/* See LICENSE file for copyright and license details. */
#include <libsimple.h>
#include <libsimple-arg.h>

NUSAGE(2, "directory-1 file-list-1 directory-2 file-list-2");


LIBSIMPLE_PURE
static int
parse_fd(const char *s, int dash_fd)
{
	int fd, d;

	if (streq(s, "/dev/stdin"))
		return STDIN_FILENO;
	if (streq(s, "/dev/stdout"))
		return STDOUT_FILENO;
	if (streq(s, "/dev/stderr"))
		return STDERR_FILENO;
	if (streq(s, "-"))
		return dash_fd;

	if (strstarts(s, "/proc/self/fd/"))
		s = &s[sizeof("/proc/self/fd/") - 1u];
	else if (strstarts(s, "/dev/fd/"))
		s = &s[sizeof("/dev/fd/") - 1u];
	else
		return -1;

	if ('0' > *s || *s > '9')
		return -1;
	fd = (int)(*s++ - '0');
	while ('0' <= *s && *s <= '9') {
		d = (int)(*s - '0');
		if (fd > (INT_MAX - d) / 10)
			return -1;
		fd = fd * 10 + d;
	}

	return *s ? -1 : fd;
}


static char **
get_file_list(const char *path, size_t *n_out)
{
	char *buf = NULL;
	size_t bufsize = 0u;
	size_t len = 0u;
	size_t off, i, j, d;
	int fd, do_close;
	ssize_t r;
	char **list = NULL;
	size_t listsize = 0u;

	*n_out = 0u;

	do_close = 0;
	fd = parse_fd(path, STDIN_FILENO);
	if (fd < 0) {
		do_close = 1;
		fd = open(path, O_RDONLY);
		if (fd < 0)
			eprintf("open %s O_RDONLY:", path);
	}

	for (;;) {
		if (len == bufsize)
			buf = erealloc(buf, bufsize += (size_t)8 << 10);
		r = read(fd, &buf[len], bufsize - len);
		if (r <= 0) {
			if (!r)
				break;
			if (errno == EINTR)
				continue;
			eprintf("read %s:", path);
		}
		len += (size_t)r;
	}

	if (do_close)
		close(fd);

	buf = erealloc(buf, len + 1u);
	buf[len++] = '\0';

	off = 0u;
	for (i = 0u; i < len; i++) {
		if (buf[i])
			continue;
		if (i == off)
			goto next;
		while (buf[off] == '/')
			off += 1u;
		if (buf[off + 0u] == '.' && buf[off + 1u] == '/')
			off += 2u;
		if (!buf[off])
			goto next;
		if (buf[off + 0u] == '.' && !buf[off + 1u])
			goto next;

		d = buf[i - 1u] == '/' ? 1u : 0u;
		buf[i - d] = '\0';
		if (!buf[off])
			goto next;

		if (*n_out == listsize)
			list = ereallocarray(list, listsize += 128u, sizeof(*list));
		list[(*n_out)++] = estrdup(&buf[off]);
		for (j = i - 1u - d; j > off; j--) {
			if (buf[j] != '/')
				continue;
			buf[j] = '\0';
			if (*n_out == listsize)
				list = ereallocarray(list, listsize += 128u, sizeof(*list));
			list[(*n_out)++] = estrdup(&buf[off]);
		}

	next:
		off = i + 1u;
	}

	free(buf);
	return list;
}


static size_t
uniq(char **list, size_t n)
{
	size_t r, w = 1u;
	if (!n)
		return 0u;
	for (r = 1u; r < n; r++) {
		if (strcmp(list[r], list[w - 1u]))
			list[w++] = list[r];
		else
			free(list[r]);
	}
	return w;
}


static int
files_equal(int fd1, const char *dir1, int fd2, const char *dir2, const char *path)
{
	static char buf1[8192];
	static char buf2[sizeof(buf1)];
	size_t len1, len2;
	ssize_t r;

	do {
		len1 = 0u;
		while (len1 < sizeof(buf1)) {
			r = read(fd1, &buf1[len1], sizeof(buf1) - len1);
			if (r <= 0) {
				if (!r)
					break;
				if (errno == EINTR)
					continue;
				eprintf("read %s/%s:", dir1, path);
			}
			len1 += (size_t)r;
		}

		len2 = 0u;
		while (len2 < sizeof(buf2)) {
			r = read(fd2, &buf2[len2], sizeof(buf2));
			if (r <= 0) {
				if (!r)
					break;
				if (errno == EINTR)
					continue;
				eprintf("read %s/%s:", dir2, path);
			}
			len2 += (size_t)r;
		}

		if (len1 != len2 || memcmp(buf1, buf2, len1))
			return 0;
	} while (len1 && len2);

	return !len1 && !len2;
}


int
main(int argc, char *argv[])
{
	struct stat st1, st2;
	const char *dir1, *dir2;
	char **files1, **files2;
	size_t nfiles1, nfiles2, i, j;
	char *target1, *target2;
	int dirfd1, dirfd2, cmp;
	int fd1, fd2;
	int ret = 0;

	libsimple_default_failure_exit = 2;

