/*
 * cli.c - argument parsing for the stupidtools entrypoint.
 *
 * Manual parsing on purpose: the flag surface is tiny and fully under
 * our control, so there is no need for getopt's permutation rules or
 * its platform quirks. Unknown options are usage errors (exit 2) with
 * the usage text on stderr; a missing buildfile is a runtime error
 * (exit 1). -- terminates option parsing so a buildfile whose name
 * starts with '-' stays addressable.
 *
 * Copyright (c) 2026 huntedbytheirs
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include "cli.h"

#include <string.h>

static const char *
program_name(const char *argv0)
{
	if (argv0 == NULL || argv0[0] == '\0') {
		return "stupidtools";
	}
	return argv0;
}

static int
is_option(const char *arg)
{
	return arg[0] == '-' && arg[1] != '\0' && strcmp(arg, "-") != 0;
}

void
cli_print_usage(FILE *stream, const char *program)
{
	fprintf(stream,
	    "Usage: %s [OPTIONS] <buildfile.kdl>\n"
	    "\n"
	    "Reads a KDL build file and emits a POSIX-sh ./configure script.\n"
	    "\n"
	    "Options:\n"
	    "  -h, --help     show this help and exit\n"
	    "  -V, --version  print version and exit\n"
	    "\n"
	    "Note: buildfile processing is not yet implemented.\n",
	    program);
}

/* Take the next positional argument, reporting usage errors to stderr.
 * Returns CLI_ACTION_ERROR (with usage printed) or CLI_ACTION_RUN. */
static enum cli_action
take_positional(const char *arg, struct cli_opts *opts)
{
	if (opts->buildfile != NULL) {
		fprintf(stderr, "%s: unexpected extra argument '%s'\n",
		    opts->program, arg);
		cli_print_usage(stderr, opts->program);
		return CLI_ACTION_ERROR;
	}
	opts->buildfile = arg;
	return CLI_ACTION_RUN;
}

enum cli_action
cli_parse(int argc, char **argv, struct cli_opts *opts)
{
	enum cli_action action;
	int i;

	opts->program = program_name(argc > 0 ? argv[0] : NULL);
	opts->buildfile = NULL;

	for (i = 1; i < argc; i++) {
		const char *arg = argv[i];

		if (!is_option(arg)) {
			action = take_positional(arg, opts);
			if (action != CLI_ACTION_RUN) {
				return action;
			}
			continue;
		}

		if (strcmp(arg, "--") == 0) {
			for (i++; i < argc; i++) {
				action = take_positional(argv[i], opts);
				if (action != CLI_ACTION_RUN) {
					return action;
				}
			}
			break;
		}

		if (strcmp(arg, "-h") == 0 || strcmp(arg, "--help") == 0) {
			cli_print_usage(stdout, opts->program);
			return CLI_ACTION_HELP;
		}

		if (strcmp(arg, "-V") == 0 || strcmp(arg, "--version") == 0) {
			return CLI_ACTION_VERSION;
		}

		fprintf(stderr, "%s: unrecognized option '%s'\n",
		    opts->program, arg);
		cli_print_usage(stderr, opts->program);
		return CLI_ACTION_ERROR;
	}

	return CLI_ACTION_RUN;
}