"use client";

import { useEffect, useMemo, useRef, useState } from "react";
import { DY_EMOJI_BASE, DY_EMOJI_GROUPS, dyEmojiUrl, type DyEmojiManifest } from "@/lib/dyEmoji";

type EmojiPickerProps = {
  onPick: (key: string) => void;
};

type Tab = "tos" | "fus";

const CHUNK = 120;
/** 最近使用一排的容量（与面板 8 列对齐，多了挤掉最旧的） */
const RECENT_MAX = 8;
const RECENT_STORAGE_KEY = "j13_dy_emoji_recent";

let manifestPromise: Promise<DyEmojiManifest | null> | null = null;

async function fetchManifest(): Promise<DyEmojiManifest | null> {
  try {
    const res = await fetch(`${DY_EMOJI_BASE}/manifest.json`);
    if (!res.ok) return null;
    const data = (await res.json()) as DyEmojiManifest;
    if (!Array.isArray(data.tos) || !Array.isArray(data.fus)) return null;
    return data;
  } catch {
    return null;
  }
}

/** 拉取表情清单（模块级缓存，全站只请求一次；仅「合成」tab 使用） */
function useDyEmojiManifest(): { manifest: DyEmojiManifest | null; failed: boolean } {
  const [state, setState] = useState<{ manifest: DyEmojiManifest | null; failed: boolean }>({
    manifest: null,
    failed: false,
  });
  useEffect(() => {
    if (!manifestPromise) manifestPromise = fetchManifest();
    let cancelled = false;
    manifestPromise.then((m) => {
      if (!cancelled) setState({ manifest: m, failed: m === null });
    });
    return () => {
      cancelled = true;
    };
  }, []);
  return state;
}

function loadRecentKeys(): string[] {
  try {
    const raw = localStorage.getItem(RECENT_STORAGE_KEY);
    if (!raw) return [];
    const arr = JSON.parse(raw);
    return Array.isArray(arr) ? arr.filter((k) => typeof k === "string").slice(0, RECENT_MAX) : [];
  } catch {
    return [];
  }
}

function saveRecentKeys(keys: string[]) {
  try {
    localStorage.setItem(RECENT_STORAGE_KEY, JSON.stringify(keys));
  } catch {
    // 隐私模式等存储不可用时静默降级为会话内记忆
  }
}

/** 记录最近使用：最新插前、去重、超出一排丢弃最旧（LRU），返回新列表 */
function pushRecentKey(k: string): string[] {
  const next = [k, ...loadRecentKeys().filter((x) => x !== k)].slice(0, RECENT_MAX);
  saveRecentKeys(next);
  return next;
}

function EmojiCell({ k, onPick }: { k: string; onPick: (k: string) => void }) {
  return (
    <button
      type="button"
      className="j13-emoji-cell"
      aria-label={`表情 ${k}`}
      title={`[:${k}:]`}
      onMouseDown={(e) => e.preventDefault()}
      onClick={() => onPick(k)}
    >
      {/* eslint-disable-next-line @next/next/no-img-element */}
      <img src={dyEmojiUrl(k)} alt="" loading="lazy" draggable={false} />
    </button>
  );
}

/**
 * 抖音表情面板：默认 tab 按分组排列（同类型相邻）+ 顶部最近使用一排；
 * 合成 tab 分块渲染避免一次挂载数千图片。
 */
export default function EmojiPicker({ onPick }: EmojiPickerProps) {
  const { manifest, failed } = useDyEmojiManifest();
  const [tab, setTab] = useState<Tab>("tos");
  const [visible, setVisible] = useState(CHUNK);
  const [recent, setRecent] = useState<string[]>(() => loadRecentKeys());
  const scrollRef = useRef<HTMLDivElement>(null);
  const sentinelRef = useRef<HTMLDivElement | null>(null);

  const fusKeys = useMemo(() => (manifest ? manifest.fus : []), [manifest]);

  // 切 tab / 清单变化时重置分块
  useEffect(() => {
    setVisible(CHUNK);
  }, [tab, manifest]);

  // 合成 tab 滚动到底部分块加载（哨兵离开/进入视口反复触发）
  useEffect(() => {
    const el = sentinelRef.current;
    if (tab !== "fus" || !el || visible >= fusKeys.length) return;
    const io = new IntersectionObserver(
      (entries) => {
        if (entries.some((e) => e.isIntersecting)) {
          setVisible((v) => Math.min(v + CHUNK, fusKeys.length));
        }
      },
      { root: scrollRef.current, rootMargin: "240px" }
    );
    io.observe(el);
    return () => io.disconnect();
  }, [tab, visible, fusKeys.length]);

  const pick = (k: string) => {
    setRecent(pushRecentKey(k));
    onPick(k);
  };

  return (
    <div className="j13-emoji-picker">
      <div className="j13-emoji-tabs" role="tablist" aria-label="表情类型">
        <button
          type="button"
          role="tab"
          aria-selected={tab === "tos"}
          className={tab === "tos" ? "is-on" : ""}
          onClick={() => setTab("tos")}
        >
          默认
        </button>
        <button
          type="button"
          role="tab"
          aria-selected={tab === "fus"}
          className={tab === "fus" ? "is-on" : ""}
          onClick={() => setTab("fus")}
        >
          合成
        </button>
      </div>
      <div className="j13-emoji-scroll" ref={scrollRef}>
        {recent.length > 0 && (
          <div className="j13-emoji-group" aria-label="最近使用">
            <div className="j13-emoji-group-label">最近</div>
            <div className="j13-emoji-grid">
              {recent.map((k) => (
                <EmojiCell key={k} k={k} onPick={pick} />
              ))}
            </div>
          </div>
        )}
        {tab === "tos"
          ? DY_EMOJI_GROUPS.map((g) => (
              <div className="j13-emoji-group" key={g.label}>
                <div className="j13-emoji-group-label">{g.label}</div>
                <div className="j13-emoji-grid">
                  {g.keys.map((k) => (
                    <EmojiCell key={k} k={k} onPick={pick} />
                  ))}
                </div>
              </div>
            ))
          : (
            <div className="j13-emoji-group">
              <div className="j13-emoji-group-label">合成</div>
              <div className="j13-emoji-grid">
                {fusKeys.slice(0, visible).map((k) => (
                  <EmojiCell key={k} k={k} onPick={pick} />
                ))}
                {fusKeys.length > visible && <div ref={sentinelRef} aria-hidden />}
              </div>
            </div>
          )}
        {tab === "fus" && !manifest && !failed && <p className="j13-emoji-empty meta">表情加载中…</p>}
        {tab === "fus" && !manifest && failed && <p className="j13-emoji-empty meta">表情加载失败</p>}
        {manifest && tab === "fus" && fusKeys.length === 0 && (
          <p className="j13-emoji-empty meta">暂无表情</p>
        )}
      </div>
    </div>
  );
}