tool: rewrite in C++

.github/PULL_REQUEST_TEMPLATE.md

@@ -13,4 +13,4 @@
 - [ ] Documented intended functionality
 - [ ] Added checks for intended functionality
 - [ ] Changed Nix files are formatted per `nixpkgs-fmt`
-- [ ] Changed Bash files are formatted per `shfmt`
+- [ ] Changed C++ files are formatted per `clang-format`

.gitignore

@@ -2,3 +2,6 @@
 result*
 
 /template/flake.lock
+
+build/
+meson-*/

Taskfile.yaml

@@ -0,0 +1,37 @@
+# https://taskfile.dev
+
+version: '3'
+
+tasks:
+  default:
+    deps: [build]
+
+  setup:
+    cmds:
+      - meson setup tool/ build/
+    status:
+      - test -d build/
+
+  build:
+    deps: [setup]
+    dir: build/
+    cmds:
+      - meson compile
+
+  fmt:
+    deps: [fmt/nix, fmt/cpp]
+  fmt/nix:
+    - nixpkgs-fmt .
+  fmt/cpp:
+    deps: [setup]
+    cmds:
+      - ninja -C build/ clang-format
+
+  lint:
+    deps: [lint/cpp]
+  lint/cpp:
+    - ninja -C build/ clang-tidy
+    - iwyu_tool.py -p=build/
+
+  clean:
+    - git clean -Xdf build/

checks/imperative-management.nix

@@ -29,8 +29,7 @@ let
     inherit name;
     nodes.machine = {
       environment.systemPackages = [
-        # wrapper clears PATH to check for implicit dependencies
-        (writeShellScriptBin "miniguest" ''PATH= exec ${miniguest}/bin/miniguest "$@"'')
+        miniguest
       ];
       system.extraDependencies = [ pinned-nixpkgs (import pinned-nixpkgs { inherit system; }).stdenvNoCC ];
       virtualisation.memorySize = 1024;
@@ -64,7 +63,7 @@ lib.optionalAttrs stdenv.isLinux {
     name = "miniguest-install-rename";
     testScript = ''
       machine.succeed("""
-        miniguest install --name=renamed_dummy /tmp/flake1#dummy
+        miniguest install --name renamed_dummy /tmp/flake1#dummy
       """)
       assert "foo" in machine.succeed("""
         cat /etc/miniguests/renamed_dummy/boot/init

nix/devshell.toml

@@ -1,30 +1,50 @@
-imports = [ "git.hooks" ]
+imports = [
+  "git.hooks",
+  "language.c",
+  "set-boost-root.nix",
+]
 
 [devshell]
 name = "miniguest"
-
-[[commands]]
-package = "bash"
+packages = [
+  "ninja", # for meson
+]
 
 [[commands]]
 package = "nixFlakes"
 
+[[commands]]
+name = "task"
+package = "go-task"
+
+[[commands]]
+package = "meson"
+
 [[commands]]
 package = "nixpkgs-fmt"
 category = "formatters"
 
 [[commands]]
-package = "shfmt"
+name = "clang-format"
+package = "clang-tools"
 category = "formatters"
 
 [[commands]]
-package = "argbash"
-category = "preprocessors"
+name = "clang-tidy"
+package = "clang-tools"
+category = "linters"
 
 [[commands]]
-package = "shellcheck"
+package = "include-what-you-use"
 category = "linters"
 
+[language.c]
+includes = [
+  "boehmgc",
+  "nixFlakes",
+  "nlohmann_json",
+]
+
 [git.hooks]
 enable = true
 pre-commit.text = """
@@ -41,5 +61,5 @@ function find_staged {
 }
 
 find_staged '*.nix' | xargs -r nixpkgs-fmt --check || exit
-find_staged '*.bash' | xargs -r shfmt -d -s || exit
+find_staged '*.hpp' '*.cpp' | xargs -r clang-format -n -Werror || exit
 """

nix/set-boost-root.nix

@@ -0,0 +1,8 @@
+{ pkgs, ... }:
+
+{
+  env = [{
+    name = "BOOST_ROOT";
+    value = pkgs.boost.dev;
+  }];
+}

tool/.clang-format

@@ -0,0 +1,5 @@
+BasedOnStyle: LLVM
+
+AllowShortFunctionsOnASingleLine: Empty
+AllowShortIfStatementsOnASingleLine: Never
+AllowShortBlocksOnASingleLine: Empty

