# This module defines a systemd service that automatically installs NixOS to the disk.
# It is intended to be used in an installation ISO.
# It expects `targetSystem` (the closure to install), `diskoScript` (the partitioning script),
# and `closureExport` (the pre-built NAR archive) to be passed as arguments.
{
  config,
  lib,
  pkgs,
  inputs,
  hostName,
  hostPlatform,
  targetSystem,
  diskoScript,
  closureExport,
  ...
}:
{
  # Ensure the entire system closure and all dependencies are included in the ISO
  environment.systemPackages = [
    pkgs.git
    pkgs.bashInteractive
    pkgs.curl
    targetSystem
  ];

  # Explicitly include the pre-built closure export and system in the ISO image
  isoImage.contents = [
    {
      source = closureExport;
      target = "/closure-export";
    }
    {
      source = targetSystem;
      target = "/system";
    }
  ];

  nixpkgs.hostPlatform = hostPlatform;

  systemd.services.auto-install = {
    description = "Automatic NixOS install for ${hostName}";
    after = [
      "network-online.target"
      "systemd-udev-settle.service"
    ];
    wants = [ "network-online.target" ];
    wantedBy = [ "multi-user.target" ];

    serviceConfig = {
      Type = "oneshot";
      StandardOutput = "journal+console";
      StandardError = "journal+console";
      Environment = "PATH=/run/current-system/sw/bin";
    };

    script = ''
      echo "=== AUTO INSTALL START for ${hostName} ==="

      echo ">>> Running disko script..."
      ${diskoScript}

      echo ">>> Importing pre-built closure into target store..."
      # Import the closure that was exported at build time
      ${pkgs.nix}/bin/nix-store --store /mnt --import < /closure-export/closure.nar > /dev/null

      echo ">>> Running nixos-install..."
      # Install with pre-built closure already imported (no evaluation or fetching needed)
      ${pkgs.nix}/bin/nixos-install \
        --no-root-passwd \
        --root /mnt \
        --system ${targetSystem} \
        --option substitute false

      echo ">>> Done. Rebooting."
      systemctl reboot
    '';
  };
}