using System;
using System.Collections.Generic;
using System.Globalization;
using System.Security.Cryptography;
using System.Text;

namespace SyncEngine.Sync
{
    public static class ChangeDetector
    {
        public static string ComputeRowHash(IEnumerable<object> values)
        {
            var sb = new StringBuilder();
            foreach (var value in values)
            {
                sb.Append(Normalize(value));
                sb.Append('|');
            }

            using (var sha = SHA256.Create())
            {
                var bytes = sha.ComputeHash(Encoding.UTF8.GetBytes(sb.ToString()));
                var hex = new StringBuilder(bytes.Length * 2);
                foreach (var b in bytes)
                {
                    hex.Append(b.ToString("x2"));
                }

                return hex.ToString();
            }
        }

        public static string Normalize(object value)
        {
            if (value == null || value == DBNull.Value)
            {
                return string.Empty;
            }

            if (value is DateTime dt)
            {
                return dt.ToUniversalTime().ToString("O");
            }

            if (value is bool b)
            {
                return b ? "1" : "0";
            }

            if (value is byte[] bytes)
            {
                return Convert.ToBase64String(bytes);
            }

            if (value is IFormattable formattable)
            {
                return formattable.ToString(null, CultureInfo.InvariantCulture).Trim();
            }

            return Convert.ToString(value, CultureInfo.InvariantCulture).Trim();
        }
    }
}