flake.nix

{
  description = "NGIpkgs";

  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
  inputs.flake-utils.url = "github:numtide/flake-utils";
  # Set default system to `x86_64-linux`,
  # as we currently only support Linux.
  # See <https://github.com/ngi-nix/ngipkgs/issues/24> for plans to support Darwin.
  inputs.systems.url = "github:nix-systems/x86_64-linux";
  inputs.flake-utils.inputs.systems.follows = "systems";
  inputs.treefmt-nix.url = "github:numtide/treefmt-nix";
  inputs.treefmt-nix.inputs.nixpkgs.follows = "nixpkgs";
  inputs.sops-nix.url = "github:Mic92/sops-nix";
  inputs.sops-nix.inputs.nixpkgs.follows = "nixpkgs";
  inputs.rust-overlay.url = "github:oxalica/rust-overlay";
  inputs.rust-overlay.inputs.flake-utils.follows = "flake-utils";
  inputs.rust-overlay.inputs.nixpkgs.follows = "nixpkgs";
  inputs.dream2nix.url = "github:nix-community/dream2nix";
  inputs.dream2nix.inputs.nixpkgs.follows = "nixpkgs";

  outputs = {
    self,
    nixpkgs,
    flake-utils,
    treefmt-nix,
    sops-nix,
    rust-overlay,
    dream2nix,
    ...
  }: let
    inherit
      (builtins)
      readDir
      mapAttrs
      attrValues
      ;

    inherit
      (nixpkgs.lib)
      concatMapAttrs
      mapAttrs'
      foldr
      recursiveUpdate
      nameValuePair
      nixosSystem
      filterAttrs
      attrByPath
      ;

    importPackages = pkgs: let
      nixosTests = let
        dir = ./tests;
        testDirs = readDir dir;

        dirToTest = name: _: let
          mkTestModule = import "${dir}/${name}";

          testModule = mkTestModule {
            inherit pkgs;
            inherit (pkgs) lib;
            modules = extendedModules;
            configurations = rawNixosConfigs;
          };
        in
          pkgs.nixosTest testModule;
      in
        mapAttrs dirToTest testDirs;

      callPackage = pkgs.newScope (
        allPackages // {inherit callPackage nixosTests;}
      );

      pkgsByName = import ./pkgs/by-name {
        inherit (pkgs) lib;
        inherit callPackage dream2nix pkgs;
      };

      explicitPkgs = import ./pkgs {
        inherit (pkgs) lib;
        inherit callPackage;
      };

      allPackages = pkgsByName // explicitPkgs;
    in
      allPackages;

    importNixpkgs = system: overlays:
      import nixpkgs {inherit system overlays;};

    rawNixosConfigs = import ./configs/all-configurations.nix;

    loadTreefmt = pkgs: treefmt-nix.lib.evalModule pkgs ./treefmt.nix;

    # Attribute set containing all modules obtained via `inputs` and defined
    # in this flake towards definition of `nixosConfigurations` and `nixosTests`.
    extendedModules =
      self.nixosModules
      // {
        sops-nix = sops-nix.nixosModules.default;
      };

    nixosConfigurations =
      mapAttrs
      (_: config: nixosSystem {modules = [config ./configs/dummy.nix] ++ attrValues extendedModules;})
      rawNixosConfigs;

    eachDefaultSystemOutputs = flake-utils.lib.eachDefaultSystem (system: let
      pkgs = importNixpkgs system [rust-overlay.overlays.default];
      treefmtEval = loadTreefmt pkgs;
      toplevel = name: config: nameValuePair "${name}-toplevel" config.config.system.build.toplevel;
    in {
      packages = importPackages pkgs;
      formatter = treefmtEval.config.build.wrapper;
      checks = mapAttrs' toplevel nixosConfigurations;
    });

    x86_64-linuxOutputs = let
      system = flake-utils.lib.system.x86_64-linux;
      pkgs = importNixpkgs system [self.overlays.default];
      treefmtEval = loadTreefmt pkgs;
      # Dream2nix is failing to pass through the meta attribute set.
      # As a workaround, consider packages with empty meta as non-broken.
      nonBrokenPkgs = filterAttrs (_: v: !(attrByPath ["meta" "broken"] false v)) self.packages.${system};
    in {
      # Github Actions executes `nix flake check` therefore this output
      # should only contain derivations that can built within CI.
      # See `.github/workflows/ci.yaml`.
      checks.${system} =
        # For `nix flake check` to *build* all packages, because by default
        # `nix flake check` only evaluates packages and does not build them.
        nonBrokenPkgs
        // {
          formatting = treefmtEval.config.build.check self;
        };

      # To generate a Hydra jobset for CI builds of all packages and tests.
      # See <https://hydra.ngi0.nixos.org/jobset/ngipkgs/main>.
      hydraJobs = let
        passthruTests = concatMapAttrs (name: value:
          if value ? passthru.tests
          then {${name} = value.passthru.tests;}
          else {})
        nonBrokenPkgs;
      in {
        packages.${system} = nonBrokenPkgs;
        tests.${system} = passthruTests;

        nixosConfigurations.${system} =
          mapAttrs
          (name: config: config.config.system.build.toplevel)
          nixosConfigurations;
      };
    };

    systemAgnosticOutputs = {
      inherit nixosConfigurations;

      nixosModules =
        (import ./modules/all-modules.nix)
        // {
          # The default module adds the default overlay on top of nixpkgs.
          # This is so that `ngipkgs` can be used alongside `nixpkgs` in a configuration.
          default.nixpkgs.overlays = [self.overlays.default];
        };

      # Overlays a package set (e.g. nixpkgs) with the packages defined in this flake.
      overlays.default = final: prev: importPackages prev;
    };
  in
    foldr recursiveUpdate {} [
      eachDefaultSystemOutputs
      x86_64-linuxOutputs
      systemAgnosticOutputs
    ];
}