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

import {
  acceptFriendRequest,
  removeRelationship,
  unblockUser,
  type RelationshipUser,
} from '@/api/friends';
import { FriendRow } from '@/components/friends/FriendRow';
import { FramedAvatar, Nickname } from '@/components/profile/Cosmetics';
import { InviteJoin } from '@/components/friends/InviteJoin';
import { UserSearch } from '@/components/friends/UserSearch';
import { Avatar } from '@/components/ui/Avatar';
import { ErrorNotice } from '@/components/ui/ErrorNotice';
import { SkeletonLines } from '@/components/ui/Skeleton';
import { Button } from '@/components/ui/primitives';
import { useFriendsStore } from '@/stores/friends';
import { useSessionStore } from '@/stores/session';
import { useUiStore } from '@/stores/ui';

/** Имя для заявки: список связей не хранит отдельного «ника». */
function displayName(user: RelationshipUser): string {
  return user.display_name === '' ? user.username : user.display_name;
}

/**
 * Раздел «Друзья»: заявки, список друзей, поиск по логину и присоединение
 * по приглашению. Личные беседы открываются в области контента (см.
 * `DirectMessageView`), а их список живёт в сайдбаре раздела.
 */
export function FriendsView() {
  const { t } = useTranslation();
  const friends = useFriendsStore((state) => state.friends);
  const incoming = useFriendsStore((state) => state.incoming);
  const outgoing = useFriendsStore((state) => state.outgoing);
  const blocked = useFriendsStore((state) => state.blocked);
  const status = useFriendsStore((state) => state.status);
  const error = useFriendsStore((state) => state.error);
  const load = useFriendsStore((state) => state.load);
  const reload = useFriendsStore((state) => state.reload);
  const dmChannels = useSessionStore((state) => state.dmChannels);
  const listOpen = useUiStore((state) => state.friendsListOpen);
  const toggleFriendsList = useUiStore((state) => state.toggleFriendsList);
  const listId = useId();

  const [searchOpen, setSearchOpen] = useState(false);

  useEffect(() => {
    void load();
  }, [load]);

  // Снятие блокировки: список перечитывается, человек снова может писать.
  const unblock = useMutation({
    mutationFn: (userId: string) => unblockUser(userId),
    onSuccess: () => reload(),
  });

  const respond = useMutation({
    mutationFn: ({ kind, userId }: { kind: 'accept' | 'decline' | 'cancel'; userId: string }) =>
      kind === 'accept' ? acceptFriendRequest(userId) : removeRelationship(userId),
    onSuccess: () => reload(),
  });

  // Пусто — только когда нет ни друзей, ни бесед, ни заявок: иначе заявку
  // было бы не увидеть.
  const isEmpty =
    friends.length === 0 &&
    dmChannels.length === 0 &&
    incoming.length === 0 &&
    outgoing.length === 0;

  return (
    <section id="app-content" className="absolute inset-0 overflow-y-auto p-4">
      <header className="flex items-center gap-2">
        <h2 className="text-sm font-semibold">{t('friends.title')}</h2>
        <Button
          variant="ghost"
          className="ml-auto"
          aria-expanded={searchOpen}
          onClick={() => setSearchOpen((value) => !value)}
        >
          {t('friends.search.open')}
        </Button>
      </header>

      <div className="mt-3">
        {searchOpen ? <UserSearch onClose={() => setSearchOpen(false)} /> : null}
      </div>

      {status === 'error' ? (
        <ErrorNotice
          error={error}
          onRetry={() => {
            void reload();
          }}
        />
      ) : null}

      {status === 'loading' && friends.length === 0 ? <SkeletonLines rows={3} /> : null}

      {incoming.length === 0 ? null : (
        <section aria-label={t('friends.requests.incoming')} className="mt-2">
          <h3 className="text-xs font-semibold uppercase tracking-wide text-fg-muted">
            {t('friends.requests.incoming')}
          </h3>
          <ul className="gl-stagger mt-1 flex flex-col gap-1" data-testid="friends-incoming">
            {incoming.map((user) => (
              <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={displayName(user)}
                  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">{displayName(user)}</span>
                  <span className="block truncate text-xs text-fg-muted">@{user.username}</span>
                </span>
                <span className="flex shrink-0 items-center gap-1">
                  <Button
                    disabled={respond.isPending}
                    onClick={() => {
                      respond.mutate({ kind: 'accept', userId: user.user_id });
                    }}
                  >
                    {t('friends.requests.accept')}
                  </Button>
                  <Button
                    variant="ghost"
                    disabled={respond.isPending}
                    onClick={() => {
                      respond.mutate({ kind: 'decline', userId: user.user_id });
                    }}
                  >
                    {t('friends.requests.decline')}
                  </Button>
                </span>
              </li>
            ))}
          </ul>
        </section>
      )}

