{ config, pkgs, lib, ... }:
let
  cfg = config.services.influxdb2.provision;

  inherit (lib)
    mkEnableOption
    mkOption
    types
    mdDoc
    flip
    mapAttrsToList
    getExe
    mkIf;

  taskOptions =
    { ... }:
    {
      options = {
        cron = mkOption {
          type = with types; nullOr str;
          default = null;
          description = mdDoc ''
          '';
        };

        every = mkOption {
          type = with types; nullOr str;
          default = null;
          description = mdDoc ''
          '';
        };

        fluxFile = mkOption {
          type = types.path;
          description = mdDoc ''
          '';
        };

        offset = mkOption {
          type = types.str;
          default = "0m";
          description = mdDoc ''
          '';
        };
      };
    };

  tasksFile =
    (pkgs.formats.json {}).generate "tasks.json"
      (flip mapAttrsToList cfg.tasks (name: value:
        {
          inherit name;
          flux_file = value.fluxFile;
          inherit (value)
            every
            cron
            offset;
        }
      ));
in
{
  options = {
    services.influxdb2.provision-magic = {
      enable = mkEnableOption "Enable InfluxDB2 provisioning";

      itpPackage = mkOption {
        type = types.package;
        default = pkgs.itp;
        description = mdDoc ''
        '';
      };

      stateFile = mkOption {
        type = types.str;
        description = mdDoc ''
        '';
      };

      organization = mkOption {
        type = types.str;
        description = mdDoc ''
        '';
      };

      tasks = mkOption {
        type = with types; attrsOf (submodule taskOptions);
        default = {};
        description = mdDoc ''
        '';
      };
    };
  };

  config = mkIf cfg.enable {
    systemd.services.influxdb2-provision = {
      after = [ "influxdb2.service" ];
      wants = [ "influxdb2.service" ];
      wantedBy = [ "multi-user.target" ];

      restartIfChanged = true;

      script = ''
        ${getExe cfg.itpPackage} -s ${cfg.stateFile} -f ${tasksFile} -o ${cfg.organization}
      '';

      serviceConfig = {
        Type = "oneshot";
        Restart = "on-failure";
        RestartSec = 3;
      };
    };

    assertions = flip mapAttrsToList cfg.tasks
      (n: v: {
        assertion = (v.cron != null && v.every == null) || (v.cron == null && v.every != null);
        message = "Exactly one of `services.influxdb2.provision.tasks.${n}.{cron, every}` must be non `null`";
      });
  };
}