# Tests that you can boot from an external disk image with the qemu-vm module.
# "External" here means that the image was not produced within the qemu-vm
# module and relies on the fileSystems option also set outside the qemu-vm
# module. Most notably, this tests that you can stop the qemu-vm module from
# overriding fileSystems with virtualisation.fileSystems so you don't have to
# replicate the previously set fileSystems in virtualisation.fileSystems.

{ lib, ... }:

let
  rootFslabel = "external";
  rootFsDevice = "/dev/disk/by-label/${rootFslabel}";

  externalModule = { config, lib, pkgs, ... }: {
    boot.loader.systemd-boot.enable = true;

    fileSystems = {
      "/".device = rootFsDevice;
    };

    system.build.diskImage = import ../lib/make-disk-image.nix {
      inherit config lib pkgs;
      label = rootFslabel;
      partitionTableType = "efi";
      format = "qcow2";
      bootSize = "32M";
      additionalSpace = "0M";
      copyChannel = false;
    };
  };
in
{
  name = "qemu-vm-external-disk-image";

  meta.maintainers = with lib.maintainers; [ nikstur ];

  nodes.machine = { config, lib, pkgs, ... }: {
    virtualisation.directBoot.enable = false;
    virtualisation.mountHostNixStore = false;
    virtualisation.useEFIBoot = true;

    # This stops the qemu-vm module from overriding the fileSystems option
    # with virtualisation.fileSystems.
    virtualisation.fileSystems = lib.mkForce { };

    imports = [ externalModule ];
  };

  testScript = { nodes, ... }: ''
    import os
    import subprocess
    import tempfile

    tmp_disk_image = tempfile.NamedTemporaryFile()

    subprocess.run([
      "${nodes.machine.virtualisation.qemu.package}/bin/qemu-img",
      "create",
      "-f",
      "qcow2",
      "-b",
      "${nodes.machine.system.build.diskImage}/nixos.qcow2",
      "-F",
      "qcow2",
      tmp_disk_image.name,
    ])

    # Set NIX_DISK_IMAGE so that the qemu script finds the right disk image.
    os.environ['NIX_DISK_IMAGE'] = tmp_disk_image.name

    machine.succeed("findmnt --kernel --source ${rootFsDevice} --target /")

    # Make sure systemd boot didn't clobber this
    machine.succeed("[ ! -e /homeless-shelter ]")
  '';
}