tool/common.cpp

@@ -0,0 +1,53 @@
+/* Copyright 2022 Julie Bettens
+ *
+ * This file is part of the Miniguest companion.
+ *
+ * The Miniguest companion is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Miniguest is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Miniguest.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "common.hpp"
+
+#include "error.hh"
+
+namespace fs = std::filesystem;
+using namespace nix;
+
+Context ContextBuilder::build() {
+  if (!symlink_path)
+    fs::create_directory(default_symlinks_dir);
+  if (!profile_path)
+    fs::create_directory(default_profiles_dir);
+  return {symlink_path.value_or(default_symlinks_dir / guest_name),
+          profile_path.value_or(default_profiles_dir / guest_name)};
+}
+
+void Context::ensure_symlink() {
+  auto st = fs::symlink_status(symlink_path);
+  if (!fs::exists(st))
+    fs::create_symlink(profile_path, symlink_path);
+  else
+    check_symlink(st);
+}
+void Context::check_symlink(const fs::file_status &st) {
+  if (!fs::is_symlink(st) || fs::read_symlink(symlink_path) != profile_path)
+    throw Error(1,
+                "not touching symlink because it's not in an expected state");
+}
+void Context::remove_symlink() {
+  auto st = fs::symlink_status(symlink_path);
+  if (fs::exists(st))
+    check_symlink(st);
+
+  fs::remove(symlink_path);
+}

tool/common.hpp

@@ -0,0 +1,45 @@
+/* Copyright 2022 Julie Bettens
+ *
+ * This file is part of the Miniguest companion.
+ *
+ * The Miniguest companion is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Miniguest is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Miniguest.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <filesystem>
+#include <optional>
+
+struct ContextBuilder final {
+  std::string guest_name;
+  std::optional<std::filesystem::path> symlink_path, profile_path;
+  std::filesystem::path default_symlinks_dir = "/etc/miniguests",
+                        default_profiles_dir =
+                            "/nix/var/nix/profiles/miniguest-profiles";
+
+  struct Context build();
+};
+
+struct Context final {
+  const std::filesystem::path symlink_path, profile_path;
+
+  void ensure_symlink();
+  void remove_symlink();
+
+private:
+  Context(std::filesystem::path symlink_path,
+          std::filesystem::path profile_path)
+      : symlink_path(symlink_path), profile_path(profile_path) {}
+  friend Context ContextBuilder::build();
+
+  void check_symlink(const std::filesystem::file_status &st);
+};

tool/create.bash

@@ -1,36 +0,0 @@
-source create_arg.bash
-
-name="$_arg_guest_name"
-
-set_color_red=$'\e[1m\e[31m'
-reset_color=$'\e(B\e[m'
-
-case "${_arg_hypervisor:?}" in
-libvirt)
-	cat <<EOF
-# Create $name using:
-virt-install \\
-  --connect qemu:///system \\
-  -n $name --os-variant nixos-unstable \\
-  --memory 1536 \\
-  --disk none \\
-  --import \\
-  --boot kernel=/etc/miniguests/$name/kernel,initrd=$guests_dir/$name/initrd \\
-  --filesystem /nix/store/,nix-store,readonly=yes,accessmode=squash \\
-  --filesystem /etc/miniguests/$name/boot/,boot,readonly=yes,accessmode=squash \\
-
-EOF
-	;;
-lxc)
-	cat <<EOF
-#$set_color_red WARNING: make sure root is uid-mapped, otherwise you might experience store corruption in the host!$reset_color
-# Create $name using:
-lxc-create $name \\
-  -f extra-config \\
-  -t local -- \\
-  -m @lxc_template@/meta.tar.xz \\
-  -f @lxc_template@/rootfs.tar.xz \\
-
-EOF
-	;;
-esac

