{ config, pkgs, ... }:
let

  inherit (config.services.dendrite.settings.global) server_name;

  matrix_host = "matrix.terranix.org";
  element_host = "element.terranix.org";
  element-web-terranix.org =
    pkgs.runCommand "element-web-with-config"
      {
        nativeBuildInputs = [ pkgs.buildPackages.jq ];
      } ''
      cp -r ${pkgs.element-web} $out
      chmod -R u+w $out
      jq '."default_server_config"."m.homeserver" = { "base_url": "https://${matrix_host}:443", "server_name": "${server_name}" }' \
        > $out/config.json < ${pkgs.element-web}/config.json
      ln -s $out/config.json $out/config.${matrix_host}.json
    '';
in
{

  # $ nix-shell -p dendrite --run 'generate-keys --private-key /tmp/key'
  sops.secrets.matrix-server-key = { };

  services.dendrite = {
    enable = true;
    httpPort = 8043;
    settings = {
      global = {
        server_name = "terranix.org";
        # `private_key` has the type `path`
        # prefix a `/` to make `path` happy
        private_key = "/$CREDENTIALS_DIRECTORY/matrix-server-key";
        trusted_third_party_id_servers = [
          "matrix.org"
          "vector.im"
          "xaos.space"
          "lassul.us"
          "thalheim.io"
          "nixos.org"
        ];
        metrics.enabled = false;
      };
      logging = [
        {
          type = "std";
          level = "warn";
        }
      ];
      client_api = {
        registration_disabled = true;
        rate_limiting.enabled = false;
        # set only for the first admin account, than remove.
        #registration_shared_secret = ""; # disable once first admin account is created
      };
      media_api = {
        dynamic_thumbnails = true;
      };
      mscs = {
        mscs = [ "msc2836" "msc2946" ];
      };
      sync_api = {
        real_ip_header = "X-Real-IP";
      };
      federation_api = {
        key_perspectives = [
          {
            server_name = "matrix.org";
            keys = [
              {
                key_id = "ed25519:auto";
                public_key = "Noi6WqcDj0QmPxCNQqgezwTlBKrfqehY1u2FyWP9uYw";
              }
              {
                key_id = "ed25519:a_RXGa";
                public_key = "l8Hft5qXKn1vfHrg3p4+W8gELQVo8N13JkluMfmn2sQ";
              }
            ];
          }
        ];
        prefer_direct_fetch = false;
      };
    };
  };

  systemd.services.dendrite.serviceConfig.LoadCredential = [
    "matrix-server-key:${config.sops.secrets.matrix-server-key.path}"
  ];

  # Verify if federation works with
  # https://federationtester.matrix.org/#terranix.org
  services.nginx.virtualHosts.${matrix_host} = {
    serverAliases = [ "terranix.org" ];
    listen = [
      {
        addr = "0.0.0.0";
        port = 443;
        ssl = true;
      }
      {
        addr = "0.0.0.0";
        port = 8448;
        ssl = true;
        extraParameters = [ "default_server" ];
      }
    ];
    forceSSL = true;
    enableACME = true;
    extraConfig = ''
      proxy_set_header Host $host;
      proxy_set_header X-Real-IP $remote_addr;
      proxy_read_timeout 600;
    '';
    locations."/".proxyPass = "http://127.0.0.1:${toString config.services.dendrite.httpPort}";
  };

  networking.firewall.allowedTCPPorts = [ 8448 ];
  networking.firewall.allowedUDPPorts = [ 8448 ];

  services.nginx.virtualHosts.${element_host} = {
    forceSSL = true;
    enableACME = true;
    extraConfig = ''
      proxy_set_header Host $host;
      proxy_set_header X-Real-IP $remote_addr;
      proxy_read_timeout 600;
    '';
    locations."/".root = element-web-terranix.org;
  };

}