using System;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Blazored.LocalStorage;
using FrontOffice.BFF.User.Protobuf.Protos.User;
using FrontOffice.Main.Utilities;
using Grpc.Core;
using Microsoft.AspNetCore.Components;
using Microsoft.AspNetCore.WebUtilities;
using MudBlazor;

namespace FrontOffice.Main.Pages.Auth;

public partial class Verify : IDisposable
{
    private const int DefaultResendCooldown = 120;
    public const int MaxVerificationAttempts = 5;
    private const string OtpPurpose = "Login";
    private const string PhoneStorageKey = "auth:phone-number";
    private const string RedirectStorageKey = "auth:redirect";
    private const string TokenStorageKey = "auth:token";

    private readonly OtpInputModel _model = new();
    private MudForm? _form;
    private bool _isBusy;
    private string? _phoneNumber;
    private string? _redirect;
    private string? _errorMessage;
    private string? _infoMessage;
    private Timer? _resendTimer;
    private int _resendRemaining;
    private int _attemptsLeft = MaxVerificationAttempts;
    private CancellationTokenSource? _operationCts;

    [Inject] private ILocalStorageService LocalStorage { get; set; } = default!;
    [Inject] private UserContract.UserContractClient UserClient { get; set; } = default!;

    private bool IsVerificationLocked => _attemptsLeft <= 0;

    protected override async Task OnInitializedAsync()
    {
        var uri = Navigation.ToAbsoluteUri(Navigation.Uri);
        var query = QueryHelpers.ParseQuery(uri.Query);
        if (query.TryGetValue("redirect", out var redirectValues))
        {
            _redirect = redirectValues.LastOrDefault();
        }

        if (query.TryGetValue("phone", out var phoneValues))
        {
            _phoneNumber = phoneValues.LastOrDefault();
        }

        if (string.IsNullOrWhiteSpace(_phoneNumber))
        {
            _phoneNumber = await LocalStorage.GetItemAsync<string>(PhoneStorageKey);
        }

        if (string.IsNullOrWhiteSpace(_phoneNumber))
        {
            NavigateBackToPhone();
            return;
        }

        await LocalStorage.SetItemAsync(PhoneStorageKey, _phoneNumber);

        if (string.IsNullOrWhiteSpace(_redirect))
        {
            var storedRedirect = await LocalStorage.GetItemAsync<string>(RedirectStorageKey);
            if (!string.IsNullOrWhiteSpace(storedRedirect))
            {
                _redirect = storedRedirect;
            }
        }

        StartResendCountdown();
    }

    private async Task VerifyOtpAsync()
    {
        _errorMessage = null;
        _infoMessage = null;

        if (_form is null)
        {
            return;
        }

        await _form.Validate();
        if (!_form.IsValid)
        {
            return;
        }

        if (IsVerificationLocked)
        {
            _errorMessage = "???????? ???? ?? ????? ????? ???. ????? ??? ???? ?????? ????.";
            return;
        }

        if (string.IsNullOrWhiteSpace(_phoneNumber))
        {
            NavigateBackToPhone();
            return;
        }

        _isBusy = true;
        var cancellationToken = PrepareOperationToken();

        try
        {
            var request = new VerifyOtpTokenRequest
            {
                Mobile = _phoneNumber,
                Purpose = OtpPurpose,
                Code = _model.Code
            };

            var response = await UserClient.VerifyOtpTokenAsync(request, cancellationToken: cancellationToken);
            if (response is null)
            {
                _errorMessage = "????? ??? ???? ????? ???. ????? ?????? ???? ????.";
                return;
            }

            if (response.Success)
            {
                if (!string.IsNullOrWhiteSpace(response.Token))
                {
                    await LocalStorage.SetItemAsync(TokenStorageKey, response.Token);
                }

                await LocalStorage.RemoveItemAsync(PhoneStorageKey);
                await LocalStorage.RemoveItemAsync(RedirectStorageKey);

                _attemptsLeft = MaxVerificationAttempts;
                _model.Code = string.Empty;

                var target = !string.IsNullOrWhiteSpace(_redirect) ? _redirect : RouteConstants.Main.MainPage;
                if (!string.IsNullOrWhiteSpace(target))
                {
                    Navigation.NavigateTo(target, forceLoad: true);
                }
                return;
            }

