# This module sets common settings related to Nix such as enabling flakes and
# using overlays everywhere.
#
# NOTE: This lives under `shared/nixos-and-darwin`. The configuration in here
# should be compatible with both nixos and nix-darwin!!
{
  pkgs,
  lib,
  config,
  flakeInputs,
  flakeOutputs,
  ...
}: {
  # Enable de facto stable features.
  nix.settings.experimental-features = ["nix-command" "flakes"];

  nixpkgs.overlays = [
    # Use local overlays.
    flakeOutputs.overlays.additions
    flakeOutputs.overlays.modifications

    # Add unstable nixpkgs.
    (final: prev: {unstable = flakeInputs.nixpkgs-unstable.legacyPackages.${pkgs.system};})

    # Add NUR packages
    flakeInputs.nur.overlays.default
  ];

  # I'm not *that* vegan.
  nixpkgs.config.allowUnfree = true;

  # This will add each flake input as a registry
  # To make nix3 commands consistent with your flake
  nix.registry = lib.mapAttrs (_: value: {flake = value;}) flakeInputs;

  nix.nixPath =
    [
      # Use overlays from this repo for building system configuration as well as system-wide.
      # See: https://nixos.wiki/wiki/Overlays#Using_nixpkgs.overlays_from_configuration.nix_as_.3Cnixpkgs-overlays.3E_in_your_NIX_PATH
      "nixpkgs-overlays=${flakeInputs.self}/overlays/compat.nix"
    ]
    # This will additionally add out inputs to the system's legacy channels
    # Making legacy nix commands consistent as well, awesome!
    ++ lib.mapAttrsToList (key: value: "${key}=${value.to.path}") config.nix.registry;

  # Add shell-utilities which are only relevant if Nix is enabled.
  environment.systemPackages = with pkgs; [
    # For running programs easily.
    nix-index # Also includes nix-locate
    flakeInputs.comma.packages.${system}.default

    # For editing secrets.
    flakeInputs.agenix.packages.${system}.default
  ];
}