using IdentityServer.Application.Services.Abstractions;
using System;
using System.Security.Authentication;
using System.Security.Cryptography;

namespace IdentityServer.Application.Services
{
    internal class HashingService : IHashingService
    {
        public string HashMd5(string text) => Hash(text, HashAlgorithmType.Md5);
        public string HashSha1(string text) => Hash(text, HashAlgorithmType.Sha1);
        public string HashSha256(string text) => Hash(text, HashAlgorithmType.Sha256);
        public string HashSha384(string text) => Hash(text, HashAlgorithmType.Sha384);
        public string HashSha512(string text) => Hash(text, HashAlgorithmType.Sha512);

        private string Hash(string text, HashAlgorithmType algorithm)
        {
            if (string.IsNullOrEmpty(text))
                throw new ArgumentException("Cannot hash null value.", nameof(text));

            using (var sha = GetHashAlgorithm(algorithm))
            {
                byte[] textData = System.Text.Encoding.UTF8.GetBytes(text);
                byte[] hash = sha.ComputeHash(textData);

                var str = BitConverter.ToString(hash);

                return str.Replace("-", String.Empty);
            }
        }

        private HashAlgorithm GetHashAlgorithm(HashAlgorithmType algorithmType)
        {
            switch (algorithmType)
            {
                case HashAlgorithmType.None:
                    throw new ArgumentException("Do not use this method with HashAlgorithmType.None.", nameof(algorithmType));

                case HashAlgorithmType.Md5:
                    return MD5.Create();

                case HashAlgorithmType.Sha1:
                    return SHA1.Create();

                case HashAlgorithmType.Sha256:
                    return SHA256.Create();

                case HashAlgorithmType.Sha384:
                    return SHA384.Create();

                case HashAlgorithmType.Sha512:
                    return SHA512.Create();

                default:
                    throw new NotImplementedException($"HashAlgorithmType {algorithmType} is not implemented.");
            }
        }
    }
}