/*
 * fold.c
 * Implementation of SUSv3 XCU fold utility
 * Copyright © 2007 Rich Felker
 * Licensed under the terms of the GNU General Public License, v2 or later
 */

#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <stdio.h>
#include <wchar.h>
#include <wctype.h>
#include <unistd.h>
#include <limits.h>
#include <locale.h>
#include <errno.h>

static void my_perror(char *prog, char *msg)
{
	char *err = strerror(errno);
	write(2, prog, strlen(prog));
	write(2, ": ", 2);
	write(2, msg, strlen(msg));
	write(2, ": ", 2);
	write(2, err, strlen(err));
	write(2, "\n", 1);
}

int main(int argc, char *argv[])
{
	int b;
	char *name;
	char dummy[MB_LEN_MAX];
	size_t i, j, len=127;
	wchar_t wc, *buf = malloc(sizeof wc * len);
	long col, out_col, width=80;
	int w;
	int splitable;
	int byte=0, space=0;
	FILE *f;
	
	if (!setlocale(LC_CTYPE, ""))
		my_perror(argv[0], "setlocale");

	while ((b = getopt(argc, argv, "bsw:")) != EOF) switch(b) {
	case 'b': byte=1; break;
	case 's': space=1; break;
	case 'w':
		width=strtoul(optarg, NULL, 10);
		break;
	default:
		return 1;
	}

	if (optind == argc) {
		f = stdin;
		name = "-";
		goto nofiles;
	}

	while (optind < argc) {
		f = fopen(name=argv[optind++], "rb");
		if (!f) {
			my_perror(argv[0], name);
			continue;
		}
nofiles:
		i = col = out_col = 0;
		splitable = -1;
		while ((wc = getwc(f))>=0) {
			if (i == len) {
				buf = realloc(buf, sizeof wc * (len=len<<1|1));
				if (!buf) {
					my_perror(argv[0], "realloc");
					return 1;
				}
			}
			buf[i++] = wc;

			if (wc == '\n') {
				col = 0;
				splitable = -1;
				goto output;
			}
			else if (byte) w = wctomb(dummy, wc);
			else if (wc == '\t') {
				w = 8-(col&7);
				if (w > width - col) w = 8;
			}
			else if (wc == '\r') col = w = 0;
			else if (wc == '\b') {
				if (col) col--;
				w = 0;
			}
			else w = wcwidth(wc);
			
			if (col && w > width - col) {
				if (putwchar('\n')==WEOF) goto werr;
				col -= out_col;
				splitable = -1;
			}
			col += w;

			if (space && iswblank(wc))
				splitable = 1;
			if (splitable) {
output:
				for (j=0; j<i; j++)
					if (putwchar(buf[j])==WEOF) goto werr;
				i = 0;
				out_col = col;
				splitable >>= 1;
			}
		}
		if (ferror(f)) my_perror(argv[0], name);
		if (f != stdin) fclose(f);
	}
	return 0;
werr:
	my_perror(argv[0], "write error");
	return 1;
}