import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import '../../app/theme/app_colors.dart';
import '../../app/theme/app_spacing.dart';

/// 6 位 OTP 验证码输入组件
///
/// 特性: 自动跳转、支持粘贴、错误状态、自动聚焦
class OtpInput extends StatefulWidget {
  final int length;
  final ValueChanged<String> onCompleted;
  final ValueChanged<String>? onChanged;
  final bool hasError;
  final bool autofocus;

  const OtpInput({
    super.key,
    this.length = 6,
    required this.onCompleted,
    this.onChanged,
    this.hasError = false,
    this.autofocus = true,
  });

  @override
  State<OtpInput> createState() => _OtpInputState();
}

class _OtpInputState extends State<OtpInput> {
  late List<TextEditingController> _controllers;
  late List<FocusNode> _focusNodes;

  @override
  void initState() {
    super.initState();
    _controllers = List.generate(widget.length, (_) => TextEditingController());
    _focusNodes = List.generate(widget.length, (_) => FocusNode());
  }

  @override
  void dispose() {
    for (final c in _controllers) {
      c.dispose();
    }
    for (final n in _focusNodes) {
      n.dispose();
    }
    super.dispose();
  }

  String get _code => _controllers.map((c) => c.text).join();

  void _onChanged(int index, String value) {
    // 粘贴完整验证码
    if (value.length > 1) {
      final digits = value.replaceAll(RegExp(r'[^\d]'), '');
      for (int i = 0; i < widget.length && i < digits.length; i++) {
        _controllers[i].text = digits[i];
      }
      final focusIdx = digits.length.clamp(0, widget.length - 1);
      _focusNodes[focusIdx].requestFocus();
      _notifyChange();
      return;
    }

    if (value.isNotEmpty && index < widget.length - 1) {
      _focusNodes[index + 1].requestFocus();
    }
    _notifyChange();
  }

  void _onKeyEvent(int index, KeyEvent event) {
    if (event is KeyDownEvent &&
        event.logicalKey == LogicalKeyboardKey.backspace &&
        _controllers[index].text.isEmpty &&
        index > 0) {
      _controllers[index - 1].clear();
      _focusNodes[index - 1].requestFocus();
      _notifyChange();
    }
  }

  void _notifyChange() {
    final code = _code;
    widget.onChanged?.call(code);
    if (code.length == widget.length) {
      widget.onCompleted(code);
    }
  }

  void clear() {
    for (final c in _controllers) {
      c.clear();
    }
    _focusNodes[0].requestFocus();
  }

  @override
  Widget build(BuildContext context) {
    return Row(
      mainAxisAlignment: MainAxisAlignment.center,
      children: List.generate(widget.length, (i) {
        final isActive = _focusNodes[i].hasFocus;
        final hasFilled = _controllers[i].text.isNotEmpty;

        return Container(
          width: 48,
          height: 56,
          margin: EdgeInsets.symmetric(horizontal: i == 0 || i == widget.length - 1 ? 0 : 4),
          child: KeyboardListener(
            focusNode: FocusNode(),
            onKeyEvent: (event) => _onKeyEvent(i, event),
            child: TextField(
              controller: _controllers[i],
              focusNode: _focusNodes[i],
              autofocus: widget.autofocus && i == 0,
              textAlign: TextAlign.center,
              keyboardType: TextInputType.number,
              maxLength: 1,
              style: const TextStyle(
                fontSize: 24,
                fontWeight: FontWeight.w700,
                color: AppColors.textPrimary,
              ),
              inputFormatters: [
                FilteringTextInputFormatter.digitsOnly,
                LengthLimitingTextInputFormatter(1),
              ],
              decoration: InputDecoration(
                counterText: '',
                contentPadding: EdgeInsets.zero,
                filled: true,
                fillColor: widget.hasError
                    ? AppColors.errorLight
                    : hasFilled
                        ? AppColors.primarySurface
                        : AppColors.gray50,
                enabledBorder: OutlineInputBorder(
                  borderRadius: AppSpacing.borderRadiusMd,
                  borderSide: BorderSide(
                    color: widget.hasError ? AppColors.error : AppColors.border,
                    width: 1.5,
                  ),
                ),
                focusedBorder: OutlineInputBorder(
                  borderRadius: AppSpacing.borderRadiusMd,
                  borderSide: BorderSide(
                    color: widget.hasError ? AppColors.error : AppColors.primary,
                    width: 2,
                  ),
                ),
              ),
              onChanged: (v) => _onChanged(i, v),
            ),
          ),
        );
      }),
    );
  }
}