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

with lib;
let
  cfg = config.fudo.paris-container;

  packages = with pkgs; [ rtorrent ];

  hostname = config.instance.hostname;

  hostSecrets = config.fudo.secrets.host-secrets."${hostname}";

  hostKeypairs = config.fudo.secrets.files.ssh.host-keypairs.paris;

  keytabFilename = keypair: "host-paris-${keypair.key-type}-private-key";

in {
  options.fudo.paris-container = with types; {
    enable = mkEnableOption "Enable Fudo Paris user server.";

    state-directory = mkOption {
      type = str;
      description = "Directory at which to store server state.";
    };

    ports = mkOption {
      type = listOf port;
      description = "List of ports to open to the public internet.";
      default = [ ];
    };

    ssh-keys = mkOption {
      type = listOf str;
      description = "List of SSH keys to use.";
      default = [ ];
    };

    ldap = {
      image = mkOption {
        type = str;
        description = "Authentik LDAP outpost Docker image.";
        default = "ghcr.io/goauthentik/ldap:latest";
      };

      port = mkOption {
        type = port;
        description = "Port on which to listen for LDAP requests.";
        default = 4389;
      };

      domain = mkOption {
        type = str;
        description =
          "Domain for which data is served. Only used for internal mapping.";
      };

      authentik-host = mkOption {
        type = str;
        description = "Hostname of the LDAP outpost provider.";
        default = "authentik.${toplevel.config.fudo.mail.primary-domain}";
      };

      outpost-token-file = mkOption {
        type = str;
        description =
          "File containing token with which to authenticate to the Authentik host.";
      };

      bind-dn = mkOption {
        type = str;
        description = "DN as which to bind with the LDAP server.";
      };

      bind-token-file = mkOption {
        type = str;
        description =
          "File containing token with which to bind with the LDAP server.";
      };

      base = mkOption {
        type = str;
        description = "Base of the LDAP server.";
        example = "dc=fudo,dc=org";
      };

      user-ou = mkOption {
        type = str;
        description = "Organizational unit containing users.";
        default = "ou=users";
      };

      group-ou = mkOption {
        type = str;
        description = "Organizational unit containing users.";
        default = "ou=groups";
      };
    };

    networking = {
      interface = mkOption {
        type = str;
        description = "Parent host interface on which to listen.";
      };

      ipv4 = mkOption {
        type = nullOr (submodule {
          options = {
            address = mkOption {
              type = str;
              description = "IP address.";
            };
            prefixLength = mkOption {
              type = int;
              description = "Significant bits in the address.";
            };
          };
        });
        default = null;
      };

      ipv6 = mkOption {
        type = nullOr (submodule {
          options = {
            address = mkOption {
              type = str;
              description = "IP address.";
            };
            prefixLength = mkOption {
              type = int;
              description = "Significant bits in the address.";
            };
          };
        });
        default = null;
      };
    };
  };

  config = mkIf cfg.enable {
    systemd.tmpfiles.rules =
      [ "d ${cfg.state-directory}/home 0700 root root - -" ];

    fudo.secrets.host-secrets."${hostname}" = {
      parisLdapEnv = {
        source-file = pkgs.writeText "paris-ldap-proxy.env"
          (concatStringsSep "\n" [
            "AUTHENTIK_HOST=${cfg.ldap.authentik-host}"
            "AUTHENTIK_TOKEN=${readFile cfg.ldap.outpost-token-file}"
            "AUTHENTIK_INSECURE=false"
          ]);
        target-file = "/run/paris/ldap.env";
      };
      parisSssdEnv = {
        source-file = pkgs.writeText "paris-sssd.env"
          "LDAP_DEFAULT_AUTHTOKEN=${readFile cfg.ldap.bind-token-file}";
        target-file = "/run/paris/sssd.env";
      };
    } // (listToAttrs (map (keypair:
      nameValuePair (keypairFilename keypair) {
        source-file = keypair.private-key;
        target-file = "/run/paris/openssh/${keypairFilename keypair}";
      }) parisKeypairs));

    virtualisation.oci-containers.containers.paris-ldap-proxy = {
      image = cfg.ldap.image;
      autoStart = true;
      ports = [ "${toString cfg.ldap.port}:389" ];
      environmentFiles = [ hostSecrets.parisLdapEnv.target-file ];
    };

    containers.paris = {
      macvlans = [ cfg.networking.interface ];
      bindMounts = {
        "/home" = {
          hostPath = "${cfg.state-directory}/home";
          isReadOnly = false;
        };
      } // (listToAttrs (map (keypair:
        nameValuePair "/run/openssh/keys/${keypairFilename keypair}" {
          hostPath = "/run/paris/openssh/${keypairFilename keypair}";
          isReadOnly = true;
        }) parisKeypairs));
      additionalCapabilities = [ "CAP_NET_ADMIN" ];
      config = {
        nixpkgs.pkgs = pkgs;

        environment.systemPackages = packages;

        services = {
          opensssh = {
            enable = true;
            startWhenNeeded = true;
            hostKeys = map (keypair: {
              path = "/run/openssh/keys/${keypairFilename keypair}";
              type = keypair.key-type;
            }) parisKeypairs;
            settings = {
              UseDns = true;
              PermitRootLogin = "no";
            };
          };

          sssd = {
            enable = true;
            kcm = true;
            environmentFile = hostSecrets.parisSssdEnv.target-file;
            config = lib.generators.toINI { } {
              sssd = {
                config_file_version = 2;
                reconnection_retries = 3;
                sbus_timeout = 30;
                services = concatStringsSep " " [ "nss" "pam" "ssh" ];
                domains = concatStringsSep " " [ cfg.ldap.domain ];
              };

              pam = { reconnection_retries = 3; };

              nss = {
                filter_groups = "root";
                filter_users = "root";
                reconnection_retries = 3;
              };

              "domain/${cfg.ldap.domain}" = {
                cache_credentials = true;
                id_provider = "ldap";
                chpass_provider = "ldap";
                auth_provider = "ldap";
                access_provider = "ldap";

                ldap_uri = "ldap://localhost:${toString cfg.ldap.port}";
                ldap_schema = "rfc2307bis";

                ldap_search_base = cfg.ldap.base;
                ldap_user_search_base = "${cfg.ldap.user-ou},${cfg.ldap.base}";
                ldap_group_search_base =
                  "${cfg.ldap.group-ou},${cfg.ldap.base}";

                ladp_user_object_class = "user";
                ldap_user_cn = "cn";
                ldap_group_object_class = "group";
                ldap_group_name = "cn";

                ldap_default_bind_dn = cfg.ldap.bind-dn;
                ldap_default_authtok = "$LDAP_DEFAULT_AUTHTOKEN";
              };
            };
          };
        };

        networking = {
          defaultGateway = {
            address = config.networking.defaultGateway.address;
            interface = "mv-${cfg.networking.interface}";
          };
          enableIPv6 = !isNull cfg.networking.ipv6;
          nameservers = config.networking.nameservers;
          firewall = {
            enable = true;
            allowedTCPPorts = [ 22 ] ++ cfg.ports;
          };
          interfaces."mv-${cfg.networking.interface}" = {
            ipv4.addresses = optional (!isNull cfg.networking.ipv4) {
              address = cfg.networking.ipv4.address;
              prefixLength = cfg.networking.ipv4.prefixLength;
            };
            ipv6.addresses = optional (!isNull cfg.networking.ipv6) {
              address = cfg.networking.ipv6.address;
              prefixLength = cfg.networking.ipv6.prefixLength;
            };
          };
        };
      };
    };
  };
}