/*
 * fref creates troff-formatted references according to specifications
 * given on standard in. The specification syntax is similar to that of
 * refer, but differs in that all identifiers are two letters instead of
 * one (like troff itself). This allows for a larger number of fields.
 *
 * To build fref, run the following commands:
 *    $ lex fref.lex
 *    $ cc -std=c89 -O2 -o fref lex.yy.c -lfl
 */

%x ENTRY

	#include <err.h>
	#include <stdarg.h>

	#define MAX 255 /* Max field length. */

	#define DO_FIELDS						\
		DO("ad",ad,e.ad)	/* Access date. */		\
		DO("bo",bo,e.bo)	/* Book. */			\
		DO("ci",ci,e.ci)	/* City. */			\
		DO("da",da,e.da)	/* Date (year). */		\
		DO("ed",ed,e.ed)	/* Editor. */			\
		DO("hr",hr,e.hr)	/* Hypertext reference. */	\
		DO("jo",jo,e.jo)	/* Journal. */			\
		DO("la",la,e.la)	/* Label. */			\
		DO("no",no,e.no)	/* TODO: Issue number. */	\
		DO("pp",pp,e.pp)	/* Pages. */			\
		DO("pu",pu,e.pu)	/* Publisher. */		\
		DO("se",se,e.se)	/* TODO: Series. */		\
		DO("ti",ti,e.ti)	/* Title. */			\
		DO("tr",tr,e.tr)	/* Translator. */		\
		DO("vo",vo,e.vo)	/* Volume. */			\
		DO("xx",xx,e.xx)	/* Extra information. */	\
	/* END */

	void field(char *);
	void entry(void);
	void harvard(void);
	int pf(char *, ...);

	extern char *optarg;
	extern int optind;

	char *name;
	int line;	/* Line at which entry begins. */
	int lines = 0;	/* Total number of lines. */

	/* Fields of current entry. */
	struct entry {
	#define DO(s,n,m) char n[MAX];
		DO_FIELDS
	#undef DO
		int a;			/* Number of authors. */
		char au[MAX][MAX];	/* Authors. */
	} e;

	/* Translation strings. */
	struct translations {
		char *and;
		char *avail;
		char *ed;
		char *p;
		char *pp;
		char *tr;
		char *vo;
	} t;

%%
\n		lines++;	ECHO;
^%.*\n		line = ++lines;	field(yytext); BEGIN(ENTRY);
<ENTRY>^%.*\n	lines++;	field(yytext);
<ENTRY>^[^%]			entry(); ECHO; BEGIN(0);
<ENTRY><<EOF>>			entry(); yyterminate();
%%

void
main(int argc, char *argv[])
{
	char *lang;
	int c;

	/* Save program name. */
	name = strrchr(argv[0], '/');
	if(name) name++;
	else name = argv[0];

	/* Parse command-line options. */
	while((c = getopt(argc, argv, "l:")) != -1)
		switch(c){
		case 'l':
			lang = optarg;
			break;
		default:
			fprintf(stderr, "usage: %s [-lLANG]\n", argv[0]);
			exit(1);
		}
	argc -= optind;
	argv += optind;

	/* Set translation strings according to -l. */
	if(strncmp(lang, "sv", 2) == 0){
		t.and = strdup("och");
		t.avail = strdup("Tillgänglig: ");
		t.ed = strdup("red. ");
		t.p = strdup("s. ");
		t.pp = strdup("ss. ");
		t.tr = strdup("Övers. ");
		t.vo = strdup("vol. ");
	}else{
		t.and = strdup("and");
		t.avail = strdup("Available: ");
		t.ed = strdup("ed. ");
		t.p = strdup("p. ");
		t.pp = strdup("pp. ");
		t.tr = strdup("Trans. ");
		t.vo = strdup("vol. ");
	}

	/* Clear entry struct. */
	memset(&e, 0, sizeof(e));

	yylex();
}

/* Save entry field. */
void
field(char *s)
{
	s++;
	s[strcspn(s, "\n")] = 0;

