From f92b5a516eddbdf33a69e95da6678eb9c9ef8c8c Mon Sep 17 00:00:00 2001
From: Bent Bisballe Nyeng <deva@aasimon.org>
Date: Tue, 4 Jun 2019 13:31:28 +0200
Subject: Add support for printing automatically generated help texts.

---
 getoptpp.hpp | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 52 insertions(+), 3 deletions(-)

(limited to 'getoptpp.hpp')

diff --git a/getoptpp.hpp b/getoptpp.hpp
index 8788dde..a2dca7f 100644
--- a/getoptpp.hpp
+++ b/getoptpp.hpp
@@ -5,6 +5,7 @@
 #include <vector>
 #include <unordered_map>
 #include <string>
+#include <cstring>
 #include <getopt.h>
 
 namespace dg {
@@ -16,19 +17,22 @@ class Options {
 		/// @param name		name of the option
 		/// @param has_arg	kind of arguments that are used (no_argument, required_argument, optional_argument)
 		/// @param val		identifies the option (see getopt documentation)
+		/// @param help_text	help text for this option
 		/// @param handle	lambda that is invoked when the option occures
-		void add(std::string const & name, int has_arg, int val, Handle handle) {
-			add(name, has_arg, nullptr, val, handle);
+		void add(std::string const & name, int has_arg, int val, std::string const & help_text, Handle handle) {
+			add(name, has_arg, nullptr, val, help_text, handle);
 		}
 
 		/// @param name		name of the option
 		/// @param has_arg	kind of arguments that are used (no_argument, required_argument, optional_argument)
 		/// @param flag		pointer that is set after the option occured
 		/// @param val		value for the flag to be set
+		/// @param help_text	help text for this option
 		/// @param handle	lambda that is invoked when the option occures
-		void add(std::string const & name, int has_arg, int* flag, int val, Handle handle) {
+		void add(std::string const & name, int has_arg, int* flag, int val, std::string const & help_text, Handle handle) {
 			// create a new option from the args
 			options.push_back({name.data(), has_arg, flag, val});
+			help_texts.push_back(help_text);
 
 			int index = val; // let val be the option's unique identifier
 			if (flag != nullptr) {
@@ -95,14 +99,59 @@ class Options {
 			// remove terminating option
 			options.pop_back();
 			assert(options.size() == handles.size());
+			assert(options.size() == help_texts.size());
 			return 0;
 		}
 
 		const std::vector<std::string> arguments() const { return args; }
 
+		void help() {
+			std::size_t width = 0;
+			for(auto const & opt : options) {
+				if(opt.name == nullptr) {
+					continue; // skip terminating option
+				}
+				width = std::max(width, std::strlen(opt.name) + (opt.has_arg != no_argument ? 0 : 3));
+			}
+			width += 1;
+
+			int index = 0;
+			for(auto const & help_text : help_texts) {
+				auto const & opt = options.at(index);
+				std::string args;
+				switch(opt.has_arg) {
+				case required_argument:
+					args = "<x>";
+					break;
+				case optional_argument:
+					args = "[x]";
+					break;
+				case no_argument:
+				default:
+					break;
+				}
+
+				std::string padding;
+				std::size_t pad_size = width - (std::strlen(opt.name) + args.size());
+				padding.append(pad_size, ' ');
+				if(opt.val >= 33 && opt.val <= 126)
+				{
+					std::cout << "  -" << static_cast<char>(opt.val) << ", --" << opt.name << " " << args << padding;
+				}
+				else
+				{
+					std::cout << "      --" << opt.name << " " << args << padding;
+				}
+
+				std::cout << help_text << std::endl;
+				++index;
+			}
+		}
+
 	private:
 		std::size_t num_flags{};
 		std::vector<option> options{};
+		std::vector<std::string> help_texts{};
 		std::vector<std::string> args;
 		std::unordered_map<int, Handle> handles{};
 };
-- 
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