3 files changed, 81 insertions, 1 deletions

diff --git a/hosts/RyanMac/configuration.nix b/hosts/RyanMac/configuration.nix
index 5e87070..8bd7131 100644
--- a/hosts/RyanMac/configuration.nix
+++ b/hosts/RyanMac/configuration.nix
@@ -45,7 +45,7 @@ in {
   # Modules
   imports = [
     inputs.nix-homebrew.darwinModules.nix-homebrew
-    ../../modules/darwin/random-wallpaper.nix
+    ../../modules/darwin/random-wallpaper/module.nix
   ];
 
   # Define the system's user and home dir location
diff --git a/modules/darwin/random-wallpaper/module.nix b/modules/darwin/random-wallpaper/module.nix
new file mode 100644
index 0000000..b20ce88
--- /dev/null
+++ b/modules/darwin/random-wallpaper/module.nix
@@ -0,0 +1,29 @@
+{ config, lib, pkgs, ... }:
+let
+  cfg = config.local.randomWallpaper;
+  wallpaper-agent-src = ./wallpaper-daemon.swift;
+in
+{
+  options.local.randomWallpaper = {
+    enable = lib.mkEnableOption "Random Rotating Wallpaper";
+    directory = lib.mkOption {
+      type = lib.types.str;
+      description = "Folder containing images";
+    };
+    interval = lib.mkOption {
+      type = lib.types.int;
+      default = 1800;
+      description = "Seconds between wallpaper changes";
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    launchd.user.agents.random-wallpaper.serviceConfig = {
+      Label = "org.rschanz.wallpaperDaemon";
+      ProgramArguments = [ "/usr/bin/swift" "${wallpaper-agent-src}" "${cfg.directory}" "${builtins.toString cfg.interval}" ];
+      RunAtLoad = true;
+      KeepAlive = true;
+      ProcessType = "Background";
+    };
+  };
+}
diff --git a/modules/darwin/random-wallpaper/wallpaper-daemon.swift b/modules/darwin/random-wallpaper/wallpaper-daemon.swift
new file mode 100644
index 0000000..72f52ef
--- /dev/null
+++ b/modules/darwin/random-wallpaper/wallpaper-daemon.swift
@@ -0,0 +1,51 @@
+import AppKit
+import Foundation
+
+if CommandLine.arguments.count != 3 {
+    print("Must have 2 args")
+    exit(1)
+}
+
+let wallpaperDir = CommandLine.arguments[1]
+let interval: TimeInterval = Double(CommandLine.arguments[2]) ?? 30.0
+
+let workspace = NSWorkspace.shared
+let imageExtensions: Set<String> = ["jpg", "jpeg", "png", "heic", "tiff", "gif", "bmp"]
+
+func images() -> [URL] {
+    let dir = URL(fileURLWithPath: wallpaperDir, isDirectory: true)
+    let entries = (try? FileManager.default.contentsOfDirectory(
+        at: dir, includingPropertiesForKeys: nil)) ?? []
+    return entries.filter { imageExtensions.contains($0.pathExtension.lowercased()) }
+}
+
+var current: URL?
+
+// setDesktopImageURL only touches the current Space (all displays).
+func apply(_ url: URL?) {
+    guard let url else { return }
+    for screen in NSScreen.screens {
+        try? workspace.setDesktopImageURL(url, for: screen, options: [:])
+    }
+}
+
+func advance() {
+    let imgs = images()
+    guard !imgs.isEmpty else { return }
+    let pool = imgs.count > 1 ? imgs.filter { $0 != current } : imgs
+    current = pool.randomElement()
+    apply(current)
+}
+
+// Whenever you switch Space, repaint it to the current image.
+workspace.notificationCenter.addObserver(
+    forName: NSWorkspace.activeSpaceDidChangeNotification,
+    object: nil, queue: .main
+) { _ in apply(current) }
+
+advance()
+Timer.scheduledTimer(withTimeInterval: interval, repeats: true) { _ in advance() }
+
+let app = NSApplication.shared
+app.setActivationPolicy(.accessory)   // no Dock icon
+app.run()