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

with lib;
let
  cfg = config.services.tandoor-recipes;
  pkg = cfg.package;

  # SECRET_KEY through an env file
  env = {
    GUNICORN_CMD_ARGS = "--bind=${cfg.address}:${toString cfg.port}";
    DEBUG = "0";
    DEBUG_TOOLBAR = "0";
    MEDIA_ROOT = "/var/lib/tandoor-recipes";
  } // optionalAttrs (config.time.timeZone != null) {
    TZ = config.time.timeZone;
  } // (
    lib.mapAttrs (_: toString) cfg.extraConfig
  );

  manage = pkgs.writeShellScript "manage" ''
    set -o allexport # Export the following env vars
    ${lib.toShellVars env}
    eval "$(${config.systemd.package}/bin/systemctl show -pUID,GID,MainPID tandoor-recipes.service)"
    exec ${pkgs.util-linux}/bin/nsenter \
      -t $MainPID -m -S $UID -G $GID \
      ${pkg}/bin/tandoor-recipes "$@"
  '';
in
{
  meta.maintainers = with maintainers; [ ambroisie ];

  options.services.tandoor-recipes = {
    enable = mkOption {
      type = lib.types.bool;
      default = false;
      description = lib.mdDoc ''
        Enable Tandoor Recipes.

        When started, the Tandoor Recipes database is automatically created if
        it doesn't exist and updated if the package has changed. Both tasks are
        achieved by running a Django migration.

        A script to manage the instance (by wrapping Django's manage.py) is linked to
        `/var/lib/tandoor-recipes/tandoor-recipes-manage`.
      '';
    };

    address = mkOption {
      type = types.str;
      default = "localhost";
      description = lib.mdDoc "Web interface address.";
    };

    port = mkOption {
      type = types.port;
      default = 8080;
      description = lib.mdDoc "Web interface port.";
    };

    extraConfig = mkOption {
      type = types.attrs;
      default = { };
      description = lib.mdDoc ''
        Extra tandoor recipes config options.

        See [the example dot-env file](https://raw.githubusercontent.com/vabene1111/recipes/master/.env.template)
        for available options.
      '';
      example = {
        ENABLE_SIGNUP = "1";
      };
    };

    package = mkPackageOption pkgs "tandoor-recipes" { };
  };

  config = mkIf cfg.enable {
    systemd.services.tandoor-recipes = {
      description = "Tandoor Recipes server";

      serviceConfig = {
        ExecStart = ''
          ${pkg.python.pkgs.gunicorn}/bin/gunicorn recipes.wsgi
        '';
        Restart = "on-failure";

        User = "tandoor_recipes";
        Group = "tandoor_recipes";
        DynamicUser = true;
        StateDirectory = "tandoor-recipes";
        WorkingDirectory = "/var/lib/tandoor-recipes";
        RuntimeDirectory = "tandoor-recipes";

        BindReadOnlyPaths = [
          "${config.environment.etc."ssl/certs/ca-certificates.crt".source}:/etc/ssl/certs/ca-certificates.crt"
          builtins.storeDir
          "-/etc/resolv.conf"
          "-/etc/nsswitch.conf"
          "-/etc/hosts"
          "-/etc/localtime"
          "-/run/postgresql"
        ];
        CapabilityBoundingSet = "";
        LockPersonality = true;
        MemoryDenyWriteExecute = true;
        PrivateDevices = true;
        PrivateUsers = true;
        ProtectClock = true;
        ProtectControlGroups = true;
        ProtectHome = true;
        ProtectHostname = true;
        ProtectKernelLogs = true;
        ProtectKernelModules = true;
        ProtectKernelTunables = true;
        RestrictAddressFamilies = [ "AF_UNIX" "AF_INET" "AF_INET6" ];
        RestrictNamespaces = true;
        RestrictRealtime = true;
        SystemCallArchitectures = "native";
        # gunicorn needs setuid
        SystemCallFilter = [ "@system-service" "~@privileged" "@resources" "@setuid" "@keyring" ];
        UMask = "0066";
      } // lib.optionalAttrs (cfg.port < 1024) {
        AmbientCapabilities = [ "CAP_NET_BIND_SERVICE" ];
        CapabilityBoundingSet = [ "CAP_NET_BIND_SERVICE" ];
      };

      wantedBy = [ "multi-user.target" ];

      preStart = ''
        ln -sf ${manage} tandoor-recipes-manage

        # Let django migrate the DB as needed
        ${pkg}/bin/tandoor-recipes migrate
      '';

      environment = env // {
        PYTHONPATH = "${pkg.python.pkgs.makePythonPath pkg.propagatedBuildInputs}:${pkg}/lib/tandoor-recipes";
      };
    };
  };
}