/*
parse.c
Copyright © 2008 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/>.
*/

/*
Contains the general parser
*/

#define __parse_c_seen__

#include <ctype.h>
#include <string.h>

#include "lwasm.h"
#include "instab.h"
#include "util.h"

// parse a line and despatch to the appropriate handlers for opcodes
int lwasm_parse_line(asmstate_t *as, lwasm_line_t *l)
{
	char *p, *p2;
	char *opc;
	int opnum;
	char *sym = NULL;

	// if this was a bad op first pass (or otherwise a no-process line)
	// ignore it
	if (l -> badop)
		return;
	
	p = l -> text;
	l -> sect = as -> csect;

	// blank lines are a no brainer
	if (!*p)
	{
		as -> context = lwasm_next_context(as);
		return 0;
	}
	
	// for output generation later but only on pass 1
	// also used by some pseudo ops on pass 2
	if (as -> passnum == 1)
		l -> codeaddr = as -> addr;
	
	// if it's a comment, return (this doesn't cause a context change)
	if (*p == '*' || *p == ';')
		return;
	
	// if we have C pre-processor directives/output, ignore it
	if (*p == '#')
		return;
	
	// if we start with a non-space character, it's a symbol
	if (!isspace(*p))
	{
		// we have a symbol specified here
		// parse it out and record it for later use
		for (p2 = p; *p2 && !isspace(*p2) && *p2 != ':'; p2++)
			/* do nothing */ ;
		
		sym = lwasm_alloc((p2 - p) + 1);
		sym[p2 - p] = '\0';
		memcpy(sym, p, p2 - p);
		
		p = p2;
		if (!*sym)
		{
			register_error(as, l, 1, "Invalid symbol");
			lwasm_free(sym);
			sym = NULL;
		}
		if (*p == ':')
			p++;
	}
	l -> sym = sym;

	// now skip any whitespace to find the opcode
	while (*p && isspace(*p))
		p++;
	
	// is the line blank?
	if (!*p && !sym)
	{
		// nothing but white space *is* a context break
		as -> context = lwasm_next_context(as);
		return;
	}
	
	// parse the opcode
	for (p2 = p; *p2 && !isspace(*p2); p2++)
		/* do nothing */ ;
	
	opc = lwasm_alloc((p2 - p) + 1);
	memcpy(opc, p, p2 - p);
	opc[p2 - p] = '\0';

	debug_message(2, "Found operation code: '%s'", opc);

	// skip intervening whitespace if present
	while (*p2 && isspace(*p2))
		p2++;

	// look up instruction in insn table
	for (opnum = 0; instab[opnum].opcode; opnum++)
	{
		if (!strcasecmp(instab[opnum].opcode, opc))
			break;
	}
	
	// if we found no operation, check if we had a comment
	// the reason this check is here is to allow for "private"
	// operation codes like "*pragma" which will be ignored by
	// other assemblers
	// also skip empty ops
	if (!(instab[opnum].opcode))
	{
		if (*opc == '*' || *opc == ';' || !*opc)
			goto done_line;
	}

	// now we have the opcode and the symbol, we can decide if we're
	// actually going to do anything with this line
	
	// we will NOT call the function if any of the following are true:
	
	// - we are skipping a condition and the operation code is not a conditional
	// - we are defining a macro and the operation code is not ENDM

	// we will call the function in any other circumstance
	
	// first condition above
	if (as -> inmacro && instab[opnum].endm == 0)
	{
		add_macro_line(as, l -> text);
		goto done_line;
	}

	// second condition above	
	if (as -> skipcond && instab[opnum].iscond == 0)
		goto done_line;

	// we've registered the symbol as needed
	// now we need to check for a macro call IFF we don't collide with
	// an operation code; otherwise, call the operation function
	if (instab[opnum].opcode)
	{
		if (instab[opnum].fn)
		{
			(instab[opnum].fn)(as, l, &p2, opnum);
		}
		else
		{
			// carp about unimplemented operation
			register_error(as, l, 1, "Unimplemented operation code: %s", opc);
		}
	}
	else
	{
		if (expand_macro(as, l, &p2, opc) == 0)
			goto done_line;

		// carp about an unknown operation code and note that fact for
		// pass 2 in case a macro appears later with the same name!
		register_error(as, l, 1, "Uknown operation code: %s", opc);
		l -> badop = 1;
	}

done_line:
	if (!(as -> skipcond || as -> inmacro))
	{
		// register symbol if the operation didn't
		if (sym && instab[opnum].setsym == 0)
		{
			if (as -> passnum == 1)
			{
				debug_message(1, "Registering symbol '%s' at %04X", sym, l -> codeaddr);
				if (lwasm_register_symbol(as, l, sym, l -> codeaddr, SYMBOL_NORM) < 0)
					l -> sym = NULL;
				else
					l -> addrset = 1;
			}
		}
	}

	l -> sect = as -> csect;
	l -> context = as -> context;
	
	lwasm_free(opc);
	if (sym)
		lwasm_free(sym);
}