/*	$NetBSD: parse.c,v 1.62 2023/05/23 12:12:29 rillig Exp $	*/

/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright (c) 1985 Sun Microsystems, Inc.
 * Copyright (c) 1980, 1993
 *	The Regents of the University of California.  All rights reserved.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__RCSID("$NetBSD: parse.c,v 1.62 2023/05/23 12:12:29 rillig Exp $");

#include <err.h>

#include "indent.h"

static void reduce(void);

static int
decl_level(void)
{
	int level = 0;
	for (int i = ps.tos - 1; i > 0; i--)
		if (ps.s_sym[i] == psym_decl)
			level++;
	return level;
}

/*
 * Shift the token onto the parser stack, or reduce it by combining it with
 * previous tokens.
 */
void
parse(parser_symbol psym)
{
	debug_blank_line();
	debug_println("parse token: %s", psym_name[psym]);

	if (psym != psym_else) {
		while (ps.s_sym[ps.tos] == psym_if_expr_stmt) {
			ps.s_sym[ps.tos] = psym_stmt;
			reduce();
		}
	}

	switch (psym) {

	case psym_decl:
		if (ps.s_sym[ps.tos] == psym_decl)
			break;	/* only put one declaration onto stack */

		break_comma = true;	/* while in a declaration, force a
					 * newline after comma */
		ps.s_sym[++ps.tos] = psym_decl;
		ps.s_ind_level[ps.tos] = ps.ind_level_follow;

		if (opt.ljust_decl)
			ps.ind_level_follow = ps.ind_level = decl_level();
		break;

	case psym_if_expr:
		if (ps.s_sym[ps.tos] == psym_if_expr_stmt_else
		    && opt.else_if) {
			/* Reduce "else if" to "if". This saves a lot of stack
			 * space in case of a long "if-else-if ... else-if"
			 * sequence. */
			ps.ind_level_follow = ps.s_ind_level[ps.tos--];
		}
		/* FALLTHROUGH */
	case psym_do:
	case psym_for_exprs:
		ps.s_sym[++ps.tos] = psym;
		ps.s_ind_level[ps.tos] = ps.ind_level = ps.ind_level_follow;
		++ps.ind_level_follow;
		break;

	case psym_lbrace:
		break_comma = false;	/* don't break comma in an initializer
					 * list */
		if (ps.s_sym[ps.tos] == psym_stmt
		    || ps.s_sym[ps.tos] == psym_decl
		    || ps.s_sym[ps.tos] == psym_stmt_list)
			++ps.ind_level_follow;	/* it is a random, isolated
						 * stmt group or a declaration
						 */
		else {
			if (code.len == 0) {
				/* it is a group as part of a while, for, etc.
				 */
				--ps.ind_level;

				/* for a switch, brace should be two levels out
				 * from the code */
				if (ps.s_sym[ps.tos] == psym_switch_expr &&
				    opt.case_indent >= 1.0F)
					--ps.ind_level;
			}
		}

		ps.s_sym[++ps.tos] = psym_lbrace;
		ps.s_ind_level[ps.tos] = ps.ind_level;
		ps.s_sym[++ps.tos] = psym_stmt;
		ps.s_ind_level[ps.tos] = ps.ind_level_follow;
		break;

	case psym_while_expr:
		if (ps.s_sym[ps.tos] == psym_do_stmt) {
			/* it is matched with do stmt */
			ps.ind_level =
			    ps.ind_level_follow = ps.s_ind_level[ps.tos];
			ps.s_sym[++ps.tos] = psym_while_expr;
			ps.s_ind_level[ps.tos] = ps.ind_level;

		} else {	/* it is a while loop */
			ps.s_sym[++ps.tos] = psym_while_expr;
			ps.s_ind_level[ps.tos] = ps.ind_level_follow;
			++ps.ind_level_follow;
		}

		break;

	case psym_else:
		if (ps.s_sym[ps.tos] != psym_if_expr_stmt)
			diag(1, "Unmatched 'else'");
		else {
			ps.ind_level = ps.s_ind_level[ps.tos];
			ps.ind_level_follow = ps.ind_level + 1;
			ps.s_sym[ps.tos] = psym_if_expr_stmt_else;
		}
		break;

	case psym_rbrace:
		/* stack should have <lbrace> <stmt> or <lbrace> <stmt_list> */
		if (ps.tos > 0 && ps.s_sym[ps.tos - 1] == psym_lbrace) {
			ps.ind_level = ps.ind_level_follow
			    = ps.s_ind_level[--ps.tos];
			ps.s_sym[ps.tos] = psym_stmt;
		} else
			diag(1, "Statement nesting error");
		break;

	case psym_switch_expr:
		ps.s_sym[++ps.tos] = psym_switch_expr;
		ps.s_case_ind_level[ps.tos] = case_ind;
		ps.s_ind_level[ps.tos] = ps.ind_level_follow;
		case_ind = (float)ps.ind_level_follow + opt.case_indent;
		ps.ind_level_follow += (int)opt.case_indent + 1;
		break;

	case psym_0:		/* a simple statement */
		break_comma = false;	/* don't break after comma in a
					 * declaration */
		ps.s_sym[++ps.tos] = psym_stmt;
		ps.s_ind_level[ps.tos] = ps.ind_level;
		break;

	default:
		diag(1, "Unknown code to parser");
		return;
	}

	if (ps.tos >= STACKSIZE - 1)
		errx(1, "Parser stack overflow");

	debug_parse_stack("before reduction");
	reduce();		/* see if any reduction can be done */
	debug_parse_stack("after reduction");
}

/*
 * Try to combine the statement on the top of the parse stack with the symbol
 * directly below it, replacing these two symbols with a single symbol.
 */
static bool
reduce_stmt(void)
{
	switch (ps.s_sym[ps.tos - 1]) {

	case psym_stmt:
	case psym_stmt_list:
		ps.s_sym[--ps.tos] = psym_stmt_list;
		return true;

	case psym_do:
		ps.s_sym[--ps.tos] = psym_do_stmt;
		ps.ind_level_follow = ps.s_ind_level[ps.tos];
		return true;

	case psym_if_expr:
		ps.s_sym[--ps.tos] = psym_if_expr_stmt;
		int i = ps.tos - 1;
		while (ps.s_sym[i] != psym_stmt &&
		    ps.s_sym[i] != psym_stmt_list &&
		    ps.s_sym[i] != psym_lbrace)
			--i;
		ps.ind_level_follow = ps.s_ind_level[i];
		/* For the time being, assume that there is no 'else' on this
		 * 'if', and set the indentation level accordingly. If an
		 * 'else' is scanned, it will be fixed up later. */
		return true;

	case psym_switch_expr:
		case_ind = ps.s_case_ind_level[ps.tos - 1];
		/* FALLTHROUGH */
	case psym_decl:		/* finish of a declaration */
	case psym_if_expr_stmt_else:
	case psym_for_exprs:
	case psym_while_expr:
		ps.s_sym[--ps.tos] = psym_stmt;
		ps.ind_level_follow = ps.s_ind_level[ps.tos];
		return true;

	default:
		return false;
	}
}

/*
 * Repeatedly try to reduce the top two symbols on the parse stack to a single
 * symbol, until no more reductions are possible.
 */
static void
reduce(void)
{
again:
	if (ps.s_sym[ps.tos] == psym_stmt && reduce_stmt())
		goto again;
	if (ps.s_sym[ps.tos] == psym_while_expr &&
	    ps.s_sym[ps.tos - 1] == psym_do_stmt) {
		ps.tos -= 2;
		goto again;
	}
}