	/* Fill corresponding field. */
#define AS(a,b) if(strncmp(s, a, 2) == 0 && (s += 3)){ strcpy(b, s); return; }
	AS("au",e.au[e.a++]);
#define DO(s,n,m) AS(s,m)
	DO_FIELDS
#undef DO

	/*
	 * As no field matched, an error is printed and the program exits
	 * with a positive value.
	 */
	fprintf(stderr, "%s: unrecognized field %%%.2s at line %d\n",
		name, s, lines);
	exit(1);
}

/* Print formatted entry. */
void
entry()
{
	/*
	   Presently, fref supports only Harvard-style citations, but
	   this allows for future extensions.
	 */
	harvard();
}

/* Print Harvard-formatted entry. */
void
harvard()
{
	int i;

	/* Print label. */
	pf("% = ", e.la);

	/* Print authors. */
	for(i = 0; i < e.a-2; i++)
		printf("%s, ", e.au[i]);
	if(i == e.a-2)
		printf("%s %s ", e.au[i++], t.and);
	if(i == e.a-1)
		printf("%s", e.au[i]);

	/* Print date. */
	(pf(" (%).\n", e.da) || (e.a ? pf(".\n") : 0));

	/* Print title, book/journal. */
	if(*e.bo || *e.jo){
		pf("%.\n", e.ti);
		pf("\\fI%\\fP", e.bo ? e.bo : e.jo);
		pf(" (*%)", t.ed, e.ed);
	}else
		pf("\\fI%\\fP", e.ti);

	/* Print volume. */
	pf(", *%", t.vo, e.vo);

	/* Print pages, converting hyphens to en dashes. */
	if(*e.pp){
		printf(", %s", strpbrk(e.pp, ",-") ? t.pp : t.p);
		for(i = 0; i < strlen(e.pp); i++){
			if(e.pp[i] == '-') putchar('\\');
			putchar(e.pp[i]);
		}
		*e.pp = 0;
	}
	pf(".\n");

	/* Print translator. */
	pf("*%.\n", t.tr, e.tr);

	/* Print city, publisher. */
	(pf("%: %.\n", e.ci, e.pu) || pf("%.\n", e.pu));

	/* Print other information. */
	pf("%.\n", e.xx);

	/* Print hypertext reference. */
	pf("*%\n", t.avail, e.hr);

	/* Print access date. */
	pf("[%]\n", e.ad);

	/* Clear unused fields. */
	e.a = 0;
#define DO(s,n,m)							\
	if(*m) fprintf(stderr, "%s: unused field %%"s" at line %d\n",	\
		name, line);						\
	*m = 0;
	DO_FIELDS
#undef DO
}

/*
 * This function interpolates any number of strings into a formatted
 * string, which is printed only if all interpolated strings are non-empty.
 * Interpolation points are marked by % or *. If a string is interpolated
 * using %, the function empties it after printing it.
 */
int
pf(char *fmt, ...)
{
	char *buf, *p, **fs;
	int i, n, sz;
	va_list ap;

	/* Count interpolated strings. */
	for(n = 0, p = fmt; *p; p++)
		if(*p == '%' || *p == '*')
			n++;

	if(!(fs = malloc(n)))
		err(1, "malloc");

	/*
	 * The strings to be interpolated are saved in fs.
	 * If any string is empty, the function returns false.
	 */
	va_start(ap, fmt);
	for(i = 0; i < n; i++){
		p = va_arg(ap, char *);
		if(!p || !*p)
			return 0;
		fs[i] = p;
	}
	va_end(ap);

	/* Print formatted string. */
	for(i = 0; *fmt; fmt++)
		switch(*fmt){
		case '%':
			printf("%s", fs[i]);
			fs[i][0] = 0;
			i++;
			break;
		case '*':
			printf("%s", fs[i]);
			i++;
			break;
		default:
			putchar(*fmt);
		}
	return 1;
}