            RegisterFailedAttempt(string.IsNullOrWhiteSpace(response.Message) ? "?? ?????? ???." : response.Message);
        }
        catch (RpcException rpcEx)
        {
            HandleVerificationFailure(rpcEx);
        }
        catch (OperationCanceledException)
        {
        }
        catch (Exception ex)
        {
            _errorMessage = ex.Message;
        }
        finally
        {
            _isBusy = false;
            ClearOperationToken();
            await InvokeAsync(StateHasChanged);
        }
    }

    private void HandleVerificationFailure(RpcException rpcEx)
    {
        switch (rpcEx.Status.StatusCode)
        {
            case StatusCode.PermissionDenied:
            case StatusCode.InvalidArgument:
            case StatusCode.Unauthenticated:
                RegisterFailedAttempt(!string.IsNullOrWhiteSpace(rpcEx.Status.Detail)
                    ? rpcEx.Status.Detail
                    : "?? ?????? ???.");
                break;
            case StatusCode.DeadlineExceeded:
            case StatusCode.NotFound:
                _errorMessage = "?? ????? ??? ???. ????? ??? ???? ?????? ????.";
                break;
            default:
                _errorMessage = !string.IsNullOrWhiteSpace(rpcEx.Status.Detail)
                    ? rpcEx.Status.Detail
                    : "????? ??? ???? ????? ???. ????? ?????? ???? ????.";
                break;
        }
    }

    private void RegisterFailedAttempt(string baseMessage)
    {
        _attemptsLeft = Math.Max(0, _attemptsLeft - 1);

        if (_attemptsLeft > 0)
        {
            _errorMessage = $"{baseMessage} {_attemptsLeft} ???? ???? ????? ???.";
        }
        else
        {
            _errorMessage = $"{baseMessage} ???????? ???? ??? ?? ????? ????? ???. ????? ??? ???? ?????? ????.";
        }
    }

    private async Task ResendOtpAsync()
    {
        if (_resendRemaining > 0 || _isBusy || string.IsNullOrWhiteSpace(_phoneNumber))
        {
            return;
        }

        _errorMessage = null;
        _infoMessage = null;
        _isBusy = true;
        var cancellationToken = PrepareOperationToken();

        try
        {
            var request = new CreateNewOtpTokenRequest
            {
                Mobile = _phoneNumber,
                Purpose = OtpPurpose
            };

            var response = await UserClient.CreateNewOtpTokenAsync(request, cancellationToken: cancellationToken);
            if (response?.Success != true)
            {
                _errorMessage = string.IsNullOrWhiteSpace(response?.Message)
                    ? "????? ???? ??? ???? ?? ??? ????? ??."
                    : response!.Message;
                return;
            }

            _infoMessage = string.IsNullOrWhiteSpace(response.Message)
                ? "?? ???? ????? ??."
                : response.Message;

            _attemptsLeft = MaxVerificationAttempts;
            _model.Code = string.Empty;
            StartResendCountdown();
        }
        catch (RpcException rpcEx)
        {
            _errorMessage = !string.IsNullOrWhiteSpace(rpcEx.Status.Detail)
                ? rpcEx.Status.Detail
                : "????? ???? ??? ???? ?? ??? ????? ??.";
        }
        catch (OperationCanceledException)
        {
        }
        catch (Exception ex)
        {
            _errorMessage = ex.Message;
        }
        finally
        {
            _isBusy = false;
            ClearOperationToken();
            await InvokeAsync(StateHasChanged);
        }
    }

    private async Task ChangePhoneAsync()
    {
        await LocalStorage.RemoveItemAsync(PhoneStorageKey);
        NavigateBackToPhone();
    }

    private void NavigateBackToPhone()
    {
        var target = "/auth/phone";
        if (!string.IsNullOrWhiteSpace(_redirect))
        {
            target += "?redirect=" + Uri.EscapeDataString(_redirect);
        }

        Navigation.NavigateTo(target, forceLoad: false);
    }

    private void StartResendCountdown(int seconds = DefaultResendCooldown)
    {
        _resendRemaining = seconds;
        _resendTimer?.Dispose();
        _resendTimer = new Timer(_ =>
        {
            var remaining = Interlocked.Add(ref _resendRemaining, -1);
            if (remaining <= 0)
            {
                Interlocked.Exchange(ref _resendRemaining, 0);
                _resendTimer?.Dispose();
                _resendTimer = null;
            }

            _ = InvokeAsync(StateHasChanged);
        }, null, 1000, 1000);
    }

    private CancellationToken PrepareOperationToken()
    {
        _operationCts?.Cancel();
        _operationCts?.Dispose();
        _operationCts = new CancellationTokenSource();
        return _operationCts.Token;
    }

    private void ClearOperationToken()
    {
        _operationCts?.Dispose();
        _operationCts = null;
    }

    public void Dispose()
    {
        _operationCts?.Cancel();
        _operationCts?.Dispose();
        _operationCts = null;

        _resendTimer?.Dispose();
        _resendTimer = null;
    }

    private sealed class OtpInputModel
    {
        [Required(ErrorMessage = "???? ???? ??? ???? ?????? ???.")]
        [RegularExpression(@"^\\d{5,6}$", ErrorMessage = "??? ???? ???? ? ?? ? ??? ????.")]
        public string Code { get; set; } = string.Empty;
    }
}