using System;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Identity;
using Bit.Core.Models.Table;
using Bit.Core.Enums;
using Bit.Core.Services;
using Microsoft.Extensions.DependencyInjection;
using Bit.Core.Models;

namespace Bit.Core.Identity
{
    public class EmailTokenProvider : IUserTwoFactorTokenProvider<User>
    {
        private readonly IServiceProvider _serviceProvider;

        public EmailTokenProvider(IServiceProvider serviceProvider)
        {
            _serviceProvider = serviceProvider;
        }

        public async Task<bool> CanGenerateTwoFactorTokenAsync(UserManager<User> manager, User user)
        {
            var provider = user.GetTwoFactorProvider(TwoFactorProviderType.Email);
            if (!HasProperMetaData(provider))
            {
                return false;
            }

            return await _serviceProvider.GetRequiredService<IUserService>().
                TwoFactorProviderIsEnabledAsync(TwoFactorProviderType.Email, user);
        }

        public Task<string> GenerateAsync(string purpose, UserManager<User> manager, User user)
        {
            var provider = user.GetTwoFactorProvider(TwoFactorProviderType.Email);
            if (!HasProperMetaData(provider))
            {
                return null;
            }

            return Task.FromResult(RedactEmail((string)provider.MetaData["Email"]));
        }

        public Task<bool> ValidateAsync(string purpose, string token, UserManager<User> manager, User user)
        {
            return _serviceProvider.GetRequiredService<IUserService>().VerifyTwoFactorEmailAsync(user, token);
        }

        private bool HasProperMetaData(TwoFactorProvider provider)
        {
            return provider?.MetaData != null && provider.MetaData.ContainsKey("Email") &&
                !string.IsNullOrWhiteSpace((string)provider.MetaData["Email"]);
        }

        private static string RedactEmail(string email)
        {
            var emailParts = email.Split('@');

            string shownPart = null;
            if (emailParts[0].Length > 2 && emailParts[0].Length <= 4)
            {
                shownPart = emailParts[0].Substring(0, 1);
            }
            else if (emailParts[0].Length > 4)
            {
                shownPart = emailParts[0].Substring(0, 2);
            }
            else
            {
                shownPart = string.Empty;
            }

            string redactedPart = null;
            if (emailParts[0].Length > 4)
            {
                redactedPart = new string('*', emailParts[0].Length - 2);
            }
            else
            {
                redactedPart = new string('*', emailParts[0].Length - shownPart.Length);
            }

            return $"{shownPart}{redactedPart}@{emailParts[1]}";
        }
    }
}
