{ config, lib, pkgs, ... }:
with builtins;
with lib;
let
  cfg = config.services.gitlab-runner;
  hasDocker = config.virtualisation.docker.enable;

  /* The whole logic of this module is to diff the hashes of the desired vs existing runners
  The hash is recorded in the runner's name because we can't do better yet
  See https://gitlab.com/gitlab-org/gitlab-runner/-/issues/29350 for more details
  */
  genRunnerName = name: service: let
      hash = substring 0 12 (hashString "md5" (unsafeDiscardStringContext (toJSON service)));
    in if service ? description && service.description != null
    then "${hash} ${service.description}"
    else "${name}_${config.networking.hostName}_${hash}";

  hashedServices = mapAttrs'
    (name: service: nameValuePair (genRunnerName name service) service) cfg.services;
  configPath = ''"$HOME"/.gitlab-runner/config.toml'';
  configureScript = pkgs.writeShellApplication {
    name = "gitlab-runner-configure";
    runtimeInputs = with pkgs; [
        bash
        gawk
        jq
        moreutils
        remarshal
        util-linux
        cfg.package
        perl
        python3
    ];
    text = if (cfg.configFile != null) then ''
      cp ${cfg.configFile} ${configPath}
      # make config file readable by service
      chown -R --reference="$HOME" "$(dirname ${configPath})"
    '' else ''
      export CONFIG_FILE=${configPath}

      mkdir -p "$(dirname ${configPath})"
      touch ${configPath}

      # update global options
      remarshal --if toml --of json ${configPath} \
        | jq -cM 'with_entries(select([.key] | inside(["runners"])))' \
        | jq -scM '.[0] + .[1]' - <(echo ${escapeShellArg (toJSON cfg.settings)}) \
        | remarshal --if json --of toml \
        | sponge ${configPath}

      # remove no longer existing services
      gitlab-runner verify --delete

      ${toShellVar "NEEDED_SERVICES" (lib.mapAttrs (name: value: 1) hashedServices)}

      declare -A REGISTERED_SERVICES

      while IFS="," read -r name token;
      do
        REGISTERED_SERVICES["$name"]="$token"
      done < <(gitlab-runner --log-format json list 2>&1 | grep Token  | jq -r '.msg +"," + .Token')

      echo "NEEDED_SERVICES: " "''${!NEEDED_SERVICES[@]}"
      echo "REGISTERED_SERVICES:" "''${!REGISTERED_SERVICES[@]}"

      # difference between current and desired state
      declare -A NEW_SERVICES
      for name in "''${!NEEDED_SERVICES[@]}"; do
        if [ ! -v 'REGISTERED_SERVICES[$name]' ]; then
          NEW_SERVICES[$name]=1
        fi
      done

      declare -A OLD_SERVICES
      # shellcheck disable=SC2034
      for name in "''${!REGISTERED_SERVICES[@]}"; do
        if [ ! -v 'NEEDED_SERVICES[$name]' ]; then
          OLD_SERVICES[$name]=1
        fi
      done

      # register new services
      ${concatStringsSep "\n" (mapAttrsToList (name: service: ''
        # TODO so here we should mention NEW_SERVICES
        if [ -v 'NEW_SERVICES["${name}"]' ] ; then
          bash -c ${escapeShellArg (concatStringsSep " \\\n " ([
            "set -a && source ${service.registrationConfigFile} &&"
            "gitlab-runner register"
            "--non-interactive"
            "--name '${name}'"
            "--executor ${service.executor}"
            "--limit ${toString service.limit}"
            "--request-concurrency ${toString service.requestConcurrency}"
            "--maximum-timeout ${toString service.maximumTimeout}"
          ] ++ service.registrationFlags
            ++ optional (service.buildsDir != null)
            "--builds-dir ${service.buildsDir}"
            ++ optional (service.cloneUrl != null)
            "--clone-url ${service.cloneUrl}"
            ++ optional (service.preCloneScript != null)
            "--pre-clone-script ${service.preCloneScript}"
            ++ optional (service.preBuildScript != null)
            "--pre-build-script ${service.preBuildScript}"
            ++ optional (service.postBuildScript != null)
            "--post-build-script ${service.postBuildScript}"
            ++ optional (service.tagList != [ ])
            "--tag-list ${concatStringsSep "," service.tagList}"
            ++ optional service.runUntagged
            "--run-untagged"
            ++ optional service.protected
            "--access-level ref_protected"
            ++ optional service.debugTraceDisabled
            "--debug-trace-disabled"
            ++ map (e: "--env ${escapeShellArg e}") (mapAttrsToList (name: value: "${name}=${value}") service.environmentVariables)
            ++ optionals (hasPrefix "docker" service.executor) (
              assert (
                assertMsg (service.dockerImage != null)
                  "dockerImage option is required for ${service.executor} executor (${name})");
              [ "--docker-image ${service.dockerImage}" ]
              ++ optional service.dockerDisableCache
              "--docker-disable-cache"
              ++ optional service.dockerPrivileged
              "--docker-privileged"
              ++ map (v: "--docker-volumes ${escapeShellArg v}") service.dockerVolumes
              ++ map (v: "--docker-extra-hosts ${escapeShellArg v}") service.dockerExtraHosts
              ++ map (v: "--docker-allowed-images ${escapeShellArg v}") service.dockerAllowedImages
              ++ map (v: "--docker-allowed-services ${escapeShellArg v}") service.dockerAllowedServices
            )
          ))} && sleep 1 || exit 1
        fi
      '') hashedServices)}

