{ config, lib, ... }:
with lib;

let
  cfg = config.hq.yggdrasil;
  hostNameHash = builtins.hashString "sha256" config.networking.hostName;
  hextets = map (i: substring (4 * i) (4 * (i + 1)) hostNameHash) [ 0 1 2 3 ];
  hostAddr = concatStringsSep ":" hextets;
in {
  options = with types; {
    hq.yggdrasil = {
      enable =
        mkEnableOption "Configure Yggdrasil access via the Yggdrasil router";

      interface = mkOption {
        type = nullOr str;
        default = "eth0";
        description = "Network interface to the C3D2 HQ ethernet";
      };
    };
  };

  config = mkIf cfg.enable {
    networking.interfaces = {
      "${cfg.interface}" = {
        "ipv6" = {
          addresses = [{
            address = "310:5217:69c0:9afc:${hostAddr}";
            prefixLength = 64;
          }];
          routes = [{
            address = "200::";
            prefixLength = 7;
            via = "310:5217:69c0:9afc::1";
          }];
        };
      };
    };
  };
}