Add option to specify manual port (#45)

include/arg_parser.hpp

@@ -2,6 +2,7 @@
 #define ARG_PARSER_HPP
 
 #include <absl/strings/string_view.h>
+#include <absl/types/optional.h>
 #include <string>
 #include <vector>
 
@@ -25,6 +26,7 @@ class ArgParser {
   absl::string_view get_help_message() const { return help_message_; };
   bool signing_disabled() const { return signing_disabled_; }
   std::vector<uint8_t> get_entropy() const;
+  const absl::optional<uint16_t>& get_port() const { return port_; }
 
 private:
   AuthProvider auth_provider_;
@@ -33,6 +35,7 @@ class ArgParser {
   bool signing_disabled_;
   bool help_wanted_;
   EntropyType entropy_type_;
+  absl::optional<uint16_t> port_;
 };
 
 #endif // ARG_PARSER_HPP

src/arg_parser.cpp

@@ -35,6 +35,11 @@ ArgParser::ArgParser(int argc, const char* const* argv) {
         "addresses listed.",
         cxxopts::value<bool>()->default_value("false"), "");
 
+    options.add_option("", "p", "port",
+                       "Port to run the authentication server on. If not "
+                       "provided, a random port will be chosen.",
+                       cxxopts::value<uint16_t>(), "");
+
     options.add_option("", "h", "help", "Print usage", cxxopts::value<bool>(),
                        "");
 
@@ -64,6 +69,10 @@ ArgParser::ArgParser(int argc, const char* const* argv) {
       throw std::runtime_error(
           absl::StrCat("invalid entropy type `", entropy_type, "`"));
     }
+
+    if (parse_result.count("port") > 0) {
+      port_ = parse_result["port"].as<uint16_t>();
+    }
   } catch (const cxxopts::option_not_exists_exception& ex) {
     throw std::runtime_error(absl::StrCat(
         "error when parsing arguments: ", ex.what(), "\n", help_message_));

src/arg_parser_test.cpp

@@ -21,6 +21,8 @@ static constexpr const char* usage_message = R"(
                        recommended to verify that the contributions listed 
                        in the transcript are actually generated by the 
                        addresses listed.
+  -p, --port arg       Port to run the authentication server on. If not 
+                       provided, a random port will be chosen.
   -h, --help           Print usage
 )";
 

src/main.cpp

@@ -14,6 +14,7 @@
 #include <cpr/cpr.h>
 #include <iostream>
 
+// NOLINTNEXTLINE(readability-function-cognitive-complexity)
 int main(int argc, char** argv) {
   try {
     const ArgParser arg_parser(argc, argv);
@@ -28,7 +29,13 @@ int main(int argc, char** argv) {
     SecretGenerator<> secret_generator(arg_parser.get_entropy(), num_secrets);
 
     const auto& auth_provider = arg_parser.get_auth_provider();
-    const auto port = port_picker::pick_unused_port();
+
+    uint16_t port = 0;
+    if (arg_parser.get_port().has_value()) {
+      port = *arg_parser.get_port();
+    } else {
+      port = port_picker::pick_unused_port();
+    }
 
     std::promise<AuthInfo> auth_info_promise;
     auto auth_callback = [&auth_info_promise](AuthInfo&& auth_info) {