{ pkgs, utils, lib, config, ... }:
with lib;
let
    cfg = config.services.btrfsScrub;
in
{
    options.services.btrfsScrub = {
        enable = mkEnableOption "Periodically run btrfs-scrub on filesystems";
        enableFailureEmail = mkOption {
            type = types.bool;
            default = true;
            description = mdDoc "Send e-mail on scrub failure";
        };
        paths = mkOption {
            type = with types; attrsOf (submodule {
                options = {
                    onCalendar = mkOption {
                        type = str;
                        default = "*-*-* 02:00:00";
                    };
                };
            });
        };
    };

    config.services.statusEmail.enable = mkIf (cfg.enable && cfg.enableFailureEmail) true;

    config.systemd.services."btrfs-scrub@" = mkIf cfg.enable {
        unitConfig = {
            Description = "Scrub btrfs volume %I";
            OnFailure = mkIf cfg.enableFailureEmail "status-email@%n.service";
        };
        serviceConfig = {
            Type = "simple";
            ExecStart = "${pkgs.btrfs-progs}/bin/btrfs scrub start -B -d %f";
            # ExecStop = "-${pkgs.btrfs-progs}/bin/btrfs scrub cancel %f";
            Nice = 19;
        };
    };

    config.systemd.timers = mkIf cfg.enable (mapAttrs' (name: value:
    let
        pathEscaped = utils.escapeSystemdPath name;
    in
    nameValuePair "btrfs-scrub-${pathEscaped}"
    {
        wantedBy = [ "timers.target" ];
        enable = true;
        timerConfig = {
            Unit = "btrfs-scrub@${pathEscaped}.service";
            OnCalendar = value.onCalendar;
            RandomizedDelaySec = "1h";
            Persistent = true;
        };
    }) cfg.paths);
}