# Deploy guard check for Jellyfin.
#
# Contract (deploy-guard-check plug-in):
# - exit 0: Jellyfin has no active playback sessions (or is unreachable, which
#   also means no users can be watching).
# - exit 1: at least one session is actively playing back media; stdout lists
#   user / title / client so the operator sees who they'd disrupt.
#
# A paused session counts as "active" — the user is at the keyboard and will
# notice a restart.
{
  config,
  lib,
  pkgs,
  service_configs,
  ...
}:
let
  apiKeyPath = config.age.secrets.jellyfin-api-key.path;
  jellyfinPort = service_configs.ports.private.jellyfin.port;

  check = pkgs.writeShellApplication {
    name = "deploy-guard-check-jellyfin";
    runtimeInputs = with pkgs; [
      curl
      jq
      coreutils
    ];
    text = ''
      api_key_path=${lib.escapeShellArg apiKeyPath}
      if [[ ! -r "$api_key_path" ]]; then
        echo "jellyfin: api key not readable at $api_key_path; skipping" >&2
        exit 0
      fi

      key=$(cat "$api_key_path")

      if ! resp=$(curl -sf --max-time 5 \
          -H "Authorization: MediaBrowser Token=$key" \
          "http://127.0.0.1:${toString jellyfinPort}/Sessions" 2>/dev/null); then
        echo "jellyfin: unreachable; assuming safe to deploy" >&2
        exit 0
      fi

      # Parse defensively — if Jellyfin returns something we can't understand
      # we prefer allowing the deploy over blocking it (the worst case is we
      # restart jellyfin while nobody is watching).
      if ! active=$(printf '%s' "$resp" | jq '[.[] | select(.NowPlayingItem)] | length' 2>/dev/null); then
        echo "jellyfin: /Sessions response not parsable; assuming safe" >&2
        exit 0
      fi

      if [[ "$active" -eq 0 ]]; then
        exit 0
      fi

      echo "Jellyfin: $active active playback session(s):"
      printf '%s' "$resp" | jq -r '
        .[]
        | select(.NowPlayingItem)
        | "  - \(.UserName // "?") \(if (.PlayState.IsPaused // false) then "paused" else "playing" end) \(.NowPlayingItem.Type // "item") \"\(.NowPlayingItem.Name // "?")\" on \(.Client // "?") / \(.DeviceName // "?")"
      '
      exit 1
    '';
  };
in
{
  imports = [
    ../../modules/server-deploy-guard.nix
  ];

  config = lib.mkIf config.services.jellyfin.enable {
    services.deployGuard.checks.jellyfin = {
      description = "Active Jellyfin playback sessions";
      command = check;
    };
  };
}