using GB5Shared.DTO.Framework.Login;
using GB5Shared.Telemetry;
using Microsoft.Extensions.Logging;
using Newtonsoft.Json;
using CRMSalesDAL.CustomCode.LeadAllocation;
using CRMSalesDAL.DTO.LeadAllocation;

namespace CRMSalesBLL.LeadAllocation;

/// <summary>
/// Smart Lead Allocation v1 — CAPACITY-BASED ONLY. The reference material's full vision (rep
/// skill-profile match, historical win-rate for similar segments, learning-opportunity stretch
/// assignments) depends on Team Development and Conversion Intelligence data that don't exist yet
/// in this codebase — deliberately NOT fabricated here. See
/// <see cref="SuggestAllocationAsync"/> for exactly what this v1 does instead.
/// </summary>
public class LeadAllocationBLL : ILeadAllocationBLL
{
    private readonly ILeadAllocationDAL _LeadAllocationDAL;
    private readonly ILogger<LeadAllocationBLL> _Logger;

    public LeadAllocationBLL(ILeadAllocationDAL leadAllocationDAL, ILogger<LeadAllocationBLL> logger)
    {
        _LeadAllocationDAL = leadAllocationDAL;
        _Logger = logger;
    }

    /// <summary>
    /// Capacity-based allocation suggestion for one Lead:
    /// <list type="number">
    /// <item>Queries every active sales rep's current OPEN deal count (TDEAL.Stage NOT IN
    /// (5,6) ClosedWon/ClosedLost) — reps with zero current deals are still considered, via a
    /// LEFT JOIN against the full MEMPLOYEE roster (see LeadAllocationQB.GET_REP_CAPACITY and its
    /// doc comment for the discovered, not live-verified, ISSALES/EMPLOYEESTATUS filter
    /// convention).</item>
    /// <item>Suggests the rep(s) with the LOWEST current open-deal count, ties broken by lowest
    /// RepId for determinism.</item>
    /// <item>Returns the suggestion WITHOUT auto-assigning — confirming it is a normal Deal save
    /// (setting DealDTO.RepId to the suggested rep), matching the "AI assists, human decides"
    /// principle already established this week for GEF. No Deal row is written by this method.</item>
    /// </list>
    /// Skill-match/win-rate refinement is deferred pending the Team Development and Conversion
    /// Intelligence passes described in the wider SalesMind AI plan — this method must not be
    /// extended to fabricate either signal ahead of those passes actually landing.
    /// </summary>
    public async Task<string> SuggestAllocationAsync(int leadId, LoginDTO loginDTO, CancellationToken ct)
    {
        try
        {
            GB5Trace.Step("suggest-lead-allocation", new { leadId });

            var capacities = (await _LeadAllocationDAL.GetRepCapacities(loginDTO, ct).ConfigureAwait(false)).ToList();

            if (capacities.Count == 0)
            {
                _Logger.LogWarning("SuggestAllocationAsync found no active sales reps for LeadId {LeadId}", leadId);
                throw new Exception("No active sales reps were found to suggest an allocation for this Lead.");
            }

            int minOpenDealCount = capacities.Min(c => c.OpenDealCount);
            var tiedCandidates = capacities
                .Where(c => c.OpenDealCount == minOpenDealCount)
                .OrderBy(c => c.RepId) // deterministic tie-break — lowest RepId wins
                .ToList();
            var winner = tiedCandidates[0];

            var suggestion = new LeadAllocationSuggestionDTO
            {
                LeadId = leadId,
                SuggestedRepId = winner.RepId,
                SuggestedRepCode = winner.RepCode,
                SuggestedRepName = winner.RepName,
                SuggestedRepOpenDealCount = winner.OpenDealCount,
                Candidates = tiedCandidates,
                GeneratedOn = DateTime.UtcNow
            };

            _Logger.LogInformation(
                "Lead {LeadId} allocation suggested: RepId {RepId} ({OpenDealCount} open deals, {CandidateCount} tied candidates)",
                leadId, winner.RepId, winner.OpenDealCount, tiedCandidates.Count);

            return JsonConvert.SerializeObject(suggestion);
        }
        catch (Exception ex)
        {
            GB5Trace.MarkFailed("suggest-lead-allocation-failed", ex);
            _Logger.LogError(ex, "SuggestAllocationAsync failed for LeadId {LeadId}", leadId);
            throw;
        }
    }
}