tool/create.cpp

@@ -0,0 +1,109 @@
+/* Copyright 2022 Julie Bettens
+ *
+ * This file is part of the Miniguest companion.
+ *
+ * The Miniguest companion is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Miniguest is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Miniguest.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "common.hpp"
+#include "manifest.hpp"
+
+#include "build-result.hh"
+#include "command.hh"
+#include "derived-path.hh"
+#include "eval-cache.hh"
+
+#include <iostream>
+#include <vector>
+
+using namespace nix;
+namespace fs = std::filesystem;
+
+struct CmdCreate : virtual EvalCommand, virtual MixProfile {
+  std::string guest_name;
+  std::optional<std::string> hypervisor;
+
+  const std::string set_color_red = "\e[1m\e[31m", reset_color = "\e(B\e[m";
+
+  CmdCreate() {
+    expectArg("name", &guest_name);
+    addFlag({
+        .longName = "type",
+        .shortName = 't',
+        .description = "hypervisor to configure (default: libvirt)",
+        .labels = {"hypervisor"},
+        .handler = {&hypervisor},
+    });
+  }
+
+  std::string description() override {
+    return "generate a command to configure the guest in the hypervisor";
+  }
+
+  std::string doc() override {
+    return R""(miniguest create [-h|--help] [-t|--hypervisor <HYPERVISOR>] <guest-name>
+	<guest-name>: name of guest to create
+	-h, --help: Prints help
+	-t, --hypervisor: hypervisor to configure. Can be one of: 'libvirt' and 'lxc' (default: 'libvirt'))"";
+  }
+
+  std::vector<std::string> prepare_command() {
+    if (*hypervisor == "libvirt")
+      return {
+          "virt-install -n " + guest_name,
+          "--connect qemu:///system",
+          "--os-variant nixos-unstable",
+          "--memory 1536",
+          "--disk none",
+          "--import",
+          "--boot kernel=/etc/miniguests/" + guest_name +
+              "/kernel,initrd=/etc/miniguests/" + guest_name + "/initrd",
+          "--filesystem /nix/store/,nix-store,readonly=yes,accessmode=squash",
+          "--filesystem /etc/miniguests/" + guest_name +
+              "/boot/,boot,readonly=yes,accessmode=squash",
+      };
+
+    else if (*hypervisor == "lxc")
+      return {
+          "lxc-create " + guest_name,
+          "-f extra-config",
+          "-t local --",
+          "-m @lxc_template@/meta.tar.xz",
+          "-f @lxc_template@/rootfs.tar.xz",
+      };
+    else
+      throw Error(2, "unknown hypervisor type");
+  }
+
+  void run(ref<Store> store) override {
+    if (!hypervisor)
+      hypervisor = "libvirt";
+
+    auto cmd = prepare_command();
+
+    if (*hypervisor == "lxc")
+      std::cout << "# " << set_color_red
+                << "WARNING: make sure root is uid-mapped, otherwise you might "
+                   "experience store corruption in the host!"
+                << reset_color << std::endl;
+    std::cout << "# Create " << guest_name << " using:" << std::endl;
+    for (auto &line : cmd)
+      std::cout << line << " \\\n  ";
+    std::cout << std::endl;
+  }
+
+  virtual ~CmdCreate() = default;
+};
+
+static auto rCmdCreate = registerCommand<CmdCreate>("create");

tool/create_arg.bash

@@ -1,5 +0,0 @@
-# ARG_POSITIONAL_SINGLE(guest-name, name of guest to create)
-# ARG_HELP(assist in creatig the guest by configuring the hypervisor)
-# ARG_OPTIONAL_SINGLE(hypervisor, t, hypervisor to configure, libvirt)
-# ARG_TYPE_GROUP_SET(hypervisors, HYPERVISOR, hypervisor, [libvirt,lxc])
-# ARGBASH_GO

tool/functions.bash

@@ -1,60 +0,0 @@
-# Copyright 2021 Julie Bettens
-#
-# This file is part of the Miniguest companion.
-#
-# The Miniguest companion is free software: you can redistribute it and/or
-# modify it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or (at your
-# option) any later version.
-#
-# Miniguest is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with Miniguest.  If not, see <https://www.gnu.org/licenses/>.
-
-function run_nix {
-	command "$nix" --experimental-features "nix-command flakes ca-references" "$@"
-}
-
-flake=
-guest_name=
-
-function parse_flake_reference {
-	[[ $1 =~ ^(.*)\#([^\#\"]*)$ ]] || die "cannot parse flake reference"
-	flake="${BASH_REMATCH[1]}"
-	guest_name="${BASH_REMATCH[2]}"
-}
-
-function install_profile {
-	[[ $# -eq 2 ]] || die "$FUNCNAME: wrong number of arguments!"
-	local guest_name="$1"
-	local target="$2"
-	run_nix profile install --profile "$profiles_dir/$guest_name" "$target" ||
-		die "unable to install $guest_name!" $?
-}
-
-function upgrade_profile {
-	[[ $# -eq 1 ]] || die "$FUNCNAME: wrong number of arguments!"
-	local guest_name="$1"
-	run_nix profile upgrade --profile "$profiles_dir/$guest_name" ||
-		die "unable to upgrade $guest_name!" $?
-}
-
-function reset_profile {
-	[[ $# -eq 1 ]] || die "$FUNCNAME: wrong number of arguments!"
-	local guest_name="$1"
-	run_nix profile remove --profile "$profiles_dir/$guest_name" '.*' ||
-		die "unable to remove guest!" $?
-}
-
-function have_control_of_symlink {
-	[[ $# -eq 1 ]] || die "$FUNCNAME: wrong number of arguments!"
-	local symlink="$guests_dir/$guest_name"
-	[[ ! -e $symlink || -L $symlink && $(readlink $symlink) -ef "$profiles_dir/$guest_name" ]] || {
-		echo >&2 "not touching $guests_dir/$guest_name because it's not in an expected state"
-		false
-	}
-}

tool/install.bash

@@ -1,29 +0,0 @@
-# Copyright 2021 Julie Bettens
-#
-# This file is part of the Miniguest companion.
-#
-# The Miniguest companion is free software: you can redistribute it and/or
-# modify it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or (at your
-# option) any later version.
-#
-# Miniguest is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with Miniguest.  If not, see <https://www.gnu.org/licenses/>.
-
-source install_arg.bash
-
-parse_flake_reference "$_arg_flake_reference"
-profile_name="${_arg_name:-$guest_name}"
-
-mkdir -p "$guests_dir" || die "" $?
-mkdir -p "$profiles_dir" || die "" $?
-
-reset_profile "$profile_name" # FIXME: need an atomic reset-and-install
-install_profile "$profile_name" "$flake#nixosConfigurations.$guest_name.config.system.build.miniguest"
-
-have_control_of_symlink "$profile_name" && ln -sf "$profiles_dir/$profile_name" "$guests_dir"

