{
  config,
  pkgs,
  lib,
  ...
}:
let
  cfg = config.programs.atuin;
  daemonCfg = cfg.daemon;

  tomlFormat = pkgs.formats.toml { };

  inherit (lib) mkIf mkOption types;
  inherit (pkgs.stdenv) isLinux isDarwin;
in
{
  meta.maintainers = with lib.maintainers; [
    hawkw
    water-sucks
  ];

  options.programs.atuin = {
    enable = lib.mkEnableOption "atuin";

    package = lib.mkPackageOption pkgs "atuin" { };

    enableBashIntegration = lib.hm.shell.mkBashIntegrationOption {
      inherit config;
      extraDescription = "If enabled, this will bind `ctrl-r` to open the Atuin history.";
    };

    enableFishIntegration = lib.hm.shell.mkFishIntegrationOption {
      inherit config;
      extraDescription = "If enabled, this will bind the up-arrow key to open the Atuin history.";
    };

    enableNushellIntegration = lib.hm.shell.mkNushellIntegrationOption { inherit config; };

    enableZshIntegration = lib.hm.shell.mkZshIntegrationOption {
      inherit config;
      extraDescription = ''
        If enabled, this will bind `ctrl-r` and the up-arrow key to open the
        Atuin history.
      '';
    };

    flags = mkOption {
      default = [ ];
      type = types.listOf types.str;
      example = [
        "--disable-up-arrow"
        "--disable-ctrl-r"
      ];
      description = ''
        Flags to append to the shell hook.
      '';
    };

    settings = mkOption {
      type =
        with types;
        let
          prim = oneOf [
            bool
            int
            str
          ];
          primOrPrimAttrs = either prim (attrsOf prim);
          entry = either prim (listOf primOrPrimAttrs);
          entryOrAttrsOf = t: either entry (attrsOf t);
          entries = entryOrAttrsOf (entryOrAttrsOf entry);
        in
        attrsOf entries // { description = "Atuin configuration"; };
      default = { };
      example = lib.literalExpression ''
        {
          auto_sync = true;
          sync_frequency = "5m";
          sync_address = "https://api.atuin.sh";
          search_mode = "prefix";
        }
      '';
      description = ''
        Configuration written to
        {file}`$XDG_CONFIG_HOME/atuin/config.toml`.

        See <https://docs.atuin.sh/configuration/config/> for the full list
        of options.
      '';
    };

    forceOverwriteSettings = mkOption {
      type = types.bool;
      default = false;
      description = ''
        When enabled, force overwriting of the Atuin configuration file
        ({file}`$XDG_CONFIG_HOME/atuin/config.toml`).
        Any existing Atuin configuration will be lost.

        Enabling this is useful when adding settings for the first time
        because Atuin writes its default config file after every single
        shell command, which can make it difficult to manually remove.
      '';
    };

    themes = mkOption {
      type = types.attrsOf (
        types.oneOf [
          tomlFormat.type
          types.path
          types.lines
        ]
      );
      description = ''
        Each theme is written to
        {file}`$XDG_CONFIG_HOME/atuin/themes/theme-name.toml`
        where the name of each attribute is the theme-name

        See <https://docs.atuin.sh/guide/theming/> for the full list
        of options.
      '';
      default = { };
      example = lib.literalExpression ''
        {
          "my-theme" = {
            theme.name = "My Theme";
            colors = {
              Base = "#000000";
              Title = "#FFFFFF";
            };
          };
        }
      '';
    };

    daemon = {
      enable = lib.mkEnableOption "Atuin daemon";

      logLevel = mkOption {
        default = null;
        type = types.nullOr (
          types.enum [
            "trace"
            "debug"
            "info"
            "warn"
            "error"
          ]
        );
        description = ''
          Verbosity of Atuin daemon logging.
        '';
      };
    };
  };

  config =
    let
      flagsStr = lib.escapeShellArgs cfg.flags;
    in
    mkIf cfg.enable (
      lib.mkMerge [
        {
          # Always add the configured `atuin` package.
          home.packages = [ cfg.package ];

          # If there are user-provided settings, generate the config file.
          xdg.configFile = lib.mkMerge [
            (mkIf (cfg.settings != { }) {
              "atuin/config.toml" = {
                source = tomlFormat.generate "atuin-config" cfg.settings;
                force = cfg.forceOverwriteSettings;
              };
            })

