infrastructure/machines/modules/malobeo/microvm_host.nix

{ config, self, lib, inputs, options, pkgs, ... }:

with lib;

let
  cfg = config.services.malobeo.microvm;
in
{
  options = {
    services.malobeo.microvm = {
      enableHostBridge = mkOption {
        default = false;
        type = types.bool;
        description = lib.mdDoc "Setup bridge device for microvms.";
      };

      enableHostBridgeUnstable = mkOption {
        default = false;
        type = types.bool;
        description = lib.mdDoc "Setup bridge device for microvms.";
      };

      deployHosts = mkOption {
        default = [];
        type = types.listOf types.str;
        description = ''
          List hostnames of MicroVMs that should be automatically initializes and autostart
        '';
      };
    };
  };


  imports = [
    inputs.microvm.nixosModules.host
  ];

  config = { 
    assertions = [
      {
        assertion = !(cfg.enableHostBridgeUnstable && cfg.enableHostBridge);
        message = ''
          Only enableHostBridge or enableHostBridgeUnstable! Not Both!
        '';
      }
    ];

    systemd.network = mkIf (cfg.enableHostBridge || cfg.enableHostBridgeUnstable) {
      enable = true;
      # create a bride device that all the microvms will be connected to
      netdevs."10-microvm".netdevConfig = {
        Kind = "bridge";
        Name = "microvm";
      };

      networks."10-microvm" = {
        matchConfig.Name = "microvm";
        networkConfig = {
          DHCPServer = true;
          IPv6SendRA = true;
        };
        addresses = if cfg.enableHostBridgeUnstable then [
          { Address = "10.0.0.1/24"; }
        ] else [
          { addressConfig.Address = "10.0.0.1/24"; }
        ];
      };

      # connect the vms to the bridge
      networks."11-microvm" = {
        matchConfig.Name = "vm-*";
        networkConfig.Bridge = "microvm";
      };
    }; 

    microvm.vms = 
    let
      # Map the values to each hostname to then generate an Attrset using listToAttrs
      mapperFunc = name: { inherit name; value = {
          # Host build-time reference to where the MicroVM NixOS is defined
          # under nixosConfigurations
          flake = inputs.malobeo; 
          # Specify from where to let `microvm -u` update later on
          updateFlake = "git+https://git.dynamicdiscord.de/kalipso/infrastructure";
        }; };
    in
    builtins.listToAttrs (map mapperFunc cfg.deployHosts);

    systemd.tmpfiles.rules = builtins.concatLists (map (name: [
      "d /var/lib/microvms/${name}/var 0755 root root - -"
      "d /var/lib/microvms/${name}/etc 0755 root root - -"
      "d /${name} 0755 root root - -"
    ]) cfg.deployHosts);

    systemd.services = builtins.foldl' (services: name: services // {
      "microvm-update@${name}" = {
        description = "Update MicroVMs automatically";
        after = [ "network-online.target" ];
        wants = [ "network-online.target" ];
        unitConfig.ConditionPathExists = "/var/lib/microvms/${name}";
        serviceConfig = {
          LimitNOFILE = "1048576";
          Type = "oneshot";
        };
        path = with pkgs; [ nix git ];
        environment.HOME = config.users.users.root.home;
        script = ''
          /run/current-system/sw/bin/microvm -Ru ${name}
        '';
      };
    }) {} (cfg.deployHosts);

    systemd.timers = builtins.foldl' (timers: name: timers // {
    "microvm-update-${name}" = {
      wantedBy = [ "timers.target" ];
      timerConfig = {
        Unit = "microvm-update@${name}.service";
        # three times per hour
        OnCalendar = "*:0,20,40:00";
        Persistent = true;
      };
    };
  }) {} (cfg.deployHosts);
  };
}