using System.Diagnostics;
using System.Globalization;
using Microsoft.Extensions.Logging;
using PowderCoating.Application.Constants;
using PowderCoating.Application.Interfaces;
using PowderCoating.Core.Entities;
using PowderCoating.Core.Interfaces;

namespace PowderCoating.Infrastructure.Services.Columbia;

/// <summary>
/// Full Columbia Coatings catalog sync: pages the API, maps each product, upserts via the shared
/// <see cref="IPowderCatalogUpsertService"/>, then reconciles discontinuations against the complete
/// pull. The discontinuation sweep runs ONLY after a successful full fetch — a partial pull (any
/// page failure throws from the client) aborts before the sweep so a transient error can never mass
/// flag the catalog as discontinued.
/// </summary>
public class ColumbiaCatalogSyncService : IColumbiaCatalogSyncService
{
    private readonly IColumbiaCoatingsApiClient _client;
    private readonly IPowderCatalogUpsertService _upsert;
    private readonly IUnitOfWork _unitOfWork;
    private readonly IPlatformSettingsService _settings;
    private readonly ILogger<ColumbiaCatalogSyncService> _logger;

    public ColumbiaCatalogSyncService(
        IColumbiaCoatingsApiClient client,
        IPowderCatalogUpsertService upsert,
        IUnitOfWork unitOfWork,
        IPlatformSettingsService settings,
        ILogger<ColumbiaCatalogSyncService> logger)
    {
        _client = client;
        _upsert = upsert;
        _unitOfWork = unitOfWork;
        _settings = settings;
        _logger = logger;
    }

    /// <inheritdoc />
    public async Task<ColumbiaSyncResult> RunSyncAsync(CancellationToken cancellationToken = default)
    {
        var result = new ColumbiaSyncResult { StartedAt = DateTime.UtcNow };
        var stopwatch = Stopwatch.StartNew();

        if (!_client.IsConfigured)
        {
            result.ErrorMessage = "Columbia API key is not configured.";
            await RecordResultAsync(result);
            return result;
        }

        try
        {
            // Full pull — throws on any page failure, which we treat as an incomplete sync.
            var products = await _client.GetAllProductsAsync(cancellationToken);
            result.TotalFetched = products.Count;

            // Map and de-duplicate by (VendorName, SKU) in case the feed repeats a SKU.
            // Exclude swatch cards and tester/sample size-variants — not standalone powder colors.
            var mapped = products
                .Where(p => !ColumbiaCatalogMapper.IsExcludedProduct(p))
                .Select(ColumbiaCatalogMapper.Map)
                .Where(m => !string.IsNullOrWhiteSpace(m.Sku))
                .GroupBy(m => $"{m.VendorName}|{m.Sku}", StringComparer.OrdinalIgnoreCase)
                .Select(g => g.First())
                .ToList();

            var upsertResult = await _upsert.UpsertAsync(mapped, result.StartedAt, cancellationToken);
            result.Inserted = upsertResult.Inserted;
            result.Updated = upsertResult.Updated;
            result.Unchanged = upsertResult.Unchanged;
            result.Skipped = upsertResult.Skipped;

            // Remove any excluded records (swatches) that were synced before the exclusion existed,
            // so they're deleted outright rather than lingering as "discontinued" powders.
            await RemoveExcludedRecordsAsync();

            // Complete pull succeeded — safe to reconcile discontinuations.
            var incomingKeys = mapped
                .Select(m => $"{m.VendorName}|{m.Sku}")
                .ToHashSet(StringComparer.OrdinalIgnoreCase);
            (result.Discontinued, result.Reactivated) =
                await ReconcileDiscontinuationsAsync(incomingKeys, result.StartedAt);

            result.Success = true;
        }
        catch (OperationCanceledException)
        {
            throw;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Columbia catalog sync failed; skipping discontinuation sweep.");
            result.Success = false;
            result.ErrorMessage = ex.Message;
        }

        stopwatch.Stop();
        result.Duration = stopwatch.Elapsed;
        await RecordResultAsync(result);
        return result;
    }

    /// <summary>
    /// Flags catalog items sourced from Columbia that were NOT in this complete pull as discontinued,
    /// and reactivates any previously-discontinued item that has reappeared. Returns (discontinued,
    /// reactivated) counts.
    /// </summary>
    private async Task<(int Discontinued, int Reactivated)> ReconcileDiscontinuationsAsync(
        HashSet<string> incomingKeys, DateTime runTimestamp)
    {
        var sourced = await _unitOfWork.PowderCatalog.FindAsync(
            p => p.Source == ColumbiaIntegrationConstants.SourceName);

        var discontinued = 0;
        var reactivated = 0;

        foreach (var item in sourced)
        {
            var present = incomingKeys.Contains($"{item.VendorName}|{item.Sku}");

            if (!present && !item.IsDiscontinued)
            {
                item.IsDiscontinued = true;
                item.UpdatedAt = runTimestamp;
                await _unitOfWork.PowderCatalog.UpdateAsync(item);
                discontinued++;
            }
            else if (present && item.IsDiscontinued)
            {
                item.IsDiscontinued = false;
                item.UpdatedAt = runTimestamp;
                await _unitOfWork.PowderCatalog.UpdateAsync(item);
                reactivated++;
            }
        }

        if (discontinued > 0 || reactivated > 0)
            await _unitOfWork.CompleteAsync();

        return (discontinued, reactivated);
    }

    /// <summary>
    /// Deletes Columbia-sourced catalog rows that should not be in the catalog (swatch cards and
    /// tester/sample size-variants). Mirrors <see cref="ColumbiaCatalogMapper.IsExcludedProduct"/>
    /// on the stored columns. A no-op once the catalog is clean; guards against records synced
    /// before the exclusion rule and ensures excluded items are removed, not flagged discontinued.
    /// </summary>
    private async Task RemoveExcludedRecordsAsync()
    {
        var excluded = (await _unitOfWork.PowderCatalog.FindAsync(p =>
            p.Source == ColumbiaIntegrationConstants.SourceName
            && (p.Sku.EndsWith("-SW")
                || p.Sku.EndsWith("-04")
                || p.ColorName.Contains("SWATCH")
                || p.ColorName.Contains("Tester")
                || p.ColorName.Contains("Sample (")))).ToList();

        if (excluded.Count == 0)
            return;

        foreach (var e in excluded)
            await _unitOfWork.PowderCatalog.DeleteAsync(e);
        await _unitOfWork.CompleteAsync();

        _logger.LogInformation("Columbia sync: removed {Count} excluded record(s) (swatch/tester/sample) from the catalog.", excluded.Count);
    }

    /// <summary>Persists the run outcome to the last-synced / last-result platform settings.</summary>
    private async Task RecordResultAsync(ColumbiaSyncResult result)
    {
        if (result.Success)
        {
            await _settings.SetAsync(
                ColumbiaIntegrationConstants.SettingLastSyncedAt,
                result.StartedAt.ToString("O", CultureInfo.InvariantCulture),
                updatedBy: "Columbia Sync");
        }

        await _settings.SetAsync(
            ColumbiaIntegrationConstants.SettingLastResult,
            result.Summary,
            updatedBy: "Columbia Sync");
    }
}