import { useState } from 'react'
import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
import { Link } from 'react-router-dom'
import {
  createCategory,
  deleteCategory,
  listCategories,
  reorderCategories,
  updateCategory,
} from '../api/client'

function Categories() {
  const queryClient = useQueryClient()
  const [newName, setNewName] = useState('')
  const [editingId, setEditingId] = useState<number | null>(null)
  const [editingName, setEditingName] = useState('')

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

  const invalidate = () => {
    queryClient.invalidateQueries({ queryKey: ['categories'] })
    queryClient.invalidateQueries({ queryKey: ['channels'] })
  }

  const createMutation = useMutation({
    mutationFn: (name: string) => createCategory(name),
    onSuccess: () => {
      setNewName('')
      invalidate()
    },
  })

  const updateMutation = useMutation({
    mutationFn: ({ id, name }: { id: number; name: string }) => updateCategory(id, name),
    onSuccess: () => {
      setEditingId(null)
      invalidate()
    },
  })

  const deleteMutation = useMutation({
    mutationFn: (id: number) => deleteCategory(id),
    onSuccess: invalidate,
  })

  const reorderMutation = useMutation({
    mutationFn: (ids: number[]) => reorderCategories(ids),
    onSuccess: invalidate,
  })

  const categories = categoriesQuery.data ?? []

  function move(index: number, direction: -1 | 1) {
    const target = index + direction
    if (target < 0 || target >= categories.length) return
    const ids = categories.map((c) => c.id)
    ;[ids[index], ids[target]] = [ids[target], ids[index]]
    reorderMutation.mutate(ids)
  }

  return (
    <div className="categories-screen">
      <Link to="/" className="back-link">
        ← Каналы
      </Link>
      <h1>Категории</h1>

      <form
        onSubmit={(e) => {
          e.preventDefault()
          if (newName.trim()) createMutation.mutate(newName.trim())
        }}
        className="category-form"
      >
        <input
          type="text"
          placeholder="Новая категория"
          value={newName}
          onChange={(e) => setNewName(e.target.value)}
        />
        <button type="submit" disabled={!newName.trim() || createMutation.isPending}>
          Создать
        </button>
      </form>
      {createMutation.isError && <p className="error">{(createMutation.error as Error).message}</p>}

      <ul className="category-list">
        {categories.map((category, index) => (
          <li key={category.id} className="category-row">
            <div className="reorder-buttons">
              <button onClick={() => move(index, -1)} disabled={index === 0} aria-label="Выше">
                ↑
              </button>
              <button onClick={() => move(index, 1)} disabled={index === categories.length - 1} aria-label="Ниже">
                ↓
              </button>
            </div>

            {editingId === category.id ? (
              <form
                className="category-edit-form"
                onSubmit={(e) => {
                  e.preventDefault()
                  if (editingName.trim()) updateMutation.mutate({ id: category.id, name: editingName.trim() })
                }}
              >
                <input value={editingName} onChange={(e) => setEditingName(e.target.value)} autoFocus />
                <button type="submit">Сохранить</button>
                <button type="button" onClick={() => setEditingId(null)}>
                  Отмена
                </button>
              </form>
            ) : (
              <>
                <span className="category-name">{category.name}</span>
                <span className="category-count">{category.channel_count} канал(ов)</span>
                <button
                  onClick={() => {
                    setEditingId(category.id)
                    setEditingName(category.name)
                  }}
                >
                  Переименовать
                </button>
                <button
                  onClick={() => {
                    if (confirm(`Удалить категорию "${category.name}"? Каналы останутся.`)) {
                      deleteMutation.mutate(category.id)
                    }
                  }}
                >
                  Удалить
                </button>
              </>
            )}
          </li>
        ))}
      </ul>

      {categories.length === 0 && !categoriesQuery.isLoading && <p>Категорий пока нет.</p>}
    </div>
  )
}

export default Categories