Parse command line with boost program_options

cli/command_line.cpp

@@ -0,0 +1,73 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+module;
+
+#include <variant>
+#include <string>
+#include <stdexcept>
+#include <algorithm>
+#include <cstring>
+
+#include <boost/program_options.hpp>
+
+export module katja.command_line;
+
+namespace katja
+{
+    export enum class command
+    {
+        updates,
+        search,
+        help
+    };
+
+    export struct command_line
+    {
+        const command type;
+        const std::vector<std::string> arguments;
+    };
+
+    export class invalid_command_error : public std::runtime_error
+    {
+        const std::string command;
+
+    public:
+        invalid_command_error()
+            : std::runtime_error("Expecting the command line to begin with a command.")
+        {
+        }
+
+        invalid_command_error(const std::string& invalid_command)
+            : command{ invalid_command },
+            std::runtime_error("Unknown command given on the command line.")
+        {
+        }
+    };
+
+    export command_line parse_command_line(int argc, const char **argv)
+    {
+        if (argc == 1)
+        {
+            throw invalid_command_error();
+        }
+        std::vector<std::string> arguments;
+        std::copy(argv + 2, argv + argc, std::back_inserter(arguments));
+
+        if (strcmp("updates", argv[1]) == 0)
+        {
+            return command_line{ command::updates, std::move(arguments) };
+        }
+        if (strcmp("search", argv[1]) == 0)
+        {
+            return command_line{ command::search, std::move(arguments) };
+        }
+        if (strcmp("help", argv[1]) == 0)
+        {
+            return command_line{ command::help, std::move(arguments) };
+        }
+        throw invalid_command_error(argv[1]);
+    }
+}