import 'package:flutter/material.dart';

/// 자동완성 텍스트 필드 위젯
///
/// 입력, 드롭다운, 포커스, 필터링, 선택 기능을 모두 포함한다.
class AutocompleteTextField extends StatefulWidget {
  final String label;
  final String value;
  final List<String> items;
  final bool isRequired;
  final String hintText;
  final void Function(String) onChanged;
  final void Function(String) onSelected;
  final FocusNode? focusNode;

  const AutocompleteTextField({
    Key? key,
    required this.label,
    required this.value,
    required this.items,
    required this.onChanged,
    required this.onSelected,
    this.isRequired = false,
    this.hintText = '',
    this.focusNode,
  }) : super(key: key);

  @override
  State<AutocompleteTextField> createState() => _AutocompleteTextFieldState();
}

class _AutocompleteTextFieldState extends State<AutocompleteTextField> {
  late final TextEditingController _controller;
  late final FocusNode _focusNode;
  late List<String> _filteredItems;
  bool _showDropdown = false;

  @override
  void initState() {
    super.initState();
    _controller = TextEditingController(text: widget.value);
    _focusNode = widget.focusNode ?? FocusNode();
    _filteredItems = List.from(widget.items);
    _controller.addListener(_onTextChanged);
    _focusNode.addListener(() {
      setState(() {
        if (_focusNode.hasFocus) {
          _showDropdown = _filteredItems.isNotEmpty;
        } else {
          _showDropdown = false;
        }
      });
    });
  }

  @override
  void didUpdateWidget(covariant AutocompleteTextField oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (widget.value != _controller.text) {
      _controller.text = widget.value;
    }
    if (widget.items != oldWidget.items) {
      _filteredItems = List.from(widget.items);
    }
  }

  @override
  void dispose() {
    if (widget.focusNode == null) {
      _focusNode.dispose();
    }
    _controller.dispose();
    super.dispose();
  }

  // 입력값 변경 시 필터링
  void _onTextChanged() {
    final text = _controller.text;
    setState(() {
      if (text.isEmpty) {
        _filteredItems = List.from(widget.items);
      } else {
        _filteredItems =
            widget.items
                .where(
                  (item) => item.toLowerCase().contains(text.toLowerCase()),
                )
                .toList();
        // 시작 부분이 일치하는 항목 우선 정렬
        _filteredItems.sort((a, b) {
          bool aStartsWith = a.toLowerCase().startsWith(text.toLowerCase());
          bool bStartsWith = b.toLowerCase().startsWith(text.toLowerCase());
          if (aStartsWith && !bStartsWith) return -1;
          if (!aStartsWith && bStartsWith) return 1;
          return a.compareTo(b);
        });
      }
      _showDropdown = _filteredItems.isNotEmpty && _focusNode.hasFocus;
      widget.onChanged(text);
    });
  }

  void _handleSelect(String value) {
    setState(() {
      _controller.text = value;
      _showDropdown = false;
    });
    widget.onSelected(value);
  }

  @override
  Widget build(BuildContext context) {
    return Stack(
      children: [
        TextFormField(
          controller: _controller,
          focusNode: _focusNode,
          decoration: InputDecoration(
            labelText: widget.label,
            hintText: widget.hintText,
          ),
          validator: (value) {
            if (widget.isRequired && (value == null || value.isEmpty)) {
              return '${widget.label}을(를) 입력해주세요';
            }
            return null;
          },
          onSaved: (value) {
            widget.onSelected(value ?? '');
          },
        ),
        if (_showDropdown)
          Positioned(
            top: 50,
            left: 0,
            right: 0,
            child: Container(
              decoration: BoxDecoration(
                color: Colors.white,
                border: Border.all(color: Colors.grey.shade300),
                borderRadius: BorderRadius.circular(4),
                boxShadow: [
                  BoxShadow(
                    color: Colors.grey.withOpacity(0.3),
                    blurRadius: 4,
                    offset: const Offset(0, 2),
                  ),
                ],
              ),
              constraints: const BoxConstraints(maxHeight: 200),
              child: ListView.builder(
                shrinkWrap: true,
                itemCount: _filteredItems.length,
                itemBuilder: (context, index) {
                  return InkWell(
                    onTap: () => _handleSelect(_filteredItems[index]),
                    child: Container(
                      padding: const EdgeInsets.symmetric(
                        horizontal: 12,
                        vertical: 8,
                      ),
                      child: Text(_filteredItems[index]),
                    ),
                  );
                },
              ),
            ),
          ),
      ],
    );
  }
}