      # check key is in array https://stackoverflow.com/questions/30353951/how-to-check-if-dictionary-contains-a-key-in-bash

      echo "NEW_SERVICES: ''${NEW_SERVICES[*]}"
      echo "OLD_SERVICES: ''${OLD_SERVICES[*]}"
      # unregister old services
      for NAME in "''${!OLD_SERVICES[@]}"
      do
        [ -n "$NAME" ] && gitlab-runner unregister \
          --name "$NAME" && sleep 1
      done

      # make config file readable by service
      chown -R --reference="$HOME" "$(dirname ${configPath})"
    '';
  };
  startScript = pkgs.writeShellScriptBin "gitlab-runner-start" ''
    export CONFIG_FILE=${configPath}
    exec gitlab-runner run --working-directory $HOME
  '';
in {
  options.services.gitlab-runner = {
    enable = mkEnableOption (lib.mdDoc "Gitlab Runner");
    configFile = mkOption {
      type = types.nullOr types.path;
      default = null;
      description = lib.mdDoc ''
        Configuration file for gitlab-runner.

        {option}`configFile` takes precedence over {option}`services`.
        {option}`checkInterval` and {option}`concurrent` will be ignored too.

        This option is deprecated, please use {option}`services` instead.
        You can use {option}`registrationConfigFile` and
        {option}`registrationFlags`
        for settings not covered by this module.
      '';
    };
    settings = mkOption {
      type = types.submodule {
        freeformType = (pkgs.formats.json { }).type;
      };
      default = { };
      description = lib.mdDoc ''
        Global gitlab-runner configuration. See
        <https://docs.gitlab.com/runner/configuration/advanced-configuration.html#the-global-section>
        for supported values.
      '';
    };
    gracefulTermination = mkOption {
      type = types.bool;
      default = false;
      description = lib.mdDoc ''
        Finish all remaining jobs before stopping.
        If not set gitlab-runner will stop immediately without waiting
        for jobs to finish, which will lead to failed builds.
      '';
    };
    gracefulTimeout = mkOption {
      type = types.str;
      default = "infinity";
      example = "5min 20s";
      description = lib.mdDoc ''
        Time to wait until a graceful shutdown is turned into a forceful one.
      '';
    };
    package = mkOption {
      type = types.package;
      default = pkgs.gitlab-runner;
      defaultText = literalExpression "pkgs.gitlab-runner";
      example = literalExpression "pkgs.gitlab-runner_1_11";
      description = lib.mdDoc "Gitlab Runner package to use.";
    };
    extraPackages = mkOption {
      type = types.listOf types.package;
      default = [ ];
      description = lib.mdDoc ''
        Extra packages to add to PATH for the gitlab-runner process.
      '';
    };
    services = mkOption {
      description = lib.mdDoc "GitLab Runner services.";
      default = { };
      example = literalExpression ''
        {
          # runner for building in docker via host's nix-daemon
          # nix store will be readable in runner, might be insecure
          nix = {
            # File should contain at least these two variables:
            # `CI_SERVER_URL`
            # `REGISTRATION_TOKEN`
            registrationConfigFile = "/run/secrets/gitlab-runner-registration";
            dockerImage = "alpine";
            dockerVolumes = [
              "/nix/store:/nix/store:ro"
              "/nix/var/nix/db:/nix/var/nix/db:ro"
              "/nix/var/nix/daemon-socket:/nix/var/nix/daemon-socket:ro"
            ];
            dockerDisableCache = true;
            preBuildScript = pkgs.writeScript "setup-container" '''
              mkdir -p -m 0755 /nix/var/log/nix/drvs
              mkdir -p -m 0755 /nix/var/nix/gcroots
              mkdir -p -m 0755 /nix/var/nix/profiles
              mkdir -p -m 0755 /nix/var/nix/temproots
              mkdir -p -m 0755 /nix/var/nix/userpool
              mkdir -p -m 1777 /nix/var/nix/gcroots/per-user
              mkdir -p -m 1777 /nix/var/nix/profiles/per-user
              mkdir -p -m 0755 /nix/var/nix/profiles/per-user/root
              mkdir -p -m 0700 "$HOME/.nix-defexpr"

