using System;
using System.ComponentModel.DataAnnotations;
using System.Threading;
using System.Threading.Tasks;
using GB5Shared.DaprCache;
using GB5Shared.DTO.Framework.AutoNumber;
using GB5Shared.DTO.Framework.Login;
using GB5Shared.EntityHandler;
using GB5Shared.GenerateAutoNumber;
using GB5Shared.Resource.Response;
using GB5Shared.Telemetry;
using GB5Shared.Validation;
using Microsoft.Extensions.Logging;
using RecruitmentDAL.CustomeCode.CandidateDemographic;
using RecruitmentDAL.DTO.CandidateDemographic;
using static GB5Shared.GB5Constant.Constant;

namespace RecruitmentBLL.CandidateDemographic
{
    // See ICandidateDemographicBLL for why there is no GetCandidateDemographic(int) method on
    // this BLL — the individual-record read path is deliberately omitted for this table.
    public class CandidateDemographicBLL : ICandidateDemographicBLL
    {
        private readonly ICandidateDemographicDAL _CandidateDemographicDAL;
        private readonly AutoNumber _AutoNumber;
        private readonly IValidation _Validation;
        private readonly KeyInvalidate _KeyInvalidate;
        private readonly BaseEntityAppService<CandidateDemographicDTO> _BaseEntityAppService;
        private readonly ILogger<CandidateDemographicBLL> _Logger;

        public CandidateDemographicBLL(
            ICandidateDemographicDAL candidateDemographicDAL,
            AutoNumber autoNumber,
            IValidation validation,
            KeyInvalidate keyInvalidate,
            BaseEntityAppService<CandidateDemographicDTO> baseEntityAppService,
            ILogger<CandidateDemographicBLL> logger)
        {
            _CandidateDemographicDAL = candidateDemographicDAL;
            _AutoNumber = autoNumber;
            _Validation = validation;
            _KeyInvalidate = keyInvalidate;
            _BaseEntityAppService = baseEntityAppService;
            _Logger = logger;
        }

        // ── Upsert-by-CandidateId, with the load-bearing consent guard for this whole feature ──
        //
        // DESIGN DECISION (per task requirement — documented here, not just at the FLS bridge call
        // site, so it holds even if a future caller invokes this BLL method directly instead of
        // going through RecruitmentFlsBridgeBLL's VoluntarySelfId handler):
        //
        // When dto.ConsentToCollect is anything other than an explicit `true` on input, this
        // method does NOT refuse the write outright. Instead it still upserts a row, but forces
        // ConsentToCollect=false and scrubs every demographic data field (GenderIdentity,
        // EthnicityRace, DisabilityStatus, VeteranStatus, AgeBand) to null before persisting —
        // i.e. a clean "asked, declined" record. Two reasons this was chosen over "don't write
        // anything at all":
        //   1. Compliance/audit value — affirmative-action-style recordkeeping (e.g. US OFCCP
        //      Section 503/VEVRAA-style self-ID programs) typically wants evidence that the
        //      invitation to self-identify was actually made and that a decline was honored, not
        //      silence indistinguishable from "never asked".
        //   2. It matches the migration's own header comment: "a candidate can decline without
        //      the system inferring anything from a blank field" — the schema already anticipates
        //      a stored declined-with-nulls row (NULL="never asked" is preserved as a distinct
        //      state from a row that exists with ConsentToCollect=0 and every field null).
        // Under no circumstances does this method persist a populated demographic field unless
        // ConsentToCollect=true was explicitly supplied in the same call — that check happens
        // BEFORE any field is read into the row.
        public async Task<string> SaveCandidateDemographic(CandidateDemographicDTO CandidateDemographicDTO, LoginDTO LoginDTO, CancellationToken ct)
        {
            if (CandidateDemographicDTO == null)
                throw new ArgumentNullException(nameof(CandidateDemographicDTO));

            AutoNumberDTO? autoNumberDTO = null;

            try
            {
                GB5Trace.Step("validate-candidatedemographic", new { CandidateDemographicDTO.CandidateId });

                if (CandidateDemographicDTO.CandidateId <= 0)
                    throw new ValidationException("CandidateId is required to save a CandidateDemographic row.");

                // ── Consent guard — see method doc comment. Runs unconditionally, before any
                //    lookup/insert/update, so it can never be bypassed by a caller that only
                //    partially fills the DTO. ──
                if (CandidateDemographicDTO.ConsentToCollect != true)
                {
                    CandidateDemographicDTO.ConsentToCollect = false;
                    CandidateDemographicDTO.GenderIdentity = null;
                    CandidateDemographicDTO.EthnicityRace = null;
                    CandidateDemographicDTO.DisabilityStatus = null;
                    CandidateDemographicDTO.VeteranStatus = null;
                    CandidateDemographicDTO.AgeBand = null;
                }

                CandidateDemographicDTO.TenantId = LoginDTO.ClientId;
                CandidateDemographicDTO.ModifiedById = LoginDTO.UserId;
                CandidateDemographicDTO.ModifiedOn = DateTime.UtcNow;
                CandidateDemographicDTO.CollectedOn = DateTime.UtcNow;

                // ── Upsert-by-CandidateId — this table is one row per Candidate (UNIQUE
                //    constraint), so every save first resolves whether an active row already
                //    exists rather than trusting an incoming CandidateDemographicId. ──
                var existing = await _CandidateDemographicDAL
                    .GetByCandidateId(CandidateDemographicDTO.CandidateId, LoginDTO, ct)
                    .ConfigureAwait(false);

                bool isNew = existing == null;
                if (isNew)
                {
                    autoNumberDTO = await _AutoNumber.GetNumberAsync(
                        1, "CANDIDATEDEMOGRAPHIC", LoginDTO).ConfigureAwait(false);

