# The WireGuard inter-hive mesh for the local host. Split out of
# ./swarm.nix because the two are different concerns with different
# audiences: that file declares WHO the peers are (consumed by
# swarm-controller's hive roster and, here, the mesh), while this one
# is plain host networking that a machine which runs no hive at all
# --- the snapshot store, for one --- still needs.
#
# The two stay coupled by data, not by structure: the per-peer
# `wireguard*` fields live on the peer submodule in ./swarm.nix, since
# that is where a peer is described, and this module reads them.
{
  lib,
  config,
  ...
}:
{
  # WireGuard mesh config for the local host.
  # When enabled, a `wg-hive` interface connects to all peers that have
  # `wireguardPublicKey` declared. Peers reachable over the mesh are
  # preferred for inter-hive traffic (no public TLS round-trip needed);
  # peers without a public key still work via normal HTTPS.
  options.services.hyperhive.swarm.wireguard = {
    enable = lib.mkOption {
      type = lib.types.bool;
      default = false;
      description = ''
        Enable the WireGuard inter-hive mesh. When true, a `wg-hive`
        interface is brought up connecting to all swarm peers that
        declare a `wireguardPublicKey`. Requires
        `privateKeyFile` to be set.
      '';
    };

    privateKeyFile = lib.mkOption {
      type = lib.types.nullOr lib.types.path;
      default = null;
      example = "/etc/wireguard/hive.key";
      description = ''
        Path to the host's WireGuard private key file. The file must
        be readable by root and should have mode 0400. Generate with
        `wg genkey > /etc/wireguard/hive.key`. Required when
        `swarm.wireguard.enable = true`.
      '';
    };

    address = lib.mkOption {
      type = lib.types.str;
      default = "";
      example = "10.100.0.1/24";
      description = ''
        IP address (with prefix) of this host on the WireGuard mesh.
        Use a /24 (or broader) prefix so the routing table covers all
        peer /32 routes. Example: `"10.100.0.1/24"` for a 256-host mesh.
      '';
    };

    listenPort = lib.mkOption {
      type = lib.types.port;
      default = 51820;
      description = ''
        UDP port the local WireGuard interface listens on. Must be
        reachable from peer hosts when they initiate the tunnel.
        Default: 51820 (standard WireGuard port).
      '';
    };

    persistentKeepalive = lib.mkOption {
      type = lib.types.nullOr lib.types.int;
      default = 25;
      example = 25;
      description = ''
        Seconds between keepalive packets sent to each peer. Useful
        when this host (or a peer) is behind NAT — keeps the UDP hole
        open. Set to null to disable. Default: 25 seconds.
      '';
    };
  };

  # Gated on the mesh itself, NOT on the c0re daemon. The mesh is host
  # networking, not a c0re feature: a swarm host that runs no hive —
  # the snapshot store, for one — still has to join the mesh, and under
  # the old `c0re.enable` gate it silently got no `wg-hive` interface
  # at all. Nothing below is c0re-specific; the peer data c0re consumes
  # (HIVE_PEER_CA_PATHS) is rendered in ./hive-c0re and stays gated
  # there.
  config = lib.mkIf config.services.hyperhive.swarm.wireguard.enable {
    assertions = [
      {
        assertion = config.services.hyperhive.swarm.wireguard.privateKeyFile != null;
        message = ''
          services.hyperhive.swarm.wireguard.enable requires
          services.hyperhive.swarm.wireguard.privateKeyFile to be set.
          Generate a key: wg genkey > /etc/wireguard/hive.key
        '';
      }
      {
        assertion = config.services.hyperhive.swarm.wireguard.address != "";
        message = ''
          services.hyperhive.swarm.wireguard.enable requires
          services.hyperhive.swarm.wireguard.address to be set
          (e.g. "10.100.0.1/24").
        '';
      }
    ];

    # WireGuard inter-hive mesh. Brings up a `wg-hive` interface and
    # connects to each peer that has `wireguardPublicKey` set.
    networking.wireguard.interfaces =
      let
        wgCfg = config.services.hyperhive.swarm.wireguard;
        # `peerHives` is `swarm.hives` minus this hive (../swarm.nix) —
        # a mesh that included our own entry would configure a tunnel to
        # ourselves.
        meshPeers = lib.filterAttrs (
          _: p: p.wireguardPublicKey != null && p.wireguardAddress != null
        ) config.services.hyperhive.swarm.peerHives;
      in
      {
        wg-hive = {
          ips = [ wgCfg.address ];
          listenPort = wgCfg.listenPort;
          privateKeyFile = wgCfg.privateKeyFile;
          peers = lib.mapAttrsToList (
            _name: p:
            {
              publicKey = p.wireguardPublicKey;
              allowedIPs = [ p.wireguardAddress ];
            }
            // lib.optionalAttrs (p.wireguardEndpoint != null) {
              endpoint = p.wireguardEndpoint;
            }
            // lib.optionalAttrs (wgCfg.persistentKeepalive != null) {
              persistentKeepalive = wgCfg.persistentKeepalive;
            }
          ) meshPeers;
        };
      };

    # Open the WireGuard UDP port on the host firewall (host-level
    # networking — not inside containers).
    networking.firewall.allowedUDPPorts = [
      config.services.hyperhive.swarm.wireguard.listenPort
    ];
  };
}