	ARGBEGIN {
	default:
		usage();
	} ARGEND;

	if (argc != 4)
		usage();

	dir1 = argv[0];
	dir2 = argv[2];
	dirfd1 = open(dir1, O_PATH);
	if (dirfd1 < 0)
		eprintf("open %s O_PATH", dir1);
	dirfd2 = open(dir2, O_PATH);
	if (dirfd2 < 0)
		eprintf("open %s O_PATH", dir2);

	files1 = get_file_list(argv[1], &nfiles1);
	files2 = get_file_list(argv[3], &nfiles2);
	libsimple_qsort_str((void *)files1, nfiles1);
	libsimple_qsort_str((void *)files2, nfiles2);
	nfiles1 = uniq(files1, nfiles1);
	nfiles2 = uniq(files2, nfiles2);

	i = j = 0u;
	while (i < nfiles1 || j < nfiles2) {
		if (i == nfiles1) {
		exclusive_to_dir2:
			weprintf("%s exists only in %s\n", files2[j], dir2);
			j++;
			ret = 1;
			continue;
		}
		if (j == nfiles2) {
		exclusive_to_dir1:
			weprintf("%s exists only in %s\n", files1[i], dir1);
			i++;
			ret = 1;
			continue;
		}

		cmp = strcmp(files1[i], files2[j]);
		if (cmp < 0)
			goto exclusive_to_dir1;
		if (cmp > 1)
			goto exclusive_to_dir2;

		if (fstatat(dirfd1, files1[i], &st1, AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT))
			eprintf("fstatat %s %s AT_SYMLINK_NOFOLLOW|AT_NO_AUTOMOUNT:", dir1, files1[i]);
		if (fstatat(dirfd2, files2[j], &st2, AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT))
			eprintf("fstatat %s %s AT_SYMLINK_NOFOLLOW|AT_NO_AUTOMOUNT:", dir2, files2[j]);

		if ((st1.st_mode & S_IFMT) != (st2.st_mode & S_IFMT)) {
			weprintf("%s has different file types in %s and %s\n", files1[i], dir1, dir2);
			ret = 1;
			goto next;
		}

		switch (st1.st_mode & S_IFMT) {
		case S_IFREG:
			if ((st1.st_mode ^ st2.st_mode) & S_IXUSR) {
				weprintf("%s is executable in one of but in not both of %s and %s\n", files1[i], dir1, dir2);
				ret = 1;
			}
			if (st1.st_size != st2.st_size) {
				weprintf("%s has different sizes in %s and %s\n", files1[i], dir1, dir2);
				ret = 1;
				goto next;
			}
			fd1 = openat(dirfd1, files1[i], O_RDONLY | O_NOFOLLOW);
			if (fd1 < 0)
				eprintf("openat %s %s O_RDONLY|O_NOFOLLOW:", dir1, files1[i]);
			fd2 = openat(dirfd2, files2[j], O_RDONLY | O_NOFOLLOW);
			if (fd2 < 0)
				eprintf("openat %s %s O_RDONLY|O_NOFOLLOW:", dir2, files2[j]);
			if (!files_equal(fd1, dir1, fd2, dir2, files1[i])) {
				weprintf("%s has different contents in %s and %s\n", files1[i], dir1, dir2);
				ret = 1;
			}
			close(fd1);
			close(fd2);
			break;

		case S_IFLNK:
			target1 = libsimple_ereadlinkat(dirfd1, files1[i]);
			target2 = libsimple_ereadlinkat(dirfd2, files2[j]);
			if (strcmp(target1, target2)) {
				weprintf("%s has different targets in %s and %s\n", files1[i], dir1, dir2);
				ret = 1;
			}
			free(target1);
			free(target2);
			break;

		case S_IFDIR:
			break;

		default:
			eprintf("%s has unsupported file type\n", files1[i]);
		}

	next:
		i++;
		j++;
	}

	close(dirfd1);
	close(dirfd2);
	while (nfiles1--)
		free(files1[nfiles1]);
	while (nfiles2--)
		free(files2[nfiles2]);
	free(files1);
	free(files2);
	return ret;
}