tool/install.cpp

@@ -0,0 +1,99 @@
+/* Copyright 2022 Julie Bettens
+ *
+ * This file is part of the Miniguest companion.
+ *
+ * The Miniguest companion is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Miniguest is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Miniguest.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "common.hpp"
+#include "manifest.hpp"
+
+#include "build-result.hh"
+#include "command.hh"
+#include "derived-path.hh"
+#include "eval-cache.hh"
+
+#include <iostream>
+#include <vector>
+
+using namespace nix;
+namespace fs = std::filesystem;
+
+struct CmdInstall : virtual InstallableCommand, virtual MixProfile {
+  std::optional<std::string> guest_name;
+
+  CmdInstall() {
+    addFlag({
+        .longName = "name",
+        .shortName = 'n',
+        .description = "Name of the guest (default: attribute name)",
+        .labels = {"name"},
+        .handler = {&guest_name},
+    });
+  }
+
+  std::string description() override {
+    return "build the guest and install it into a nix profile";
+  }
+
+  std::string doc() override {
+    return R""(miniguest install [-n|--name <arg>] <flake-reference>
+	<flake-reference>: guest to build
+	-n, --name: name of the profile (no default))"";
+  }
+
+  Strings getDefaultFlakeAttrPaths() override {
+    return {"nixosConfigurations.default"};
+  }
+  Strings getDefaultFlakeAttrPathPrefixes() override {
+    return {"nixosConfigurations."};
+  }
+
+  void run(ref<Store> store) override {
+    auto evalState = getEvalState();
+
+    if (!guest_name)
+      guest_name = installable->getCursor(*evalState)->getAttrPath().back();
+
+    ContextBuilder bld;
+    bld.guest_name = *guest_name;
+    if (profile)
+      bld.profile_path = *profile;
+
+    Context ctx = bld.build();
+    profile = ctx.profile_path.native();
+
+    auto installableFlake =
+        std::static_pointer_cast<InstallableFlake>(installable);
+    for (auto &a : installableFlake->attrPaths)
+      a += ".config.system.build.miniguest";
+    auto result = Installable::build(getEvalStore(), store, Realise::Outputs,
+                                     {installable});
+
+    auto [attrPath, resolvedRef, drv] = installableFlake->toDerivation();
+
+    ProfileManifest manifest(*getEvalState(), *profile);
+    ProfileElement element;
+    element.source = {installableFlake->flakeRef, resolvedRef, attrPath};
+    element.updateStorePaths(getEvalStore(), store, result);
+    manifest.elements = {element};
+    updateProfile(manifest.build(store));
+
+    ctx.ensure_symlink();
+  }
+
+  virtual ~CmdInstall() = default;
+};
+
+static auto rCmdInstall = registerCommand<CmdInstall>("install");

tool/install_arg.bash

@@ -1,21 +0,0 @@
-# Copyright 2021 Julie Bettens
-#
-# This file is part of the Miniguest companion.
-#
-# The Miniguest companion is free software: you can redistribute it and/or
-# modify it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or (at your
-# option) any later version.
-#
-# Miniguest is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with Miniguest.  If not, see <https://www.gnu.org/licenses/>.
-
-# ARG_HELP(build the guest and install it into a nix profile)
-# ARG_POSITIONAL_SINGLE(flake-reference, guest to build)
-# ARG_OPTIONAL_SINGLE(name, n, name of the profile)
-# ARGBASH_GO

tool/main.bash

@@ -1,45 +0,0 @@
-#! @bash@/bin/sh
-
-# Copyright 2021 Julie Bettens
-#
-# This file is part of the Miniguest companion.
-#
-# The Miniguest companion is free software: you can redistribute it and/or
-# modify it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or (at your
-# option) any later version.
-#
-# Miniguest is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with Miniguest.  If not, see <https://www.gnu.org/licenses/>.
-
-source main_arg.bash
-
-guests_dir="$_arg_guests_dir"
-profiles_dir="/nix/var/nix/profiles/miniguest-profiles"
-nix="$_arg_nix"
-
-source functions.bash
-
-set -- "${_arg_leftovers[@]}" # reset parameters to subcommand arguments
-case "${_arg_command:?}" in
-install)
-	source install.bash
-	;;
-upgrade)
-	source upgrade.bash
-	;;
-remove)
-	source remove.bash
-	;;
-create)
-	source create.bash
-	;;
-template)
-	source template.bash
-	;;
-esac

