/* xlread - xlisp expression input routine */

#ifdef AZTEC
#include "stdio.h"
#include "setjmp.h"
#else
#include <stdio.h>
#include <setjmp.h>
#include <ctype.h>
#endif

#include "xlisp.h"

/* external variables */
extern jmp_buf *xljmpbuf;
extern struct node *s_quote;
extern struct node *xlstack;
extern int xlplevel;

/* external routines */
extern FILE *fopen();

/* forward declarations */
FORWARD struct node *plist();
FORWARD struct node *pstring();
FORWARD struct node *pquote();
FORWARD struct node *pname();

/* xlload - load a file of xlisp expressions */
int xlload(name)
  char *name;
{
    jmp_buf loadjmpbuf,*oldjmpbuf;
    struct node *oldstk,fptr,val;
    char fname[50];
    FILE *fp;

    /* create a new stack frame */
    oldstk = xlsave(&fptr,&val,NULL);

    /* add the default extension */
    strcpy(fname,name); strcat(fname,".lsp");

    /* open the file */
    if ((fp = fopen(fname,"r")) == NULL)
	return (FALSE);

    /* allocate a file node */
    fptr.n_ptr = newnode(FPTR);
    fptr.n_ptr->n_fp = fp;
    fptr.n_ptr->n_savech = 0;

    /* setup to trap errors */
    oldjmpbuf = xljmpbuf;
    if (setjmp(xljmpbuf = loadjmpbuf)) {
	fclose(fp);
	longjmp(xljmpbuf = oldjmpbuf,1);
    }

    /* read and evaluate each expression in the file */
    while (xlread(fptr.n_ptr,&val.n_ptr))
	xleval(val.n_ptr);

    /* restore error trapping context and previous stack frame */
    xljmpbuf = oldjmpbuf;
    xlstack = oldstk;

    /* close the file */
    fclose(fp);

    /* return successfully */
    return (TRUE);
}

/* xlread - read an xlisp expression */
int xlread(fptr,pval)
  struct node *fptr,**pval;
{
    /* initialize */
    xlplevel = 0;

    /* parse an expression */
    return (parse(fptr,pval));
}

/* parse - parse an xlisp expression */
LOCAL int parse(fptr,pval)
  struct node *fptr,**pval;
{
    int ch;

    /* keep looking for a node skipping comments */
    while (TRUE)

	/* check next character for type of node */
	switch (ch = nextch(fptr)) {
	case EOF:
		return (FALSE);
	case '\'':			/* a quoted expression */
		*pval = pquote(fptr);
		return (TRUE);
	case '(':			/* a sublist */
		*pval = plist(fptr);
		return (TRUE);
	case ')':			/* closing paren - shouldn't happen */
		xlfail("extra right paren");
	case '.':			/* dot - shouldn't happen */
		xlfail("misplaced dot");
	case ';':			/* a comment */
		pcomment(fptr);
		break;
	case '"':			/* a string */
		*pval = pstring(fptr);
		return (TRUE);
	default:
		if (issym(ch))		/* a name */
		    *pval = pname(fptr);
		else
		    xlfail("invalid character");
		return (TRUE);
	}
}

/* pcomment - parse a comment */
LOCAL pcomment(fptr)
  struct node *fptr;
{
    int ch;

    /* skip to end of line */
    while ((ch = checkeof(fptr)) != EOF && ch != '\n')
	;
}

/* plist - parse a list */
LOCAL struct node *plist(fptr)
  struct node *fptr;
{
    struct node *oldstk,val,*lastnptr,*nptr;
    int ch;

    /* increment the nesting level */
    xlplevel += 1;

    /* create a new stack frame */
    oldstk = xlsave(&val,NULL);

    /* skip the opening paren */
    xlgetc(fptr);

    /* keep appending nodes until a closing paren is found */
    lastnptr = NULL;
    for (lastnptr = NULL; (ch = nextch(fptr)) != ')'; lastnptr = nptr) {

	/* check for end of file */
	if (ch == EOF)
	    badeof();

	/* check for a dotted pair */
	if (ch == '.') {

	    /* skip the dot */
	    xlgetc(fptr);

	    /* make sure there's a node */
	    if (lastnptr == NULL)
		xlfail("invalid dotted pair");

	    /* parse the expression after the dot */
	    if (!parse(fptr,&lastnptr->n_listnext))
		badeof();

	    /* make sure its followed by a close paren */
	    if (nextch(fptr) != ')')
		xlfail("invalid dotted pair");

	    /* done with this list */
	    break;
	}

	/* allocate a new node and link it into the list */
	nptr = newnode(LIST);
	if (lastnptr == NULL)
	    val.n_ptr = nptr;
	else
	    lastnptr->n_listnext = nptr;

