{ pkgs, lib, config, modulesPath, ... }:
{
  imports = [
    "${modulesPath}/profiles/minimal.nix"
    "${modulesPath}/profiles/qemu-guest.nix"
    "${modulesPath}/virtualisation/qemu-vm.nix"
  ];

  config = {
    services.qemuGuest.enable = true;
    system.stateVersion = "23.05";

    fileSystems."/" = {
      device = "/dev/disk/by-label/nixos";
      fsType = "ext4";
      autoResize = true;
    };

    boot = {
      growPartition = true;
      loader.timeout = 5;
    };

    virtualisation = {
      diskSize = 8000; # MB
      memorySize = 2048; # MB

      # We don't want to use tmpfs, otherwise the nix store's size will be bounded
      # by a fraction of available RAM.
      writableStoreUseTmpfs = false;

      forwardPorts = [{
        guest.port = 22;
        host.port = 2222;
      } {
        guest.port = 9090;
        host.port = 9090;
      } {
        guest.port = 8081;
        host.port = 8081;
      }];
    };

    # So that we can ssh into the VM, see e.g.
    # http://blog.patapon.info/nixos-local-vm/#accessing-the-vm-with-ssh
    services.openssh.enable = true;
    services.openssh.settings.PermitRootLogin = "yes";
    # Give root an empty password to ssh in.
    users.extraUsers.root.password = "";
    users.users.root.openssh.authorizedKeys.keys = [
      "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIMNeQYLFauAbzDyIbKC86NUh9yZfiyBm/BtIdkcpZnSU"
    ];
    users.mutableUsers = false;
    networking.firewall.enable = false;

    environment.systemPackages = with pkgs; [
      git
      htop
      neovim
    ];

    services.mysql = {
      enable = true;
      package = pkgs.mariadb;
      ensureUsers = [{
        name = "root";
        ensurePermissions = {
          "*.*" = "ALL PRIVILEGES";
        };
      }];
      ensureDatabases = [ "root" ];
    };

    services.redis.servers = {
      # Queue, naming it "" makes it use default values.
      "".enable = true;

      socketio = {
        enable = true;
        port = 12311;
      };
    };

    users.users.erpnext = {
      description = "User to run erpnext";
      group = "erpnext";
      isSystemUser = true;
      home = "/var/lib/erpnext";
      createHome = true;
    };

    systemd.services.setup-mysql = {
      enable = true;
      before = [ "erpnext.service" ];
      after = [ "mysql.service" ];
      wantedBy = [ "erpnext.service" ];
      partOf = [ "erpnext.service" ];
      script = ''
        ${pkgs.mariadb-client}/bin/mysql -e "SET PASSWORD FOR 'root'@'localhost' = PASSWORD('password')";
      '';
      serviceConfig = {
        RemainAfterExit = true;
        Type = "oneshot";
      };
    };

    systemd.services.ensure-bench-dir = {
      enable = true;
      before = [ "erpnext.service" ];
      wantedBy = [ "erpnext.service" ];
      partOf = [ "erpnext.service" ];
      script = ''
        for subdir in apps sites config/pids logs; do
          mkdir -p /var/lib/erpnext/bench/$subdir
        done
      '';
      serviceConfig = {
        RemainAfterExit = true;
        Type = "oneshot";
        User = "erpnext";
      };
    };

    services.nginx = {
      enable = true;
      appendHttpConfig = builtins.readFile "${pkgs.erpnext-nginx-conf}";
    };

    systemd.services.erpnext =
      let
        penv = pkgs.python3-erpnext.buildEnv.override {
          extraLibs = [
            pkgs.python3-erpnext.pkgs.frappe
            pkgs.python3-erpnext.pkgs.erpnext
            pkgs.python3-erpnext.pkgs.bench
          ];
        };
        appsFile = pkgs.writeText "erpnext-apps.txt" ''
          frappe
          erpnext
        '';

        # In a module, this could be provided by a use as a file as it could
        # contain secrets and we don't want this in the nix-store. But here it
        # is OK.
        commonSiteConfig = pkgs.writeText "erpnext-common_site_config.json" ''
          {
            "db_host": "localhost",
            "db_port": 3306,
            "db_name": "erpnext" ,
            "db_password": "erpnext" ,
            "redis_cache": "redis://localhost:6379?db=0",
            "redis_queue": "redis://localhost:6379?db=1",
            "redis_socketio": "redis://localhost:6379?db=2",
            "socketio_port": 3000
          }
        '';
      in
        {
          enable = true;
          wantedBy = [ "multi-user.target" ];
          after = [ "mysql.service" "redis.service" "redis-socketio.service" ];
          description = "ERPNext";
          confinement = {
            enable = true;
            packages = [ pkgs.mariadb-client pkgs.nodejs penv ];
          };
          script = ''
            export PYTHON_PATH=${penv}/${pkgs.python3-erpnext.sitePackages}
            export PATH="${pkgs.mariadb-client}/bin:${pkgs.nodejs}/bin:${penv}/bin:$PATH"

            # Upstream initializes the DB with this command
            # TODO: Make this idempotent
            cd /var/lib/erpnext/bench/sites
            bench new-site localhost --mariadb-root-password password --admin-password admin || true
            bench --site localhost install-app erpnext

            # TODO: Run these as systemd units
            node /var/lib/erpnext/bench/apps/frappe/socketio.js &
            gunicorn --chdir="/var/lib/erpnext/bench/sites" --bind=0.0.0.0:9090 --threads=4 --workers=2 --worker-class=gthread --worker-tmp-dir=/dev/shm --timeout=120 --preload frappe.app:application
          '';
          serviceConfig = {
            User = "erpnext";
            NoNewPrivileges = true;
            Type = "simple";
            BindReadOnlyPaths = [
              "/etc/hosts:/etc/hosts"
              "${pkgs.frappe-app}:${pkgs.frappe-app}"
              "${pkgs.frappe-app}/share/apps/frappe:/var/lib/erpnext/bench/apps/frappe"
              "${pkgs.erpnext-app}:${pkgs.erpnext-app}"
              "${pkgs.erpnext-app}/share/apps/erpnext:/var/lib/erpnext/bench/apps/erpnext"
              "${pkgs.frappe-erpnext-assets}/share/sites/assets:/var/lib/erpnext/bench/sites/assets"
              "${appsFile}:/var/lib/erpnext/bench/sites/apps.txt"
              "${commonSiteConfig}:/var/lib/erpnext/bench/sites/common_site_config.json"
              "${penv}:/var/lib/erpnext/bench/env"
            ];
            BindPaths = [
              "/var/lib/erpnext:/var/lib/erpnext"
            ];
          };
        };
  };
}