tool/main.cpp

@@ -0,0 +1,79 @@
+/* Copyright 2022 Julie Bettens
+ *
+ * This file is part of the Miniguest companion.
+ *
+ * The Miniguest companion is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Miniguest is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Miniguest.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "command.hh"
+#include "common-args.hh"
+#include "shared.hh"
+
+using namespace nix;
+
+struct MiniguestArgs final : virtual MultiCommand, virtual MixCommonArgs {
+  bool helpRequested = false;
+
+  MiniguestArgs()
+      : MultiCommand(RegisterCommand::getCommandsFor({})),
+        MixCommonArgs("miniguest") {
+    addFlag({
+        .longName = "help",
+        .description = "Show usage information.",
+        .handler = {[&]() { helpRequested = true; }},
+    });
+  }
+
+  std::string description() override {
+    return "Companion tool for Miniguest lightweight NixOS images";
+  }
+
+  std::string doc() override {
+    std::string doc = "Available subcommands:";
+    for (auto [name, cmd] : commands) {
+      auto line = "  " + name + ":";
+      line.resize(16, ' ');
+      line += cmd()->description();
+      doc.push_back('\n');
+      doc.append(line);
+    }
+    return doc;
+  }
+};
+
+void main0(int argc, char **argv) {
+  initNix();
+  initGC();
+  MiniguestArgs args;
+
+  settings.experimentalFeatures = {Xp::Flakes};
+
+  args.parseCmdline(argvToStrings(argc, argv));
+  if (args.helpRequested) {
+    Args &cmd = args.command ? static_cast<Args &>(*args.command->second)
+                             : static_cast<Args &>(args);
+    std::cout << cmd.description() << std::endl;
+    std::cout << cmd.doc() << std::endl;
+    return;
+  }
+  if (!args.command)
+    throw UsageError("no subcommand specified");
+
+  args.command->second->prepare();
+  args.command->second->run();
+}
+
+int main(int argc, char **argv) {
+  return nix::handleExceptions(argv[0], [=]() { main0(argc, argv); });
+}

tool/main_arg.bash

@@ -1,23 +0,0 @@
-# Copyright 2021 Julie Bettens
-#
-# This file is part of the Miniguest companion.
-#
-# The Miniguest companion is free software: you can redistribute it and/or
-# modify it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or (at your
-# option) any later version.
-#
-# Miniguest is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with Miniguest.  If not, see <https://www.gnu.org/licenses/>.
-
-# ARG_POSITIONAL_SINGLE(command, subcommand to run)
-# ARG_TYPE_GROUP_SET(commands, COMMAND, command, [install,upgrade,remove,create,template,help])
-# ARG_OPTIONAL_SINGLE(guests-dir, , directory containing guests profiles, /etc/miniguests)
-# ARG_OPTIONAL_SINGLE(nix, , path to the nix binary, @nixFlakes@/bin/nix)
-# ARG_LEFTOVERS(subcommand arguments)
-# ARGBASH_GO