              . ''${pkgs.nix}/etc/profile.d/nix.sh

              ''${pkgs.nix}/bin/nix-env -i ''${concatStringsSep " " (with pkgs; [ nix cacert git openssh ])}

              ''${pkgs.nix}/bin/nix-channel --add https://nixos.org/channels/nixpkgs-unstable
              ''${pkgs.nix}/bin/nix-channel --update nixpkgs
            ''';
            environmentVariables = {
              ENV = "/etc/profile";
              USER = "root";
              NIX_REMOTE = "daemon";
              PATH = "/nix/var/nix/profiles/default/bin:/nix/var/nix/profiles/default/sbin:/bin:/sbin:/usr/bin:/usr/sbin";
              NIX_SSL_CERT_FILE = "/nix/var/nix/profiles/default/etc/ssl/certs/ca-bundle.crt";
            };
            tagList = [ "nix" ];
          };
          # runner for building docker images
          docker-images = {
            # File should contain at least these two variables:
            # `CI_SERVER_URL`
            # `REGISTRATION_TOKEN`
            registrationConfigFile = "/run/secrets/gitlab-runner-registration";
            dockerImage = "docker:stable";
            dockerVolumes = [
              "/var/run/docker.sock:/var/run/docker.sock"
            ];
            tagList = [ "docker-images" ];
          };
          # runner for executing stuff on host system (very insecure!)
          # make sure to add required packages (including git!)
          # to `environment.systemPackages`
          shell = {
            # File should contain at least these two variables:
            # `CI_SERVER_URL`
            # `REGISTRATION_TOKEN`
            registrationConfigFile = "/run/secrets/gitlab-runner-registration";
            executor = "shell";
            tagList = [ "shell" ];
          };
          # runner for everything else
          default = {
            # File should contain at least these two variables:
            # `CI_SERVER_URL`
            # `REGISTRATION_TOKEN`
            registrationConfigFile = "/run/secrets/gitlab-runner-registration";
            dockerImage = "debian:stable";
          };
        }
      '';
      type = types.attrsOf (types.submodule {
        options = {
          registrationConfigFile = mkOption {
            type = types.path;
            description = lib.mdDoc ''
              Absolute path to a file with environment variables
              used for gitlab-runner registration.
              A list of all supported environment variables can be found in
              `gitlab-runner register --help`.