            (mkIf (cfg.themes != { }) (
              lib.mapAttrs' (
                name: theme:
                lib.nameValuePair "atuin/themes/${name}.toml" {
                  source =
                    if lib.isString theme then
                      pkgs.writeText "atuin-theme-${name}" theme
                    else if builtins.isPath theme || lib.isStorePath theme then
                      theme
                    else
                      tomlFormat.generate "atuin-theme-${name}" theme;
                }
              ) cfg.themes
            ))
          ];

          programs.bash.initExtra = mkIf cfg.enableBashIntegration ''
            if [[ :$SHELLOPTS: =~ :(vi|emacs): ]]; then
              source "${pkgs.bash-preexec}/share/bash/bash-preexec.sh"
              eval "$(${lib.getExe cfg.package} init bash ${flagsStr})"
            fi
          '';

          programs.zsh.initContent = mkIf cfg.enableZshIntegration ''
            if [[ $options[zle] = on ]]; then
              eval "$(${lib.getExe cfg.package} init zsh ${flagsStr})"
            fi
          '';

          programs.fish.interactiveShellInit = mkIf cfg.enableFishIntegration ''
            ${lib.getExe cfg.package} init fish ${flagsStr} | source
          '';

          programs.nushell = mkIf cfg.enableNushellIntegration {
            extraConfig = ''
              source ${
                pkgs.runCommand "atuin-nushell-config.nu"
                  {
                    nativeBuildInputs = [ pkgs.writableTmpDirAsHomeHook ];
                  }
                  ''
                    ${lib.getExe cfg.package} init nu ${flagsStr} >> "$out"
                  ''
              }
            '';
          };
        }

        (mkIf daemonCfg.enable (
          lib.mkMerge [
            {
              assertions = [
                {
                  assertion = lib.versionAtLeast cfg.package.version "18.2.0";
                  message = ''
                    The Atuin daemon requires at least version 18.2.0 or later.
                  '';
                }
                {
                  assertion = isLinux || isDarwin;
                  message = "The Atuin daemon can only be configured on either Linux or macOS.";
                }
              ];

              programs.atuin.settings = {
                daemon = {
                  enabled = true;
                };
              };
            }
            (mkIf isLinux {
              programs.atuin.settings = {
                daemon = {
                  systemd_socket = true;
                };
              };

              systemd.user.services.atuin-daemon = {
                Unit = {
                  Description = "Atuin daemon";
                  Requires = [ "atuin-daemon.socket" ];
                };
                Install = {
                  Also = [ "atuin-daemon.socket" ];
                  WantedBy = [ "default.target" ];
                };
                Service = {
                  ExecStart = "${lib.getExe cfg.package} daemon";
                  Environment = lib.optionals (daemonCfg.logLevel != null) [ "ATUIN_LOG=${daemonCfg.logLevel}" ];
                  Restart = "on-failure";
                  RestartSteps = 3;
                  RestartMaxDelaySec = 6;
                };
              };

              systemd.user.sockets.atuin-daemon =
                let
                  socket_dir = if lib.versionAtLeast cfg.package.version "18.4.0" then "%t" else "%D/atuin";
                in
                {
                  Unit = {
                    Description = "Atuin daemon socket";
                  };
                  Install = {
                    WantedBy = [ "sockets.target" ];
                  };
                  Socket = {
                    ListenStream = "${socket_dir}/atuin.sock";
                    SocketMode = "0600";
                    RemoveOnStop = true;
                  };
                };
            })
            (mkIf isDarwin {
              programs.atuin.settings = {
                daemon = {
                  socket_path = lib.mkDefault "${config.xdg.dataHome}/atuin/daemon.sock";
                };
              };

              launchd.agents.atuin-daemon = {
                enable = true;
                config = {
                  ProgramArguments = [
                    "${lib.getExe cfg.package}"
                    "daemon"
                  ];
                  EnvironmentVariables = lib.optionalAttrs (daemonCfg.logLevel != null) {
                    ATUIN_LOG = daemonCfg.logLevel;
                  };
                  KeepAlive = {
                    Crashed = true;
                    SuccessfulExit = false;
                  };
                  ProcessType = "Background";
                };
              };
            })
          ]
        ))
      ]
    );
}