tool/manifest.hpp

@@ -0,0 +1,257 @@
+/** Copyright Nix contributors
+ * Distributed under the GNU LGPL-2.1 license
+ *
+ * from Nix 2.8.1
+ */
+#include "archive.hh"
+#include "builtins/buildenv.hh"
+#include "command.hh"
+#include "common-args.hh"
+#include "derivations.hh"
+#include "flake/flakeref.hh"
+#include "names.hh"
+#include "profiles.hh"
+#include "shared.hh"
+#include "store-api.hh"
+
+#include <iomanip>
+#include <nlohmann/json.hpp>
+#include <regex>
+
+// don't reformat copypasted code
+// clang-format off
+
+namespace nix {
+// from nix/profile.cc
+struct ProfileElementSource
+{
+    FlakeRef originalRef;
+    // FIXME: record original attrpath.
+    FlakeRef resolvedRef;
+    std::string attrPath;
+    // FIXME: output names
+
+    bool operator < (const ProfileElementSource & other) const
+    {
+        return
+            std::pair(originalRef.to_string(), attrPath) <
+            std::pair(other.originalRef.to_string(), other.attrPath);
+    }
+};
+
+struct ProfileElement
+{
+    StorePathSet storePaths;
+    std::optional<ProfileElementSource> source;
+    bool active = true;
+    // FIXME: priority
+
+    std::string describe() const
+    {
+        if (source)
+            return fmt("%s#%s", source->originalRef, source->attrPath);
+        StringSet names;
+        for (auto & path : storePaths)
+            names.insert(DrvName(path.name()).name);
+        return concatStringsSep(", ", names);
+    }
+
+    std::string versions() const
+    {
+        StringSet versions;
+        for (auto & path : storePaths)
+            versions.insert(DrvName(path.name()).version);
+        return showVersions(versions);
+    }
+
+    bool operator < (const ProfileElement & other) const
+    {
+        return std::tuple(describe(), storePaths) < std::tuple(other.describe(), other.storePaths);
+    }
+
+    void updateStorePaths(
+        ref<Store> evalStore,
+        ref<Store> store,
+        const BuiltPaths & builtPaths)
+    {
+        // FIXME: respect meta.outputsToInstall
+        storePaths.clear();
+        for (auto & buildable : builtPaths) {
+            std::visit(overloaded {
+                [&](const BuiltPath::Opaque & bo) {
+                    storePaths.insert(bo.path);
+                },
+                [&](const BuiltPath::Built & bfd) {
+                    for (auto & output : bfd.outputs)
+                        storePaths.insert(output.second);
+                },
+            }, buildable.raw());
+        }
+    }
+};
+
+struct ProfileManifest
+{
+    std::vector<ProfileElement> elements;
+
+    ProfileManifest() { }
+
+    ProfileManifest(EvalState & state, const Path & profile)
+    {
+        auto manifestPath = profile + "/manifest.json";
+
+        if (pathExists(manifestPath)) {
+            auto json = nlohmann::json::parse(readFile(manifestPath));
+
+            auto version = json.value("version", 0);
+            std::string sUrl;
+            std::string sOriginalUrl;
+            switch(version){
+                case 1:
+                    sUrl = "uri";
+                    sOriginalUrl = "originalUri";
+                    break;
+                case 2:
+                    sUrl = "url";
+                    sOriginalUrl = "originalUrl";
+                    break;
+                default:
+                    throw Error("profile manifest '%s' has unsupported version %d", manifestPath, version);
+            }
+
+            for (auto & e : json["elements"]) {
+                ProfileElement element;
+                for (auto & p : e["storePaths"])
+                    element.storePaths.insert(state.store->parseStorePath((std::string) p));
+                element.active = e["active"];
+                if (e.value(sUrl,"") != "") {
+                    element.source = ProfileElementSource{
+                        parseFlakeRef(e[sOriginalUrl]),
+                        parseFlakeRef(e[sUrl]),
+                        e["attrPath"]
+                    };
+                }
+                elements.emplace_back(std::move(element));
+            }
+        }
+
+	/*
+        else if (pathExists(profile + "/manifest.nix")) {
+            // FIXME: needed because of pure mode; ugly.
+            state.allowPath(state.store->followLinksToStore(profile));
+            state.allowPath(state.store->followLinksToStore(profile + "/manifest.nix"));
+
+            auto drvInfos = queryInstalled(state, state.store->followLinksToStore(profile));
+
+            for (auto & drvInfo : drvInfos) {
+                ProfileElement element;
+                element.storePaths = {drvInfo.queryOutPath()};
+                elements.emplace_back(std::move(element));
+            }
+        }
+	*/
+    }
+
+    std::string toJSON(Store & store) const
+    {
+        auto array = nlohmann::json::array();
+        for (auto & element : elements) {
+            auto paths = nlohmann::json::array();
+            for (auto & path : element.storePaths)
+                paths.push_back(store.printStorePath(path));
+            nlohmann::json obj;
+            obj["storePaths"] = paths;
+            obj["active"] = element.active;
+            if (element.source) {
+                obj["originalUrl"] = element.source->originalRef.to_string();
+                obj["url"] = element.source->resolvedRef.to_string();
+                obj["attrPath"] = element.source->attrPath;
+            }
+            array.push_back(obj);
+        }
+        nlohmann::json json;
+        json["version"] = 2;
+        json["elements"] = array;
+        return json.dump();
+    }
+
+    StorePath build(ref<Store> store)
+    {
+        auto tempDir = createTempDir();
+
+        StorePathSet references;
+
+        Packages pkgs;
+        for (auto & element : elements) {
+            for (auto & path : element.storePaths) {
+                if (element.active)
+                    pkgs.emplace_back(store->printStorePath(path), true, 5);
+                references.insert(path);
+            }
+        }
+
+        buildProfile(tempDir, std::move(pkgs));
+
+        writeFile(tempDir + "/manifest.json", toJSON(*store));
+
+        /* Add the symlink tree to the store. */
+        StringSink sink;
+        dumpPath(tempDir, sink);
+
+        auto narHash = hashString(htSHA256, sink.s);
+
+        ValidPathInfo info {
+            store->makeFixedOutputPath(FileIngestionMethod::Recursive, narHash, "profile", references),
+            narHash,
+        };
+        info.references = std::move(references);
+        info.narSize = sink.s.size();
+        info.ca = FixedOutputHash { .method = FileIngestionMethod::Recursive, .hash = info.narHash };
+
+        StringSource source(sink.s);
+        store->addToStore(info, source);
+
+        return std::move(info.path);
+    }
+
+    static void printDiff(const ProfileManifest & prev, const ProfileManifest & cur, std::string_view indent)
+    {
+        auto prevElems = prev.elements;
+        std::sort(prevElems.begin(), prevElems.end());
+
+        auto curElems = cur.elements;
+        std::sort(curElems.begin(), curElems.end());
+
+        auto i = prevElems.begin();
+        auto j = curElems.begin();
+
+        bool changes = false;
+
+        while (i != prevElems.end() || j != curElems.end()) {
+            if (j != curElems.end() && (i == prevElems.end() || i->describe() > j->describe())) {
+                std::cout << fmt("%s%s: ∅ -> %s\n", indent, j->describe(), j->versions());
+                changes = true;
+                ++j;
+            }
+            else if (i != prevElems.end() && (j == curElems.end() || i->describe() < j->describe())) {
+                std::cout << fmt("%s%s: %s -> ∅\n", indent, i->describe(), i->versions());
+                changes = true;
+                ++i;
+            }
+            else {
+                auto v1 = i->versions();
+                auto v2 = j->versions();
+                if (v1 != v2) {
+                    std::cout << fmt("%s%s: %s -> %s\n", indent, i->describe(), v1, v2);
+                    changes = true;
+                }
+                ++i;
+                ++j;
+            }
+        }
+
+        if (!changes)
+            std::cout << fmt("%sNo changes.\n", indent);
+    }
+};
+}

