{ pkgs, lib, config, ... }:

#
# Build with:
#
# nix build '((import <nixpkgs/nixos/lib/eval-config.nix> { modules = [ ./configuration.nix ]; }).config.system.build.sdImage)'
#

let
  extlinux-conf-builder =
    import ../../system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.nix {
      pkgs = pkgs.buildPackages;
    };
in

{
  imports = [
    <nixpkgs/nixos/modules/profiles/base.nix>
    <nixpkgs/nixos/modules/profiles/installation-device.nix>
    <nixpkgs/nixos/modules/installer/cd-dvd/sd-image.nix>

    # Custom sets up some things specific to the user.

    # Sets stuff like:
    # - timezone (time.timeZone)
    # - users (users.users.<user>)
    # - authorized ssh keys (users.users.<user>.openssh.authorizedKeys)
    # - wifi password (networking.wireless.networks)
    # - ddclient (services.ddclient)
    # - miniupnpc

    ./custom.nix
  ];

  sdImage = {
    populateBootCommands = let
      configTxt = pkgs.writeText "config.txt" ''
        # Prevent the firmware from smashing the framebuffer setup done by the mainline kernel
        # when attempting to show low-voltage or overtemperature warnings.
        avoid_warnings=1

        [pi0]
        kernel=u-boot-rpi0.bin

        [pi1]
        kernel=u-boot-rpi1.bin
      '';
      in ''
        (cd ${pkgs.raspberrypifw}/share/raspberrypi/boot && cp bootcode.bin fixup*.dat start*.elf $NIX_BUILD_TOP/boot/)
        cp ${pkgs.ubootRaspberryPiZero}/u-boot.bin boot/u-boot-rpi0.bin
        cp ${pkgs.ubootRaspberryPi}/u-boot.bin boot/u-boot-rpi1.bin
        cp ${configTxt} boot/config.txt
        ${extlinux-conf-builder} -t 3 -c ${config.system.build.toplevel} -d ./boot
      '';
  };

  boot.loader.grub.enable = false;
  boot.loader.generic-extlinux-compatible.enable = true;
  boot.consoleLogLevel = lib.mkDefault 7;
  boot.kernelPackages = pkgs.linuxPackages_rpi;
  boot.kernelParams = [
    "panic=1"
    "boot.panic_on_fail"
  ];

  # Setup cross compilation.
  nixpkgs = {
    overlays = [(self: super: {
      libnl = super.libnl.override { pythonSupport = false; };
      gobject-introspection = super.gobject-introspection.override {
        x11Support = false;
      };
      dbus = super.dbus.override { x11Support = false; };
    }) ];
    config = {};
    crossSystem = lib.systems.elaborate lib.systems.examples.raspberryPi;
    localSystem = { system = "x86_64-linux"; };
  };

  # Enable tools for remote installation.
  services.openssh.enable = true;
  networking.wireless.enable = true;
  security.sudo.enable = true;
  hardware.enableRedistributableFirmware = true;

  # Setup headless mode.
  systemd.enableEmergencyMode = false;
  documentation.enable = false;
  services.nixosManual.showManual = lib.mkForce false;

  # Disable some stuff that doesn’t cross compile.
  services.nscd.enable = false;
  services.udisks2.enable = false;
  boot.supportedFilesystems = lib.mkForce [ "vfat" ];
  environment.systemPackages = lib.mkForce [ ];
  security.polkit.enable = false;
  fonts.fontconfig.enable = false;
  programs.command-not-found.enable = false;
  programs.ssh.setXAuthLocation = false;
  security.pam.services.su.forwardXAuth = lib.mkForce false;

}