From 7574f425c08a8469304038ac89318fe359dfc16f Mon Sep 17 00:00:00 2001
From: Andre Noll <maan@tuebingen.mpg.de>
Date: Sun, 28 Apr 2024 04:01:50 +0200
Subject: [PATCH] Implement help subommand.

---
 dss.c     | 50 +++++++++++++++++++++++++++++++++++++++++++++-----
 dss.suite | 21 +++++++++++++++++++++
 2 files changed, 66 insertions(+), 5 deletions(-)

diff --git a/dss.c b/dss.c
index 0992ec6..8e369ca 100644
--- a/dss.c
+++ b/dss.c
@@ -1837,20 +1837,57 @@ static void handle_version_and_help(void)
 	exit(EXIT_SUCCESS);
 }
 
-static void show_subcommand_summary(void)
+static void show_subcommand_summary(bool verbose)
 {
 	const struct lls_command *cmd;
 	int i;
 
-	printf("Available subcommands:\n");
+	printf("Available subcommands: ");
+	if (!verbose) {
+		for (i = 1; (cmd = lls_cmd(i, dss_suite)); i++) {
+			if (i > 1)
+				printf(", ");
+			printf("%s", lls_command_name(cmd));
+		}
+		return;
+	}
+	printf("\n");
 	for (i = 1; (cmd = lls_cmd(i, dss_suite)); i++) {
 		const char *name = lls_command_name(cmd);
 		const char *purpose = lls_purpose(cmd);
 		printf("%-11s%s\n", name, purpose);
 	}
-	exit(EXIT_SUCCESS);
 }
 
+static int com_help(void)
+{
+	int ret;
+	char *errctx, *help;
+	const char *arg;
+	const struct lls_command *cmd;
+
+	ret = lls_check_arg_count(sublpr, 0, 1, &errctx);
+	if (ret < 0)
+		return lopsub_error(ret, &errctx);
+	if (lls_num_inputs(sublpr) == 0) {
+		show_subcommand_summary(OPT_GIVEN(HELP, LONG));
+		return 0;
+	}
+	arg = lls_input(0, sublpr);
+	ret = lls_lookup_subcmd(arg, dss_suite, &errctx);
+	if (ret < 0)
+		return lopsub_error(ret, &errctx);
+	cmd = lls_cmd(ret, dss_suite);
+	if (OPT_GIVEN(HELP, LONG))
+		help = lls_long_help(cmd);
+	else
+		help = lls_short_help(cmd);
+	printf("%s\n", help);
+	free(help);
+	return 0;
+}
+EXPORT_CMD_HANDLER(help);
+
 int main(int argc, char **argv)
 {
 	int ret;
@@ -1869,8 +1906,11 @@ int main(int argc, char **argv)
 		goto out;
 	handle_version_and_help();
 	num_inputs = lls_num_inputs(lpr);
-	if (num_inputs == 0)
-		show_subcommand_summary();
+	if (num_inputs == 0) { /* show verbose summary */
+		show_subcommand_summary(true);
+		ret = 0;
+		goto out;
+	}
 	ret = lls_lookup_subcmd(argv[argc - num_inputs], dss_suite, &errctx);
 	if (ret < 0) {
 		ret = lopsub_error(ret, &errctx);
diff --git a/dss.suite b/dss.suite
index f9cf8af..6d1ed4a 100644
--- a/dss.suite
+++ b/dss.suite
@@ -540,6 +540,27 @@ caption = Subcommands
 		exits successfully or prints information about the first syntax error
 		detected and terminates with exit code 1.
 	[/description]
+[subcommand help]
+	purpose = list available subcommands or print subcommand-specific help
+	non-opts-name = [subcommand]
+	[description]
+		Without any arguments, help prints the list of available
+		subcommands. When called with a subcommand name argument, it prints
+		the help text of the given subcommand.
+	[/description]
+	[option long]
+		short_opt = l
+		summary = show the long help text
+		[help]
+			If the optional argument is supplied, the long help text contains the
+			synopsis, the purpose and the description of the specified subcommand,
+			followed by the option list including summary and help text of each
+			option. Without --long, the short help is shown instead. This omits
+			the description of the subcommand and the option help.
+
+			If no subcommand is supplied but --long is given, the list contains the
+			purpose of each subcommand.
+		[/help]
 
 [section copyright]
 	Written by Andre Noll
-- 
2.39.2