              Ones that you probably want to set is

              `CI_SERVER_URL=<CI server URL>`

              `REGISTRATION_TOKEN=<registration secret>`

              WARNING: make sure to use quoted absolute path,
              or it is going to be copied to Nix Store.
            '';
          };
          registrationFlags = mkOption {
            type = types.listOf types.str;
            default = [ ];
            example = [ "--docker-helper-image my/gitlab-runner-helper" ];
            description = lib.mdDoc ''
              Extra command-line flags passed to
              `gitlab-runner register`.
              Execute `gitlab-runner register --help`
              for a list of supported flags.
            '';
          };
          environmentVariables = mkOption {
            type = types.attrsOf types.str;
            default = { };
            example = { NAME = "value"; };
            description = lib.mdDoc ''
              Custom environment variables injected to build environment.
              For secrets you can use {option}`registrationConfigFile`
              with `RUNNER_ENV` variable set.
            '';
          };
          description = mkOption {
            type = types.nullOr types.str;
            default = null;
            description = lib.mdDoc ''
              Name/description of the runner.
            '';
          };
          executor = mkOption {
            type = types.str;
            default = "docker";
            description = lib.mdDoc ''
              Select executor, eg. shell, docker, etc.
              See [runner documentation](https://docs.gitlab.com/runner/executors/README.html) for more information.
            '';
          };
          buildsDir = mkOption {
            type = types.nullOr types.path;
            default = null;
            example = "/var/lib/gitlab-runner/builds";
            description = lib.mdDoc ''
              Absolute path to a directory where builds will be stored
              in context of selected executor (Locally, Docker, SSH).
            '';
          };
          cloneUrl = mkOption {
            type = types.nullOr types.str;
            default = null;
            example = "http://gitlab.example.local";
            description = lib.mdDoc ''
              Overwrite the URL for the GitLab instance. Used if the Runner can’t connect to GitLab on the URL GitLab exposes itself.
            '';
          };
          dockerImage = mkOption {
            type = types.nullOr types.str;
            default = null;
            description = lib.mdDoc ''
              Docker image to be used.
            '';
          };
          dockerVolumes = mkOption {
            type = types.listOf types.str;
            default = [ ];
            example = [ "/var/run/docker.sock:/var/run/docker.sock" ];
            description = lib.mdDoc ''
              Bind-mount a volume and create it
              if it doesn't exist prior to mounting.
            '';
          };
          dockerDisableCache = mkOption {
            type = types.bool;
            default = false;
            description = lib.mdDoc ''
              Disable all container caching.
            '';
          };
          dockerPrivileged = mkOption {
            type = types.bool;
            default = false;
            description = lib.mdDoc ''
              Give extended privileges to container.
            '';
          };
          dockerExtraHosts = mkOption {
            type = types.listOf types.str;
            default = [ ];
            example = [ "other-host:127.0.0.1" ];
            description = lib.mdDoc ''
              Add a custom host-to-IP mapping.
            '';
          };
          dockerAllowedImages = mkOption {
            type = types.listOf types.str;
            default = [ ];
            example = [ "ruby:*" "python:*" "php:*" "my.registry.tld:5000/*:*" ];
            description = lib.mdDoc ''
              Whitelist allowed images.
            '';
          };
          dockerAllowedServices = mkOption {
            type = types.listOf types.str;
            default = [ ];
            example = [ "postgres:9" "redis:*" "mysql:*" ];
            description = lib.mdDoc ''
              Whitelist allowed services.
            '';
          };
          preCloneScript = mkOption {
            type = types.nullOr types.path;
            default = null;
            description = lib.mdDoc ''
              Runner-specific command script executed before code is pulled.
            '';
          };
          preBuildScript = mkOption {
            type = types.nullOr types.path;
            default = null;
            description = lib.mdDoc ''
              Runner-specific command script executed after code is pulled,
              just before build executes.
            '';
          };
          postBuildScript = mkOption {
            type = types.nullOr types.path;
            default = null;
            description = lib.mdDoc ''
              Runner-specific command script executed after code is pulled
              and just after build executes.
            '';
          };
          tagList = mkOption {
            type = types.listOf types.str;
            default = [ ];
            description = lib.mdDoc ''
              Tag list.
            '';
          };
          runUntagged = mkOption {
            type = types.bool;
            default = false;
            description = lib.mdDoc ''
              Register to run untagged builds; defaults to
              `true` when {option}`tagList` is empty.
            '';
          };
          limit = mkOption {
            type = types.int;
            default = 0;
            description = lib.mdDoc ''
              Limit how many jobs can be handled concurrently by this service.
              0 (default) simply means don't limit.
            '';
          };
          requestConcurrency = mkOption {
            type = types.int;
            default = 0;
            description = lib.mdDoc ''
              Limit number of concurrent requests for new jobs from GitLab.
            '';
          };
          maximumTimeout = mkOption {
            type = types.int;
            default = 0;
            description = lib.mdDoc ''
              What is the maximum timeout (in seconds) that will be set for
              job when using this Runner. 0 (default) simply means don't limit.
            '';
          };
          protected = mkOption {
            type = types.bool;
            default = false;
            description = lib.mdDoc ''
              When set to true Runner will only run on pipelines
              triggered on protected branches.
            '';
          };
          debugTraceDisabled = mkOption {
            type = types.bool;
            default = false;
            description = lib.mdDoc ''
              When set to true Runner will disable the possibility of
              using the `CI_DEBUG_TRACE` feature.
            '';
          };
        };
      });
    };
    clear-docker-cache = {
      enable = mkOption {
        type = types.bool;
        default = false;
        description = lib.mdDoc ''
          Whether to periodically prune gitlab runner's Docker resources. If
          enabled, a systemd timer will run {command}`clear-docker-cache` as
          specified by the `dates` option.
        '';
      };

      flags = mkOption {
        type = types.listOf types.str;
        default = [ ];
        example = [ "prune" ];
        description = lib.mdDoc ''
          Any additional flags passed to {command}`clear-docker-cache`.
        '';
      };

      dates = mkOption {
        default = "weekly";
        type = types.str;
        description = lib.mdDoc ''
          Specification (in the format described by
          {manpage}`systemd.time(7)`) of the time at
          which the prune will occur.
        '';
      };

