/*
 * Copyright (c) 1980 Regents of the University of California. All rights
 * reserved.  The Berkeley software License Agreement specifies the terms and
 * conditions for redistribution. 
 */

#ifndef lint
static char     sccsid[] = "@(#)parse.c     5.2 (Berkeley) 8/28/85";
#endif not lint

/*-
 *
 *                        Copyright (C) 1976
 *                              by the
 *                        Board of Trustees
 *                              of the
 *                      University of Illinois
 *
 *                       All rights reserved
 *
 *
 * FILE NAME:
 *      parse.c
 *
 * PURPOSE:
 *      Contains the routines which keep track of the parse stack.
 *
 * GLOBALS:
 *      ps.p_stack =    The parse stack, set by both routines
 *      ps.il =         Stack of indentation levels, set by parse
 *      ps.cstk =               Stack of case statement indentation levels, set by parse
 *      ps.tos =                Pointer to top of stack, set by both routines.
 *
 * FUNCTIONS:
 *      parse
 *      reduce
 */
/*-
 * Copyright (C) 1976 by the Board of Trustees of the University of Illinois 
 *
 * All rights reserved 
 *
 *
 * NAME: parse 
 *
 * FUNCTION: Parse is given one input which is a "maxi token" just scanned
 * from input.  Maxi tokens are signifigant constructs such as else, {,
 * do, if (...), etc.  Parse works with reduce to maintain a parse stack
 * of these constructs.  Parse is responsible for the "shift" portion of
 * the parse algorithm, and reduce handles the "reduce" portion. 
 *
 * HISTORY: initial coding      November 1976   D A Willcox of CAC 
 *
 */

#include "./indent_globs.h";
#include "./indent_codes.h";




parse(tk)
	int             tk;	/* the code for the construct scanned */
{
	int             i;

#ifdef debug
	printf("%2d - %s\n", tk, token);
#endif
	while (ps.p_stack[ps.tos] == ifhead && tk != elselit) {
		/* true if we have an if without an else */
		ps.p_stack[ps.tos] = stmt;	/* apply the if(..) stmt ::=
						 * stmt reduction */
		reduce();	/* see if this allows any reduction */
	}


	switch (tk) {		/* go on and figure out what to do with the
				 * input */

	case decl:		/* scanned a declaration word */
		ps.search_brace = btype_2;
		/* indicate that following brace should be on same line */
		if (ps.p_stack[ps.tos] != decl) {	/* only put one
							 * declaration onto
							 * stack */
			break_comma = true;	/* while in declaration,
						 * newline should be forced
						 * after comma */
			ps.p_stack[++ps.tos] = decl;
			ps.il[ps.tos] = ps.i_l_follow;

			if (ps.ljust_decl) {	/* only do if we want left
						 * justified declarations */
				ps.ind_level = 0;
				for (i = ps.tos - 1; i > 0; --i)
					if (ps.p_stack[i] == decl)
						++ps.ind_level;	/* indentation is number
								 * of declaration levels
								 * deep we are */
				ps.i_l_follow = ps.ind_level;
			}
		}
		break;

	case ifstmt:		/* scanned if (...) */
		if (ps.p_stack[ps.tos] == elsehead && ps.else_if)	/* "else if ..." */
			ps.i_l_follow = ps.il[ps.tos];
	case dolit:		/* 'do' */
	case forstmt:		/* for (...) */
		ps.p_stack[++ps.tos] = tk;
		ps.il[ps.tos] = ps.ind_level = ps.i_l_follow;
		++ps.i_l_follow;/* subsequent statements should be indented 1 */
		ps.search_brace = btype_2;
		break;

	case lbrace:		/* scanned { */
		break_comma = false;	/* don't break comma in an initial
					 * list */
		if (ps.p_stack[ps.tos] == stmt || ps.p_stack[ps.tos] == decl
		    || ps.p_stack[ps.tos] == stmtl)
			++ps.i_l_follow;	/* it is a random, isolated
						 * stmt group or a
						 * declaration */
		else {
			if (s_code == e_code) {
				/*
				 * only do this if there is nothing on the
				 * line 
				 */
				--ps.ind_level;
				/*
				 * it is a group as part of a while, for,
				 * etc. 
				 */
				if (ps.p_stack[ps.tos] == swstmt && ps.case_indent)
					--ps.ind_level;
				/*
				 * for a switch, brace should be two levels
				 * out from the code 
				 */
			}
		}

		ps.p_stack[++ps.tos] = lbrace;
		ps.il[ps.tos] = ps.ind_level;
		ps.p_stack[++ps.tos] = stmt;
		/* allow null stmt between braces */
		ps.il[ps.tos] = ps.i_l_follow;
		break;

	case whilestmt:	/* scanned while (...) */
		if (ps.p_stack[ps.tos] == dohead) {
			/* it is matched with do stmt */
			ps.ind_level = ps.i_l_follow = ps.il[ps.tos];
			ps.p_stack[++ps.tos] = whilestmt;
			ps.il[ps.tos] = ps.ind_level = ps.i_l_follow;
		} else {	/* it is a while loop */
			ps.p_stack[++ps.tos] = whilestmt;
			ps.il[ps.tos] = ps.i_l_follow;
			++ps.i_l_follow;
			ps.search_brace = btype_2;
		}

