fastfetch: add module

PR #5363

modules/programs/fastfetch.nix

@@ -0,0 +1,65 @@
+{ pkgs, lib, config, ... }:
+
+let
+  inherit (lib) mkEnableOption mkPackageOption mkOption mkIf literalExpression;
+
+  cfg = config.programs.fastfetch;
+
+  jsonFormat = pkgs.formats.json { };
+in {
+  meta.maintainers = with lib.hm.maintainers; [ afresquet ];
+
+  options.programs.fastfetch = {
+    enable = mkEnableOption "Fastfetch";
+
+    package = mkPackageOption pkgs "fastfetch" { };
+
+    settings = mkOption {
+      type = jsonFormat.type;
+      default = { };
+      example = literalExpression ''
+        {
+          logo = {
+            source = "nixos_small";
+            padding = {
+              right = 1;
+            };
+          };
+          display = {
+            binaryPrefix = "si";
+            color = "blue";
+            separator = "  ";
+          };
+          modules = [
+            {
+              type = "datetime";
+              key = "Date";
+              format = "{1}-{3}-{11}";
+            }
+            {
+              type = "datetime";
+              key = "Time";
+              format = "{14}:{17}:{20}";
+            }
+            "break"
+            "player"
+            "media"
+          ];
+        };
+      '';
+      description = ''
+        Configuration written to {file}`$XDG_CONFIG_HOME/fastfetch/config.jsonc`.
+        See <https://github.com/fastfetch-cli/fastfetch/wiki/Json-Schema>
+        for the documentation.
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    home.packages = [ cfg.package ];
+
+    xdg.configFile."fastfetch/config.jsonc" = mkIf (cfg.settings != { }) {
+      source = jsonFormat.generate "config.jsonc" cfg.settings;
+    };
+  };
+}