      package = mkOption {
        default = config.virtualisation.docker.package;
        defaultText = literalExpression "config.virtualisation.docker.package";
        example = literalExpression "pkgs.docker";
        description = lib.mdDoc "Docker package to use for clearing up docker cache.";
      };
    };
  };
  config = mkIf cfg.enable {
    warnings = mapAttrsToList
      (n: v: "services.gitlab-runner.services.${n}.`registrationConfigFile` points to a file in Nix Store. You should use quoted absolute path to prevent this.")
      (filterAttrs (n: v: isStorePath v.registrationConfigFile) cfg.services);

    environment.systemPackages = [ cfg.package ];
    systemd.services.gitlab-runner = {
      description = "Gitlab Runner";
      documentation = [ "https://docs.gitlab.com/runner/" ];
      after = [ "network.target" ]
        ++ optional hasDocker "docker.service";
      requires = optional hasDocker "docker.service";
      wantedBy = [ "multi-user.target" ];
      environment = config.networking.proxy.envVars // {
        HOME = "/var/lib/gitlab-runner";
      };
      path = with pkgs; [
        bash
        gawk
        jq
        moreutils
        remarshal
        util-linux
        cfg.package
      ] ++ cfg.extraPackages;
      reloadIfChanged = true;
      serviceConfig = {
        # Set `DynamicUser` under `systemd.services.gitlab-runner.serviceConfig`
        # to `lib.mkForce false` in your configuration to run this service as root.
        # You can also set `User` and `Group` options to run this service as desired user.
        # Make sure to restart service or changes won't apply.
        DynamicUser = true;
        StateDirectory = "gitlab-runner";
        SupplementaryGroups = optional hasDocker "docker";
        ExecStartPre = "!${configureScript}/bin/gitlab-runner-configure";
        ExecStart = "${startScript}/bin/gitlab-runner-start";
        ExecReload = "!${configureScript}/bin/gitlab-runner-configure";
      } // optionalAttrs cfg.gracefulTermination {
        TimeoutStopSec = "${cfg.gracefulTimeout}";
        KillSignal = "SIGQUIT";
        KillMode = "process";
      };
    };
    # Enable periodic clear-docker-cache script
    systemd.services.gitlab-runner-clear-docker-cache = {
      description = "Prune gitlab-runner docker resources";
      restartIfChanged = false;
      unitConfig.X-StopOnRemoval = false;

      serviceConfig.Type = "oneshot";

      path = [ cfg.clear-docker-cache.package pkgs.gawk ];

      script = ''
        ${pkgs.gitlab-runner}/bin/clear-docker-cache ${toString cfg.clear-docker-cache.flags}
      '';

      startAt = optional cfg.clear-docker-cache.enable cfg.clear-docker-cache.dates;
    };
    # Enable docker if `docker` executor is used in any service
    virtualisation.docker.enable = mkIf (
      any (s: s.executor == "docker") (attrValues cfg.services)
    ) (mkDefault true);
  };
  imports = [
    (mkRenamedOptionModule [ "services" "gitlab-runner" "packages" ] [ "services" "gitlab-runner" "extraPackages" ] )
    (mkRemovedOptionModule [ "services" "gitlab-runner" "configOptions" ] "Use services.gitlab-runner.services option instead" )
    (mkRemovedOptionModule [ "services" "gitlab-runner" "workDir" ] "You should move contents of workDir (if any) to /var/lib/gitlab-runner" )

    (mkRenamedOptionModule [ "services" "gitlab-runner" "checkInterval" ] [ "services" "gitlab-runner" "settings" "check_interval" ] )
    (mkRenamedOptionModule [ "services" "gitlab-runner" "concurrent" ] [ "services" "gitlab-runner" "settings" "concurrent" ] )
    (mkRenamedOptionModule [ "services" "gitlab-runner" "sentryDSN" ] [ "services" "gitlab-runner" "settings" "sentry_dsn" ] )
    (mkRenamedOptionModule [ "services" "gitlab-runner" "prometheusListenAddress" ] [ "services" "gitlab-runner" "settings" "listen_address" ] )

    (mkRenamedOptionModule [ "services" "gitlab-runner" "sessionServer" "listenAddress" ] [ "services" "gitlab-runner" "settings" "session_server" "listen_address" ] )
    (mkRenamedOptionModule [ "services" "gitlab-runner" "sessionServer" "advertiseAddress" ] [ "services" "gitlab-runner" "settings" "session_server" "advertise_address" ] )
    (mkRenamedOptionModule [ "services" "gitlab-runner" "sessionServer" "sessionTimeout" ] [ "services" "gitlab-runner" "settings" "session_server" "session_timeout" ] )
  ];
}