tool/meson.build

@@ -0,0 +1,34 @@
+project('miniguest', 'cpp',
+  version : '0.2',
+  default_options : ['warning_level=1',
+                     'cpp_std=c++17'])
+
+add_project_arguments('-DSYSTEM="x86_64-linux"', language: 'cpp')  # TODO
+
+
+# Nix dependency
+nixlibs = [
+  dependency('boost'), # transitive
+  dependency('nlohmann_json'), # transitive
+
+  dependency('nix-main'),
+  dependency('nix-expr'),
+  dependency('nix-cmd'),
+  dependency('nix-store'),
+]
+add_project_arguments('-Wno-non-virtual-dtor', language: 'cpp')  # present in Nix headers
+
+
+src = [
+  'main.cpp',
+  'install.cpp',
+  'remove.cpp',
+  'upgrade.cpp',
+  'create.cpp',
+  'common.cpp',
+]
+exe = executable('miniguest', src,
+  dependencies : nixlibs,
+  install : true)
+
+test('basic', exe)

tool/package.nix

@@ -1,4 +1,4 @@
-# Copyright 2021 Julie Bettens
+# Copyright 2022 Julie Bettens
 # 
 # Permission to use, copy, modify, and/or distribute this software for any
 # purpose with or without fee is hereby granted, provided that the above
@@ -12,41 +12,21 @@
 # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 # OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
-{ lib, stdenvNoCC, argbash, bash, coreutils, miniguest-lxc-template, nixFlakes, shellcheck, makeWrapper }:
+{ lib, stdenv, boost, miniguest-lxc-template, meson, ninja, nixFlakes, nlohmann_json, pkg-config }:
 
-stdenvNoCC.mkDerivation {
+stdenv.mkDerivation {
   pname = "miniguest";
-  version = "0.1.4";
+  version = "0.2";
   src = builtins.path { name = "source"; path = ./.; };
-  inherit bash nixFlakes;
   lxc_template = miniguest-lxc-template;
 
-  nativeBuildInputs = [ argbash makeWrapper ];
+  nativeBuildInputs = [ meson ninja nlohmann_json pkg-config ];
+  buildInputs = [ boost nixFlakes ];
 
-  buildPhase = ''
-    for f in *.bash; do
+  postPatch = ''
+    for f in *.cpp; do
       substituteAllInPlace $f
     done
-    for f in *_arg.bash; do
-      argbash --strip=all -i "$f"
-    done
-  '';
-
-  installPhase = ''
-    mkdir -p $out/{libexec/miniguest,bin}
-      mv *.bash $out/libexec/miniguest
-      chmod +x $out/libexec/miniguest/main.bash
-      # keep PATH open ended since Nix pulls from the environment e.g. git
-      makeWrapper $out/libexec/miniguest/main.bash $out/bin/miniguest \
-        --prefix PATH ":" "$out/libexec/miniguest:${coreutils}/bin"
-  '';
-
-  doInstallCheck = true;
-
-  installCheckInputs = [ shellcheck ];
-
-  installCheckPhase = ''
-    shellcheck -e SC2123 -x -s bash $out/bin/miniguest
   '';
 
   meta = with lib; {

tool/remove.bash

@@ -1,7 +0,0 @@
-source remove_arg.bash
-
-guest_name="$_arg_guest_name"
-
-reset_profile "$guest_name"
-
-have_control_of_symlink "$guest_name" && rm -f "$guests_dir/$guest_name"

