/* This program transforms a MetaPost input file into a Troff input
 * file by stripping out btex...etex and verbatimtex...etex sections.
 * Leading and trailing spaces and tabs are removed from the extracted
 * material and it is surrounded by the preceeding and following strings
 * defined immediately below.  The input file should be given as argument 1
 * and the resulting TeX file is written on standard output.
 */

#include <stdio.h>
#define bufsize 1000

char*	predoc = ".po 0\n";
char*	postdoc = "";
char*	pretex1 = ".lf %d %s\n";		/* first instance */
char*	pretex = ".bp\n.lf line %d %s\n";	/* subsequent instances */
char*	posttex = "\n";
char*	preverb = ".lf %d %s\n";
char*	postverb = "\n";

char *mpname;
FILE *mpfile;
int lnno = 0;		/* current line number */
int texcnt = 0;		/* btex..etex blocks so far */
char buf[bufsize];	/* the input line */
char *bb, *tt, *aa;	/* start of before, token, and after strings */

void usage(nam)
	char *nam;
{
	fprintf(stderr, "Usage: %s <mp-file>\n", nam);
	exit(1);
}

void err(msg)
	char *msg;
{
	fprintf(stderr, "! Error in %s at line %d: %s\n", mpname, lnno, msg);
	exit(1);
}

char *getline()	/* returns NULL on EOF or error, otherwise buf */
{
	char *s;

	if (fgets(buf, bufsize, mpfile)==NULL)
		return NULL;
	lnno++;
	buf[bufsize-1] = '\n';
	for (s=buf; *s!='\n'; s++) /* do nothing */;
	if (s==&buf[bufsize-1]) err("Line is too long");
	*s = 0;
	return buf;
}


/* Return nonzero if a prefix of string s matches the null-terminated string t
 * and the next character is not a letter of an underscore.
 */
int match_str(s, t)
	char *s, *t;
{
	while (*t!=0) {
		if (*s!=*t) return 0;
		s++; t++;
	}
	switch (*s) {
	case 'a': case 'c': case 'd': case 'f': case 'g': case 'h':
	case 'i': case 'j': case 'k': case 'l': case 'm': case 'n':
	case 'o': case 'p': case 'q': case 'r': case 's': case 't':
	case 'u': case 'w': case 'x': case 'y': case 'z': case '_':
	case 'A': case 'B': case 'C': case 'D': case 'E': case 'F':
	case 'G': case 'H': case 'I': case 'J': case 'K': case 'L':
	case 'M': case 'N': case 'O': case 'P': case 'Q': case 'R':
	case 'S': case 'T': case 'U': case 'V': case 'W': case 'X':
	case 'Y': case 'Z': case 'b': case 'e': case 'v':
		return 0;
	default:
		return 1;
	}
}


/* This function tries to express s as the concatination of three strings
 * b, t, a, with the global pointers bb, tt, and aa set to the start of the
 * corresponding strings.  String t is either a quote mark, a percent sign,
 * or an alphabetic token "btex", "etex", or "verbatimtex".  (An alphabetic
 * token is a maximal sequence of letters and underscores.)  If there are
 * several possible substrings t, we choose the leftmost one.  If there is
 * no such t, we set b=s and return 0.
 */
int getbta(s)
	char *s;
{
	int ok=1;	/* zero if last character was a-z, A-Z, or _ */

	bb = s;
	for (tt=bb; *tt!=0; tt++)
		switch (*tt) {
		case '"': case '%':
			aa = tt+1;
			return 1;
		case 'b':
			if (ok && match_str(tt,"btex")) {
				aa = tt+4;
				return 1;
			} else ok=0;
			break;
		case 'e':
			if (ok && match_str(tt,"etex")) {
				aa = tt+4;
				return 1;
			} else ok=0;
			break;
		case 'v':
			if (ok && match_str(tt,"verbatimtex")) {
				aa = tt+11;
				return 1;
			} else ok=0;
			break;
		case 'a': case 'c': case 'd': case 'f': case 'g': case 'h':
		case 'i': case 'j': case 'k': case 'l': case 'm': case 'n':
		case 'o': case 'p': case 'q': case 'r': case 's': case 't':
		case 'u': case 'w': case 'x': case 'y': case 'z': case '_':
		case 'A': case 'B': case 'C': case 'D': case 'E': case 'F':
		case 'G': case 'H': case 'I': case 'J': case 'K': case 'L':
		case 'M': case 'N': case 'O': case 'P': case 'Q': case 'R':
		case 'S': case 'T': case 'U': case 'V': case 'W': case 'X':
		case 'Y': case 'Z':
			ok = 0;
			break;
		default:
			ok = 1;
		}
	aa = tt;
	return 0;
}


void copytex()
{
	char *s;	/* where a string to print stops */
	char c;

	do {	if (*aa==0)
			if ((aa=getline())!=NULL) printf("\n");
			else err("btex section does not end");
		if (getbta(aa) && *tt=='e') {
			s = tt-1;
			while (s>=bb && (*s==' ' || *s=='\t'))
				s--;
			s++;
		} else {
			if (*tt=='b') err("btex in TeX mode");
			if (*tt=='v') err("verbatimtex in TeX mode");
			s = aa;
		}
		c = *s;
		*s = 0;
		printf("%s", bb);
		*s = c;
	} while (*tt!='e');
}


void do_line()
{
	aa = buf;
	while (getbta(aa))
		if (*tt=='%') break;
		else if (*tt=='"') {
			do if (!getbta(aa)) err("string does not end");
			while (*tt!='"');
		} else if (*tt=='b') {
			if (texcnt++ ==0) printf(pretex1,lnno,mpname);
			else printf(pretex,lnno,mpname);
			while (*aa==' ' || *aa=='\t') aa++;
			copytex();
			printf("%s",posttex);
		} else if (*tt=='v') {
			printf(preverb,lnno,mpname);
			while (*aa==' ' || *aa=='\t') aa++;
			copytex();
			printf("%s",postverb);
		} else err("unmatched etex");
}



void main(argc, argv)
	char *argv[];
{
	if (argc!=2) usage(argv[0]);
	mpname = argv[1];
	mpfile = fopen(mpname, "r");
	if (mpname==NULL) usage(argv[0]);
	printf("%s",predoc);
	while (getline()!=NULL)
		do_line();
	printf("%s",postdoc);
	exit(0);
}