import * as React from 'react';
import { Slot, Slottable } from '@radix-ui/react-slot';
import { cva, type VariantProps } from 'class-variance-authority';
import { Loader2 } from 'lucide-react';

import { cn } from '../../shared/utils';

const buttonVariants = cva(
  "inline-flex items-center justify-center gap-2 whitespace-nowrap rounded-[var(--radius-button)] text-sm font-medium transition-colors disabled:pointer-events-none disabled:opacity-50 [&_svg]:pointer-events-none [&_svg:not([class*='size-'])]:size-4 shrink-0 [&_svg]:shrink-0 outline-none focus-visible:border-ring focus-visible:ring-ring/50 focus-visible:ring-[3px] aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 aria-invalid:border-destructive",
  {
    variants: {
      variant: {
        default: 'bg-primary text-primary-foreground hover:bg-primary/90',
        destructive:
          'bg-destructive text-destructive-foreground hover:bg-destructive/90 focus-visible:ring-destructive/20 dark:focus-visible:ring-destructive/40',
        outline: 'border border-border bg-background hover:bg-accent hover:text-accent-foreground',
        secondary: 'bg-secondary text-secondary-foreground hover:bg-secondary/80',
        ghost: 'hover:bg-accent hover:text-accent-foreground',
        link: 'text-primary underline-offset-4 hover:underline',
        success:
          'bg-success text-success-foreground hover:bg-success/90 focus-visible:ring-success/20 dark:focus-visible:ring-success/40',
        info: 'bg-info text-info-foreground hover:bg-info/90 focus-visible:ring-info/20 dark:focus-visible:ring-info/40',
        warning:
          'bg-warning text-warning-foreground hover:bg-warning/90 focus-visible:ring-warning/20 dark:focus-visible:ring-warning/40',
      },
      size: {
        default: 'h-9 px-4 py-2 has-[>svg]:px-3',
        sm: 'h-8 rounded-[var(--radius-button)] gap-1.5 px-3 has-[>svg]:px-2.5',
        lg: 'h-10 rounded-[var(--radius-button)] px-6 has-[>svg]:px-4',
        icon: 'size-9 rounded-[var(--radius-button)]',
      },
    },
    defaultVariants: {
      variant: 'default',
      size: 'default',
    },
  }
);

/**
 * Props for the Button component.
 *
 * @interface ButtonProps
 */
export interface ButtonProps
  extends React.ComponentProps<'button'>, VariantProps<typeof buttonVariants> {
  /**
   * If true, renders the child element in place of the `<button>` tag,
   * injecting button styles. Useful for router links (`<Link href="...">`).
   */
  asChild?: boolean;
  /** If true, disables the button and shows a loading spinner while preserving the button width. */
  loading?: boolean;
}

/**
 * Primary interaction trigger button.
 *
 * @description
 * The mandatory component for all clickable actions that are not native navigation.
 * Supports 9 visual variants (default, destructive, outline, secondary, ghost, link, success, info, warning)
 * and 4 sizes (default, sm, lg, icon).
 *
 * @ai-rules
 * 1. NEVER use a raw `<button>` element.
 * 2. For forms, use `type="submit"` — the browser default inside a `<form>` is already submit.
 * 3. To look like a link but act as a button, use `variant="link"`.
 * 4. To act as a router link with button styling, use `asChild` wrapping a `<Link>` component.
 * 5. Use `loading={true}` during async operations — it disables and shows a spinner.
 */
const Button = React.forwardRef<HTMLButtonElement, ButtonProps>(
  ({ className, variant, size, asChild = false, loading = false, children, ...props }, ref) => {
    const Comp = asChild ? Slot : 'button';

    return (
      <Comp
        data-slot="button"
        className={cn(buttonVariants({ variant, size, className }))}
        disabled={loading || props.disabled}
        ref={ref}
        {...props}
      >
        {loading ? (
          <>
            <Loader2 className="animate-spin" />
            <Slottable>{children}</Slottable>
          </>
        ) : (
          <Slottable>{children}</Slottable>
        )}
      </Comp>
    );
  }
);

Button.displayName = 'Button';

export { Button, buttonVariants };