import Link from "next/link";
import { useEffect, useId, useRef, useState, type KeyboardEvent } from "react";
import type { DocLink } from "@/lib/docs";
import { collectionEntries, collectionIcon, collectionLabel, collectionTone } from "@/lib/collections";
import { Icon } from "./Icon";

export function CategoryNavigation({ docs, current }: { docs: DocLink[]; current?: string }) {
  const navigation = useRef<HTMLElement>(null);
  const triggers = useRef(new Map<string, HTMLButtonElement>());
  const [open, setOpen] = useState<string | null>(null);
  const id = useId();
  const categories = [...new Set(docs.map((doc) => doc.category))];
  const collections = collectionEntries(docs);
  const selected = docs.find((doc) => doc.slug === current);

  useEffect(() => {
    function outside(event: PointerEvent) {
      if (event.target instanceof Node && !navigation.current?.contains(event.target)) setOpen(null);
    }
    function escape(event: globalThis.KeyboardEvent) {
      if (event.key !== "Escape" || !open) return;
      if (navigation.current?.contains(document.activeElement)) {
        event.preventDefault();
        triggers.current.get(open)?.focus();
      }
      setOpen(null);
    }
    document.addEventListener("pointerdown", outside);
    document.addEventListener("keydown", escape);
    return () => {
      document.removeEventListener("pointerdown", outside);
      document.removeEventListener("keydown", escape);
    };
  }, [open]);

  function focusItem(panel: string, last = false) {
    requestAnimationFrame(() => {
      const links = document.getElementById(panel)?.querySelectorAll<HTMLAnchorElement>("a");
      links?.[last ? links.length - 1 : 0]?.focus();
    });
  }
  function move(event: KeyboardEvent<HTMLDivElement>) {
    if (!["ArrowDown", "ArrowUp", "Home", "End"].includes(event.key)) return;
    const links = [...event.currentTarget.querySelectorAll<HTMLAnchorElement>("a")];
    const index = links.indexOf(document.activeElement as HTMLAnchorElement);
    if (index < 0) return;
    event.preventDefault();
    const next = event.key === "Home" ? 0 : event.key === "End" ? links.length - 1 :
      (index + (event.key === "ArrowDown" ? 1 : -1) + links.length) % links.length;
    links[next]?.focus();
  }

  return <nav ref={navigation} className="top-nav category-navigation" aria-label="文档分类"
    onBlur={(event) => {
      if (!event.currentTarget.contains(event.relatedTarget as Node | null)) setOpen(null);
    }}>
    <ul>
      <li><Link className="category-home" href="/" aria-current={!current ? "page" : undefined} onClick={() => setOpen(null)}>文档中心</Link></li>
      {categories.map((category, index) => {
        const panel = `${id}-category-${index}`;
        const expanded = open === category;
        return <li className="category-menu" key={category}
          onPointerEnter={(event) => { if (event.pointerType === "mouse") setOpen(category); }}
          onPointerLeave={(event) => { if (event.pointerType === "mouse") setOpen(null); }}>
          <button ref={(element) => { if (element) triggers.current.set(category, element); else triggers.current.delete(category); }}
            type="button" className="category-trigger" data-category={category}
            data-active={selected?.category === category || undefined}
            aria-expanded={expanded} aria-controls={panel}
            onClick={() => setOpen(expanded ? null : category)}
            onKeyDown={(event) => {
              if (event.key === "ArrowDown" || event.key === "ArrowUp") {
                event.preventDefault();
                setOpen(category);
                focusItem(panel, event.key === "ArrowUp");
              }
            }}>
            {category}<Icon name="chevron" size={11} />
          </button>
          <div id={panel} className="category-panel" hidden={!expanded} onKeyDown={move}>
            <p className="category-panel-title">{category}</p>
            {collections.filter(({entry}) => entry.category === category).map(({name, entry}) => <Link
              key={name} href={`/docs/${entry.slug}`} data-tone={collectionTone(name)}
              aria-current={current === entry.slug ? "page" : selected?.collection === name ? "true" : undefined}
              onClick={() => setOpen(null)}>
              <Icon name={collectionIcon(name)} size={19} />
              <span><strong>{collectionLabel(name)}</strong><small>{entry.description}</small></span>
            </Link>)}
          </div>
        </li>;
      })}
    </ul>
  </nav>;
}