{ pkgs, lib, config, ... }:
let
  cfg = config.container-services;

  healthcheck = with pkgs.lib; {
    test = mkOption {
      type = types.oneOf types.str (types.listOf types.str);
    };
    interval = mkOption {
      type = types.str;
      default = "30s";
    };
    startupInterval = mkOption {
      type = types.str;
      default = "30s";
    };
    startPeriod = mkOption {
      type = types.str;
      default = "0s";
    };
  };

  service = with pkgs.lib; {
    name = mkOption {
      type = types.nilOr types.str;
      default = nil;
    };

    alias = mkOption {
      type = types.nilOr types.str;
      default = nil;
    };

    dependsOn = mkOption {
      type = types.listOf service;
      default = [ ];
    };

    image = mkOption {
      type = types.str;
    };

    volumes = mkOption {
      type = types.listOf types.str;
      default = [ ];
    };

    ports = mkOption {
      type = types.listOf types.str;
      default = [ ];
    };

    environment = mkOption {
      type = types.attrsOf types.str;
      default = { };
    };

    environmentFiles = mkOption {
      type = types.listOf types.str;
      default = [ ];
    };

    cmd = mkOption {
      type = types.nilOr (types.listOf types.str);
      default = nil;
    };

    healthCheck = mkOption {
      type = types.nilOr (types.submodule healthcheck);
      default = nil;
    };
  };

  pod = with pkgs.lib; {
    name = mkOption {
      type = types.nilOr str;
      default = nil;
    };

    description = mkOption {
      type = types.nilOr str;
      default = nil;
    };

    services = mkOption {
      type = types.attrsOf (types.submodule service);
      default = { };
    };
  };

  backend = config.virtualisation.oci-containers.backend;
  volumeName = pod: name: "${pod.name}-${name}";
  volumeServiceName = pod: name: "${backend}-volume-${volumeName pod name}";
  volumeServiceRef = pod: name: config.systemd.services."${backend}-volume-${volumeName pod name}".name + ".service";
  serviceName = pod: service: "${backend}-${pod.name}-${service.name}";
  serviceRef = pod: service: config.systemd.services."${backend}-${pod.name}-${service.name}".name + ".service";
  networkName = pod: "${pod.name}-default";
  networkServiceName = pod: "${backend}-network-${pod.name}";
  networkServiceRef = pod: config.systemd.services."${backend}-network-${pod.name}".name + ".service";
  podName = pod: "${backend}-pod-${pod.name}";
  podRef = pod: config.systemd.targets."${backend}-pod-${pod.name}".name + ".target";
  namedVolumes = service: lib.filter (volume: (! ((lib.hasPrefix "/" volume) || (lib.hasPrefix "./" volume)))) (lib.map (volume: lib.head (lib.splitString ":" volume)) service.volumes);
  oneShotService = { pod, description, script }: {
    path = [ (if backend == "podman" then pkgs.podman else pkgs.docker) ];
    serviceConfig = {
      Type = "oneshot";
      RemainAfterExit = true;
    };
    inherit description;
    inherit script;
    partOf = [ podRef pod ];
    wantedBy = [ podRef pod ];
  };
in
{
  options = with pkgs.lib; {
    container-services = mkOption {
      type = types.attrsOf (types.submodule pod);
      default = { };
    };
  };

  config = {
    container-services = lib.mapAttrs
      (name: pod: {
        name = lib.mkDefault pod.name;
        services = lib.mapAttrs
          (name: service: {
            name = lib.mkDefault name;
          })
          pod.services;
      })
      cfg;

    systemd.targets = lib.mapAttrs' (_: pod:
      lib.nameValuePair (podName pod) {
        wantedBy = [ "multi-user.target" ];
        unitConfig = {
          Description = pod.description or pod.name;
        };
      }
    );

    systemd.services = lib.foldl
      (services: pod: lib.mergeAttrsList [
        services
        {
          "${networkServiceName pod}" = oneShotService {
            description = "Network for ${pod.name}";
            script = ''
              ${backend} network inspect ${networkName pod} || ${backend} network create ${networkName pod}
            '';
          };
        }
        (lib.mapAttrs'
          (_: service:
            let
              dependencies =
                (lib.map (service: serviceRef pod.name service.name) service.dependsOn) ++
                (lib.map (name: volumeServiceRef pod.name name) (namedVolumes service)) ++
                (networkServiceRef pod);
            in
            lib.nameValuePair (serviceName pod service) {
              serviceConfig = {
                Restart = lib.mkOverride 500 "always";
              };
              after = dependencies;
              requires = dependencies;
              partOf = [ (podRef pod) ];
              wantedBy = [ (podRef pod) ];
            }
          )
          pod.services)
        (lib.listToAttrs (lib.flatten (
          lib.map
            (service: (
              lib.map
                (volume: {
                  name = volumeServiceName pod volume;
                  value = oneShotService {
                    description = "Volume ${volume} of ${pod.name}";
                    script = ''
                      ${backend} volume inspect ${volumeName pod volume} || ${backend} volume create ${volumeName pod volume}
                    '';
                  };
                })
                namedVolumes)
            )
            pod.services)))
      ])
      { }
      cfg;

    virtualisation.oci-containers.containers = lib.foldl
      (containers: pod: containers // (
        lib.mapAttrs' (_: service:
          lib.nameValuePair (serviceName pod service) {
            image = service.image;
            volumes = service.volumes;
            log-driver = "journal";
            ports = service.ports;
            environment = service.environment;
            environmentFiles = service.environmentFiles;
            cmd = service.cmd;
            extraOptions = [
              "--network-alias=${service.alias or service.name}"
              "--network=${networkName pod}"
            ] ++ (if (service.healthCheck != null) then [
              "--health-cmd=${
                if (builtins.isList service.healthCheck.test)
                then builtins.toJSON service.healthCheck.test
                else service.healthCheck.test
              }"
              "--health-interval=${service.healthCheck.interval}"
              "--health-startup-interval=${service.healthCheck.startupInterval}"
              "--health-start-period=${service.healthCheck.startPeriod}"
            ] else [ ]);
          }
        )
      ))
      { }
      cfg;
  };
}