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

with lib;

{
  enable = mkOption {
    default = false;
    example = true;
    description = lib.mdDoc ''
      Whether to enable GitHub Actions runner.

      Note: GitHub recommends using self-hosted runners with private repositories only. Learn more here:
      [About self-hosted runners](https://docs.github.com/en/actions/hosting-your-own-runners/about-self-hosted-runners).
    '';
    type = lib.types.bool;
  };

  url = mkOption {
    type = types.str;
    description = lib.mdDoc ''
      Repository to add the runner to.

      Changing this option triggers a new runner registration.

      IMPORTANT: If your token is org-wide (not per repository), you need to
      provide a github org link, not a single repository, so do it like this
      `https://github.com/nixos`, not like this
      `https://github.com/nixos/nixpkgs`.
      Otherwise, you are going to get a `404 NotFound`
      from `POST https://api.github.com/actions/runner-registration`
      in the configure script.
    '';
    example = "https://github.com/nixos/nixpkgs";
  };

  tokenFile = mkOption {
    type = types.path;
    description = lib.mdDoc ''
      The full path to a file which contains either

      * a fine-grained personal access token (PAT),
      * a classic PAT
      * or a runner registration token

      Changing this option or the `tokenFile`’s content triggers a new runner registration.

      We suggest using the fine-grained PATs. A runner registration token is valid
      only for 1 hour after creation, so the next time the runner configuration changes
      this will give you hard-to-debug HTTP 404 errors in the configure step.

      The file should contain exactly one line with the token without any newline.
      (Use `echo -n '…token…' > …token file…` to make sure no newlines sneak in.)

      If the file contains a PAT, the service creates a new registration token
      on startup as needed.
      If a registration token is given, it can be used to re-register a runner of the same
      name but is time-limited as noted above.

      For fine-grained PATs:

      Give it "Read and Write access to organization/repository self hosted runners",
      depending on whether it is organization wide or per-repository. You might have to
      experiment a little, fine-grained PATs are a `beta` Github feature and still subject
      to change; nonetheless they are the best option at the moment.

      For classic PATs:

      Make sure the PAT has a scope of `admin:org` for organization-wide registrations
      or a scope of `repo` for a single repository.

      For runner registration tokens:

      Nothing special needs to be done, but updating will break after one hour,
      so these are not recommended.
    '';
    example = "/run/secrets/github-runner/nixos.token";
  };

  name = let
    # Same pattern as for `networking.hostName`
    baseType = types.strMatching "^$|^[[:alnum:]]([[:alnum:]_-]{0,61}[[:alnum:]])?$";
  in mkOption {
    type = if includeNameDefault then baseType else types.nullOr baseType;
    description = lib.mdDoc ''
      Name of the runner to configure. Defaults to the hostname.

      Changing this option triggers a new runner registration.
    '';
    example = "nixos";
  } // (if includeNameDefault then {
    default = config.networking.hostName;
    defaultText = literalExpression "config.networking.hostName";
  } else {
    default = null;
  });

  runnerGroup = mkOption {
    type = types.nullOr types.str;
    description = lib.mdDoc ''
      Name of the runner group to add this runner to (defaults to the default runner group).

      Changing this option triggers a new runner registration.
    '';
    default = null;
  };

  extraLabels = mkOption {
    type = types.listOf types.str;
    description = lib.mdDoc ''
      Extra labels in addition to the default (`["self-hosted", "Linux", "X64"]`).

      Changing this option triggers a new runner registration.
    '';
    example = literalExpression ''[ "nixos" ]'';
    default = [ ];
  };

  replace = mkOption {
    type = types.bool;
    description = lib.mdDoc ''
      Replace any existing runner with the same name.

      Without this flag, registering a new runner with the same name fails.
    '';
    default = false;
  };

  extraPackages = mkOption {
    type = types.listOf types.package;
    description = lib.mdDoc ''
      Extra packages to add to `PATH` of the service to make them available to workflows.
    '';
    default = [ ];
  };

  extraEnvironment = mkOption {
    type = types.attrs;
    description = lib.mdDoc ''
      Extra environment variables to set for the runner, as an attrset.
    '';
    example = {
      GIT_CONFIG = "/path/to/git/config";
    };
    default = {};
  };

  serviceOverrides = mkOption {
    type = types.attrs;
    description = lib.mdDoc ''
      Modify the systemd service. Can be used to, e.g., adjust the sandboxing options.
      See {manpage}`systemd.exec(5)` for more options.
    '';
    example = {
      ProtectHome = false;
      RestrictAddressFamilies = [ "AF_PACKET" ];
    };
    default = {};
  };

  package = mkPackageOption pkgs "github-runner" { };

  ephemeral = mkOption {
    type = types.bool;
    description = lib.mdDoc ''
      If enabled, causes the following behavior:

      - Passes the `--ephemeral` flag to the runner configuration script
      - De-registers and stops the runner with GitHub after it has processed one job
      - On stop, systemd wipes the runtime directory (this always happens, even without using the ephemeral option)
      - Restarts the service after its successful exit
      - On start, wipes the state directory and configures a new runner

      You should only enable this option if `tokenFile` points to a file which contains a
      personal access token (PAT). If you're using the option with a registration token, restarting the
      service will fail as soon as the registration token expired.
    '';
    default = false;
  };

  user = mkOption {
    type = types.nullOr types.str;
    description = lib.mdDoc ''
      User under which to run the service. If null, will use a systemd dynamic user.
    '';
    default = null;
    defaultText = literalExpression "username";
  };

  workDir = mkOption {
    type = with types; nullOr str;
    description = lib.mdDoc ''
      Working directory, available as `$GITHUB_WORKSPACE` during workflow runs
      and used as a default for [repository checkouts](https://github.com/actions/checkout).
      The service cleans this directory on every service start.

      A value of `null` will default to the systemd `RuntimeDirectory`.
    '';
    default = null;
  };

  nodeRuntimes = mkOption {
    type = with types; nonEmptyListOf (enum [ "node16" "node20" ]);
    default = [ "node20" ];
    description = mdDoc ''
      List of Node.js runtimes the runner should support.
    '';
  };
}