import { useEffect, useState } from 'react';
import { useMutation, useQuery } from '@tanstack/react-query';
import { useTranslation } from 'react-i18next';

import {
  acceptFriendRequest,
  searchUsers,
  sendFriendRequest,
  userSearchQueryKey,
  type RelationshipUser,
} from '@/api/friends';
import { Avatar } from '@/components/ui/Avatar';
import { ErrorNotice } from '@/components/ui/ErrorNotice';
import { Field } from '@/components/ui/Field';
import { Button } from '@/components/ui/primitives';
import { SkeletonLines } from '@/components/ui/Skeleton';
import { useOpenDirectChannel } from '@/components/friends/useOpenDirectChannel';
import { useFriendsStore } from '@/stores/friends';

/** Пауза перед запросом: пользователь обычно печатает логин целиком. */
export const SEARCH_DEBOUNCE_MS = 400;
/** Сервер требует минимум два символа (`q` в `GET /users/search`). */
export const SEARCH_MIN_LENGTH = 2;

interface UserSearchProps {
  onClose: () => void;
}

/**
 * Поиск пользователей по логину с debounce и заявкой в друзья.
 *
 * Состояние связи берём из стора друзей, а не из ответа поиска: после
 * «Добавить в друзья» кнопка сразу становится «Заявка отправлена».
 * Компонент монтируется только при открытом поиске — состояние не залипает.
 */
export function UserSearch({ onClose }: UserSearchProps) {
  const { t } = useTranslation();
  const [value, setValue] = useState('');
  const [query, setQuery] = useState('');

  const friends = useFriendsStore((state) => state.friends);
  const outgoing = useFriendsStore((state) => state.outgoing);
  const reload = useFriendsStore((state) => state.reload);
  const openDm = useOpenDirectChannel();

  useEffect(() => {
    const trimmed = value.trim();
    const timer = window.setTimeout(() => setQuery(trimmed), SEARCH_DEBOUNCE_MS);
    return () => {
      window.clearTimeout(timer);
    };
  }, [value]);

  const search = useQuery({
    queryKey: userSearchQueryKey(query),
    queryFn: ({ signal }) => searchUsers(query, signal),
    enabled: query.length >= SEARCH_MIN_LENGTH,
    retry: 0,
  });

  const add = useMutation({
    mutationFn: (user: RelationshipUser) => sendFriendRequest({ username: user.username }),
    onSuccess: () => reload(),
  });

  const accept = useMutation({
    mutationFn: (userId: string) => acceptFriendRequest(userId),
    onSuccess: () => reload(),
  });

  const results = search.data ?? [];
  const tooShort = value.trim().length > 0 && value.trim().length < SEARCH_MIN_LENGTH;

  return (
    <section
      aria-label={t('friends.search.title')}
      className="gl-popover-down mb-3 rounded-[var(--radius-lg)] border border-border/60 bg-surface-1 p-3"
      data-testid="friends-search"
    >
      <div className="flex items-start gap-2">
        <div className="flex-1">
          <Field
            label={t('friends.search.label')}
            placeholder={t('friends.search.placeholder')}
            value={value}
            maxLength={32}
            autoFocus
            onChange={(event) => setValue(event.target.value)}
            onKeyDown={(event) => {
              if (event.key === 'Escape') {
                onClose();
              }
            }}
            hint={tooShort ? t('friends.search.hint') : undefined}
          />
        </div>
        <Button variant="ghost" className="mt-6" onClick={onClose}>
          {t('friends.search.close')}
        </Button>
      </div>

      {search.isFetching ? <SkeletonLines className="mt-3" rows={2} /> : null}

      {search.isError ? (
        <ErrorNotice
          className="mt-3"
          error={search.error}
          onRetry={() => {
            void search.refetch();
          }}
        />
      ) : null}

      {!search.isFetching && query.length >= SEARCH_MIN_LENGTH && results.length === 0 ? (
        <p className="mt-3 text-sm text-fg-muted">{t('friends.search.empty')}</p>
      ) : null}

      <ul className="gl-stagger mt-2 flex flex-col gap-1">
        {results.map((user) => {
          const alreadyFriend = friends.some((item) => item.user_id === user.user_id);
          const requested =
            !alreadyFriend && outgoing.some((item) => item.user_id === user.user_id);
          const incoming = !alreadyFriend && user.relationship === 'incoming';
          return (
            <li
              key={user.user_id}
              className="flex items-center gap-3 rounded-[var(--radius-md)] px-2 py-1.5 hover:bg-surface-2"
            >
              <Avatar
                name={user.display_name}
                seed={user.user_id}
                fileId={user.avatar_file_id}
                size="md"
              />
              <span className="min-w-0 flex-1">
                <span className="block truncate text-sm font-medium">{user.display_name}</span>
                <span className="block truncate text-xs text-fg-muted">@{user.username}</span>
              </span>
              <span className="flex shrink-0 items-center gap-1">
                {alreadyFriend ? (
                  <span className="px-2 text-xs text-fg-muted">{t('friends.search.friend')}</span>
                ) : requested ? (
                  <span className="px-2 text-xs text-fg-muted">
                    {t('friends.search.requested')}
                  </span>
                ) : incoming ? (
                  <Button
                    disabled={accept.isPending}
                    onClick={() => {
                      accept.mutate(user.user_id);
                    }}
                  >
                    {t('friends.requests.accept')}
                  </Button>
                ) : (
                  <Button
                    variant="ghost"
                    disabled={add.isPending}
                    onClick={() => {
                      add.reset();
                      add.mutate(user);
                    }}
                  >
                    {t(add.isPending ? 'friends.search.adding' : 'friends.search.add')}
                  </Button>
                )}
                <Button
                  disabled={openDm.isPending}
                  onClick={() => {
                    openDm.mutate(user.user_id);
                  }}
                >
                  {t('friends.search.message')}
                </Button>
              </span>
            </li>
          );
        })}
      </ul>

      {add.isError ? <ErrorNotice className="mt-3" error={add.error} /> : null}
      {accept.isError ? <ErrorNotice className="mt-3" error={accept.error} /> : null}
      {openDm.isError ? <ErrorNotice className="mt-3" error={openDm.error} /> : null}
    </section>
  );
}