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

with lib;

let

  cfg = config.gtk;
  cfg2 = config.gtk.gtk2;
  cfg3 = config.gtk.gtk3;
  cfg4 = config.gtk.gtk4;

  toGtk3Ini = generators.toINI {
    mkKeyValue = key: value:
      let value' = if isBool value then boolToString value else toString value;
      in "${escape [ "=" ] key}=${value'}";
  };

  formatGtk2Option = n: v:
    let
      v' = if isBool v then
        boolToString value
      else if isString v then
        ''"${v}"''
      else
        toString v;
    in "${escape [ "=" ] n} = ${v'}";

  themeType = types.submodule {
    options = {
      package = mkOption {
        type = types.nullOr types.package;
        default = null;
        example = literalExpression "pkgs.gnome.gnome-themes-extra";
        description = ''
          Package providing the theme. This package will be installed
          to your profile. If `null` then the theme
          is assumed to already be available in your profile.

          For the theme to apply to GTK 4, this option is mandatory.
        '';
      };

      name = mkOption {
        type = types.str;
        example = "Adwaita";
        description = "The name of the theme within the package.";
      };
    };
  };

  iconThemeType = types.submodule {
    options = {
      package = mkOption {
        type = types.nullOr types.package;
        default = null;
        example = literalExpression "pkgs.adwaita-icon-theme";
        description = ''
          Package providing the icon theme. This package will be installed
          to your profile. If `null` then the theme
          is assumed to already be available in your profile.
        '';
      };

      name = mkOption {
        type = types.str;
        example = "Adwaita";
        description = "The name of the icon theme within the package.";
      };
    };
  };

  cursorThemeType = types.submodule {
    options = {
      package = mkOption {
        type = types.nullOr types.package;
        default = null;
        example = literalExpression "pkgs.vanilla-dmz";
        description = ''
          Package providing the cursor theme. This package will be installed
          to your profile. If `null` then the theme
          is assumed to already be available in your profile.
        '';
      };

      name = mkOption {
        type = types.str;
        example = "Vanilla-DMZ";
        description = "The name of the cursor theme within the package.";
      };

      size = mkOption {
        type = types.nullOr types.int;
        default = null;
        example = 16;
        description = ''
          The size of the cursor.
        '';
      };
    };
  };

in {
  meta.maintainers = [ maintainers.rycee ];

  imports = [
    (mkRemovedOptionModule [ "gtk" "gtk3" "waylandSupport" ] ''
      This options is not longer needed and can be removed.
    '')
  ];

  options = {
    gtk = {
      enable = mkEnableOption "GTK 2/3 configuration";

      font = mkOption {
        type = types.nullOr hm.types.fontType;
        default = null;
        description = ''
          The font to use in GTK+ 2/3 applications.
        '';
      };

      cursorTheme = mkOption {
        type = types.nullOr cursorThemeType;
        default = null;
        description = "The cursor theme to use.";
      };

      iconTheme = mkOption {
        type = types.nullOr iconThemeType;
        default = null;
        description = "The icon theme to use.";
      };

      theme = mkOption {
        type = types.nullOr themeType;
        default = null;
        description = "The GTK+2/3 theme to use.";
      };

      gtk2 = {
        extraConfig = mkOption {
          type = types.lines;
          default = "";
          example = "gtk-can-change-accels = 1";
          description = ''
            Extra configuration lines to add verbatim to
            {file}`~/.gtkrc-2.0`.
          '';
        };

        configLocation = mkOption {
          type = types.path;
          default = "${config.home.homeDirectory}/.gtkrc-2.0";
          defaultText =
            literalExpression ''"''${config.home.homeDirectory}/.gtkrc-2.0"'';
          example =
            literalExpression ''"''${config.xdg.configHome}/gtk-2.0/gtkrc"'';
          description = ''
            The location to put the GTK configuration file.
          '';
        };
      };

      gtk3 = {
        bookmarks = mkOption {
          type = types.listOf types.str;
          default = [ ];
          example = [ "file:///home/jane/Documents" ];
          description = "Bookmarks in the sidebar of the GTK file browser";
        };

        extraConfig = mkOption {
          type = with types; attrsOf (oneOf [ bool int str ]);
          default = { };
          example = {
            gtk-cursor-blink = false;
            gtk-recent-files-limit = 20;
          };
          description = ''
            Extra configuration options to add to
            {file}`$XDG_CONFIG_HOME/gtk-3.0/settings.ini`.
          '';
        };

