overlaydirs/main.cc

/* SPDX-License-Identifier: Apache-2.0
 * (c) 2025, Konstantin Demin
 */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif

#include <cerrno>
#include <cstdio>
#include <cstdlib>

extern "C" {
	#include <unistd.h>
}

#include "overlay.hh"

static
void usage(int retcode = 0)
{
	static const char usage_msg[] =
	"overlaydirs 0.0.1\n"
	"Usage:\n"
	"  overlaydirs --help\n"
	"    show this message\n"
	"  overlaydirs --list [--no-sort|--zero] <source directory> [..<source directory>]\n"
	// TODO: shell-escape mode
	/* "  overlaydirs --list [--no-sort|--zero|--escape] <source directory> [..<source directory>]\n" */
	"    list entries\n"
	"  overlaydirs --merge <target directory> <source directory> [..<source directory>]\n"
	"    symlinks entries into <target directory>\n"
	"\n"
	"  --no-sort  - don't sort entries\n"
	"  --zero     - separate entries with NUL instead of LF\n"
	// TODO: shell-escape mode
	/*
	"  --escape   - shell-escape strings\n"
	"\n"
	"Notes:\n"
	" - flags \"--zero\" and \"--escape\" are mutually exclusive.\n"
	*/
	;

	(void) write(STDERR_FILENO, usage_msg, sizeof(usage_msg));

	exit(retcode);
}

static int main_list(int argc, char * argv[]);
static int main_merge(int argc, char * argv[]);

int main(int argc, char * argv[])
{
	if (argc < 2) usage(0);

	if ((strcmp(argv[1], "-h") == 0) || (strcmp(argv[1], "--help") == 0))
		usage(0);
	else if (strcmp(argv[1], "--list") == 0)
		return main_list(argc, argv);
	else if (strcmp(argv[1], "--merge") == 0)
		return main_merge(argc, argv);
	else
		usage(EINVAL);

	return 0;
}

static int main_list(int argc, char * argv[])
{
	if (argc < 3) usage(EINVAL);

	print_mode print_m = print_mode::_default;
	sort_mode sort_m = sort_mode::_default;

	int arg_start = 2;
	while (arg_start < argc) {
		char * _arg = argv[arg_start];

		if (strncmp(_arg, "--", 2) != 0) break;

		if (strcmp(_arg, "--") == 0) {
			arg_start++;
			break;
		}
		else if (strcmp(_arg, "--no-sort") == 0) {
			arg_start++;
			if (sort_m != sort_mode::_default) {
				(void) fprintf(stderr, "overlaydirs: no-sort mode already set\n");
			}
			sort_m = sort_mode::none;
		}
		else if (strcmp(_arg, "--zero") == 0) {
			arg_start++;
			if (print_m != print_mode::_default) {
				(void) fprintf(stderr, "overlaydirs: output mode already set\n");
			}
			print_m = print_mode::zero;
		}
		// TODO
		/*
		else if (strcmp(_arg, "--escape") == 0) {
			arg_start++;
			if (print_m != print_mode::_default) {
				(void) fprintf(stderr, "overlaydirs: output mode already set\n");
			}
			print_m = print_mode::shell_escape;
		}
		*/
		else {
			(void) fprintf(stderr, "overlaydirs: unknown option \"%s\"\n", _arg);
			// nevertheless, continue and try argument as a directory
			break;
		}
	}

	auto roots = std::vector<ovl_dirspec_t>();
	for (int i = arg_start; i < argc; i++) {
		ovl_dirspec_t t;
		if (!arg_to_rootspec(argv[i], &t, ovl_rootspec_flags::relative)) continue;
		roots.push_back(t);
	}
	if (roots.empty()) {
		(void) fprintf(stderr, "overlaydirs: no usable sources found\n");
		return EINVAL;
	}

	auto ovl = process_overlay(roots, sort_m);
	// not needed anymore
	roots.clear();
	roots.shrink_to_fit();

	list_overlay(ovl, print_m);
	return 0;
}

static int main_merge(int argc, char * argv[])
{
	if (argc < 4) usage(EINVAL);

	ovl_dirspec_t target;
	if (!arg_to_rootspec(argv[2], &target, ovl_rootspec_flags::relative)) {
		(void) fprintf(stderr, "overlaydirs: not a directory: \"%s\"\n", argv[2]);
		return EINVAL;
	}
	if (!is_empty_dir(target.fd)) {
		(void) fprintf(stderr, "overlaydirs: target directory is not empty\n");
		return EEXIST;
	}

	auto roots = std::vector<ovl_dirspec_t>();
	for (int i = 3; i < argc; i++) {
		ovl_dirspec_t t;
		if (!arg_to_rootspec(argv[i], &t)) continue;
		roots.push_back(t);
	}
	if (roots.empty()) {
		(void) fprintf(stderr, "overlaydirs: no usable sources found\n");
		return EINVAL;
	}

	auto ovl = process_overlay(roots);
	// not needed anymore
	roots.clear();
	roots.shrink_to_fit();

	int rv = merge_overlay(ovl, target);
	if (rv == -1) {
		(void) fprintf(stderr, "overlaydirs: target directory is not empty\n");
		return EEXIST;
	}

	return rv;
}