      {outgoing.length === 0 ? null : (
        <section aria-label={t('friends.requests.outgoing')} className="mt-4">
          <h3 className="text-xs font-semibold uppercase tracking-wide text-fg-muted">
            {t('friends.requests.outgoing')}
          </h3>
          <ul className="gl-stagger mt-1 flex flex-col gap-1" data-testid="friends-outgoing">
            {outgoing.map((user) => (
              <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={displayName(user)}
                  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">{displayName(user)}</span>
                  <span className="block truncate text-xs text-fg-muted">@{user.username}</span>
                </span>
                <Button
                  variant="ghost"
                  disabled={respond.isPending}
                  onClick={() => {
                    respond.mutate({ kind: 'cancel', userId: user.user_id });
                  }}
                >
                  {t('friends.requests.cancel')}
                </Button>
              </li>
            ))}
          </ul>
        </section>
      )}

      {isEmpty ? (
        <div
          className="flex flex-col items-center justify-center gap-3 px-4 py-12 text-center"
          data-testid="friends-empty"
        >
          <h3 className="text-lg font-semibold">{t('friends.empty.title')}</h3>
          <p className="max-w-md text-sm text-fg-muted">{t('friends.empty.body')}</p>
          <Button onClick={() => setSearchOpen(true)}>{t('friends.empty.search')}</Button>
        </div>
      ) : (
        <section aria-label={t('friends.list.label')} className="mt-4">
          {/*
            Список свёрнут по умолчанию: раскрывается снизу вверх, состояние
            переживает перезагрузку страницы (zustand + localStorage).
          */}
          <button
            type="button"
            aria-expanded={listOpen}
            aria-controls={listId}
            data-testid="friends-list-toggle"
            disabled={friends.length === 0}
            className="flex items-center gap-1 rounded-[var(--radius-sm)] px-2 py-1 text-xs font-semibold uppercase tracking-wide text-fg-muted transition-colors duration-[var(--duration-fast)] hover:text-fg disabled:cursor-default disabled:hover:text-fg-muted"
            onClick={toggleFriendsList}
          >
            <span aria-hidden="true" className={listOpen ? 'gl-caret-open' : 'gl-caret'}>
              ▾
            </span>
            {t('friends.list.toggle', { count: friends.length })}
          </button>
          <div
            id={listId}
            className="gl-reveal-up"
            data-state={listOpen ? 'open' : 'closed'}
            data-testid="friends-list-region"
            aria-hidden={listOpen ? undefined : true}
          >
            {!listOpen ? null : friends.length === 0 ? (
              <p className="px-2 py-1 text-sm text-fg-muted">{t('friends.friendsEmpty')}</p>
            ) : (
              <ul
                className="gl-stagger mt-1 flex flex-col gap-0.5"
                data-testid="friends-list"
                aria-label={t('friends.list.label')}
              >
                {friends.map((friend) => (
                  <FriendRow key={friend.user_id} friend={friend} />
                ))}
              </ul>
            )}
          </div>
        </section>
      )}

      {blocked.length === 0 ? null : (
        <section aria-label={t('friends.blocked.section')} className="mt-4">
          <h3 className="px-2 py-1 text-xs font-semibold uppercase tracking-wide text-fg-muted">
            {t('friends.blocked.section', { count: blocked.length })}
          </h3>
          <ul className="gl-stagger mt-1 flex flex-col gap-0.5" data-testid="friends-blocked">
            {blocked.map((user) => (
              <li
                key={user.user_id}
                data-testid={`blocked-row-${user.user_id}`}
                className="flex items-center gap-3 rounded-[var(--radius-sm)] px-2 py-1.5 hover:bg-surface-2"
              >
                <FramedAvatar
                  name={displayName(user)}
                  seed={user.user_id}
                  fileId={user.avatar_file_id}
                  size="md"
                  cosmetics={user.cosmetics}
                />
                <span className="min-w-0 flex-1">
                  <Nickname
                    name={displayName(user)}
                    cosmetics={user.cosmetics}
                    className="text-sm font-medium"
                  />
                  <span className="block truncate text-xs text-fg-muted">@{user.username}</span>
                </span>
                <Button
                  variant="ghost"
                  data-testid={`blocked-unblock-${user.user_id}`}
                  disabled={unblock.isPending}
                  onClick={() => unblock.mutate(user.user_id)}
                >
                  {t('friends.blocked.unblock')}
                </Button>
              </li>
            ))}
          </ul>
        </section>
      )}

      {respond.isError ? <ErrorNotice className="mt-3" error={respond.error} /> : null}
      {unblock.isError ? <ErrorNotice className="mt-3" error={unblock.error} /> : null}

      <InviteJoin className="mt-8" />
    </section>
  );
}