AI Citation

"use client";

import { cn } from "@/lib/utils";
import { ArrowUpRight, Globe } from "lucide-react";
import { AnimatePresence, motion, useReducedMotion } from "motion/react";
import { type ReactNode, useEffect, useRef, useState } from "react";

const SPRING_DEFAULT = {
  bounce: 0.1,
  duration: 0.25,
  type: "spring" as const,
};
/** Grace period so the pointer can cross the gap between pill and card. */
const CLOSE_DELAY_MS = 120;
const CARD_WIDTH_PX = 288;

export type AICitationProps = {
  className?: string;
  /** Excerpt or description shown in the card. */
  description?: string;
  /**
   * The source's mark for the card header — a real isotype or an `<img>`.
   *
   * A node rather than a URL so a brand's own SVG can be passed straight in.
   */
  favicon?: ReactNode;
  /** The number or short label shown in the pill. */
  label: string | number;
  title: string;
  url: string;
};

const hostOf = (url: string): string => {
  try {
    return new URL(url).hostname.replace(/^www\./, "");
  } catch {
    return url;
  }
};

/**
 * An inline citation that can be peeked at.
 *
 * The card scales up **from the pill** rather than fading in centred: with a
 * transform origin at the bottom of the marker, the growth points back at what
 * was clicked, so the pointer never loses the thread. It opens on hover and on
 * focus, and closes on Escape — a hover-only preview is unreachable by keyboard
 * and unusable on touch.
 */
const AICitation = ({
  className,
  description,
  favicon,
  label,
  title,
  url,
}: AICitationProps) => {
  const shouldReduceMotion = useReducedMotion();
  const [isOpen, setIsOpen] = useState(false);
  const closeTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null);

  const open = () => {
    if (closeTimeoutRef.current) {
      clearTimeout(closeTimeoutRef.current);
      closeTimeoutRef.current = null;
    }
    setIsOpen(true);
  };

  const scheduleClose = () => {
    closeTimeoutRef.current = setTimeout(
      () => setIsOpen(false),
      CLOSE_DELAY_MS
    );
  };

  useEffect(
    () => () => {
      if (closeTimeoutRef.current) {
        clearTimeout(closeTimeoutRef.current);
      }
    },
    []
  );

  useEffect(() => {
    if (!isOpen) {
      return;
    }
    const handle = (event: KeyboardEvent) => {
      if (event.key === "Escape") {
        setIsOpen(false);
      }
    };
    window.addEventListener("keydown", handle);
    return () => window.removeEventListener("keydown", handle);
  }, [isOpen]);

  return (
    // biome-ignore lint/a11y/noStaticElementInteractions: the wrapper only tracks hover and focus to reveal a preview of the link it contains; the link itself is the interactive element and works without it
    // biome-ignore lint/a11y/noNoninteractiveElementInteractions: same — progressive disclosure around a real anchor, not an interactive span
    <span
      className={cn("relative inline-block align-super", className)}
      onBlur={scheduleClose}
      onFocus={open}
      onMouseEnter={open}
      onMouseLeave={scheduleClose}
    >
      <a
        aria-describedby={isOpen ? `${url}-card` : undefined}
        className="inline-flex h-4 min-w-4 items-center justify-center rounded-full border border-border bg-muted px-1 font-medium text-[10px] text-muted-foreground no-underline transition-colors hover:border-foreground/30 hover:text-foreground"
        href={url}
        rel="noopener noreferrer"
        target="_blank"
      >
        {label}
      </a>

      <AnimatePresence>
        {isOpen ? (
          <motion.span
            animate={{ opacity: 1, scale: 1, y: 0 }}
            className="absolute bottom-full left-1/2 z-50 mb-1.5 block rounded-xl border border-border bg-background p-3 text-left align-baseline shadow-lg"
            exit={
              shouldReduceMotion
                ? { opacity: 0, transition: { duration: 0 } }
                : { opacity: 0, scale: 0.94, y: 4 }
            }
            id={`${url}-card`}
            initial={
              shouldReduceMotion
                ? { opacity: 1, scale: 1, y: 0 }
                : { opacity: 0, scale: 0.94, y: 4 }
            }
            style={{
              // Origin at the bottom centre — where the pill is — so the card
              // grows out of the marker instead of appearing over it.
              transformOrigin: "bottom center",
              translateX: "-50%",
              width: CARD_WIDTH_PX,
            }}
            transition={shouldReduceMotion ? { duration: 0 } : SPRING_DEFAULT}
          >
            <span className="mb-1 flex items-center gap-1.5">
              <span className="flex size-3.5 shrink-0 items-center justify-center overflow-hidden rounded-sm text-muted-foreground *:size-full *:fill-foreground *:object-cover">
                {favicon ?? <Globe aria-hidden="true" size={11} />}
              </span>
              <span className="truncate text-muted-foreground text-xs">
                {hostOf(url)}
              </span>
              <ArrowUpRight
                aria-hidden="true"
                className="ml-auto text-muted-foreground"
                size={12}
              />
            </span>

            <span className="block font-medium text-foreground text-sm leading-snug">
              {title}
            </span>

            {description ? (
              <span className="mt-1 block text-muted-foreground text-xs leading-relaxed">
                {description}
              </span>
            ) : null}
          </motion.span>
        ) : null}
      </AnimatePresence>
    </span>
  );
};

export default AICitation;