wezterm: support color schemes

Allows users to specify TOML color schemes using Nix.

modules/programs/wezterm.nix

@@ -5,6 +5,7 @@ with lib;
 let
 
   cfg = config.programs.wezterm;
+  tomlFormat = pkgs.formats.toml { };
 
 in {
   options.programs.wezterm = {
@@ -44,13 +45,45 @@ in {
         how to configure.
       '';
     };
+
+    colorSchemes = mkOption {
+      type = types.attrsOf (tomlFormat.type);
+      default = { };
+      example = literalExpression ''
+        myCoolTheme = {
+          ansi = [
+            "#222222" "#D14949" "#48874F" "#AFA75A"
+            "#599797" "#8F6089" "#5C9FA8" "#8C8C8C"
+          ];
+          brights = [
+            "#444444" "#FF6D6D" "#89FF95" "#FFF484"
+            "#97DDFF" "#FDAAF2" "#85F5DA" "#E9E9E9"
+          ];
+          background = "#1B1B1B";
+          cursor_bg = "#BEAF8A";
+          cursor_border = "#BEAF8A";
+          cursor_fg = "#1B1B1B";
+          foreground = "#BEAF8A";
+          selection_bg = "#444444";
+          selection_fg = "#E9E9E9";
+        };
+      '';
+      description = ''
+        Attribute set of additional color schemes to be written to
+        <filename>$XDG_CONFIG_HOME/wezterm/colors</filename>, where each key is
+        taken as the name of the corresponding color scheme. See
+        <link xlink:href="https://wezfurlong.org/wezterm/config/appearance.html#defining-a-color-scheme-in-a-separate-file"/>
+        for more details of the TOML color scheme format.
+      '';
+    };
+
   };
 
   config = mkIf cfg.enable {
     home.packages = [ cfg.package ];
 
-    xdg.configFile."wezterm/wezterm.lua" = {
-      text = ''
+    xdg.configFile = {
+      "wezterm/wezterm.lua".text = ''
         -- Generated by Home Manager.
         -- See https://wezfurlong.org/wezterm/
 
@@ -60,6 +93,9 @@ in {
 
         ${cfg.extraConfig}
       '';
-    };
+    } // mapAttrs' (name: value:
+      nameValuePair "wezterm/colors/${name}.toml" {
+        source = tomlFormat.generate "${name}.toml" { colors = value; };
+      }) cfg.colorSchemes;
   };
 }