        extraCss = mkOption {
          type = types.lines;
          default = "";
          description = ''
            Extra configuration lines to add verbatim to
            {file}`$XDG_CONFIG_HOME/gtk-3.0/gtk.css`.
          '';
        };
      };

      gtk4 = {
        extraConfig = mkOption {
          type = with types; attrsOf (either bool (either int str));
          default = { };
          example = {
            gtk-cursor-blink = false;
            gtk-recent-files-limit = 20;
          };
          description = ''
            Extra configuration options to add to
            {file}`$XDG_CONFIG_HOME/gtk-4.0/settings.ini`.
          '';
        };

        extraCss = mkOption {
          type = types.lines;
          default = "";
          description = ''
            Extra configuration lines to add verbatim to
            {file}`$XDG_CONFIG_HOME/gtk-4.0/gtk.css`.
          '';
        };
      };
    };
  };

  config = mkIf cfg.enable (let
    gtkIni = optionalAttrs (cfg.font != null) {
      gtk-font-name =
        let fontSize = if cfg.font.size != null then cfg.font.size else 10;
        in "${cfg.font.name} ${toString fontSize}";
    } // optionalAttrs (cfg.theme != null) { gtk-theme-name = cfg.theme.name; }
      // optionalAttrs (cfg.iconTheme != null) {
        gtk-icon-theme-name = cfg.iconTheme.name;
      } // optionalAttrs (cfg.cursorTheme != null) {
        gtk-cursor-theme-name = cfg.cursorTheme.name;
      } // optionalAttrs
      (cfg.cursorTheme != null && cfg.cursorTheme.size != null) {
        gtk-cursor-theme-size = cfg.cursorTheme.size;
      };

    gtk4Css =
      lib.optionalString (cfg.theme != null && cfg.theme.package != null) ''
        /**
         * GTK 4 reads the theme configured by gtk-theme-name, but ignores it.
         * It does however respect user CSS, so import the theme from here.
        **/
        @import url("file://${cfg.theme.package}/share/themes/${cfg.theme.name}/gtk-4.0/gtk.css");
      '' + cfg4.extraCss;

    dconfIni = optionalAttrs (cfg.font != null) {
      font-name =
        let fontSize = if cfg.font.size != null then cfg.font.size else 10;
        in "${cfg.font.name} ${toString fontSize}";
    } // optionalAttrs (cfg.theme != null) { gtk-theme = cfg.theme.name; }
      // optionalAttrs (cfg.iconTheme != null) {
        icon-theme = cfg.iconTheme.name;
      } // optionalAttrs (cfg.cursorTheme != null) {
        cursor-theme = cfg.cursorTheme.name;
      } // optionalAttrs
      (cfg.cursorTheme != null && cfg.cursorTheme.size != null) {
        cursor-size = cfg.cursorTheme.size;
      };

    optionalPackage = opt:
      optional (opt != null && opt.package != null) opt.package;
  in {
    home.packages = concatMap optionalPackage [
      cfg.font
      cfg.theme
      cfg.iconTheme
      cfg.cursorTheme
    ];

    home.file.${cfg2.configLocation}.text =
      concatMapStrings (l: l + "\n") (mapAttrsToList formatGtk2Option gtkIni)
      + cfg2.extraConfig + "\n";

    home.sessionVariables.GTK2_RC_FILES = cfg2.configLocation;

    xdg.configFile."gtk-3.0/settings.ini".text =
      toGtk3Ini { Settings = gtkIni // cfg3.extraConfig; };

    xdg.configFile."gtk-3.0/gtk.css" =
      mkIf (cfg3.extraCss != "") { text = cfg3.extraCss; };

    xdg.configFile."gtk-3.0/bookmarks" = mkIf (cfg3.bookmarks != [ ]) {
      text = concatMapStrings (l: l + "\n") cfg3.bookmarks;
    };

    xdg.configFile."gtk-4.0/settings.ini".text =
      toGtk3Ini { Settings = gtkIni // cfg4.extraConfig; };

    xdg.configFile."gtk-4.0/gtk.css" = mkIf (gtk4Css != "") { text = gtk4Css; };

    dconf.settings."org/gnome/desktop/interface" = dconfIni;
  });
}