Rewrote turborepo. Hopefully this is a bit more clean & easy to understand for me.

packages/ui/src/button.tsx

@@ -1,20 +1,59 @@
-"use client";
+import type { VariantProps } from "class-variance-authority";
+import * as React from "react";
+import { cn } from "@/lib/utils";
+import { Slot } from "@radix-ui/react-slot";
+import { cva } from "class-variance-authority";
 
-import { ReactNode } from "react";
+const buttonVariants = cva(
+  "focus-visible:border-ring focus-visible:ring-ring/50 aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 aria-invalid:border-destructive inline-flex shrink-0 items-center justify-center gap-2 rounded-md text-sm font-medium whitespace-nowrap transition-all outline-none focus-visible:ring-[3px] disabled:pointer-events-none disabled:opacity-50 [&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4",
+  {
+    variants: {
+      variant: {
+        default:
+          "bg-primary text-primary-foreground hover:bg-primary/90 shadow-xs",
+        destructive:
+          "bg-destructive hover:bg-destructive/90 focus-visible:ring-destructive/20 dark:focus-visible:ring-destructive/40 dark:bg-destructive/60 text-white shadow-xs",
+        outline:
+          "bg-background hover:bg-accent hover:text-accent-foreground dark:bg-input/30 dark:border-input dark:hover:bg-input/50 border shadow-xs",
+        secondary:
+          "bg-secondary text-secondary-foreground hover:bg-secondary/80 shadow-xs",
+        ghost:
+          "hover:bg-accent hover:text-accent-foreground dark:hover:bg-accent/50",
+        link: "text-primary underline-offset-4 hover:underline",
+      },
+      size: {
+        default: "h-9 px-4 py-2 has-[>svg]:px-3",
+        sm: "h-8 gap-1.5 rounded-md px-3 has-[>svg]:px-2.5",
+        lg: "h-10 rounded-md px-6 has-[>svg]:px-4",
+        icon: "size-9",
+      },
+    },
+    defaultVariants: {
+      variant: "default",
+      size: "default",
+    },
+  },
+);
 
-interface ButtonProps {
-  children: ReactNode;
-  className?: string;
-  appName: string;
+function Button({
+  className,
+  variant,
+  size,
+  asChild = false,
+  ...props
+}: React.ComponentProps<"button"> &
+  VariantProps<typeof buttonVariants> & {
+    asChild?: boolean;
+  }) {
+  const Comp = asChild ? Slot : "button";
+
+  return (
+    <Comp
+      data-slot="button"
+      className={cn(buttonVariants({ variant, size, className }))}
+      {...props}
+    />
+  );
 }
 
-export const Button = ({ children, className, appName }: ButtonProps) => {
-  return (
-    <button
-      className={className}
-      onClick={() => alert(`Hello from your ${appName} app!`)}
-    >
-      {children}
-    </button>
-  );
-};
+export { Button, buttonVariants };