import { useMemo, useState } from 'react'
import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
import { Link } from 'react-router-dom'
import { getSyncStatus, listCategories, listChannels, logout, syncSubscriptions } from '../api/client'
import ChannelCard from '../components/ChannelCard'
import CategoryNav, { type CategoryFilter } from '../components/CategoryNav'

function Channels() {
  const [search, setSearch] = useState('')
  const [filter, setFilter] = useState<CategoryFilter>('all')
  const queryClient = useQueryClient()

  const categoriesQuery = useQuery({ queryKey: ['categories'], queryFn: listCategories })

  const channelsQuery = useQuery({
    queryKey: ['channels', filter],
    queryFn: () =>
      listChannels({
        categoryId: typeof filter === 'number' ? filter : undefined,
        uncategorized: filter === 'uncategorized',
      }),
  })

  const filteredChannels = useMemo(() => {
    const data = channelsQuery.data ?? []
    if (!search.trim()) return data
    const needle = search.trim().toLowerCase()
    return data.filter((c) => c.title.toLowerCase().includes(needle))
  }, [channelsQuery.data, search])

  const syncStatusQuery = useQuery({
    queryKey: ['sync-status'],
    queryFn: getSyncStatus,
    refetchInterval: (query) => (query.state.data?.subscriptions.running ? 1500 : false),
  })

  const syncMutation = useMutation({
    mutationFn: syncSubscriptions,
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['channels'] })
      queryClient.invalidateQueries({ queryKey: ['sync-status'] })
    },
  })

  const logoutMutation = useMutation({
    mutationFn: logout,
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['auth-status'] })
    },
  })

  const running = syncStatusQuery.data?.subscriptions.running
  const categories = categoriesQuery.data ?? []

  return (
    <div className="channels-screen">
      <header>
        <h1>Каналы</h1>
        <div className="actions">
          <Link to="/">Лента</Link>
          <Link to="/categories">Категории</Link>
          <button onClick={() => syncMutation.mutate()} disabled={running}>
            {running ? 'Синхронизация...' : 'Обновить сейчас'}
          </button>
          <button onClick={() => logoutMutation.mutate()}>Выйти</button>
        </div>
      </header>

      {syncMutation.isError && <p className="error">{(syncMutation.error as Error).message}</p>}
      {syncStatusQuery.data?.subscriptions.status === 'failed' && (
        <p className="error">Последняя синхронизация завершилась ошибкой: {syncStatusQuery.data.subscriptions.error}</p>
      )}

      <div className="layout">
        <CategoryNav categories={categories} value={filter} onChange={setFilter} />

        <div className="content">
          <input
            type="text"
            placeholder="Поиск по названию канала"
            value={search}
            onChange={(e) => setSearch(e.target.value)}
          />

          {channelsQuery.isLoading && <p>Загрузка...</p>}
          {channelsQuery.isError && <p className="error">Не удалось загрузить каналы</p>}

          <ul className="channel-list">
            {filteredChannels.map((channel) => (
              <ChannelCard key={channel.id} channel={channel} categories={categories} />
            ))}
          </ul>

          {channelsQuery.data && channelsQuery.data.length === 0 && (
            <p>Каналы не найдены{filter === 'all' ? '. Нажми "Обновить сейчас".' : ' в этой категории.'}</p>
          )}
          {channelsQuery.data && channelsQuery.data.length > 0 && filteredChannels.length === 0 && (
            <p>Ничего не найдено по запросу "{search}".</p>
          )}
        </div>
      </div>
    </div>
  )
}

export default Channels