using AutoMapper;
using IdentityServer.Domain.Entities;
using IdentityServer.Domain.Models;
using Newtonsoft.Json;
using System;
using System.Text;
using System.Text.RegularExpressions;

namespace IdentityServer.Application.Services
{
    internal class TokenService : ITokenService
    {
        private readonly IMapper _mapper;

        public TokenService(IMapper mapper)
        {
            _mapper = mapper;
        }

        public string GenerateTokenRaw(AppUser user)
        {
            var tokenCore = GenerateToken(user);
            var tokenCoreString = JsonConvert.SerializeObject(tokenCore);
            var tokenCoreBytes = Encoding.UTF8.GetBytes(tokenCoreString);
            var tokenRaw = Convert.ToBase64String(tokenCoreBytes);
            return tokenRaw;
        }

        private TokenCore GenerateToken(AppUser user)
        {
            var tokenCore = _mapper.Map<TokenCore>(user);
            tokenCore.LockStamp = Regex.Replace(Convert.ToBase64String(Guid.NewGuid().ToByteArray()), "[/+=]", "");
            return tokenCore;
        }

        public TokenCore ExtractTokenCore(string tokenRaw)
        {
            var valid = ValidateTokenRaw(tokenRaw);
            if (!valid)
                return null;

            var tokenCoreBytes = Convert.FromBase64String(tokenRaw);
            var tokenCoreString = Encoding.UTF8.GetString(tokenCoreBytes);
            var tokenCore = JsonConvert.DeserializeObject<TokenCore>(tokenCoreString);
            return tokenCore;
        }

        private bool ValidateTokenRaw(string tokenRaw)
        {
            if (string.IsNullOrWhiteSpace(tokenRaw))
                return false;

            if (!StringIsBase64(tokenRaw))
                return false;

            return true;
        }

        private bool StringIsBase64(string str)
        {
            str = str.Trim();
            return (str.Length % 4 == 0) && Regex.IsMatch(str, @"^[a-zA-Z0-9+/]*={0,3}$", RegexOptions.None);
        }
    }
}