if (flags & SYMBOL_COMPLEX)
	{
		if (l -> exprs[0] == NULL)
		{
			val = l -> exprvals[0];
			flags &= ~SYMBOL_COMPLEX;
		}
	}
	
	// first check if the symbol is valid
	// the following characters are allowed in a symbol:
	// [a-zA-Z0-9._$?@] and any byte value larger than 0x7F
	// although symbols should be restricted to the 7 bit range
	// symbols must start with [a-zA-Z._]
	if (!strchr("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz._@?", *sym))
	{
		register_error(as, l, 1, "Bad symbol: %s", sym);
		return -1;
	}
	
	if (*sym == '@' && isdigit(sym[1]))
	{
		register_error(as, l, 1, "Bad symbol: %s", sym);
		return -1;
	}
	
	for (p = sym; *p; p++)
	{
		if (!strchr("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz._$?@0123456789", *sym))
		{
			register_error(as, l, 1, "Bad symbol: %s", sym);
			return -1;
		}
		// flag local symbols while we're at it...
		if (*p == '?' || *p == '@')
			scontext = as -> context;
	}
	
	debug_message(3, "lwasm_register_symbol(): registering '%s' (%d) at %04X; flags=%d", sym, scontext, val, flags);
	
	// now look it for to see if it is a duplicate
	se = lwasm_find_symbol(as, sym, scontext);
	if (se)
	{
		if (flags & SYMBOL_FORCE && as -> passnum != 2)
		{
			register_error(as, l, 1, "Multiply defined symbol: %s", sym);
			return -1;
		}
		if (!(flags & SYMBOL_SET) || (flags & SYMBOL_SET && !(se -> flags & SYMBOL_SET)))
		{
			register_error(as, l, 1, "Mulitply defined symbol: %s", sym);
			return -1;
		}
	}
	if (se)
	{
		se -> value = val;
		if (flags & SYMBOL_COMPLEX)
		{
			se -> expr = l -> exprs[0];
		}
		else
		{
			se -> expr = NULL;
		}
		return;
	}

	// if not a duplicate, register it with the value
	se = lwasm_alloc(sizeof(lwasm_symbol_ent_t));
	if (as -> symhead)
	{
		se -> prev = NULL;
		se -> next = as -> symhead;
		as -> symhead -> prev = se;
		as -> symhead = se;
	}
	else
	{
		se -> next = NULL;
		se -> prev = NULL;
		as -> symhead = se;
		as -> symtail = se;
	}
	se -> value = val;
	if (flags & SYMBOL_COMPLEX)
		se -> expr = l -> exprs[0];
	se -> sym = lwasm_strdup(sym);
	se -> context = scontext;

	if (!(flags & SYMBOL_EXTERN))
		se -> sect = as -> csect;
	else
		se -> sect = NULL;

	se -> expr = NULL;
	se -> flags = flags;
	se -> externalname = NULL;

	return 0;
}

lwasm_symbol_ent_t *lwasm_find_symbol(asmstate_t *as, char *sym, int scontext)
{
	lwasm_symbol_ent_t *se;
	static int st = 0;
	
	for (se = as -> symhead; se; se = se -> next)
	{
		if (scontext == se -> context && !strcmp(sym, se -> sym))
		{
			return se;
		}
	}
	if (as -> passnum == 2 && st == 0 && scontext == -1 && as -> outformat == OUTPUT_OBJ && as -> pragmas & PRAGMA_UNDEFEXTERN)
	{
		// we want undefined symbols to be considered external
		// we didn't find it on a lookup so register it as external
		// but we only do so when looking up in global context
		st = 1;
		if (lwasm_register_symbol(as, NULL, sym, 0, SYMBOL_EXTERN))
		{
			st = 0;
			return NULL;
		}
		st = 0;
		
		// find the newly registered symbol and return it
		for (se = as -> symhead; se; se = se -> next)
		{
			if (scontext == se -> context && !strcmp(sym, se -> sym))
			{
				return se;
			}
		}
	}
		
	return NULL;
}

// reset the value of a symbol - should not be used normally
// it is intended for use by such operations as EQU
// returns -1 if the symbol is not registered
int lwasm_set_symbol(asmstate_t *as, char *sym, int scontext, int val)
{
	lwasm_symbol_ent_t *se;
	
	se = lwasm_find_symbol(as, sym, scontext);
	if (!se)
		return -1;
	
	se -> value = val;
	return 0;
}

void lwasm_list_symbols(asmstate_t *as, FILE *lf)
{
	lwasm_symbol_ent_t *se;
	
	for (se = as -> symhead; se; se = se -> next)
	{
		if (se -> expr)
		{
			fprintf(lf, "<incompl>");
		}
		else if (se -> value > 0xffff || se -> value < -0x8000)
		{
			fprintf(lf, "%08X ", se -> value);
		}
		else
		{
			fprintf(lf, "    %04X ", se -> value);
		}
		if (se -> context < 0)
			fputc('G', lf);
		else
			fputc('L', lf);
		
		if (se -> flags & SYMBOL_SET)
			fputc('S', lf);
		else if (se -> flags & SYMBOL_EXTERN)
			fputc('E', lf);
		else
			fputc(' ', lf);
		
		fprintf(lf, " %s", se -> sym);
		
		if (se -> context >= 0)
			fprintf(lf, " (%d)", se -> context);
		
		if (se -> sect)
		{
			fprintf(lf, " [%s]", se -> sect -> name);
		}
		
		fputc('\n', lf);
	}
}