import { useMemo, useState } from 'react';
import TreeSelect from 'antd/es/tree-select';
import Input from 'antd/es/input';
import Button from 'antd/es/button';
import Divider from 'antd/es/divider';
import message from 'antd/es/message';
import { Category, createCategory, fetchAdminCategories } from '../api';
import { buildCategoryTree, CategoryNode } from '../filters';

interface CategoryTreeOption {
  value: number;
  title: string;
  children?: CategoryTreeOption[];
}

function toTreeData(nodes: CategoryNode[]): CategoryTreeOption[] {
  return nodes.map((node) => ({
    value: node.id,
    title: node.name,
    children: node.children.length ? toTreeData(node.children) : undefined
  }));
}

interface Props {
  // Supplied by antd's Form.Item. `id` has to be forwarded or the field loses
  // its association with the rendered <label>, which breaks both screen readers
  // and any lookup by label.
  value?: number;
  onChange?: (value: number | undefined) => void;
  id?: string;
  categories: Category[];
  onCategoriesChanged: (categories: Category[]) => void;
}

// Pulled out of the item form so that typing a new category name re-renders
// only this control. Left inline, every keystroke re-rendered the whole
// Inventory component and rebuilt the tree data, which visibly jittered the
// open popup and moved the buttons under the pointer.
export default function CategoryTreeSelect({ value, onChange, id, categories, onCategoriesChanged }: Props) {
  const [newCategoryName, setNewCategoryName] = useState('');
  const [creating, setCreating] = useState(false);

  const treeData = useMemo(() => toTreeData(buildCategoryTree(categories)), [categories]);

  // Tags can be invented from the item form, so categories should be too —
  // otherwise adding an item in a new category means abandoning a half-filled
  // form. New categories land at the top level; nesting is done in the
  // Categories tab, keeping this control to a single decision.
  async function handleCreate() {
    const name = newCategoryName.trim();
    if (!name) return;

    setCreating(true);
    try {
      const created = await createCategory(name, null);
      onCategoriesChanged(await fetchAdminCategories());
      onChange?.(created.id);
      setNewCategoryName('');
      message.success(`Category "${created.name}" added`);
    } catch (err) {
      message.error(`Couldn't create category — ${(err as Error).message}`);
    } finally {
      setCreating(false);
    }
  }

  return (
    <TreeSelect
      allowClear
      showSearch
      placeholder="Uncategorized"
      // Deliberately not treeDefaultExpandAll: expanding a large tree on open
      // makes the popup reflow while it measures, and buries the create field
      // below every row. Search is the better affordance past a screenful.
      treeNodeFilterProp="title"
      listHeight={256}
      treeData={treeData}
      id={id}
      value={value}
      onChange={onChange}
      style={{ width: '100%' }}
      popupRender={(menu) => (
        <>
          {/* Above the tree, not below it. Under a long list the control is
              both invisible without scrolling and positioned by the list's
              measured height, so it shifts as the virtualized rows settle. */}
          <div style={{ display: 'flex', gap: 8, padding: '8px 8px 0' }}>
            <Input
              placeholder="New category name"
              value={newCategoryName}
              onChange={(event) => setNewCategoryName(event.target.value)}
              // Without this the tree steals the keystrokes for its own
              // type-ahead and arrow-key navigation.
              onKeyDown={(event) => event.stopPropagation()}
              onPressEnter={handleCreate}
            />
            <Button type="primary" loading={creating} onClick={handleCreate}>
              Create category
            </Button>
          </div>
          <Divider style={{ margin: '8px 0' }} />
          {menu}
        </>
      )}
    />
  );
}