util.nix/nixos/module/hectic/service/sentinèlla.nix

{ 
  inputs,
  flake,
  self,
}:
{ 
  pkgs,
  lib,
  config,
  ...
}: let
  system = pkgs.stdenv.hostPlatform.system;
  cfg = config.hectic.services."sentinèlla";
in {
  options = {
    hectic.services."sentinèlla" = {
      probe = {
        enable = lib.mkEnableOption "sentinèlla probe — HTTP server exposing this node's health";
        port = lib.mkOption {
          type    = lib.types.port;
          default = 5988;
          description = "TCP port the probe listens on.";
        };
        urls = lib.mkOption {
          type    = with lib.types; listOf str;
          default = [];
          description = "URLs the probe health-checks on GET /status.";
        };
        volumes = lib.mkOption {
          type    = with lib.types; listOf str;
          default = [];
          description = "Mount points reported on GET /disk. Empty means all volumes.";
        };
        authFile = lib.mkOption {
          type    = with lib.types; nullOr path;
          default = null;
          example = "config.sops.secrets.\"sentinella-probe-auth\".path";
          description = "Path to a file with lines of the form user:pass for Basic Auth.";
        };
        environmentFile = lib.mkOption {
          type    = with lib.types; nullOr path;
          default = null;
          description = ''
            Optional environment file for secrets. Supported variables:
              PORT=
              URLS=
              VOLUMES=
              AUTH_FILE=
          '';
        };
      };

      watcher = {
        enable = lib.mkEnableOption "sentinèlla watcher — polls peers discovered via DNS and sends Telegram alerts";
        peersDns = lib.mkOption {
          type    = lib.types.str;
          example = "peers.sentinella.com";
          description = ''
            DNS name with multiple A records, one per peer node.
            Configure externally (e.g. Cloudflare) with TTL 60:
              peers.sentinella.com  A  1.2.3.4
              peers.sentinella.com  A  5.6.7.8
          '';
        };
        self = lib.mkOption {
          type    = with lib.types; nullOr str;
          default = null;
          example = "1.2.3.4";
          description = ''
            Override the auto-detected local IP. When null (default) the watcher
            uses hostname -I to find all local IPs and excludes them from the
            peer list automatically. Set this only if the node is behind NAT or
            has a floating IP that hostname -I does not report correctly.
          '';
        };
        peersPort = lib.mkOption {
          type    = lib.types.port;
          default = 5988;
          description = "Port all peer probes listen on.";
        };
        peersScheme = lib.mkOption {
          type    = lib.types.str;
          default = "http";
          description = "URL scheme used when connecting to peers (http or https).";
        };
        pollingIntervalSec = lib.mkOption {
          type    = lib.types.int;
          default = 3;
          description = "Seconds between polling rounds.";
        };
        tgToken = lib.mkOption {
          type    = with lib.types; nullOr str;
          default = null;
          description = "Telegram bot token. Prefer environmentFile for secrets.";
        };
        tgChatId = lib.mkOption {
          type    = with lib.types; nullOr str;
          default = null;
          description = "Telegram chat ID. Prefer environmentFile for secrets.";
        };
        environmentFile = lib.mkOption {
          type    = with lib.types; nullOr path;
          default = null;
          example = "config.sops.secrets.\"sentinella-watcher-env\".path";
          description = ''
            Optional environment file for secrets. Supported variables:
              TG_TOKEN=
              TG_CHAT_ID=
              PEERS_TOKEN=   # Basic Auth token sent to all peers
              SELF=
              PEERS_DNS=
          '';
        };
      };
    };
  };

  config = lib.mkMerge [
    (lib.mkIf cfg.probe.enable {
      systemd.services."sentinella-probe" = {
        description = "sentinèlla probe — node health HTTP server";
        after       = [ "network.target" ];
        wantedBy    = [ "multi-user.target" ];
        serviceConfig = lib.mkMerge [
          {
            Type            = "simple";
            ExecStart       = "${self.packages.${system}."sentinèlla"}/bin/probe";
            Restart         = "always";
            RestartSec      = "5s";
            TimeoutStopSec  = "30s";
            KillSignal      = "SIGTERM";
            KillMode        = "mixed";
            RemainAfterExit = false;
            StandardOutput  = "journal";
            StandardError   = "journal";
            Environment = lib.filter (s: s != "") [
              "PORT=${builtins.toString cfg.probe.port}"
              (lib.optionalString (cfg.probe.urls    != []) "URLS=${lib.concatStringsSep " " cfg.probe.urls}")
              (lib.optionalString (cfg.probe.volumes != []) "VOLUMES=${lib.concatStringsSep " " cfg.probe.volumes}")
              (lib.optionalString (cfg.probe.authFile != null) "AUTH_FILE=${cfg.probe.authFile}")
            ];
          }
          (lib.mkIf (cfg.probe.environmentFile != null) {
            EnvironmentFile = cfg.probe.environmentFile;
          })
        ];
      };
    })

    (lib.mkIf cfg.watcher.enable {
      systemd.services."sentinella-watcher" = {
        description = "sentinèlla watcher — p2p peer monitor";
        after       = [ "network.target" ];
        wantedBy    = [ "multi-user.target" ];
        serviceConfig = lib.mkMerge [
          {
            Type            = "simple";
            ExecStart       = "${self.packages.${system}."sentinèlla"}/bin/watcher";
            Restart         = "always";
            RestartSec      = "5s";
            TimeoutStopSec  = "30s";
            KillSignal      = "SIGTERM";
            KillMode        = "mixed";
            RemainAfterExit = false;
            StandardOutput  = "journal";
            StandardError   = "journal";
            StateDirectory  = "sentinella";
            Environment = lib.filter (s: s != "") [
              "PEERS_DNS=${cfg.watcher.peersDns}"
              (lib.optionalString (cfg.watcher.self     != null) "SELF=${cfg.watcher.self}")
              "PEERS_PORT=${builtins.toString cfg.watcher.peersPort}"
              "PEERS_SCHEME=${cfg.watcher.peersScheme}"
              "POLLING_INTERVAL_SEC=${builtins.toString cfg.watcher.pollingIntervalSec}"
              "STATE_DIR=/var/lib/sentinella"
              (lib.optionalString (cfg.watcher.tgToken  != null) "TG_TOKEN=${cfg.watcher.tgToken}")
              (lib.optionalString (cfg.watcher.tgChatId != null) "TG_CHAT_ID=${cfg.watcher.tgChatId}")
            ];
          }
          (lib.mkIf (cfg.watcher.environmentFile != null) {
            EnvironmentFile = cfg.watcher.environmentFile;
          })
        ];
      };
    })
  ];
}