"use client";

import { ArrowDown, ArrowUp } from "lucide-react";
import { useEffect, useState } from "react";
import { AdminSettingsActions, AdminSettingsGroup, AdminSwitch } from "@/components/admin";
import { apiUpdateSiteSettings, type PublicSettings } from "@/lib/api";
import { MOBILE_TABS, normalizeMobileTabs, type MobileTabKey } from "@/lib/mobileTabs";
import { toast } from "@/lib/toast";

/** 底栏入口说明 */
const TAB_META: Record<MobileTabKey, { label: string; hint: string }> = {
  home: { label: "首页", hint: "站点首页" },
  library: { label: "书库", hint: "书库列表页入口" },
  compose: { label: "发帖", hint: "发帖工作台入口（中央主按钮，无对应首页）" },
  messages: { label: "消息", hint: "私聊/群聊列表；游客不显示" },
  me: { label: "我的", hint: "个人主页；未登录指向登录页" },
};

type TabSwitches = Record<MobileTabKey, boolean>;

function switchesOf(tabs: MobileTabKey[]): TabSwitches {
  return {
    home: tabs.includes("home"),
    library: tabs.includes("library"),
    compose: tabs.includes("compose"),
    messages: tabs.includes("messages"),
    me: tabs.includes("me"),
  };
}

/** 完整顺序：已启用项按配置顺序在前，未启用项按默认顺序追加在后 */
function orderOf(tabs: MobileTabKey[]): MobileTabKey[] {
  const enabled = normalizeMobileTabs(tabs);
  const rest = MOBILE_TABS.filter((key) => !enabled.includes(key));
  return [...enabled, ...rest];
}

/** 移动端底栏：开关 + 顺序调整，保存启用的 tab 子集（数组顺序即前台展示顺序） */
export default function MobileTabBarPanel({
  initial,
  onSaved,
  onDirtyChange,
}: {
  initial: PublicSettings;
  onSaved?: (next: PublicSettings) => void;
  onDirtyChange?: (dirty: boolean) => void;
}) {
  const [order, setOrder] = useState<MobileTabKey[]>(() => orderOf(initial.mobile_tabs));
  const [on, setOn] = useState<TabSwitches>(() => switchesOf(normalizeMobileTabs(initial.mobile_tabs)));
  const [savedPayload, setSavedPayload] = useState<MobileTabKey[]>(() => normalizeMobileTabs(initial.mobile_tabs));
  const [saving, setSaving] = useState(false);
  const [error, setError] = useState("");

  const payload = order.filter((key) => on[key]);
  const dirty = JSON.stringify(payload) !== JSON.stringify(savedPayload);

  useEffect(() => {
    onDirtyChange?.(dirty);
  }, [dirty, onDirtyChange]);

  const move = (i: number, dir: -1 | 1) => {
    setError("");
    setOrder((prev) => {
      const j = i + dir;
      if (j < 0 || j >= prev.length) return prev;
      const next = [...prev];
      const [row] = next.splice(i, 1);
      next.splice(j, 0, row);
      return next;
    });
  };

  const discard = () => {
    setOrder(orderOf(savedPayload));
    setOn(switchesOf(savedPayload));
    setError("");
  };

  const save = async () => {
    if (saving || !dirty) return;
    if (payload.length === 0) {
      setError("至少保留一个入口");
      toast("至少保留一个入口");
      return;
    }
    setSaving(true);
    setError("");
    try {
      const res = await apiUpdateSiteSettings({ mobile_tabs: [...payload] });
      const nextSaved = normalizeMobileTabs(res.mobile_tabs);
      setSavedPayload(nextSaved);
      setOrder(orderOf(nextSaved));
      setOn(switchesOf(nextSaved));
      onSaved?.(res);
      toast("已保存，移动端底栏已更新", "ok");
    } catch (e) {
      const msg = e instanceof Error ? e.message : "保存失败";
      setError(msg);
      toast(msg);
    } finally {
      setSaving(false);
    }
  };

  return (
    <AdminSettingsGroup
      id="settings-mobile-tabbar"
      title="移动端底栏"
      description="控制移动端底部导航显示哪些入口及顺序；底栏只在各入口自己的首页显示。"
      footer={
        <AdminSettingsActions
          dirty={dirty}
          saving={saving}
          saveLabel="保存"
          error={error}
          saveDisabled={payload.length === 0}
          onSave={() => void save()}
          onDiscard={discard}
        />
      }
    >
      <div className="flex flex-col gap-2">
        {order.map((key, i) => (
          <div
            key={key}
            className="flex items-center gap-2 rounded-xl px-2 py-2"
            style={{ border: "1px solid var(--line)", background: "var(--panel)" }}
          >
            <div className="min-w-0 flex-1">
              <div className="text-[13.5px] font-semibold" style={{ color: "var(--ink)" }}>
                {TAB_META[key].label}
              </div>
              <div className="meta text-[12px]">{TAB_META[key].hint}</div>
            </div>
            <div className="flex items-center gap-1 shrink-0">
              <button
                type="button"
                className="admin-icon-btn"
                aria-label={`上移${TAB_META[key].label}`}
                disabled={i === 0 || saving}
                onClick={() => move(i, -1)}
              >
                <ArrowUp size={14} />
              </button>
              <button
                type="button"
                className="admin-icon-btn"
                aria-label={`下移${TAB_META[key].label}`}
                disabled={i === order.length - 1 || saving}
                onClick={() => move(i, 1)}
              >
                <ArrowDown size={14} />
              </button>
              <AdminSwitch
                checked={on[key]}
                disabled={saving}
                onChange={() => {
                  setError("");
                  setOn((prev) => ({ ...prev, [key]: !prev[key] }));
                }}
                label={`底栏显示${TAB_META[key].label}`}
              />
            </div>
          </div>
        ))}
        <ul className="admin-url-style-notes meta mt-1 text-[12px]">
          <li>顺序即前台底栏展示顺序；未启用的入口保留排序位置，重新启用后按当前顺序插入。</li>
          <li>至少保留一个入口；全部关闭将无法保存。</li>
          <li>排行榜不在底栏展示，移动端入口由首页抽屉承担。</li>
        </ul>
      </div>
    </AdminSettingsGroup>
  );
}