import { ChevronRight } from "lucide-react";
import { useEffect, useRef, useState } from "react";
import { Link } from "react-router";
import { useDiscoverSection } from "~/api/discover.ts";
import { Button } from "~/components/ui/button.tsx";
import { errorMessage } from "~/lib/api.ts";
import { ChipRow } from "./chips.tsx";
import { DiscoverCard, DiscoverCardSkeleton } from "./discover-card.tsx";
import {
  apiQuery,
  CATEGORIES,
  normalize,
  type RecommendSection,
  sectionsOf,
  toSearchParams,
} from "./discover-state.ts";
import { useDiscoverActions } from "./use-discover-actions.tsx";

// 推荐(对照 MP recommend.vue):按分区横排,分区进入视口附近才加载(各分区各自请求、并发),
// 每区「查看全部」带同样的参数切到探索。顶部按 全部 / 电影 / 剧集 / 动画 / 榜单 筛分区。

const CARD_W = "w-32 shrink-0 sm:w-36";

/** 进入视口(提前 600px)后为 true;没有 IntersectionObserver 时直接 true */
function useNearViewport<T extends Element>() {
  const ref = useRef<T>(null);
  const [near, setNear] = useState(() => typeof IntersectionObserver === "undefined");
  useEffect(() => {
    if (near || !ref.current) return;
    const io = new IntersectionObserver((es) => es.some((e) => e.isIntersecting) && setNear(true), {
      rootMargin: "600px 0px",
    });
    io.observe(ref.current);
    return () => io.disconnect();
  }, [near]);
  return [ref, near] as const;
}

export function RecommendView({
  category,
  onCategory,
}: {
  category: string;
  onCategory: (c: string | undefined) => void;
}) {
  const actions = useDiscoverActions();
  return (
    <div className="space-y-7">
      <ChipRow label="分类" options={CATEGORIES.slice(1)} allLabel="全部" value={category} onChange={onCategory} />
      {sectionsOf(category).map((s) => (
        <Section key={s.key} section={s} actions={actions} />
      ))}
      {actions.dialogs}
    </div>
  );
}

function Section({ section, actions }: { section: RecommendSection; actions: ReturnType<typeof useDiscoverActions> }) {
  const [ref, near] = useNearViewport<HTMLElement>();
  const state = normalize(section.explore);
  const q = useDiscoverSection(apiQuery(state), near);
  const items = q.data?.items ?? [];
  const id = `discover-${section.key}`;
  return (
    <section ref={ref} aria-labelledby={id} className="min-w-0" data-section={section.key}>
      <div className="mb-2 flex items-center justify-between gap-2">
        <h2 id={id} className="text-body font-semibold text-foreground">
          {section.title}
        </h2>
        <Button asChild variant="ghost" size="sm">
          <Link to={`?${toSearchParams(state)}`}>
            查看全部
            <ChevronRight />
          </Link>
        </Button>
      </div>
      {q.isError ? (
        <div className="flex items-center gap-3 rounded-xl border border-dashed border-border px-4 py-6 text-caption text-muted-foreground">
          <span className="min-w-0 truncate">{errorMessage(q.error, "加载失败")}</span>
          <Button variant="outline" size="sm" onClick={() => void q.refetch()}>
            重试
          </Button>
        </div>
      ) : q.isSuccess && items.length === 0 ? (
        <p className="rounded-xl border border-dashed border-border px-4 py-6 text-caption text-muted-foreground">
          这一栏暂时没有作品。
        </p>
      ) : (
        <ul className="scroll-bleed flex gap-3 overflow-x-auto">
          {q.isSuccess
            ? items.slice(0, 20).map((it) => (
                <li key={`${it.source}:${it.id}`} className={CARD_W}>
                  <DiscoverCard item={it} busy={actions.busyOf(it)} onAction={(a) => void actions.act(it, a)} />
                </li>
              ))
            : Array.from({ length: 8 }, (_, i) => (
                <li key={i} className={CARD_W}>
                  <DiscoverCardSkeleton />
                </li>
              ))}
        </ul>
      )}
    </section>
  );
}