tool/remove.cpp

@@ -0,0 +1,71 @@
+/* Copyright 2022 Julie Bettens
+ *
+ * This file is part of the Miniguest companion.
+ *
+ * The Miniguest companion is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Miniguest is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Miniguest.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "common.hpp"
+#include "manifest.hpp"
+
+#include "build-result.hh"
+#include "command.hh"
+#include "derived-path.hh"
+#include "eval-cache.hh"
+
+#include <iostream>
+#include <vector>
+
+using namespace nix;
+namespace fs = std::filesystem;
+
+struct CmdRemove : virtual EvalCommand, virtual MixProfile {
+  std::string guest_name;
+
+  CmdRemove() {
+    expectArg("name", &guest_name);
+  }
+
+  std::string description() override {
+    return "uninstall a guest";
+  }
+
+  std::string doc() override {
+    return R""(miniguest remove [-h|--help] <guest-name>
+	<guest-name>: name of guest to remove
+	-h, --help: Prints help)"";
+  }
+
+  void run(ref<Store> store) override {
+    ContextBuilder bld;
+    bld.guest_name = guest_name;
+    if (profile)
+      bld.profile_path = *profile;
+
+    Context ctx = bld.build();
+    profile = ctx.profile_path.native();
+
+    // reset profile first
+    ProfileManifest manifest(*getEvalState(), *profile);
+    manifest.elements.clear();
+    updateProfile(manifest.build(store));
+
+    // then clean the symlink
+    ctx.remove_symlink();
+  }
+
+  virtual ~CmdRemove() = default;
+};
+
+static auto rCmdRemove = registerCommand<CmdRemove>("remove");

tool/remove_arg.bash

@@ -1,2 +0,0 @@
-# ARG_POSITIONAL_SINGLE(guest-name, name of guest to remove)
-# ARGBASH_GO

tool/template.bash

@@ -1,5 +0,0 @@
-source template_arg.bash
-
-dest_dir="$_arg_dest_dir"
-
-run_nix flake new -t github:bbjubjub2494/miniguest "$dest_dir"

tool/template_arg.bash

@@ -1,2 +0,0 @@
-# ARG_POSITIONAL_SINGLE(dest-dir, destination directory)
-# ARGBASH_GO

tool/upgrade.bash

@@ -1,5 +0,0 @@
-source upgrade_arg.bash
-
-guest_name="$_arg_guest_name"
-
-upgrade_profile "$guest_name"

tool/upgrade.cpp

@@ -0,0 +1,86 @@
+/* Copyright 2022 Julie Bettens
+ *
+ * This file is part of the Miniguest companion.
+ *
+ * The Miniguest companion is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Miniguest is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Miniguest.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "common.hpp"
+#include "manifest.hpp"
+
+#include "build-result.hh"
+#include "command.hh"
+#include "derived-path.hh"
+#include "eval-cache.hh"
+
+#include <iostream>
+#include <vector>
+
+using namespace nix;
+namespace fs = std::filesystem;
+
+struct CmdUpgrade : virtual EvalCommand, virtual MixProfile {
+  std::string guest_name;
+
+  CmdUpgrade() {
+    expectArg("name", &guest_name);
+  }
+
+  std::string description() override {
+    return "upgrade a guest through its flake reference";
+  }
+
+  std::string doc() override {
+    return R""(miniguest upgrade [-h|--help] <guest-name>
+	<guest-name>: name of guest to upgrade
+	-h, --help: Prints help)"";
+  }
+
+  void run(ref<Store> store) override {
+    ContextBuilder bld;
+    bld.guest_name = guest_name;
+    if (profile)
+      bld.profile_path = *profile;
+
+    Context ctx = bld.build();
+    profile = ctx.profile_path.native();
+
+    ProfileManifest manifest(*getEvalState(), *profile);
+
+    for (auto &element : manifest.elements) {
+      if (!element.source || element.source->originalRef.input.isLocked())
+        continue;
+
+      auto installable = std::make_shared<InstallableFlake>(
+          nullptr, getEvalState(), FlakeRef(element.source->originalRef), "",
+          Strings{element.source->attrPath}, Strings{}, flake::LockFlags{});
+      auto [attrPath, resolvedRef, drv] = installable->toDerivation();
+      if (element.source->resolvedRef == resolvedRef)
+        continue;
+      printInfo("upgrading '%s' from flake '%s' to '%s'",
+                element.source->attrPath, element.source->resolvedRef,
+                resolvedRef);
+      auto result = Installable::build(getEvalStore(), store, Realise::Outputs,
+                                       {installable});
+
+      element.source = {installable->flakeRef, resolvedRef, attrPath};
+      element.updateStorePaths(getEvalStore(), store, result);
+    }
+    updateProfile(manifest.build(store));
+  }
+
+  virtual ~CmdUpgrade() = default;
+};
+
+static auto rCmdUpgrade = registerCommand<CmdUpgrade>("upgrade");

tool/upgrade_arg.bash

@@ -1,2 +0,0 @@
-# ARG_POSITIONAL_SINGLE(guest-name, name of guest to upgrade)
-# ARGBASH_GO