inputs:
with inputs;
let
  # System types to support.
  supportedSystems = [
    "x86_64-linux"
    "aarch64-linux"
    "aarch64-darwin"
  ];

  # Helper function to generate an attrset '{ x86_64-linux = f "x86_64-linux"; ... }'.
  forAllSystems = nixpkgs.lib.genAttrs supportedSystems;

  overlayedNixpkgs =
    system:
    import nixpkgs {
      inherit system;
      config = {
        allowUnfree = true;
      };
      overlays = [
        (self: super: {
          unstable = import nixpkgs-unstable { inherit system; };
          personal = import ./packages/overlay.nix self super;
        })
      ];
    };

  nixosSystem =
    {
      system,
      modules,
      ...
    }@args:
    nixpkgs.lib.nixosSystem (
      {
        inherit system;
        pkgs = overlayedNixpkgs system;
        inherit modules;
        specialArgs = {
          inherit pkgsUnstable;
          inherit inputs;
        };
      }
      // args
    );

  mkHomeConfiguration =
    { modules, system }:
    home-manager.lib.homeManagerConfiguration {
      pkgs = import nixpkgs {
        inherit system;
        overlays = [
          agenix.overlays.default
          scriptura.overlays.default
          (self: super: {
            personal = import ./packages/overlay.nix self super;
            iqan = iqan.packages.${system}.iqan;
          })
        ];
      };

      extraSpecialArgs = {
        inherit inputs;
      };

      modules = [
        nixvim.homeModules.nixvim
        scriptura.homeModules.scriptura
      ]
      ++ modules;
    };
in
{
  nixosConfigurations = {
    # build with `nixos-rebuild build-image --image-variant iso-installer`
    minimal-iso = nixosSystem {
      system = "x86_64-linux";
      modules = [ ./system/hosts/installer.nix ];
    };
    prefect = nixosSystem {
      system = "x86_64-linux";
      modules = (
        with nixos-hardware.nixosModules;
        [
          ./system/hosts/prefect.nix
          common-cpu-amd-pstate
          common-cpu-amd-zenpower
          common-pc-ssd
          common-pc
          "${nixos-hardware}/common/gpu/nvidia/ada-lovelace"
        ]
      );
    };
    r5 = nixosSystem {
      system = "aarch64-linux";
      modules = [
        agenix.nixosModules.default
        srvos.nixosModules.server
        nanopi.nixosModules.r5s
        ./system/hosts/r5.nix
        ./system/hosts/r5-hardware.nix
      ];
    };
    hasel = nixosSystem {
      system = "x86_64-linux";
      modules = [
        srvos.nixosModules.server
        agenix.nixosModules.default
        ./packages/modules/nixos/laminar.nix
        ./packages/modules/nixos/bark.nix
        ./system/hosts/hasel.nix
      ];
    };
    ulme = nixosSystem {
      system = "x86_64-linux";
      modules = [
        srvos.nixosModules.server
        agenix.nixosModules.default
        ./packages/modules/nixos/bark.nix
        ./system/hosts/ulme.nix
      ];
    };
  };
  darwinConfigurations = {
    marvin = darwin.lib.darwinSystem {
      system = "aarch64-darwin";
      modules = [
        srvos.darwinModules.desktop
        ./system/hosts/marvin.nix
      ];
    };
  };
  homeConfigurations = {
    "alin@marvin" = mkHomeConfiguration {
      system = "aarch64-darwin";
      modules = [
        ./user/hosts/marvin.nix
        ./private/ssh.nix
      ];
    };
    "alin@prefect" = mkHomeConfiguration {
      system = "x86_64-linux";
      modules = [
        ./user/hosts/prefect.nix
        ./private/ssh.nix
      ];
    };
    "alin@r5" = mkHomeConfiguration {
      system = "aarch64-linux";
      modules = [
        ./user/hosts/r5.nix
      ];
    };
    "alin@hasel" = mkHomeConfiguration {
      system = "x86_64-linux";
      modules = [
        ./user/hosts/server.nix
        {
          home.stateVersion = "26.05";
        }
      ];
    };
    "alin@ulme" = mkHomeConfiguration {
      system = "x86_64-linux";
      modules = [
        ./user/hosts/server.nix
        {
          home.stateVersion = "26.05";
        }
      ];
    };

  };

  devShells = forAllSystems (
    system:
    let
      pkgs = import nixpkgs { inherit system; };
    in
    {
      default = pkgs.mkShellNoCC {
        packages = with pkgs; [
          just
          nh
          home-manager
          nixos-rebuild
          nixos-option
        ];
      };
      secrets = pkgs.mkShellNoCC {
        packages = [ agenix.packages.${system}.default ];
      };
    }
  );
}