using GB5Shared.DTO.Framework.Login;
using GB5Shared.Resource.Response;
using Microsoft.Extensions.Logging;
using TCMSBLL.Interfaces;
using TCMSDAL.DTO;
using TCMSDAL.Interfaces;

namespace TCMSBLL.Implementations;

/// <summary>
/// Business logic for Defect Tracking and CAPA (Corrective/Preventive Action) workflow.
///
/// Key responsibilities:
///   1. Defect CRUD — validate mandatory fields, enforce tenant scoping via LoginDTO.
///   2. Pattern library — maintain the root-cause pattern codebook (MISSING-NEG-VALIDATION, etc.).
///   3. CAPA gap report — cross-module pattern coverage: which modules lack a test for a given defect pattern.
///   4. Auto-stub: on save, logs a warning so QC can manually create the @skip regression stub.
///              Full auto-creation deferred until ITCMSTestCaseBLL is injectable here without circular DI.
/// </summary>
public class TCMSDefectBLL : ITCMSDefectBLL
{
    private readonly ITCMSDefectDAL         _Dal;
    private readonly ILogger<TCMSDefectBLL> _Logger;

    private static readonly HashSet<string> ValidPriorities =
        new(StringComparer.OrdinalIgnoreCase) { "P1", "P2", "P3" };

    private static readonly HashSet<string> ValidStatuses =
        new(StringComparer.OrdinalIgnoreCase)
            { "Open", "InProgress", "Fixed", "Verified", "Closed" };

    public TCMSDefectBLL(
        ITCMSDefectDAL dal,
        ILogger<TCMSDefectBLL> logger)
    {
        _Dal    = dal;
        _Logger = logger;
    }

    // ── Defect pattern library ────────────────────────────────────────────────

    public async Task<IEnumerable<TCMSDefectPatternDTO>> GetDefectPatternListAsync(
        LoginDTO login, CancellationToken ct)
        => await _Dal.GetDefectPatternListAsync(login, ct).ConfigureAwait(false);

    public async Task<string> SaveDefectPatternAsync(
        TCMSDefectPatternDTO dto, LoginDTO login, CancellationToken ct)
    {
        if (string.IsNullOrWhiteSpace(dto.PatternCode))
            return "Pattern Code is required.";
        if (string.IsNullOrWhiteSpace(dto.Description))
            return "Description is required.";

        try
        {
            await _Dal.SaveDefectPatternAsync(dto, login, ct).ConfigureAwait(false);
            return dto.PatternId == 0 ? SuccessResponse.SaveSuccess : SuccessResponse.UpdateSuccess;
        }
        catch (Exception ex)
        {
            _Logger.LogError(ex, "SaveDefectPattern failed for code '{Code}'", dto.PatternCode);
            throw;
        }
    }

    // ── Defect CRUD ───────────────────────────────────────────────────────────

    public async Task<TCMSDefectDTO?> GetDefectAsync(
        int defectId, LoginDTO login, CancellationToken ct)
        => await _Dal.GetDefectAsync(defectId, login, ct).ConfigureAwait(false);

    public async Task<IEnumerable<TCMSDefectListDTO>> GetDefectListAsync(
        int? moduleId, string? status, int? patternId, LoginDTO login, CancellationToken ct)
        => await _Dal.GetDefectListAsync(moduleId, status, patternId, login, ct)
            .ConfigureAwait(false);

    /// <summary>
    /// Creates a new defect entry.
    /// After saving, logs a reminder for QC to create the @skip regression test stub manually.
    /// (Automated stub insertion is deferred — see class-level doc comment.)
    /// </summary>
    public async Task<string> SaveDefectAsync(
        TCMSDefectDTO dto, LoginDTO login, CancellationToken ct)
    {
        if (string.IsNullOrWhiteSpace(dto.Title))     return "Title is required.";
        if (dto.ModuleId == 0)                         return "Module is required.";
        if (string.IsNullOrWhiteSpace(dto.Entity))    return "Entity is required.";
        if (string.IsNullOrWhiteSpace(dto.Operation)) return "Operation is required.";
        if (string.IsNullOrWhiteSpace(dto.Priority))  return "Priority is required.";

        if (!ValidPriorities.Contains(dto.Priority))
            return $"Priority must be P1, P2, or P3.";

        try
        {
            int defectId = await _Dal.InsertDefectAsync(dto, login, ct).ConfigureAwait(false);

            _Logger.LogInformation(
                "Defect D-{Id} '{Title}' created in module {Module} by user {User}. " +
                "QC: create @skip @regression @from-defect-{Id} stub in TCMS Test Cases.",
                defectId, dto.Title, dto.ModuleId, login.UserId, defectId);

            return $"{SuccessResponse.SaveSuccessMessage} {defectId}";
        }
        catch (Exception ex)
        {
            _Logger.LogError(ex, "SaveDefect failed for '{Title}'", dto.Title);
            throw;
        }
    }

    /// <summary>
    /// Updates defect status, root-cause pattern, and linked test-case pointer.
    /// Only mutable fields after creation: Status, RootCausePatternId, RequiresRca, LinkedTestCaseId.
    /// </summary>
    public async Task<string> UpdateDefectAsync(
        TCMSDefectDTO dto, LoginDTO login, CancellationToken ct)
    {
        if (dto.DefectId == 0)                     return "DefectId is required.";
        if (string.IsNullOrWhiteSpace(dto.Title))  return "Title is required.";
        if (string.IsNullOrWhiteSpace(dto.Status)) return "Status is required.";

        if (!ValidStatuses.Contains(dto.Status))
            return $"Status must be one of: {string.Join(", ", ValidStatuses)}.";

        try
        {
            await _Dal.UpdateDefectAsync(dto, login, ct).ConfigureAwait(false);

            _Logger.LogInformation(
                "Defect D-{Id} status updated to '{Status}' by user {User}",
                dto.DefectId, dto.Status, login.UserId);

            return SuccessResponse.UpdateSuccess;
        }
        catch (Exception ex)
        {
            _Logger.LogError(ex, "UpdateDefect failed for D-{Id}", dto.DefectId);
            throw;
        }
    }

    // ── CAPA gap report ───────────────────────────────────────────────────────

    /// <summary>
    /// Returns the cross-module pattern coverage matrix:
    /// for each (defect pattern × module) pair, shows whether at least one test case
    /// covers that pattern in that module.
    /// </summary>
    public async Task<IEnumerable<TCMSCapaGapDTO>> GetCapaGapReportAsync(
        LoginDTO login, CancellationToken ct)
        => await _Dal.GetCapaGapReportAsync(login, ct).ConfigureAwait(false);
}