From 5781f45c46d7f6c55f87528ab1e754d070bc99ee Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Thu, 3 Dec 2020 17:55:27 +0100
Subject: [PATCH] Allow registering subcommands of subcommands

---
 src/nix/command.cc | 16 +++++++++++++++-
 src/nix/command.hh | 13 +++++++++++--
 src/nix/main.cc    |  2 +-
 3 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/src/nix/command.cc b/src/nix/command.cc
index 9a38c77f1..596217775 100644
--- a/src/nix/command.cc
+++ b/src/nix/command.cc
@@ -11,7 +11,21 @@ extern char * * environ __attribute__((weak));
 
 namespace nix {
 
-Commands * RegisterCommand::commands = nullptr;
+RegisterCommand::Commands * RegisterCommand::commands = nullptr;
+
+nix::Commands RegisterCommand::getCommandsFor(const std::vector<std::string> & prefix)
+{
+    nix::Commands res;
+    for (auto & [name, command] : *RegisterCommand::commands)
+        if (name.size() == prefix.size() + 1) {
+            bool equal = true;
+            for (size_t i = 0; i < prefix.size(); ++i)
+                if (name[i] != prefix[i]) equal = false;
+            if (equal)
+                res.insert_or_assign(name[prefix.size()], command);
+        }
+    return res;
+}
 
 void NixMultiCommand::printHelp(const string & programName, std::ostream & out)
 {
diff --git a/src/nix/command.hh b/src/nix/command.hh
index d60c8aeb6..6882db195 100644
--- a/src/nix/command.hh
+++ b/src/nix/command.hh
@@ -176,20 +176,29 @@ struct StorePathCommand : public InstallablesCommand
 /* A helper class for registering commands globally. */
 struct RegisterCommand
 {
+    typedef std::map<std::vector<std::string>, std::function<ref<Command>()>> Commands;
     static Commands * commands;
 
-    RegisterCommand(const std::string & name,
+    RegisterCommand(std::vector<std::string> && name,
         std::function<ref<Command>()> command)
     {
         if (!commands) commands = new Commands;
         commands->emplace(name, command);
     }
+
+    static nix::Commands getCommandsFor(const std::vector<std::string> & prefix);
 };
 
 template<class T>
 static RegisterCommand registerCommand(const std::string & name)
 {
-    return RegisterCommand(name, [](){ return make_ref<T>(); });
+    return RegisterCommand({name}, [](){ return make_ref<T>(); });
+}
+
+template<class T>
+static RegisterCommand registerCommand2(std::vector<std::string> && name)
+{
+    return RegisterCommand(std::move(name), [](){ return make_ref<T>(); });
 }
 
 Buildables build(ref<Store> store, Realise mode,
diff --git a/src/nix/main.cc b/src/nix/main.cc
index a75f8ae65..6d8c66406 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -59,7 +59,7 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs
     bool useNet = true;
     bool refresh = false;
 
-    NixArgs() : MultiCommand(*RegisterCommand::commands), MixCommonArgs("nix")
+    NixArgs() : MultiCommand(RegisterCommand::getCommandsFor({})), MixCommonArgs("nix")
     {
         categories.clear();
         categories[Command::catDefault] = "Main commands";