{
  description = "Portable NixOS + Home Manager configuration with sops secrets and disko";

  inputs = {
    # Core
    nixpkgs.url = "github:nixos/nixpkgs/nixos-25.11";
    nixpkgs-unstable.url = "github:nixos/nixpkgs/nixos-unstable";

    # Flakes
    flake-utils.url = "github:numtide/flake-utils";

    # Home Manager
    home-manager = {
      url = "github:nix-community/home-manager/release-25.11";
      inputs.nixpkgs.follows = "nixpkgs";
    };

    # Secrets management
    sops-nix = {
      url = "github:mic92/sops-nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };

    # Disk partitioning
    disko = {
      url = "github:nix-community/disko";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = { self, nixpkgs, nixpkgs-unstable, flake-utils, home-manager, sops-nix, disko }:
    let
      mkPkgs = system: import nixpkgs {
        inherit system;
        config.allowUnfree = true;
      };

      mkPkgsUnstable = system: import nixpkgs-unstable {
        inherit system;
        config.allowUnfree = true;
      };

      mkOverlayUnstable = system:
        final: prev: { unstable = mkPkgsUnstable system; };

      # Set enableHomeManager = false for servers or minimal installs that
      # don't need user-level dotfile/package management.
      mkNixosSystem = { system, hostModule, enableHomeManager ? true }:
        let
          pkgs-unstable = mkPkgsUnstable system;
        in nixpkgs.lib.nixosSystem {
          inherit system;

          specialArgs = {
            inherit sops-nix disko pkgs-unstable;
          };

          modules = [
            {
              nixpkgs.overlays = [ (mkOverlayUnstable system) ];
            }
            sops-nix.nixosModules.sops
            disko.nixosModules.disko

            hostModule
            ./nixos/default.nix
          ] ++ nixpkgs.lib.optionals enableHomeManager [
            home-manager.nixosModules.home-manager
            {
              home-manager.useGlobalPkgs = true;
              home-manager.useUserPackages = true;
              home-manager.extraSpecialArgs = {
                inherit pkgs-unstable sops-nix;
              };
              home-manager.users.eliaskohout = import ./home/default.nix;
            }
          ];
        };

      mkHomeConfig = system: home-manager.lib.homeManagerConfiguration {
        pkgs = import nixpkgs {
          inherit system;
          config.allowUnfree = true;
          overlays = [ (mkOverlayUnstable system) ];
        };
        extraSpecialArgs = {
          pkgs-unstable = mkPkgsUnstable system;
          inherit sops-nix;
        };
        modules = [
          ./home/default.nix
        ];
      };

      defaultSystem = "x86_64-linux";
      pkgs = mkPkgs defaultSystem;

      mkDevShell = pkgs: pkgs.mkShell {
        buildInputs = with pkgs; [
          nix
          nixpkgs-fmt
          sops
          age
          git
        ];

        shellHook = ''
          echo "NixOS Configuration Development Shell"
          echo "Available commands:"
          echo "  - nix flake check              # Check flake validity"
          echo "  - nix flake show               # Show all outputs"
          echo "  - sudo nixos-rebuild switch --flake .#hostname"
          echo "  - home-manager switch --flake .#youruser@linux"
          echo "  - sops secrets/secrets.yaml    # Edit encrypted secrets"
        '';
      };

    in {

      # ============================================
      # NixOS System Configurations
      # ============================================

      nixosConfigurations = {

        # x86_64 laptop (most common)
        laptop = mkNixosSystem {
          system = "x86_64-linux";
          hostModule = ./hosts/laptop/default.nix;
        };

        # x86_64 server (no home-manager — minimal system-only config)
        server = mkNixosSystem {
          system = "x86_64-linux";
          hostModule = ./hosts/server/default.nix;
          enableHomeManager = false;
        };

        # ARM64 UTM Virtual Machine (Apple Silicon)
        macvm-nix = mkNixosSystem {
          system = "aarch64-linux";
          hostModule = ./hosts/macvm-nix/default.nix;
        };
      };

      # ============================================
      # Home Manager Standalone (Non-NixOS systems)
      # ============================================

      homeConfigurations = {
        "eliaskohout@linux"     = mkHomeConfig "x86_64-linux";
        "eliaskohout@linux-arm" = mkHomeConfig "aarch64-linux";
      };

      # ============================================
      # Development Shell
      # ============================================

      devShells = {
        x86_64-linux.default = mkDevShell (mkPkgs "x86_64-linux");
        aarch64-linux.default = mkDevShell (mkPkgs "aarch64-linux");
      };

      # ============================================
      # Installer Script
      # ============================================

      apps = let
        mkInstaller = system: {
          type = "app";
          program = toString ((mkPkgs system).writeShellScript "installer" ''
          set -e

          if [ -z "$1" ]; then
            echo "Usage: nix run .#installer -- <hostname>"
            echo "Example: nix run .#installer -- laptop"
            exit 1
          fi

          HOSTNAME=$1
          FLAKE_DIR=$(pwd)

          if [ ! -f /etc/os-release ]; then
            echo "Cannot determine OS"
            exit 1
          fi

          . /etc/os-release

          if [ "$ID" != "nixos" ]; then
            echo "Not on NixOS - installing home-manager only"
            home-manager switch --flake "$FLAKE_DIR#youruser@linux"
            echo "Home manager configured"
            exit 0
          fi

          # Detect ISO/live environment: /nix/.rw-store is a tmpfs overlay
          if grep -q "tmpfs /nix/.rw-store" /proc/mounts 2>/dev/null; then
            echo "ISO environment detected - running full install for: $HOSTNAME"

            # Step 1: Expand tmpfs and set up zram swap BEFORE downloading anything
            echo "--- Step 1/4: Expanding tmpfs and enabling zram swap ---"
            sudo mount -o remount,size=4G /nix/.rw-store
            if sudo modprobe zram 2>/dev/null; then
              echo 2G | sudo tee /sys/block/zram0/disksize > /dev/null
              sudo mkswap /dev/zram0
              sudo swapon /dev/zram0
              echo "zram swap enabled"
            else
              echo "zram not available, continuing without it"
            fi

            # Step 2: Partition and format disk
            echo "--- Step 2/4: Running disko ---"
            sudo nix --extra-experimental-features "nix-command flakes" run \
              github:nix-community/disko/latest -- \
              --mode destroy,format,mount \
              --flake "$FLAKE_DIR#$HOSTNAME"

            # Step 3: Create swap file on installed root for nixos-install
            echo "--- Step 3/4: Creating 2GB swap file on target disk ---"
            sudo dd if=/dev/zero of=/mnt/swapfile bs=1M count=2048 status=progress
            sudo chmod 600 /mnt/swapfile
            sudo mkswap /mnt/swapfile
            sudo swapon /mnt/swapfile

            # Step 4: Install NixOS
            echo "--- Step 4/4: Running nixos-install ---"
            sudo nixos-install --flake "$FLAKE_DIR#$HOSTNAME"

            echo "Installation complete! Remove the ISO and reboot."
          else
            echo "Installed NixOS detected - switching configuration"
            sudo nixos-rebuild switch --flake "$FLAKE_DIR#$HOSTNAME"
            echo "NixOS system configured"
          fi
          '');
        };
      in {
        x86_64-linux.installer = mkInstaller "x86_64-linux";
        aarch64-linux.installer = mkInstaller "aarch64-linux";
      };

    };
}