{ config, lib, pkgs, ... }:
with lib;
let
  cfg = config.services.hashicorp-envoy;

  serviceFormat = pkgs.formats.json {};
in
{
  options.services.hashicorp-envoy = mkOption {
    description = mdDoc ''
    '';
    type = types.attrsOf (types.submodule {
      options = {
        service = mkOption {
          description = mdDoc ''
          '';
          type = serviceFormat.type;
        };

        environment = mkOption {
          description = mdDoc ''
          '';
          type = with types; attrsOf str;
          default = {};
        };

        adminBind = mkOption {
          description = mdDoc ''
          '';
          type = types.str;
        };

        consulPackage = mkOption {
          description = mdDoc ''
          '';
          type = types.package;
          default = pkgs.consul;
        };

        envoyPackage = mkOption {
          description = mdDoc ''
          '';
          type = types.package;
          default = pkgs.envoy;
        };
      };
    });
    default = {};
  };

  config = {
    services.hashicorp = flip mapAttrs' cfg (name: value:
      nameValuePair
        "envoy-${name}"
        {
          enable = true;
          package = pkgs.consul;
          command = "connect envoy";
          extraArguments = [
            "-sidecar-for" value.service.id
            "-admin-bind" value.adminBind
            "-address" (value.service.connect.sidecar_service.address or "0.0.0.0" + ":" + toString value.service.connect.sidecar_service.port or "19000")
          ];
          extraPackages = [ value.envoyPackage ];
          dontUseConfig = true;
        }
    );

    systemd.services = flip mapAttrs' cfg (name: value:
      nameValuePair
        "hashicorp-envoy-${name}"
        {
          preStart = "${value.consulPackage}/bin/consul services register ${serviceFormat.generate "${name}-service.json" { service = value.service; }}";
          postStop = "${value.consulPackage}/bin/consul services deregister -id=${value.service.id}";
          environment = value.environment;
        }
    );
  };
}