{ lib, config, pkgs, ... }:

/*
Wireguard VPN server

References:

- https://nixos.wiki/wiki/WireGuard
- https://wireguard.how/client/ios/
*/

let
  ports = import ../Cloud/Ports.nix;
  ips = "10.100.0.1/24";

  # a micro-library for creating iptables rules
  iptables = rec {
    bin = "${pkgs.iptables/bin/iptables}";
    append = {source}: lib.concatSep " " [
      bin
      "--table" "nat"
      "--append" "POSTROUTING"
      "--source" source
      "--out-interface" "eth0"
      "--jump" "MASQUERADE"
    ];
    delete = {source}: lib.concatSep " " [
      bin
      "--table" "nat"
      "--delete" "POSTROUTING"
      "--source" source
      "--out-interface" "eth0"
      "--jump" "MASQUERADE"
    ];

  };
in {
  networking.nat.enable = true;
  networking.nat.externalInterface = "eth0";
  networking.nat.internalInterfaces = [ "wg0" ];
  networking.firewall.allowedUDPPorts = [ ports.wireguard ];

  networking.wireguard.enable = true;

  networking.wireguard.interfaces = {
    wg0 = {
      ips = [ ips ];
      allowedIPsAsRoutes = true;
      listenPort = ports.wireguard;
      postSetup = ''
        ${pkgs.iptables}/bin/iptables -t nat -A POSTROUTING -s ${ips} -o eth0 -j MASQUERADE
      '';

      postShutdown = ''
        ${pkgs.iptables}/bin/iptables -t nat -D POSTROUTING -s ${ips} -o eth0 -j MASQUERADE
      '';

      privateKeyFile = "/var/wireguard/private";

      peers = [
        #{ # helium
        #  publicKey = "TODO";
        #  allowedIPs = [ "10.100.0.2/32" ];
        #}
        { # ben's iPhone
          publicKey = "SIBIfPLhzuV1S1FZtm5JQtDbl0ehnH+Y3CpoZ2eZ3gc=";
          allowedIPs = [ "10.100.0.3/32" ];
        }
      ];
    };
  };
}