import { useState } from 'react';
import Dialog from '@mui/material/Dialog';
import DialogTitle from '@mui/material/DialogTitle';
import DialogContent from '@mui/material/DialogContent';
import DialogActions from '@mui/material/DialogActions';
import Button from '@mui/material/Button';
import List from '@mui/material/List';
import ListItemButton from '@mui/material/ListItemButton';
import ListItemText from '@mui/material/ListItemText';
import Collapse from '@mui/material/Collapse';
import ExpandLess from '@mui/icons-material/ExpandLess';
import ExpandMore from '@mui/icons-material/ExpandMore';
import CheckIcon from '@mui/icons-material/Check';
import FolderIcon from '@mui/icons-material/Folder';
import FolderOpenIcon from '@mui/icons-material/FolderOpen';
import Box from '@mui/material/Box';
import { getCategoryChildren, categoryDisplayName } from '../../store/categorySlice';
function CategoryNode({
  categories,
  categoryId,
  rootCategoryId,
  selectedId,
  onSelect,
  expandedIds,
  onToggleExpand,
  depth = 0,
}) {
  const node = categories[String(categoryId)];
  if (!node) return null;

  const children = getCategoryChildren(categories, categoryId);
  const hasChildren = children.length > 0;
  const isSelected = selectedId != null && String(selectedId) === String(categoryId);
  const isExpanded = expandedIds.has(categoryId);
  const label = categoryDisplayName(node.name, node.id, rootCategoryId);

  return (
    <>
      <ListItemButton
        selected={isSelected}
        onClick={() => onSelect(categoryId)}
        sx={{ pl: 1 + depth * 1.5 }}
      >
        <Box sx={{ minWidth: 24, display: 'flex', alignItems: 'center' }}>
          {hasChildren ? (
            isExpanded ? <FolderOpenIcon fontSize="small" /> : <FolderIcon fontSize="small" />
          ) : null}
        </Box>
        <ListItemText primary={label} />
        {isSelected && <CheckIcon fontSize="small" color="primary" sx={{ ml: 1 }} />}
        {hasChildren && (
          isExpanded ? (
            <ExpandLess onClick={(e) => { e.stopPropagation(); onToggleExpand(categoryId, false); }} />
          ) : (
            <ExpandMore onClick={(e) => { e.stopPropagation(); onToggleExpand(categoryId, true); }} />
          )
        )}
      </ListItemButton>
      {hasChildren && (
        <Collapse in={isExpanded} timeout="auto" unmountOnExit>
          <List disablePadding>
            {children.map((child) => (
              <CategoryNode
                key={child.id}
                categories={categories}
                categoryId={child.id}
                rootCategoryId={rootCategoryId}
                selectedId={selectedId}
                onSelect={onSelect}
                expandedIds={expandedIds}
                onToggleExpand={onToggleExpand}
                depth={depth + 1}
              />
            ))}
          </List>
        </Collapse>
      )}
    </>
  );
}

function buildDefaultExpanded(categories, rootCategoryId, currentCategoryIds) {
  const ids = new Set();
  if (!categories || !rootCategoryId) return ids;
  for (const catId of currentCategoryIds ?? []) {
    let id = catId;
    while (id != null) {
      const node = categories[String(id)];
      if (!node) break;
      ids.add(id);
      if (node.parentId == null || node.parentId === 0) break;
      id = node.parentId;
    }
  }
  return ids;
}

export default function CategoryPickerDialog({
  open,
  onClose,
  categories,
  rootCategoryId,
  currentCategoryIds,
  onSelect,
}) {
  const [selectedId, setSelectedId] = useState(null);
  const [expandedIds, setExpandedIds] = useState(
    () => buildDefaultExpanded(categories, rootCategoryId, currentCategoryIds),
  );

  const handleToggleExpand = (id, expand) => {
    setExpandedIds((prev) => {
      const next = new Set(prev);
      if (expand) next.add(id);
      else next.delete(id);
      return next;
    });
  };

  const handleConfirm = () => {
    if (selectedId == null) return;
    const categoryIds = currentCategoryIds.filter((id) => String(id) !== String(selectedId));
    categoryIds.push(selectedId);
    onSelect?.(categoryIds);
    onClose();
  };

  return (
    <Dialog open={open} onClose={onClose} maxWidth="xs" fullWidth>
      <DialogTitle>Kategorie zuweisen</DialogTitle>
      <DialogContent dividers sx={{ p: 0 }}>
        {categories && rootCategoryId != null ? (
          <List dense disablePadding>
            <CategoryNode
              categories={categories}
              categoryId={rootCategoryId}
              rootCategoryId={rootCategoryId}
              selectedId={selectedId}
              onSelect={setSelectedId}
              expandedIds={expandedIds}
              onToggleExpand={handleToggleExpand}
            />
          </List>
        ) : (
          <Box sx={{ p: 2, textAlign: 'center', color: 'text.secondary' }}>
            Lade Kategorien…
          </Box>
        )}
      </DialogContent>
      <DialogActions>
        <Button onClick={onClose}>Abbrechen</Button>
        <Button onClick={handleConfirm} disabled={selectedId == null} variant="contained">
          Zuweisen
        </Button>
      </DialogActions>
    </Dialog>
  );
}