                    CandidateDemographicDTO.CandidateDemographicId = autoNumberDTO.StartNumber;
                    CandidateDemographicDTO.CreatedById = LoginDTO.UserId;
                    CandidateDemographicDTO.CreatedOn = DateTime.UtcNow;
                }
                else
                {
                    CandidateDemographicDTO.CandidateDemographicId = existing!.CandidateDemographicId;
                    CandidateDemographicDTO.CreatedById = existing.CreatedById;
                    CandidateDemographicDTO.CreatedOn = existing.CreatedOn;
                }

                GB5Trace.Step("save-candidatedemographic", new { CandidateDemographicDTO.CandidateId, isNew, CandidateDemographicDTO.ConsentToCollect });

                await _BaseEntityAppService.ExecuteSaveAsync(
                    EntityConstant.OBJECTRECRUITMENTCANDIDATEDEMOGRAPHIC,
                    isNew
                        ? EventTypeConstant.SAVERECRUITMENTCANDIDATEDEMOGRAPHICEVENTTYPEID
                        : EventTypeConstant.UPDATERECRUITMENTCANDIDATEDEMOGRAPHICEVENTTYPEID,
                    CandidateDemographicDTO,
                    LoginDTO,
                    async tx =>
                    {
                        _ = isNew
                            ? await _CandidateDemographicDAL.SaveCandidateDemographic(CandidateDemographicDTO, LoginDTO, tx, ct).ConfigureAwait(false)
                            : await _CandidateDemographicDAL.UpdateCandidateDemographic(CandidateDemographicDTO, LoginDTO, tx, ct).ConfigureAwait(false);
                        return CandidateDemographicDTO.CandidateDemographicId;
                    },
                    null, -1, -1, null, isNew).ConfigureAwait(false);

                GB5Trace.Step("event-publish", new
                {
                    EventTypeId = isNew
                        ? EventTypeConstant.SAVERECRUITMENTCANDIDATEDEMOGRAPHICEVENTTYPEID
                        : EventTypeConstant.UPDATERECRUITMENTCANDIDATEDEMOGRAPHICEVENTTYPEID
                });

                var cacheKey = new CacheKeyGeneration().KeyGeneration(
                    CandidateDemographicDTO.CandidateDemographicId,
                    EntityConstant.OBJECTRECRUITMENTCANDIDATEDEMOGRAPHIC,
                    CacheKeyLevel.CLIENT_LEVEL,
                    LoginDTO);

                await _KeyInvalidate.AllInvalidateCache(cacheKey).ConfigureAwait(false);

                // Never log any actual demographic field value (GenderIdentity/EthnicityRace/
                // DisabilityStatus/VeteranStatus/AgeBand) — only ids and the consent flag.
                _Logger.LogInformation(
                    "CandidateDemographic {CandidateDemographicId} for Candidate {CandidateId} {Action} by user {UserId} (ConsentToCollect={ConsentToCollect})",
                    CandidateDemographicDTO.CandidateDemographicId, CandidateDemographicDTO.CandidateId,
                    isNew ? "saved" : "updated", LoginDTO.UserId, CandidateDemographicDTO.ConsentToCollect);

                return isNew
                    ? $"{SuccessResponse.SaveSuccessMessage} {CandidateDemographicDTO.CandidateDemographicId}"
                    : SuccessResponse.UpdateSuccess;
            }
            catch (ValidationException vex)
            {
                GB5Trace.MarkFailed("save-candidatedemographic-failed", vex);
                if (autoNumberDTO != null && CandidateDemographicDTO.CandidateDemographicId > 0)
                    await _AutoNumber.RollbackAutoNumber("CANDIDATEDEMOGRAPHIC", CandidateDemographicDTO.CandidateDemographicId, LoginDTO).ConfigureAwait(false);

                throw new Exception(vex.Message);
            }
            catch (Exception ex)
            {
                GB5Trace.MarkFailed("save-candidatedemographic-failed", ex);
                _Logger.LogError(ex, "SaveCandidateDemographic failed for CandidateId {CandidateId}", CandidateDemographicDTO.CandidateId);

                if (autoNumberDTO != null && CandidateDemographicDTO.CandidateDemographicId > 0)
                {
                    await _AutoNumber.RollbackAutoNumber(
                        "CANDIDATEDEMOGRAPHIC",
                        CandidateDemographicDTO.CandidateDemographicId,
                        LoginDTO).ConfigureAwait(false);
                }
                throw;
            }
        }

        public async Task<string> DeleteCandidateDemographic(int CandidateDemographicId, LoginDTO LoginDTO, CancellationToken ct)
        {
            try
            {
                GB5Trace.Step("delete-candidatedemographic", new { CandidateDemographicId });

                var result = await _CandidateDemographicDAL.DeleteCandidateDemographic(CandidateDemographicId, LoginDTO, ct)
                    .ConfigureAwait(false);

                var cacheKey = new CacheKeyGeneration().KeyGeneration(
                    CandidateDemographicId,
                    EntityConstant.OBJECTRECRUITMENTCANDIDATEDEMOGRAPHIC,
                    CacheKeyLevel.CLIENT_LEVEL,
                    LoginDTO);

                await _KeyInvalidate.AllInvalidateCache(cacheKey).ConfigureAwait(false);

                _Logger.LogInformation("CandidateDemographic {CandidateDemographicId} deleted by user {UserId}", CandidateDemographicId, LoginDTO.UserId);

                return result;
            }
            catch (Exception ex)
            {
                GB5Trace.MarkFailed("delete-candidatedemographic-failed", ex);
                _Logger.LogError(ex, "DeleteCandidateDemographic failed for CandidateDemographicId {CandidateDemographicId}", CandidateDemographicId);
                throw;
            }
        }
    }
}