import type { ComponentPropsWithRef, ElementType, ReactNode, SyntheticEvent } from "react";

import "./Button.css";

export type ButtonVariant = "primary" | "secondary" | "dark" | "danger" | "ghost";

/** Figma calls these Small / Medium / Large; they resolve to 36 / 48 / 52px. */
export type ButtonSize = "sm" | "md" | "lg";

/**
 * Each size owns a published type role rather than a raw font-size, and the
 * role's line-height is what makes the button land on its designed height.
 */
const TYPE_ROLE: Record<ButtonSize, string> = {
  sm: "body-sm-bold",
  md: "body-md-bold",
  lg: "body-lg-bold",
};

type ButtonOwnProps = {
  variant?: ButtonVariant;
  size?: ButtonSize;
  /** Rendered in the inline-start 24px slot - the left in LTR, the right in RTL. */
  iconStart?: ReactNode;
  /** Rendered in the inline-end slot. Pass `<ArrowIcon />` for the CTA arrow. */
  iconEnd?: ReactNode;
  /** Keeps the label's box, overlays a spinner and sets `aria-busy`. */
  isLoading?: boolean;
  disabled?: boolean;
  /** Stretch to the width of the parent (`display: grid` instead of inline). */
  fullWidth?: boolean;
  className?: string;
  children?: ReactNode;
};

export type ButtonProps<E extends ElementType = "button"> = ButtonOwnProps & {
  /**
   * The element to render. Defaults to `button`; pass react-router's `Link`
   * (plus its `to`) for navigation, or `"a"` for an external href. Props of the
   * chosen element are type-checked, so `as={Link}` requires `to`.
   */
  as?: E;
} & Omit<ComponentPropsWithRef<E>, keyof ButtonOwnProps | "as">;

function cx(...parts: Array<string | false | null | undefined>): string {
  return parts.filter(Boolean).join(" ");
}

function blockActivation(event: SyntheticEvent): void {
  event.preventDefault();
  event.stopPropagation();
}

/**
 * The SHARP-ER button - figma frame 14:487.
 *
 * Polymorphic: renders a native `<button>` by default and anything else through
 * `as`. `ref` is an ordinary prop in React 19, so it travels with the rest of
 * the element props and lands on whichever element `as` selected.
 */
export function Button<E extends ElementType = "button">({
  as,
  variant = "primary",
  size = "md",
  iconStart,
  iconEnd,
  isLoading = false,
  disabled = false,
  fullWidth = false,
  className,
  children,
  ...rest
}: ButtonProps<E>) {
  const Component = (as ?? "button") as ElementType;
  const isNativeButton = Component === "button";
  const isDisabled = disabled || isLoading;
  const elementProps = rest as Record<string, unknown>;

  /**
   * A native button gets the real `disabled` attribute. Anything else (a Link,
   * an anchor) has no such attribute, so it is taken out of the tab order and
   * its activation is swallowed instead. Both forms carry `aria-disabled`.
   */
  const stateProps: Record<string, unknown> = isNativeButton
    ? {
        // Default to a plain button so a button inside a form never submits it
        // by accident; pass type="submit" explicitly when that is the intent.
        type: (elementProps.type as string | undefined) ?? "button",
        disabled: isDisabled,
      }
    : isDisabled
      ? { tabIndex: -1, onClick: blockActivation }
      : {};

  return (
    <Component
      {...elementProps}
      {...stateProps}
      data-variant={variant}
      data-size={size}
      data-loading={isLoading ? "true" : undefined}
      aria-busy={isLoading || undefined}
      aria-disabled={isDisabled || undefined}
      className={cx("sh-btn", TYPE_ROLE[size], fullWidth && "sh-btn--block", className)}
    >
      <span className="sh-btn__content">
        {iconStart ? <span className="sh-btn__icon">{iconStart}</span> : null}
        <span className="sh-btn__label">{children}</span>
        {iconEnd ? <span className="sh-btn__icon">{iconEnd}</span> : null}
      </span>
      {isLoading ? <span className="sh-btn__spinner" aria-hidden="true" /> : null}
    </Component>
  );
}

/* ----------------------------------------------------------------------------
   USAGE  (kept as a comment - the project has no Storybook)

   import { Link } from "react-router";
   import { ArrowIcon, Button } from "~/components/ui/Button";

   // The home hero CTA, Home EN 253:4799 / Home AR 85:5029.
   // The arrow sits inline-end, so RTL moves it to the left and mirrors it.
   <Button as={Link} to="/en/about" size="lg" iconEnd={<ArrowIcon />}>
     Discover SHARP-ER
   </Button>

   // Every variant, all three sizes.
   <Button variant="primary">Apply</Button>
   <Button variant="secondary" size="sm">Read more</Button>
   <Button variant="dark" size="lg">Download the report</Button>
   <Button variant="danger">Withdraw application</Button>
   <Button variant="ghost" iconEnd={<ArrowIcon />}>All news</Button>

   // Submitting a form: aria-busy is set and the label keeps its box.
   <Button type="submit" isLoading={isSubmitting} fullWidth>Send message</Button>

   // Disabled - aria-disabled on both the native and the link form.
   <Button disabled>Applications closed</Button>
   <Button as={Link} to="/en/events" disabled>Registration closed</Button>

   // A "previous" control, mirrored the other way.
   <Button variant="ghost" iconStart={<ArrowIcon direction="backward" />}>
     Previous
   </Button>

   // An external link keeps anchor semantics and prop typing.
   <Button as="a" href="https://europa.eu" target="_blank" rel="noreferrer">
     European Union
   </Button>
   ------------------------------------------------------------------------- */