/*  @(#)lex.c 1.9 89/12/11
 *
 *  Lexical routines used by the popi program.
 *
 *  Popi was originally written by Gerard J. Holzmann - AT&T Bell Labs.
 *  This version is based on the code in his Prentice Hall book,
 *  "Beyond Photography - the digital darkroom," ISBN 0-13-074410-7,
 *  which is copyright (c) 1988 by Bell Telephone Laboratories, Inc. 
 *
 *  Permission is given to distribute these extensions, as long as these
 *  introductory messages are not removed, and no monies are exchanged.
 *
 *  No responsibility is taken for any errors or inaccuracies inherent
 *  either to the comments or the code of this program, but if reported
 *  (see README file) then an attempt will be made to fix them.
 */

#include <stdio.h>
#include <ctype.h>
#include <math.h>
#include "popi.h"

/* prototypes for local functions */
int	Getch P((void));
int	getnumber P((int));
int	getstring P((int));
int	follow P((int, int, int));

int	CharPos = 0,	/* Current character pos on input line */
	OldPos = 0,	/* previous character pos on input line */
	TokPos = 0;	/* position of the beginning of the current token */
char	ErrBuf[256];
double	lexfract;
double	hypot();

static int
Getch()
{
    int	c;

    c = disp_getchar();

    OldPos = CharPos;

    if (c == '\t')
	CharPos = (CharPos - 1) % 8 + 8;
    else if (c == '\n')
	CharPos = 0;
    else
	++CharPos;

    DEBUG((Debug, "Getch() => '%c'\n", c));

    if (LogStr)
	PUTC(c, LogStr);

    return c;
}

/* Skip to the end of the line */
void
Skip()
{
    while (lat != '\n' && lat != EOF)
	lat = Getch();
    lat = '\n';
}

void
error(errtype)
int	errtype;
{
    DEBUG((Debug, "error: type %d, pos %d msg '%s'\n", errtype, TokPos, ErrBuf));
    if (!noerr)			/* Already printed a message */
	return;
    disp_error(errtype, TokPos);
    Skip();
    noerr = FALSE;		/* an error has occurred */

    if (LogStr)
	FPRINTF(LogStr, "Error: %s\n", ErrBuf);
}

static int
getnumber(first)
int first;
{
    int c;

    lexval = first - '0';
    lexfract = 0.0;
    while (isdigit(c = Getch()))
	lexval = 10 * lexval + c - '0';

    /* Some of the special routines use floating values */
    if (c == '.')
    {
	double div = 10.0;

	while (isdigit(c = Getch()))
	{
	    lexfract += (c - '0') / div;
	    div *= 10.0;
	}
    }
    pushback(c);
    return VALUE;
}

static int
getstring(first)
int first;
{
    int		c = first;
    char	*str = text;

    do
    {
        *str++ = (char) c;
        c = Getch();
    }
    while (isalpha(c) || c == '_' || isdigit(c));
    *str = '\0';
    pushback(c);

    if (strcmp(text, "new") == 0)		return NEW;
    else if (strcmp(text, "sin") == 0)		return SIN;
    else if (strcmp(text, "cos") == 0)		return COS;
    else if (strcmp(text, "atan") == 0)		return ATAN;
    else if (strcmp(text, "hypot") == 0)	return HYPOT;
    else if (strcmp(text, "abs") == 0)		return ABS;
    else if (strcmp(text, "log") == 0)		return LOG;
    else if (strcmp(text, "sqrt") == 0)		return SQRT;
    else if (strcmp(text, "rand") == 0)		return RAND;

    for (c = 0; c < nsrc; c++)
	if (src[c].str && strcmp(src[c].str, text) == 0)
	{
	    lexval = c - 1;
	    return INAME;
	}

    if (strlen(text) > 1)
	return NAME;
    return first;
}

static int
follow(tok, ifyes, ifno)
int tok, ifyes, ifno;
{
    int c;

    if ((c = Getch()) == tok)
	return ifyes;
    pushback(c);
    return ifno;
}

/*
 *	Set the global lookahead token "lat".
 */
void
lex()
{
    DEBUG((Debug, "lex():\n"));

    do        /* ignore white space */
	lat = Getch();
    while (lat == ' ' || lat == '\t');

    TokPos = CharPos;

    if (isdigit(lat))
	lat = getnumber(lat);
    else if (isalpha(lat) || lat == '_')
	lat = getstring(lat);

    switch (lat)
    {
	case EOF:
	    lat = 'q';
	    break;

	case '*':
	    lat = follow('*', POW, lat);
	    break;

        case '>':
	    lat = follow('=', GE, lat);
            lat = follow('>', RSHIFT, lat);
            break;

        case '<':
	    lat = follow('=', LE, lat);
            lat = follow('<', LSHIFT, lat);
            break;

        case '!':
            lat = follow('=', NE, lat);
            break;

        case '=':
	    lat = follow('=', EQ, lat);
            break;

        case '|':
	    lat = follow('|', OR, lat);
            break;

        case '&':
	    lat = follow('&', AND, lat);
            break;

        case 'Z':
	    lat = VALUE;
            lexval = Zmax;
            break;

        case 'Y':
	    lat = VALUE;
            lexval = Ysize - 1;
            break;

        case 'X':
	    lat = VALUE;
            lexval = Xsize - 1;
            break;

        case 'R':
	    lat = VALUE;
            lexval = (int) hypot(Xsize / 2.0, Ysize / 2.0);
            break;

        case 'A':
	    lat = VALUE;
            lexval = 360;
            break;

	case '"':
	    {
		char	*str;
	        
		str = text;
		while ((lat = Getch()) != EOF && lat != '\n' && lat != '"')
		    *str++ = (char) lat;
		*str = '\0';
		if (lat != '"')
		{
		    SPRINTF(ErrBuf, "Expected matching '\"'");
		    error(ERR_PARSE);
		    return;
		}
	    }
	    lat = FNAME;
	    break;

	case ';':	/* comment to end of line */
	    Skip();
	    lat = '\n';
	    break;

        default:
	    break;
    }

    if (Debug)
    {
	if (lat < 127 && isprint(lat))
	    DEBUG((Debug, "lex() => '%c' (%d)\n", lat, lat));
	else
	    DEBUG((Debug, "lex() => (%d)\n", lat));
    }
}

void
pushback(c)
int c;
{
    DEBUG((Debug, "pushback('%c')\n", c));
    disp_ungetc(c);
    CharPos = OldPos;
}