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

with lib;

let
  cfg = config.clerie.anycast_healthchecker;
  configFile = pkgs.writeText "anycast-healthchecker.conf" ''
    [DEFAULT]
    interface              = lo

    [daemon]
    pidfile                = /run/anycast-healthchecker/anycast-healthchecker.pid
    ipv4                   = true
    ipv6                   = true
    bird_conf              = /var/lib/anycast-healthchecker/anycast-prefixes.conf
    bird6_conf             = /var/lib/anycast-healthchecker/anycast-prefixes6.conf
    bird_variable          = ACAST_PS_ADVERTISE
    bird6_variable         = ACAST6_PS_ADVERTISE
    bird_reconfigure_cmd   = birdc configure
    bird6_reconfigure_cmd  = birdc configure
    dummy_ip_prefix        = 10.189.200.255/32
    dummy_ip6_prefix       = 2001:db8::1/128
    bird_keep_changes      = false
    bird6_keep_changes     = false
    bird_changes_counter   = 128
    bird6_changes_counter  = 128
    purge_ip_prefixes      = false
    loglevel               = debug
    log_maxbytes           = 104857600
    log_backups            = 8
    json_stdout            = false
    json_log_file          = false
    json_log_server        = false
  '';

  checksDir = pkgs.writeTextDir "checks.conf" (
    concatStringsSep "\n" (
      mapAttrsToList (
        name: check: ''
          [${name}]
          ip_prefix         = ${check.ip_prefix}
          check_cmd         = ${check.cmd}
        '' + (
          concatStringsSep "\n" (
               optional (check.timeout != null)  "check_timeout     = ${toString check.timeout}"
            ++ optional (check.rise != null)     "check_rise        = ${toString check.rise}"
            ++ optional (check.fail != null)     "check_fail        = ${toString check.fail}"
            ++ optional (check.interval != null) "check_interval    = ${toString check.interval}"
          )
        )
      ) cfg.checks
    )
  );

  checkOpts = { config, ... }@moduleAttrs: {

    options = {

      enable = mkOption {
        type = types.bool;
        default = true;
      };
      timeout = mkOption {
        type = with types; nullOr int;
        default = null;
      };
      rise = mkOption {
        type = with types; nullOr int;
        default = null;
      };
      fail = mkOption {
        type = with types; nullOr int;
        default = null;
      };
      interval = mkOption {
        type = with types; nullOr int;
        default = null;
      };
      ip_prefix = mkOption {
        type = types.str;
      };
      cmd = mkOption {
        type = types.str;
        default = "${pkgs.curl}/bin/curl --fail --silent http://${moduleAttrs.config.ip_prefix}";
      };
    };

  };

in {

  options = {

    clerie.anycast_healthchecker = {

      enable = mkEnableOption "anycast healthchecker";

      checks = mkOption {
        type = with types; attrsOf (submodule checkOpts);
      };

    };

  };


  config = mkIf cfg.enable {

    systemd.services.anycast_healthchecker = {
      wantedBy = [ "multi-user.target" ];
      serviceConfig = {
        RuntimeDirectory = "anycast-healthchecker";
        StateDirectory = "anycast-healthchecker";
        User = "bird2";
        Group = "bird2";
        ExecStart = "${pkgs.anycast_healthchecker}/bin/anycast-healthchecker -f ${configFile} -d ${checksDir}";
      };
      path = with pkgs; [ bird2 ];
    };

  };
}