	/* initialize the new node */
	if (!parse(fptr,&nptr->n_listvalue))
	    badeof();
    }

    /* skip the closing paren */
    xlgetc(fptr);

    /* restore the previous stack frame */
    xlstack = oldstk;

    /* decrement the nesting level */
    xlplevel -= 1;

    /* return successfully */
    return (val.n_ptr);
}

/* pstring - parse a string */
LOCAL struct node *pstring(fptr)
  struct node *fptr;
{
    struct node *oldstk,val;
    char sbuf[STRMAX+1];
    int ch,i,d1,d2,d3;

    /* create a new stack frame */
    oldstk = xlsave(&val,NULL);

    /* skip the opening quote */
    xlgetc(fptr);

    /* loop looking for a closing quote */
    for (i = 0; i < STRMAX && (ch = checkeof(fptr)) != '"'; i++) {
	switch (ch) {
	case EOF:
		badeof();
	case '\\':
		switch (ch = checkeof(fptr)) {
		case 'e':
			ch = '\033';
			break;
		case 'n':
			ch = '\n';
			break;
		case 'r':
			ch = '\r';
			break;
		case 't':
			ch = '\t';
			break;
		default:
			if (ch >= '0' && ch <= '7') {
			    d1 = ch - '0';
			    d2 = checkeof(fptr) - '0';
			    d3 = checkeof(fptr) - '0';
			    ch = (d1 << 6) + (d2 << 3) + d3;
			}
			break;
		}
	}
	sbuf[i] = ch;
    }
    sbuf[i] = 0;

    /* initialize the node */
    val.n_ptr = newnode(STR);
    val.n_ptr->n_str = strsave(sbuf);
    val.n_ptr->n_strtype = DYNAMIC;

    /* restore the previous stack frame */
    xlstack = oldstk;

    /* return the new string */
    return (val.n_ptr);
}

/* pquote - parse a quoted expression */
LOCAL struct node *pquote(fptr)
  struct node *fptr;
{
    struct node *oldstk,val;

    /* create a new stack frame */
    oldstk = xlsave(&val,NULL);

    /* skip the quote character */
    xlgetc(fptr);

    /* allocate two nodes */
    val.n_ptr = newnode(LIST);
    val.n_ptr->n_listvalue = s_quote;
    val.n_ptr->n_listnext = newnode(LIST);

    /* initialize the second to point to the quoted expression */
    if (!parse(fptr,&val.n_ptr->n_listnext->n_listvalue))
	badeof();

    /* restore the previous stack frame */
    xlstack = oldstk;

    /* return the quoted expression */
    return (val.n_ptr);
}

/* pname - parse a symbol name */
LOCAL struct node *pname(fptr)
  struct node *fptr;
{
    char sname[STRMAX+1];
    struct node *val;
    int ch,i;

    /* get symbol name */
    for (i = 0; i < STRMAX && issym(xlpeek(fptr)); )
	sname[i++] = xlgetc(fptr);
    sname[i] = 0;

    /* check for a number or enter the symbol into the oblist */
    return (isnumber(sname,&val) ? val : xlenter(sname,DYNAMIC));
}

/* nextch - look at the next non-blank character */
LOCAL int nextch(fptr)
  struct node *fptr;
{
    int ch;

    /* return and save the next non-blank character */
    while ((ch = xlpeek(fptr)) != EOF && isspace(ch))
	xlgetc(fptr);
    return (ch);
}

/* checkeof - get a character and check for end of file */
LOCAL int checkeof(fptr)
  struct node *fptr;
{
    int ch;

    if ((ch = xlgetc(fptr)) == EOF)
	badeof();
    return (ch);
}

/* badeof - unexpected eof */
LOCAL badeof()
{
    xlfail("unexpected EOF");
}

/* isnumber - check if this string is a number */
int isnumber(str,pval)
  char *str; struct node **pval;
{
    char *p;
    int d;

    /* initialize */
    p = str; d = 0;

    /* check for a sign */
    if (*p == '+' || *p == '-')
	p++;

    /* check for a string of digits */
    while (isdigit(*p))
	p++, d++;

    /* make sure there was at least one digit and this is the end */
    if (d == 0 || *p)
	return (FALSE);

    /* convert the string to an integer and return successfully */
    *pval = newnode(INT);
    (*pval)->n_int = atoi(*str == '+' ? ++str : str);
    return (TRUE);
}

/* issym - check whether a character if valid in a symbol name */
LOCAL int issym(ch)
  int ch;
{
    if (ch <= ' ' ||
    	ch == '(' ||
    	ch == ')' ||
    	ch == ';' || 
    	ch == '.' ||
    	ch == '"' ||
    	ch == '\'')
	return (FALSE);
    else
	return (TRUE);
}