{ config, lib, ... }:
let
  inherit (lib) mkOption types;
  cfg = config.infra-net;
  leafSubmodule = lib.types.submodule {
    options = {
      mac = mkOption {
        type = types.str;
        description = ''
          Adresse MAC de l'interface préexistante sur le réseau INFRA.
        '';
        example = "AA:BB:CC:DD:EE:FF";
      };
      id = mkOption {
        type = types.ints.between 1 65535;
        description = ''
          Identifiant de la machine dans le réseau INFRA.
        '';
        example = 194;
      };
    };
  };
  hubDefSubmodule = lib.type.submodule {
    options = {
      hid = mkOption {
        type = types.ints.between 1 255;
        description = ''
          Identifiant du concentrateur sur la maille WireGuard.
        '';
        example = 12;
      };
      public-key = mkOption {
        type = types.str;
        description = ''
          Clé publique WireGuard du concentrateur.
        '';
        example = "LwhiJgtHtYQT4Ug6tgD0RDlUhhNga5tIyiWN2A6dCnk=";
      };
      address = mkOption {
        type = types.str;
        description = ''
          Adresse IP publique du concentrateur.
        '';
        example = "1.2.3.4";
      };
      port = mkOption {
        type = types.port;
        description = ''
          Port WireGuard public du concentrateur.
        '';
        default = 51039;
        example = 51039;
      };
    };
  };
  hubSubmodule = lib.types.submodule {
    options = {
      name = mkOption {
        type = types.str;
        description = ''
          Nom d'hôte du concentrateur.
        '';
        default = config.networking.hostName;
      };
      all-hubs = mkOption {
        type = types.attrsOf hubDefSubmodule;
        description = ''
          Définitions de l'ensemble des concentrateurs.
        '';
      };
      private-key-path = mkOption {
        type = types.path;
        description = ''
          Chemin vers la clé privée WireGuard du concentrateur.
        '';
      };
      wg-port = mkOption {
        type = types.port;
        description = ''
          Port d'écoute WireGuard du concentrateur.
        '';
        default = 51039;
        example = 51039;
      };
      id = mkOption {
        type = types.ints.between 1 65535;
        description = ''
          Identifiant de la machine dans le réseau INFRA.
        '';
        example = 194;
      };
      mac = mkOption {
        type = types.str;
        description = ''
          Adresse MAC de l'interface virtuelle à du concentrateur sur
          le réseau INFRA.
        '';
        example = "AA:BB:CC:DD:EE:FF";
      };
    };
  };
  mkAddresses = id: let
    a = id / 256;
    b = id - 256 * a;
  in [
    "fd0a:66d3:1c19:42::${toString a}:${toString b}/64"
    "10.42.${toString a}.${toString b}/16"
  ];
  mkHubAddress = hub: "fd0a:66d3:1c19:1000::${toString hub.hid}";
  mkPeer = hub: {
    PublicKey = hub.public-key;
    Endpoint = "${hub.address}:${hub.port}";
    AllowedIPs = mkHubAddress hub;
  };
  vxlanPort = 4789;
  vni = 42;
  selfHub = cfg.hub.all-hubs."${cfg.hub.name}";
  otherHubs = lib.filterAttrs (n: _: n != cfg.hub.name) cfg.hub.all-hubs;
  mkBridgeFDB = hub: {
    MACAddress = "00:00:00:00:00:00";
    Destination = "${mkHubAddress hub}";
    VNI = vni;
  };
in {
  options.infra-net = {
    leaf = mkOption {
      type = types.nullOr leafSubmodule;
      default = null;
      description = ''
        Configuration de l'interface d'une feuille du réseau INFRA.
      '';
    };
    hub = lib.mkOption {
      type = lib.types.nullOr hubSubmodule;
      default = null;
      description = ''
        Configuration des interfaces d'un concentrateur du réseau INFRA.
      '';
    };
  };

  config = let
    hubNetwork = {
      links = {
        "10-wg-infra" = {
          netdevConfig = {
            Name = "wg-infra";
            Kind = "wireguard";
          };
          wireguardConfig = {
            ListenPort = cfg.hub.wg-port;
            PrivateKey = "@wg-infra-key";
          };
          wireguardPeers = map mkPeer otherHubs;
        };
        "10-vxl-infra" = {
          netdevConfig = {
            Name = "vxl-infra";
            Kind = "vxlan";
          };
          vxlanConfig = {
            Local = mkHubAddress selfHub;
            VNI = vni;
            MacLearning = true;
            DestinationPort = vxlanPort;
          };
        };
        "10-br-infra".netdevConfig = {
          Name = "br-infra";
          Kind = "bridge";
          MACAddress = cfg.hub.mac;
        };
      };
      networks = {
        "10-wg-infra" = {
          matchConfig.Name = "wg-infra";
          networkConfig = {
            Address = "${mkHubAddress selfHub}/64";
            VXLAN = "vxl-infra";
          };
        };
        "10-vxl-infra" = {
          matchConfig.Name = "vxl-infra";
          networkConfig = {
            LinkLocalAddressing = false;
            Bridge = "br-infra";
          };
          bridgeFDBs = map mkBridgeFDB otherHubs;

        };
        "10-br-infra" = {
          matchConfig.Name = "br-infra";
          address = mkAddresses cfg.hub.id;
        };
      };
    };
    leafNetwork = {
      links."10-infra" = {
        matchConfig.MACAddress = cfg.leaf.mac;
        linkConfig.Name = "infra";
      };
      networks."10-infra" = {
        matchConfig.Name = "infra";
        address = mkAddresses cfg.leaf.id;
      };
    };
  in {
    systemd.network = lib.mkMerge [
      (lib.mkIf (cfg.hub != null) hubNetwork)
      (lib.mkIf (cfg.leaf != null) leafNetwork)
    ];

    systemd.services.systemd-networkd.serviceConfig.LoadCredential =
      lib.mkIf (cfg.hub != null)
      [ "wg-infra-key:${cfg.hub.private-key-path}" ];
  };
}