{ config, lib, pkgs, ... }:

let
  cfg = config.services.coronafs;
  tomlFormat = pkgs.formats.toml { };
  coronafsConfigFile = tomlFormat.generate "coronafs.toml" {
    listen_addr = "0.0.0.0:${toString cfg.port}";
    advertise_host = cfg.advertiseHost;
    data_dir = toString cfg.dataDir;
    export_bind_addr = cfg.exportBindAddr;
    export_base_port = cfg.exportBasePort;
    export_port_count = cfg.exportPortCount;
    export_shared_clients = cfg.exportSharedClients;
    export_cache_mode = cfg.exportCacheMode;
    export_aio_mode = cfg.exportAioMode;
    export_discard_mode = cfg.exportDiscardMode;
    export_detect_zeroes_mode = cfg.exportDetectZeroesMode;
    preallocate = cfg.preallocate;
    sync_on_write = cfg.syncOnWrite;
    qemu_nbd_path = "${pkgs.qemu}/bin/qemu-nbd";
    qemu_img_path = "${pkgs.qemu}/bin/qemu-img";
    log_level = "info";
  };
in
{
  options.services.coronafs = {
    enable = lib.mkEnableOption "CoronaFS block volume service";

    port = lib.mkOption {
      type = lib.types.port;
      default = 50088;
      description = "Port for the CoronaFS control API.";
    };

    advertiseHost = lib.mkOption {
      type = lib.types.str;
      default = "127.0.0.1";
      description = "Host or IP placed into exported NBD URIs.";
      example = "10.0.0.11";
    };

    exportBindAddr = lib.mkOption {
      type = lib.types.str;
      default = "0.0.0.0";
      description = "Bind address for qemu-nbd exports.";
    };

    exportBasePort = lib.mkOption {
      type = lib.types.port;
      default = 11000;
      description = "First TCP port reserved for CoronaFS NBD exports.";
    };

    exportPortCount = lib.mkOption {
      type = lib.types.int;
      default = 512;
      description = "Number of NBD export ports reserved for CoronaFS volumes.";
    };

    exportSharedClients = lib.mkOption {
      type = lib.types.int;
      default = 32;
      description = "Maximum number of concurrent clients per exported CoronaFS volume.";
    };

    exportCacheMode = lib.mkOption {
      type = lib.types.enum [ "none" "writeback" "writethrough" "directsync" "unsafe" ];
      default = "none";
      description = "qemu-nbd cache mode for CoronaFS exports.";
    };

    exportAioMode = lib.mkOption {
      type = lib.types.enum [ "native" "io_uring" "threads" ];
      default = "io_uring";
      description = "qemu-nbd AIO mode for CoronaFS exports.";
    };

    exportDiscardMode = lib.mkOption {
      type = lib.types.enum [ "ignore" "unmap" ];
      default = "unmap";
      description = "qemu-nbd discard handling for CoronaFS exports.";
    };

    exportDetectZeroesMode = lib.mkOption {
      type = lib.types.enum [ "off" "on" "unmap" ];
      default = "unmap";
      description = "qemu-nbd detect-zeroes mode for CoronaFS exports.";
    };

    preallocate = lib.mkOption {
      type = lib.types.bool;
      default = true;
      description = "Preallocate blank CoronaFS volumes with fallocate when possible.";
    };

    syncOnWrite = lib.mkOption {
      type = lib.types.bool;
      default = false;
      description = "Force sync_all after volume import writes.";
    };

    dataDir = lib.mkOption {
      type = lib.types.path;
      default = "/var/lib/coronafs";
      description = "Data directory for CoronaFS volumes, metadata, and export pid files.";
    };

    package = lib.mkOption {
      type = lib.types.package;
      default = pkgs.coronafs-server or (throw "coronafs-server package not found");
      description = "Package to use for CoronaFS.";
    };
  };

  config = lib.mkIf cfg.enable {
    users.users.coronafs = {
      isSystemUser = true;
      group = "coronafs";
      description = "CoronaFS service user";
      home = cfg.dataDir;
    };

    users.groups.coronafs = { };

    systemd.services.coronafs = {
      description = "CoronaFS Block Volume Service";
      wantedBy = [ "multi-user.target" ];
      after = [ "network.target" ];
      path = [ pkgs.qemu pkgs.util-linux pkgs.procps pkgs.coreutils ];

      serviceConfig = {
        Type = "simple";
        User = "coronafs";
        Group = "coronafs";
        UMask = "0007";
        Restart = "on-failure";
        RestartSec = "5s";
        StateDirectory = "coronafs";
        StateDirectoryMode = "0750";
        ReadWritePaths = [ cfg.dataDir ];
        ExecStart = "${cfg.package}/bin/coronafs-server --config ${coronafsConfigFile}";
      };
    };

    systemd.tmpfiles.rules = [
      "d ${toString cfg.dataDir} 0750 coronafs coronafs -"
      "d ${toString cfg.dataDir}/volumes 0750 coronafs coronafs -"
      "d ${toString cfg.dataDir}/metadata 0750 coronafs coronafs -"
      "d ${toString cfg.dataDir}/pids 0750 coronafs coronafs -"
    ];
  };
}