using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;
using GB5Shared.DTO.Framework.Criteria;
using GB5Shared.DTO.Framework.Login;
using GB5Shared.QueryExecutor;
using GB5Shared.Telemetry;
using RecruitmentDAL.DTO.Reports;
using RecruitmentDAL.Reports;

namespace RecruitmentBLL.Reports
{
    // HR/executive recruitment analytics rollup (Phase 5 of the Recruitment build-out plan) —
    // org-wide, no recruiter grouping: requisitions by RequisitionType/RequisitionStatus, planned
    // headcount vs. actual hires in the period, and average cost-per-hire.
    //
    // AvgCostPerHire is a deliberate v1 proxy (raw MJOBOFFER.CTC only, no recruiter/agency fees,
    // sourcing spend, or onboarding cost folded in) — see HrRecruitmentAnalyticsDTO.AvgCostPerHire's
    // doc comment. Not presented as a finance-grade figure.
    //
    // "Actual hires" reuses CandidateConversionBLL's exact structural signal for a genuine hire
    // (Terminal stage AND stage-history Outcome=Passed(2)) rather than diverging with a new
    // definition — see that class's doc comment for why Terminal alone is insufficient.
    //
    // Live transactional analytics — CacheKeyLevel.NOT_REQUIRED at the endpoint, never cached, per
    // CLAUDE.md's caching anti-pattern guidance.
    public class HrRecruitmentAnalyticsReportBLL : IHrRecruitmentAnalyticsReportBLL
    {
        private const int DEFAULT_MAX_RESULT_CAP = 500;

        private readonly IHrRecruitmentAnalyticsReportDAL _dal;

        public HrRecruitmentAnalyticsReportBLL(IHrRecruitmentAnalyticsReportDAL dal)
        {
            _dal = dal;
        }

        public async Task<PagedResult<HrRecruitmentAnalyticsDTO>> GetHrRecruitmentAnalytics(
            int firstNumber, int maxResult, CriteriaDTO criteriaDTO, LoginDTO login, CancellationToken ct)
        {
            try
            {
                GB5Trace.Step("parse-criteria-hr-recruitment-analytics", new { firstNumber, maxResult });
                var criteria = RecruitmentReportCriteriaParser.Parse(criteriaDTO);
                var cappedMaxResult = maxResult > 0 ? Math.Min(maxResult, DEFAULT_MAX_RESULT_CAP) : DEFAULT_MAX_RESULT_CAP;

                GB5Trace.Step("query-hr-recruitment-analytics", new { firstNumber, cappedMaxResult });
                return await _dal.GetHrRecruitmentAnalytics(firstNumber, cappedMaxResult, criteria, login, ct).ConfigureAwait(false);
            }
            catch (Exception ex)
            {
                GB5Trace.MarkFailed("hr-recruitment-analytics-failed", ex);
                throw;
            }
        }

        public async IAsyncEnumerable<HrRecruitmentAnalyticsDTO> GetHrRecruitmentAnalyticsStream(
            int firstNumber, int maxResult, CriteriaDTO criteriaDTO, LoginDTO login,
            [EnumeratorCancellation] CancellationToken ct)
        {
            GB5Trace.Step("stream-hr-recruitment-analytics", new { firstNumber, maxResult });
            var criteria = RecruitmentReportCriteriaParser.Parse(criteriaDTO);
            var cappedMaxResult = maxResult > 0 ? Math.Min(maxResult, DEFAULT_MAX_RESULT_CAP) : DEFAULT_MAX_RESULT_CAP;

            await foreach (var row in _dal.GetHrRecruitmentAnalyticsStream(firstNumber, cappedMaxResult, criteria, login, ct).ConfigureAwait(false))
                yield return row;
        }
    }
}