# This file defines the root of all external dependency imports (i.e.
# third-party code) in the TVL package tree.
#
# There are two categories of third-party programs:
#
# 1) Programs in nixpkgs, the NixOS package set. For these, you might
#    want to look at //third_party/nixpkgs (for the package set
#    imports) and //third_party/overlays (for modifications in these
#    imported package sets).
#
# 2) Third-party software packaged in this repository. This is all
#    other folders below //third_party, other than the ones mentioned
#    above.

{ pkgs, ... }:

{
  # Expose a partially applied NixOS, expecting an attribute set with
  # a `configuration` key. Exposing it like this makes it possible to
  # modify some of the base configuration used by NixOS.
  #
  # This partially reimplements the code in
  # <nixpkgs/nixos/default.nix> as we need to modify its internals to
  # be able to pass `specialArgs`. We depend on this because `depot`
  # needs to be partially evaluated in NixOS configuration before
  # module imports are resolved.
  nixos = {
    configuration,
    specialArgs ? {},
    system ? builtins.currentSystem,
    ...
  }:
  let
    eval = import "${pkgs.path}/nixos/lib/eval-config.nix" {
      inherit specialArgs system;
      modules = [ configuration ];
    };

    # This is for `nixos-rebuild build-vm'.
    vmConfig = (import "${pkgs.path}/nixos/lib/eval-config.nix" {
      inherit specialArgs system;
      modules = [
        configuration
        "${pkgs.path}/nixos/modules/virtualisation/qemu-vm.nix"
      ];
    }).config;
  in {
    inherit (eval) pkgs config options;
    system = eval.config.system.build.toplevel;
    vm = vmConfig.system.build.vm;
  };
}