using IO.Swagger.Models.db;
using IO.Swagger.Models.RequestDto;
using IO.Swagger.Services;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.ChangeTracking;
using System;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace IO.Swagger.Repositories
{
    /// <summary>
    /// The EF implementation of this interface
    /// </summary>
    /// <seealso cref="IUserRepository" />
    public class UserRepository : IUserRepository
    {
        private readonly BankDbContext bankDbContext;

        /// <summary>
        /// Initializes a new instance of the <see cref="UserRepository"/> class.
        /// </summary>
        /// <param name="bankDbContext">The bank database context.</param>
        public UserRepository(BankDbContext bankDbContext)
        {
            this.bankDbContext = bankDbContext;
        }

        /// <inheritdoc/>
        public async Task<User> RegisterUser(AuthRegisterBody request)
        {
            request.Email = request.Email.ToLower();
            if (await bankDbContext.Users.CountAsync((User u) => u.Email == request.Email) > 0)
                return null;

            // Generate a random salt
            byte[] saltBytes = RandomNumberGenerator.GetBytes(16);
            string salt = Convert.ToBase64String(saltBytes);
            // Hash the password along with the salt
            string hashedPassword = HashPassword(salt, request.Password);

            // Create and insert the user
            User newUser = new()
            {
                PasswordHash = hashedPassword,
                Salt = salt,
                Email = request.Email,
                FirstName = request.FirstName,
                LastName = request.LastName
            };

            _ = await bankDbContext.Users.AddAsync(newUser);
            _ = await bankDbContext.SaveChangesAsync();
            return newUser;
        }

        /// <inheritdoc/>
        public async Task<User> LoginUser(AuthLoginBody request)
        {
            request.Email = request.Email.ToLower();
            User user = await bankDbContext.Users.FirstOrDefaultAsync(u => u.Email.Equals(request.Email));
            if (user == null)
                return null;

            string hashedPassword = HashPassword(user.Salt, request.Password);
            return hashedPassword != user.PasswordHash ? null : user;
        }

        /// <inheritdoc/>
        public async Task<User> RetrieveUser(int userId)
        {
            return await bankDbContext.Users.FirstOrDefaultAsync(u => u.Id == userId);
        }

        /// <summary>
        /// Hashes the password.
        /// </summary>
        /// <param name="salt">The salt to apply.</param>
        /// <param name="password">The password to hash.</param>
        /// <returns>The hashed and salted password</returns>
        private static string HashPassword(string salt, string password)
        {
            string saltedPassword = password + salt;
            byte[] passwordBytes = Encoding.UTF8.GetBytes(saltedPassword);
            byte[] hashedBytes = SHA256.HashData(passwordBytes);
            string hashedPassword = Convert.ToBase64String(hashedBytes);
            return hashedPassword;
        }
    }
}