		break;

	case elselit:		/* scanned an else */

		if (ps.p_stack[ps.tos] != ifhead)
			diag(1, "Unmatched 'else'");
		else {
			ps.ind_level = ps.il[ps.tos];	/* indentation for else
							 * should be same as for
							 * if */
			ps.i_l_follow = ps.ind_level + 1;	/* everything following
								 * should be in 1 level */
			ps.p_stack[ps.tos] = elsehead;
			/* remember if with else */
			ps.search_brace = btype_2;
		}

		break;

	case rbrace:		/* scanned a } */
		/* stack should have <lbrace> <stmt> or <lbrace> <stmtl> */
		if (ps.p_stack[ps.tos - 1] == lbrace) {
			ps.ind_level = ps.i_l_follow = ps.il[--ps.tos];
			ps.p_stack[ps.tos] = stmt;
		} else
			diag(1, "Stmt nesting error.");
		break;

	case swstmt:		/* had switch (...) */
		ps.p_stack[++ps.tos] = swstmt;
		ps.cstk[ps.tos] = case_ind;
		/* save current case indent level */
		ps.il[ps.tos] = ps.i_l_follow;
		case_ind = ps.i_l_follow + ps.case_indent;	/* cases should be one
								 * level down from
								 * switch */
		ps.i_l_follow += ps.case_indent + 1;	/* statements should be
							 * two levels in */
		ps.search_brace = btype_2;
		break;

	case semicolon:	/* this indicates a simple stmt */
		break_comma = false;	/* turn off flag to break after
					 * commas in a declaration */
		ps.p_stack[++ps.tos] = stmt;
		ps.il[ps.tos] = ps.ind_level;
		break;

	default:		/* this is an error */
		diag(1, "Unknown code to parser");
		return;


	}			/* end of switch */

	reduce();		/* see if any reduction can be done */
#ifdef debug
	for (i = 1; i <= ps.tos; ++i)
		printf("(%d %d)", ps.p_stack[i], ps.il[i]);
	printf("\n");
#endif
	return;
}

/*
 * Copyright (C) 1976 by the Board of Trustees of the University of Illinois 
 *
 * All rights reserved 
 *
 *
 * NAME: reduce 
 *
 * FUNCTION: Implements the reduce part of the parsing algorithm 
 *
 * ALGORITHM: The following reductions are done.  Reductions are repeated until
 * no more are possible. 
 *
 * Old TOS              New TOS <stmt> <stmt>   <stmtl> <stmtl> <stmt>  <stmtl>
 * do <stmt>       "dostmt" if <stmt>      "ifstmt" switch <stmt>  <stmt>
 * decl <stmt>  <stmt> "ifelse" <stmt>  <stmt> for <stmt>       <stmt> while
 * <stmt> <stmt> "dostmt" while   <stmt> 
 *
 * On each reduction, ps.i_l_follow (the indentation for the following line) is
 * set to the indentation level associated with the old TOS. 
 *
 * PARAMETERS: None 
 *
 * RETURNS: Nothing 
 *
 * GLOBALS: ps.cstk ps.i_l_follow = ps.il ps.p_stack = ps.tos = 
 *
 * CALLS: None 
 *
 * CALLED BY: parse  
 *
 * HISTORY: initial coding      November 1976   D A Willcox of CAC 
 *
 */
/*----------------------------------------------*\
 * |   REDUCTION PHASE
\*----------------------------------------------*/
reduce()
{

	register int    i;

	for (;;) {		/* keep looping until there is nothing left
				 * to reduce */

		switch (ps.p_stack[ps.tos]) {

		case stmt:
			switch (ps.p_stack[ps.tos - 1]) {

			case stmt:
			case stmtl:
				/* stmtl stmt or stmt stmt */
				ps.p_stack[--ps.tos] = stmtl;
				break;

			case dolit:	/* <do> <stmt> */
				ps.p_stack[--ps.tos] = dohead;
				ps.i_l_follow = ps.il[ps.tos];
				break;

			case ifstmt:
				/* <if> <stmt> */
				ps.p_stack[--ps.tos] = ifhead;
				for (i = ps.tos - 1;
				     (
				      ps.p_stack[i] != stmt
				      &&
				      ps.p_stack[i] != stmtl
				      &&
				      ps.p_stack[i] != lbrace
				      );
				     --i);
				ps.i_l_follow = ps.il[i];
				/*
				 * for the time being, we will 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 
				 */
				break;

			case swstmt:
				/* <switch> <stmt> */
				case_ind = ps.cstk[ps.tos - 1];

			case decl:	/* finish of a declaration */
			case elsehead:
				/* <<if> <stmt> else> <stmt> */
			case forstmt:
				/* <for> <stmt> */
			case whilestmt:
				/* <while> <stmt> */
				ps.p_stack[--ps.tos] = stmt;
				ps.i_l_follow = ps.il[ps.tos];
				break;

			default:	/* <anything else> <stmt> */
				return;

			}	/* end of section for <stmt> on top of stack */
			break;

		case whilestmt:/* while (...) on top */
			if (ps.p_stack[ps.tos - 1] == dohead) {
				/* it is termination of a do while */
				ps.p_stack[--ps.tos] = stmt;
				break;
			} else
				return;

		default:	/* anything else on top */
			return;

		}
	}
}