{ config, lib }:
with lib;

let
  cfg = config.hq.yggdrasil;
  hostNameHash = hashString "sha256" 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";
      };
    };
  };

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