{ config, lib, pkgs, ... }:
let
  cfg = config.my.services.monitoring.loki;
in
{
  options.my.services.monitoring.loki = with lib; {
    enable = mkEnableOption "loki observability stack";
    listenAddress = mkOption {
      type = types.str;
      default = "0.0.0.0";
      description = lib.mdDoc ''
        Address to listen on.
      '';
    };
    listenPort = mkOption {
      type = types.port;
      default = 3100;
      description = lib.mdDoc ''
        Port to listen on.
      '';
    };
  };

  config = lib.mkIf cfg.enable {
    services.loki = {
      enable = true;
      configuration = {
        # no need for authentication, since we're binding on the
        # wireguard interface, we can trust the connections.
        auth_enabled = false;

        server = {
          http_listen_port = 3100;
          http_listen_address = cfg.listenAddress;
        };

        ingester = {
          lifecycler = {
            address = cfg.listenAddress;
            ring = {
              kvstore = { store = "inmemory"; };
              replication_factor = 1;
            };
            final_sleep = "0s";
          };

          # Any chunk not receiving new logs in this time will be flushed
          chunk_idle_period = "1h";

          # All chunks will be flushed when they hit this age, default is 1h
          max_chunk_age = "1h";

          # Loki will attempt to build chunks up to 1.5MB, flushing first if
          # chunk_idle_period or max_chunk_age is reached first
          chunk_target_size = 1048576;

          # Must be greater than index read cache TTL if using an index cache (Default
          # index read cache TTL is 5m)
          chunk_retain_period = "30s";

          # Chunk transfers disabled
          max_transfer_retries = 0;
        };

        schema_config = {
          configs = [{
            from = "2020-10-24";
            store = "boltdb-shipper";
            object_store = "filesystem";
            schema = "v11";
            index = {
              prefix = "index_";
              period = "24h";
            };
          }];
        };

        storage_config = {
          boltdb_shipper = {
            active_index_directory = "/var/lib/loki/boltdb-shipper-active";
            cache_location = "/var/lib/loki/boltdb-shipper-cache";

            # Can be increased for faster performance over longer query periods,
            # uses more disk space
            cache_ttl = "24h";

            shared_store = "filesystem";
          };

          filesystem = { directory = "/var/lib/loki/chunks"; };
        };

        limits_config = {
          reject_old_samples = true;
          reject_old_samples_max_age = "168h";
        };

        chunk_store_config = { max_look_back_period = "0s"; };

        table_manager = {
          retention_deletes_enabled = false;
          retention_period = "0s";
        };

        compactor = {
          working_directory = "/var/lib/loki/boltdb-shipper-compactor";
          shared_store = "filesystem";
        };
      };
    };
  };
}