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

with lib;

let
  cfg = config.services.frab;

  package = pkgs.frab;

  databaseConfig = builtins.toJSON { production = cfg.database; };

  frabEnv = {
    RAILS_ENV = "production";
    RACK_ENV = "production";
    SECRET_KEY_BASE = cfg.secretKeyBase;
    FRAB_HOST = cfg.host;
    FRAB_PROTOCOL = cfg.protocol;
    FROM_EMAIL = cfg.fromEmail;
    RAILS_SERVE_STATIC_FILES = "1";
  } // cfg.extraEnvironment;

  frab-rake = pkgs.stdenv.mkDerivation {
    name = "frab-rake";
    buildInputs = [ package.env pkgs.makeWrapper ];
    phases = "installPhase fixupPhase";
    installPhase = ''
      mkdir -p $out/bin
      makeWrapper ${package.env}/bin/bundle $out/bin/frab-bundle \
          ${concatStrings (mapAttrsToList (name: value: "--set ${name} '${value}' ") frabEnv)} \
          --set PATH '${lib.makeBinPath (with pkgs; [ nodejs file imagemagick ])}:$PATH' \
          --set RAKEOPT '-f ${package}/share/frab/Rakefile' \
          --run 'cd ${package}/share/frab'
      makeWrapper $out/bin/frab-bundle $out/bin/frab-rake \
          --add-flags "exec rake"
     '';
  };

in

{
  options = {
    services.frab = {
      enable = mkOption {
        type = types.bool;
        default = false;
        description = ''
          Enable the frab service.
        '';
      };

      host = mkOption {
        type = types.str;
        example = "frab.example.com";
        description = ''
          Hostname under which this frab instance can be reached.
        '';
      };

      protocol = mkOption {
        type = types.str;
        default = "https";
        example = "http";
        description = ''
          Either http or https, depending on how your Frab instance
          will be exposed to the public.
        '';
      };

      fromEmail = mkOption {
        type = types.str;
        default = "frab@localhost";
        description = ''
          Email address used by frab.
        '';
      };

      listenAddress = mkOption {
        type = types.str;
        default = "localhost";
        description = ''
          Address or hostname frab should listen on.
        '';
      };

      listenPort = mkOption {
        type = types.int;
        default = 3000;
        description = ''
          Port frab should listen on.
        '';
      };

      statePath = mkOption {
        type = types.str;
        default = "/var/lib/frab";
        description = ''
          Directory where frab keeps its state.
        '';
      };

      user = mkOption {
        type = types.str;
        default = "frab";
        description = ''
          User to run frab.
        '';
      };

      group = mkOption {
        type = types.str;
        default = "frab";
        description = ''
          Group to run frab.
        '';
      };

      secretKeyBase = mkOption {
        type = types.str;
        description = ''
          Your secret key is used for verifying the integrity of signed cookies.
          If you change this key, all old signed cookies will become invalid!

          Make sure the secret is at least 30 characters and all random,
          no regular words or you'll be exposed to dictionary attacks.
        '';
      };

      database = mkOption {
        type = types.attrs;
        default = {
          adapter = "sqlite3";
          database = "/var/lib/frab/db.sqlite3";
          pool = 5;
          timeout = 5000;
        };
        example = {
          adapter = "postgresql";
          database = "frab";
          host = "localhost";
          username = "frabuser";
          password = "supersecret";
          encoding = "utf8";
          pool = 5;
        };
        description = ''
          Rails database configuration for Frab as Nix attribute set.
        '';
      };

      extraEnvironment = mkOption {
        type = types.attrs;
        default = {};
        example = {
          FRAB_CURRENCY_UNIT = "€";
          FRAB_CURRENCY_FORMAT = "%n%u";
          EXCEPTION_EMAIL = "frab-owner@example.com";
          SMTP_ADDRESS = "localhost";
          SMTP_PORT = "587";
          SMTP_DOMAIN = "localdomain";
          SMTP_USER_NAME = "root";
          SMTP_PASSWORD = "toor";
          SMTP_AUTHENTICATION = "1";
          SMTP_NOTLS = "1";
        };
        description = ''
          Additional environment variables to set for frab for further
          configuration. See the frab documentation for more information.
        '';
      };
    };
  };

  config = mkIf cfg.enable {
    environment.systemPackages = [ frab-rake ];

    users.users = [
      { name = cfg.user;
        group = cfg.group;
        home = "${cfg.statePath}";
        isSystemUser = true;
      }
    ];

    users.groups = [ { name = cfg.group; } ];

    systemd.tmpfiles.rules = [
      "d '${cfg.statePath}/system/attachments' - ${cfg.user} ${cfg.group} - -"
    ];

    systemd.services.frab = {
      after = [ "network.target" "gitlab.service" ];
      wantedBy = [ "multi-user.target" ];
      environment = frabEnv;

      preStart = ''
        ln -sf ${pkgs.writeText "frab-database.yml" databaseConfig} /run/frab/database.yml
        ln -sf ${cfg.statePath}/system /run/frab/system

        if ! test -e "${cfg.statePath}/db-setup-done"; then
          ${frab-rake}/bin/frab-rake db:setup
          touch ${cfg.statePath}/db-setup-done
        else
          ${frab-rake}/bin/frab-rake db:migrate
        fi
      '';

      serviceConfig = {
        PrivateTmp = true;
        PrivateDevices = true;
        Type = "simple";
        User = cfg.user;
        Group = cfg.group;
        TimeoutSec = "300s";
        Restart = "on-failure";
        RestartSec = "10s";
        RuntimeDirectory = "frab";
        WorkingDirectory = "${package}/share/frab";
        ExecStart = "${frab-rake}/bin/frab-bundle exec rails server " +
          "--binding=${cfg.listenAddress} --port=${toString cfg.listenPort}";
      };
    };

  };
}