using GB5Shared.DTO.Framework.Login;
using MMDAL.CustomCode.InspectionParamSetEngine;
using MMDAL.DTO.InspectionParamSetOverride;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace MMBLL.InspectionParamSetEngine
{
    // ─────────────────────────────────────────────────────────────────────────
    //  InspectionParamSetEngineBLL
    //
    //  Stateless resolution algorithm over MINSPECTIONTYPEPARAMETERSET:
    //    1. Fetch all rows whose wildcarded (PartyId, ItemId) key matches the
    //       context, for the given (always-concrete) InspectionTypeId.
    //    2. Keep only the max-specificity tier — return ALL ParameterSets in
    //       that tier (a tier can legitimately carry more than one, same
    //       many-to-many shape the default tier already allows today).
    //       Specificity > 0 => Source "Override"; == 0 => "InspectionTypeDefault".
    //    3. If literally no rows exist for that InspectionTypeId at all, fall
    //       back to Item.QualityParameterSetId (today's actual ultimate
    //       fallback via foundry.ItemParamter.Picklist on the FE).
    //
    //  No transactions — read-only resolution.
    // ─────────────────────────────────────────────────────────────────────────
    public class InspectionParamSetEngineBLL : IInspectionParamSetEngineBLL
    {
        private readonly IInspectionParamSetEngineDAL _EngineDAL;

        public InspectionParamSetEngineBLL(IInspectionParamSetEngineDAL engineDAL)
        {
            _EngineDAL = engineDAL;
        }

        public async Task<IEnumerable<ResolvedParameterSetDTO>> ResolveEffectiveParameterSetsAsync(
            InspectionParamSetResolveContextDTO context, LoginDTO loginDTO, CancellationToken ct)
        {
            try
            {
                var asOfDate = context.AsOfDate ?? DateTime.UtcNow;

                var candidates = (await _EngineDAL.GetMatchingRulesAsync(
                    context.PartyId, context.ItemId, context.InspectionTypeId, asOfDate, loginDTO, ct)
                    .ConfigureAwait(false)).ToList();

                if (candidates.Count > 0)
                {
                    int maxSpecificity = candidates.Max(c => c.MatchedSpecificity);
                    var source = maxSpecificity > 0 ? "Override" : "InspectionTypeDefault";

                    return candidates
                        .Where(c => c.MatchedSpecificity == maxSpecificity)
                        .Select(c => new ResolvedParameterSetDTO
                        {
                            ParameterSetId     = c.ParameterSetId,
                            ParameterSetCode   = c.ParameterSetCode,
                            ParameterSetName   = c.ParameterSetName,
                            IsRequired         = c.IsRequired,
                            SlNo               = c.SlNo,
                            MatchedSpecificity = c.MatchedSpecificity,
                            Source             = source
                        })
                        .ToList();
                }

                // No rows at all for this InspectionTypeId — ultimate fallback.
                var itemDefault = await _EngineDAL
                    .GetItemQualityParameterSetDefaultAsync(context.ItemId, loginDTO, ct)
                    .ConfigureAwait(false);

                if (itemDefault == null)
                    return Enumerable.Empty<ResolvedParameterSetDTO>();

                itemDefault.Source = "ItemQualityParameterSetDefault";
                itemDefault.IsRequired = true;
                return new[] { itemDefault };
            }
            catch (Exception)
            {
                throw;
            }
        }
    }
}