using System.Security.Cryptography;
using System.Text;
using GB5Shared.DTO.Framework.Login;
using GB5Shared.GenerateAutoNumber;
using GB5Shared.Resource.Response;
using KmsDAL.CustomCode.KmGap;
using KmsDAL.DTO.KmGap;

namespace KmsBLL.KmGap
{
    public class KmGapBLL : IKmGapBLL
    {
        private readonly IKmGapDAL _dal;
        private readonly AutoNumber _autoNumber;

        public KmGapBLL(IKmGapDAL dal, AutoNumber autoNumber)
        {
            _dal = dal;
            _autoNumber = autoNumber;
        }

        public async Task RecordGap(KmRecordGapDTO dto, LoginDTO login, CancellationToken ct)
        {
            dto.TenantId = login.ClientId;
            dto.CreatedById = login.UserId;

            // Hash for dedup — matches SQL: md5(lower(trim(QUERYTEXT)))
            dto.QueryHash = ComputeQueryHash(dto.QueryText);

            if (dto.BestArtifactId <= 0) dto.BestArtifactId = -1;

            // Get new ID — the MERGE will use it only on INSERT (not on UPDATE)
            var autoNum = await _autoNumber.GetNumberAsync(1, "TKMGAP", login);
            await _dal.UpsertKmGap(dto, autoNum.StartNumber, login, ct);
        }

        public async Task<string> GetKmGaps(byte gapStatus, int page, int pageSize, LoginDTO login, CancellationToken ct)
            => await _dal.GetKmGaps(gapStatus, page, pageSize, login, ct);

        public async Task<string> ResolveGap(KmResolveGapDTO dto, LoginDTO login, CancellationToken ct)
        {
            if (dto.NewStatus != 2 && dto.NewStatus != 3)
                throw new ArgumentException("NewStatus must be 2 (Resolved) or 3 (WontFix).");

            if (string.IsNullOrWhiteSpace(dto.ResolutionNotes))
                throw new ArgumentException("ResolutionNotes is required.");

            await _dal.UpdateKmGapStatus(dto, login, ct);
            return $"{SuccessResponse.UpdateSuccessMessage} — Gap resolved.";
        }

        private static string ComputeQueryHash(string query)
        {
            var normalised = query.Trim().ToLowerInvariant();
            var bytes = MD5.HashData(Encoding.UTF8.GetBytes(normalised));
            return Convert.ToHexString(bytes).ToLowerInvariant();
        }
    }
}