nix: generate application package build script

This takes some metadata, sandbox options, a launch script and a list of home-manager modules. The result needs to be executed in an environment with nix daemon access, and it produces the final package file.

Signed-off-by: Ophestra <cat@gensokyo.uk>

.gitignore

@@ -4,6 +4,7 @@
 *.dll
 *.so
 *.dylib
+*.pkg
 /fortify
 
 # Test binary, built with `go test -c`

bundle.nix

@@ -0,0 +1,161 @@
+{
+  nixpkgsFor,
+  system,
+  nixpkgs,
+  home-manager,
+}:
+
+{
+  lib,
+  writeScript,
+  runtimeShell,
+  writeText,
+  vmTools,
+  runCommand,
+
+  nix,
+
+  name ? throw "name is required",
+  version ? throw "version is required",
+  pname ? "${name}-${version}",
+  modules ? [ ],
+  script ? ''
+    exec "$SHELL" "$@"
+  '',
+
+  id ? name,
+  app_id ? throw "app_id is required",
+  groups ? [ ],
+  userns ? false,
+  net ? true,
+  dev ? false,
+  no_new_session ? false,
+  map_real_uid ? false,
+  direct_wayland ? false,
+  system_bus ? null,
+  session_bus ? null,
+
+  allow_wayland ? true,
+  allow_x11 ? false,
+  allow_dbus ? true,
+  allow_pulse ? true,
+  gpu ? allow_wayland || allow_x11,
+}:
+
+let
+  inherit (lib) optionals;
+
+  homeManagerConfiguration = home-manager.lib.homeManagerConfiguration {
+    pkgs = nixpkgsFor.${system};
+    inherit modules;
+  };
+
+  launcher = writeScript "fortify-${pname}" ''
+    #!${runtimeShell} -el
+    ${script}
+  '';
+
+  extraNixOSConfig =
+    { pkgs, ... }:
+    {
+      environment.systemPackages = [ pkgs.nix ];
+    };
+  nixos = nixpkgs.lib.nixosSystem {
+    inherit system;
+    modules = [
+      extraNixOSConfig
+      { nix.settings.experimental-features = [ "flakes" ]; }
+      { nix.settings.experimental-features = [ "nix-command" ]; }
+      { boot.isContainer = true; }
+      { system.stateVersion = "22.11"; }
+    ];
+  };
+
+  etc = vmTools.runInLinuxVM (
+    runCommand "etc" { } ''
+      mkdir -p /etc
+      ${nixos.config.system.build.etcActivationCommands}
+
+      # remove unused files
+      rm -rf /etc/sudoers
+
+      mkdir -p $out
+      tar -C /etc -cf "$out/etc.tar" .
+    ''
+  );
+
+  extendSessionDefault = id: ext: {
+    filter = true;
+
+    talk = [ "org.freedesktop.Notifications" ] ++ ext.talk;
+    own =
+      (optionals (id != null) [
+        "${id}.*"
+        "org.mpris.MediaPlayer2.${id}.*"
+      ])
+      ++ ext.own;
+
+    inherit (ext) call broadcast;
+  };
+
+  info = builtins.toJSON {
+    inherit
+      name
+      version
+      id
+      app_id
+      launcher
+      groups
+      userns
+      net
+      dev
+      no_new_session
+      map_real_uid
+      direct_wayland
+      system_bus
+      gpu
+      ;
+
+    session_bus =
+      if session_bus != null then
+        (session_bus (extendSessionDefault id))
+      else
+        (extendSessionDefault id {
+          talk = [ ];
+          own = [ ];
+          call = { };
+          broadcast = { };
+        });
+
+    enablements =
+      (if allow_wayland then 1 else 0)
+      + (if allow_x11 then 2 else 0)
+      + (if allow_dbus then 4 else 0)
+      + (if allow_pulse then 8 else 0);
+
+    current_system = nixos.config.system.build.toplevel;
+    activation_package = homeManagerConfiguration.activationPackage;
+  };
+in
+
+writeScript "fortify-${pname}-bundle-prelude" ''
+  #!${runtimeShell} -el
+  OUT="$(mktemp -d)"
+  TAR="$(mktemp -u)"
+  set -x
+
+  nix copy --no-check-sigs --to "$OUT" "${nix}" "${nixos.config.system.build.toplevel}"
+  nix store --store "$OUT" optimise
+  chmod -R +r "$OUT/nix/var"
+  nix copy --no-check-sigs --to "file://$OUT/res?compression=zstd&compression-level=19&parallel-compression=true" "${homeManagerConfiguration.activationPackage}" "${launcher}"
+  mkdir -p "$OUT/etc"
+  tar -C "$OUT/etc" -xf "${etc}/etc.tar"
+  cp "${writeText "bundle.json" info}" "$OUT/bundle.json"
+
+  # creating an intermediate file improves zstd performance
+  tar -C "$OUT" -cf "$TAR" .
+  chmod +w -R "$OUT" && rm -rf "$OUT"
+
+  zstd -T0 -19 -fo "${pname}.pkg" "$TAR"
+  rm "$TAR"
+''

flake.nix

@@ -29,6 +29,21 @@
     {
       nixosModules.fortify = import ./nixos.nix;
 
+      fortifyBundle = forAllSystems (
+        system:
+        nixpkgsFor.${system}.callPackage (
+          import ./bundle.nix {
+            inherit
+              nixpkgsFor
+              system
+              self
+              nixpkgs
+              home-manager
+              ;
+          }
+        )
+      );
+
       checks = forAllSystems (
         system:
         let