import 'dart:async';
import 'package:flutter/material.dart';
import 'package:hmg_patient_app_new/core/utils/size_utils.dart';
import 'package:hmg_patient_app_new/extensions/widget_extensions.dart';
import 'package:hmg_patient_app_new/presentation/authentication/register_step2.dart';
import 'package:hmg_patient_app_new/theme/colors.dart';
import 'package:hmg_patient_app_new/widgets/appbar/app_bar_widget.dart';

class OTPVerificationPage extends StatefulWidget {
  final String phoneNumber;

  const OTPVerificationPage({Key? key, required this.phoneNumber}) : super(key: key);

  @override
  State<OTPVerificationPage> createState() => _OTPVerificationPageState();
}

class _OTPVerificationPageState extends State<OTPVerificationPage> {
  final int _otpLength = 4;
  late final List<TextEditingController> _controllers;
  late final List<FocusNode> _focusNodes;

  Timer? _resendTimer;
  int _resendTime = 60;
  bool _isOtpComplete = false;

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

    // Focus the first field once the screen is built
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (_focusNodes.isNotEmpty) {
        FocusScope.of(context).requestFocus(_focusNodes[0]);
      }
    });
  }

  @override
  void dispose() {
    for (final c in _controllers) c.dispose();
    for (final f in _focusNodes) f.dispose();
    _resendTimer?.cancel();
    super.dispose();
  }

  void _startResendTimer() {
    _resendTimer = Timer.periodic(const Duration(seconds: 1), (timer) {
      if (_resendTime > 0) {
        setState(() => _resendTime--);
      } else {
        timer.cancel();
      }
    });
  }

  void _onOtpChanged(int index, String value) {
    if (value.length == 1 && index < _otpLength - 1) {
      _focusNodes[index + 1].requestFocus();
    } else if (value.isEmpty && index > 0) {
      _focusNodes[index - 1].requestFocus();
    }
    _checkOtpCompletion();
  }

  void _checkOtpCompletion() {
    final isComplete = _controllers.every((c) => c.text.isNotEmpty);

    if (isComplete != _isOtpComplete) {
      setState(() => _isOtpComplete = isComplete);

      if (isComplete) {
        _verifyOtp();
      }
    }
  }

  void _resendOtp() {
    if (_resendTime == 0) {
      setState(() => _resendTime = 60);
      _startResendTimer();
      autoFillOtp("1234");

      // call resend API here
    }
  }

  String _getMaskedPhoneNumber() {
    final phone = widget.phoneNumber;
    return phone.length > 4 ? '05xxxxxx${phone.substring(phone.length - 2)}' : phone;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: CustomAppBar(
        hideLogoAndLang: true,
        onBackPressed: () {
          Navigator.of(context).pop();
        },
        onLanguageChanged: (lang) {},
      ),
      body: SingleChildScrollView(
        child: Padding(
          padding: EdgeInsets.symmetric(horizontal: 24.h),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            children: [
              SizedBox(height: 40.h),
              Text(
                'OTP Verification',
                style: TextStyle(fontSize: 24.fSize, fontWeight: FontWeight.bold),
              ),
              SizedBox(height: 16.h),
              Text(
                'We have sent you the OTP code on ${_getMaskedPhoneNumber()} via SMS for registration verification',
                style: TextStyle(fontSize: 16.fSize, color: Colors.grey),
              ),
              SizedBox(height: 40.h),

              // OTP Input Fields
              SizedBox(
                height: 100,
                child: Row(
                  mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                  children: List.generate(_otpLength, (index) {
                    return ValueListenableBuilder<TextEditingValue>(
                      valueListenable: _controllers[index],
                      builder: (context, value, _) {
                        final hasText = value.text.isNotEmpty;

                        return AnimatedContainer(
                          duration: const Duration(milliseconds: 200),
                          curve: Curves.easeInOut,
                          width: 70.h,
                          margin: EdgeInsets.symmetric(horizontal: 4.h),
                          decoration: RoundedRectangleBorder()
                              .toSmoothCornerDecoration(color: _isOtpComplete ? AppColors.successColor : (hasText ? AppColors.blackBgColor : AppColors.whiteColor), borderRadius: 16),
                          child: Center(
                            child: TextField(
                              controller: _controllers[index],
                              focusNode: _focusNodes[index],
                              textAlign: TextAlign.center,
                              keyboardType: TextInputType.number,
                              maxLength: 1,
                              style: TextStyle(
                                fontSize: 40.fSize,
                                fontWeight: FontWeight.bold,
                                color: AppColors.whiteColor,
                              ),
                              decoration: InputDecoration(
                                counterText: '',
                                filled: true,
                                fillColor: Colors.transparent,
                                border: OutlineInputBorder(
                                  borderRadius: BorderRadius.circular(18),
                                  borderSide: BorderSide.none,
                                ),
                              ),
                              onChanged: (v) => _onOtpChanged(index, v),
                            ),
                          ),
                        );
                      },
                    );
                  }),
                ),
              ),

              const SizedBox(height: 32),

              // Resend OTP
              Row(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  const Text("Didn't receive it? "),
                  if (_resendTime > 0)
                    Text(
                      'resend in (${_resendTime.toString().padLeft(2, '0')}:00). ',
                      style: const TextStyle(color: Colors.grey),
                    )
                  else
                    GestureDetector(
                      onTap: _resendOtp,
                      child: const Text(
                        'Resend',
                        style: TextStyle(
                          color: AppColors.primaryRedColor,
                          fontWeight: FontWeight.bold,
                        ),
                      ),
                    ),
                ],
              ),
            ],
          ),
        ),
      ),
    );
  }

  void _verifyOtp() {
    final otp = _controllers.map((c) => c.text).join();
    debugPrint('Verifying OTP: $otp');

    ScaffoldMessenger.of(context).showSnackBar(
      SnackBar(content: Text('Verifying OTP: $otp')),
    );

    Navigator.of(context).push(MaterialPageRoute(builder: (BuildContext context) => RegisterNewStep2(null, {"nationalID": "12345678654321"})));
  }

  /// Auto fill OTP into text fields
  void autoFillOtp(String otp) {
    if (otp.length != _otpLength) return;

    for (int i = 0; i < _otpLength; i++) {
      _controllers[i].text = otp[i];
    }

    // Move focus to the last field
    _focusNodes[_otpLength - 1].requestFocus();

    // Trigger completion check and color update
    _checkOtpCompletion();
  }
}