"use client";

import { useId, useState, type MouseEvent, type ReactNode } from "react";
import { motion, useReducedMotion } from "motion/react";

export type BubbleDockItem = {
  label: string;
  href: string;
  /** Icon (an svg works best). */
  icon: ReactNode;
};

type BubbleDockProps = {
  items: BubbleDockItem[];
  /** href of the active link at start. Defaults to the first item. */
  active?: string;
  /** Called on click. Call e.preventDefault() to stop the browser following the link. */
  onSelect?: (item: BubbleDockItem, e: MouseEvent<HTMLAnchorElement>) => void;
  /** Bar height in pixels. The bubble is the same size. */
  size?: number;
  /** Bar and bubble colour. */
  color?: string;
  /** Colour of the icon inside the bubble. */
  activeColor?: string;
  /** Name read out by screen readers. */
  label?: string;
  /** Icon / label colour on the bar. Width comes from the parent (full width). */
  className?: string;
};

/* BubbleDock: a tab bar where the active icon rises in a bubble that melts out of the bar, and the bubble rolls to whichever tab you pick. */
export function BubbleDock({
  items,
  active,
  onSelect,
  size = 60,
  color = "#241e44",
  activeColor = "#a78bfa",
  label = "Tabs",
  className = "text-white/60",
}: BubbleDockProps) {
  const reduce = useReducedMotion();
  const filterId = `bubble-${useId().replace(/:/g, "")}`;
  const [current, setCurrent] = useState(active ?? items[0]?.href);
  const index = Math.max(0, items.findIndex((i) => i.href === current));
  const n = items.length || 1;
  const rise = size * 0.5;
  const roll = reduce ? { duration: 0 } : { type: "spring" as const, stiffness: 260, damping: 24 };

  return (
    <nav aria-label={label} className={`relative w-full ${className}`} style={{ height: size + rise, paddingTop: rise }}>
      <svg aria-hidden className="absolute h-0 w-0">
        <filter id={filterId}>
          <feGaussianBlur in="SourceGraphic" stdDeviation={size / 6} result="blur" />
          <feColorMatrix in="blur" values="1 0 0 0 0  0 1 0 0 0  0 0 1 0 0  0 0 0 24 -10" result="goo" />
          <feComposite in="SourceGraphic" in2="goo" operator="atop" />
        </filter>
      </svg>

      {/* Bar + bubble share one goo filter so they melt together. */}
      <div aria-hidden className="absolute inset-x-0 bottom-0" style={{ top: 0, filter: `url(#${filterId})` }}>
        <div className="absolute inset-x-0 bottom-0 rounded-[22px]" style={{ height: size, background: color }} />
        <motion.div
          className="absolute rounded-full"
          initial={false}
          animate={{ left: `${((index + 0.5) / n) * 100}%` }}
          transition={roll}
          style={{ width: size, height: size, top: rise * 0.15, marginLeft: -size / 2, background: color }}
        />
      </div>

      {/* Coloured core inside the bubble, kept outside the filter so it stays crisp. */}
      <motion.div
        aria-hidden
        className="absolute rounded-full"
        initial={false}
        animate={{ left: `${((index + 0.5) / n) * 100}%` }}
        transition={roll}
        style={{
          width: size * 0.74,
          height: size * 0.74,
          top: rise * 0.15 + size * 0.13,
          marginLeft: -size * 0.37,
          background: activeColor,
          boxShadow: `0 6px 18px -4px ${activeColor}`,
        }}
      />

      <ul className="relative grid h-full" style={{ gridTemplateColumns: `repeat(${n}, minmax(0, 1fr))` }}>
        {items.map((item, i) => {
          const on = i === index;
          return (
            <li key={item.href} className="relative">
              <a
                href={item.href}
                aria-current={on ? "page" : undefined}
                onClick={(e) => {
                  setCurrent(item.href);
                  onSelect?.(item, e);
                }}
                className="relative flex h-full flex-col items-center justify-center rounded-[18px] outline-none focus-visible:ring-2 focus-visible:ring-white/70 focus-visible:ring-inset"
              >
                <motion.span
                  aria-hidden
                  className={`grid size-6 place-items-center transition-colors duration-300 [&>svg]:size-full ${on ? "text-[#0b0a14]" : ""}`}
                  initial={false}
                  // Lift the icon from the bar centre to the bubble centre.
                  animate={{ y: on ? -rise * 0.85 : 0 }}
                  transition={roll}
                >
                  {item.icon}
                </motion.span>
                <motion.span
                  className="absolute bottom-2 text-[11px] font-medium text-white"
                  initial={false}
                  animate={{ opacity: on ? 1 : 0, y: on ? 0 : 6 }}
                  transition={{ duration: reduce ? 0 : 0.25, delay: on && !reduce ? 0.1 : 0 }}
                >
                  {item.label}
                </motion.span>
              </a>
            </li>
          );
        })}
      </ul>
    </nav>
  );
}