let
  # Common Power Saving Config (TLP)
  powerSaving = {
    services.power-profiles-daemon.enable = lib.mkForce false;
    services.tlp = {
      enable = lib.mkForce true;
      settings = {
        CPU_SCALING_GOVERNOR_ON_BAT = "powersave";
        CPU_ENERGY_PERF_POLICY_ON_BAT = "power";
        CPU_BOOST_ON_BAT = 0;
        PLATFORM_PROFILE_ON_BAT = "low-power";
      };
    };
  };

  # Common No-dGPU Config (Expansion Shell)
  noDgpuBase = {
    systemd.services.dgpu-guard.enable = false; 
    services.xserver.videoDrivers = lib.mkForce [ "modesetting" ];
    boot.blacklistedKernelModules = [ "nvidia" "nvidia_modeset" "nvidia_uvm" "nvidia_drm" ];
    hardware.nvidia = {
      modesetting.enable = lib.mkForce false;
      powerManagement.enable = lib.mkForce false;
      open = lib.mkForce false;
      nvidiaSettings = lib.mkForce false;
      prime.offload.enable = lib.mkForce false;
    };
  };
in
{ config, pkgs, lib, ... }:

{
  imports =
    [ 
      ../../common
      ./hardware-configuration.nix
    ];

  networking.hostName = "electra"; 

  # ==========================================
  # 1. HARDWARE SPECIFICS (Framework 16)
  # ==========================================
  hardware.enableAllFirmware = true; 
  hardware.cpu.amd.updateMicrocode = true;

  # Fingerprint Reader
  services.fprintd.enable = true;
  security.pam.services.sudo.fprintAuth = true;
  security.pam.services.kde.fprintAuth = true;
  security.pam.services.sddm.fprintAuth = false;

  # ==========================================
  # 2. GRAPHICS & KERNEL (Strix Point + RTX 5070)
  # ==========================================
  
  # Kernel Params for Strix Point iGPU
  boot.kernelParams = [ "amdgpu.gttsize=32768" ];
  boot.initrd.kernelModules = [ "amdgpu" ];

  # Graphics Drivers
  hardware.graphics = {
    enable = true;
    enable32Bit = true;
  };

  services.xserver.videoDrivers = [ "nvidia" ];

  hardware.nvidia = {
    modesetting.enable = true;
    powerManagement.enable = true;
    powerManagement.finegrained = true;
    open = true;
    nvidiaSettings = true;
    package = config.boot.kernelPackages.nvidiaPackages.beta;

    prime = {
      offload = {
        enable = true;
        enableOffloadCmd = true;
      };
      amdgpuBusId = "PCI:194:0:0"; 
      nvidiaBusId = "PCI:193:0:0";
    };
  };

  # ==========================================
  # 3. HARDWARE GUARD (dGPU Check)
  # ==========================================
  # This prevents a black-screen hang if you boot into an NVIDIA mode 
  # but have the dGPU physically removed.
  systemd.services.dgpu-guard = {
    description = "Check for dGPU presence before starting display manager";
    before = [ "display-manager.service" ];
    wantedBy = [ "display-manager.service" ];
    script = ''
      # Check if device 01:00.0 is NVIDIA (Vendor 10de)
      if ! ${pkgs.pciutils}/bin/lspci -d 10de: -s 01:00.0 | grep -q "NVIDIA"; then
        echo "ERROR: NVIDIA dGPU not found at expected Bus ID!"
        echo "You are likely in a dGPU-enabled boot mode but the module is removed."
        echo "Falling back to console to prevent black screen hang."
        exit 1
      fi
    '';
    serviceConfig = {
      Type = "oneshot";
      RemainAfterExit = true;
    };
    # Only run this check if the NVIDIA driver is actually requested
    unitConfig.ConditionPathExists = "/proc/modules"; # Basic sanity check
  };

  # ==========================================
  # 4. SPECIALISATIONS
  # ==========================================
  specialisation = {
    
    # --- WITH dGPU MODES ---
    
    # 1. Gaming Mode (Zen Kernel + Max Performance)
    gaming-zen.configuration = {
      system.nixos.tags = [ "Gaming-Zen" ];
      boot.kernelPackages = lib.mkForce pkgs.linuxPackages_zen;
      hardware.nvidia.powerManagement.finegrained = lib.mkForce false; 
    };

    # 2. dGPU Battery Mode (NVIDIA + TLP)
    dgpu-battery.configuration = lib.recursiveUpdate powerSaving {
      system.nixos.tags = [ "dGPU-Battery" ];
    };

    # --- WITHOUT dGPU MODES ---

    # 3. No dGPU Mode (Expansion Shell + Balanced)
    no-dgpu.configuration = lib.recursiveUpdate noDgpuBase {
      system.nixos.tags = [ "No-dGPU" ];
    };

    # 4. No dGPU Battery Mode (Expansion Shell + TLP)
    no-dgpu-battery.configuration = lib.recursiveUpdate (lib.recursiveUpdate noDgpuBase powerSaving) {
      system.nixos.tags = [ "No-dGPU-Battery" ];
    };
  };
}