using Microsoft.Extensions.Logging;
using PowderCoating.Application.Interfaces;
using PowderCoating.Core.Entities;
using PowderCoating.Core.Interfaces;

namespace PowderCoating.Infrastructure.Services;

/// <summary>
/// Single upsert path for the platform <see cref="PowderCatalogItem"/> master list, shared by the
/// JSON file import and the Columbia API sync. Match key is (VendorName, SKU), case-insensitive.
/// </summary>
public class PowderCatalogUpsertService : IPowderCatalogUpsertService
{
    private readonly IUnitOfWork _unitOfWork;
    private readonly ILogger<PowderCatalogUpsertService> _logger;

    public PowderCatalogUpsertService(IUnitOfWork unitOfWork, ILogger<PowderCatalogUpsertService> logger)
    {
        _unitOfWork = unitOfWork;
        _logger = logger;
    }

    /// <inheritdoc />
    public async Task<PowderCatalogUpsertResult> UpsertAsync(
        IReadOnlyList<PowderCatalogItem> incoming,
        DateTime runTimestamp,
        CancellationToken cancellationToken = default)
    {
        var result = new PowderCatalogUpsertResult();

        // Load existing rows for just the vendors we're touching, keyed by (vendor|sku) lower-cased.
        var vendorNames = incoming
            .Select(i => i.VendorName)
            .Where(v => !string.IsNullOrWhiteSpace(v))
            .Distinct(StringComparer.OrdinalIgnoreCase)
            .ToList();

        var existing = (await _unitOfWork.PowderCatalog.FindAsync(p => vendorNames.Contains(p.VendorName)))
            .ToDictionary(KeyOf, StringComparer.OrdinalIgnoreCase);

        var toAdd = new List<PowderCatalogItem>();

        foreach (var item in incoming)
        {
            if (string.IsNullOrWhiteSpace(item.Sku) || string.IsNullOrWhiteSpace(item.ColorName))
            {
                result.Skipped++;
                continue;
            }

            if (existing.TryGetValue(KeyOf(item), out var record))
            {
                if (ApplyFeedFields(record, item))
                {
                    record.UpdatedAt = runTimestamp;
                    record.LastSyncedAt = runTimestamp;
                    await _unitOfWork.PowderCatalog.UpdateAsync(record);
                    result.Updated++;
                }
                else
                {
                    result.Unchanged++;
                }
            }
            else
            {
                item.CreatedAt = runTimestamp;
                item.LastSyncedAt = runTimestamp;
                toAdd.Add(item);
                result.Inserted++;
            }
        }

        if (toAdd.Count > 0)
            await _unitOfWork.PowderCatalog.AddRangeAsync(toAdd);

        await _unitOfWork.CompleteAsync();

        // Push current catalog price + product data down to any tenant inventory linked to these
        // catalog rows, so quotes reflect the current price.
        var propagated = await PropagateToLinkedInventoryAsync();

        _logger.LogInformation(
            "Powder catalog upsert: {Inserted} inserted, {Updated} updated, {Unchanged} unchanged, {Skipped} skipped; {Propagated} linked inventory item(s) refreshed.",
            result.Inserted, result.Updated, result.Unchanged, result.Skipped, propagated);

        return result;
    }

    /// <summary>
    /// Keeps tenant inventory in step with the catalog (across all companies): first self-heals by
    /// linking any unlinked item to its catalog row by identity, then refreshes every linked item
    /// with the catalog's current price and product data. Returns the number of items touched.
    /// </summary>
    public async Task<int> PropagateToLinkedInventoryAsync()
    {
        var linkedCount = await LinkUnlinkedInventoryAsync();
        var refreshedCount = await RefreshLinkedInventoryAsync();
        return linkedCount + refreshedCount;
    }

    /// <summary>
    /// Self-heals the catalog link: finds inventory items with no <see cref="InventoryItem.PowderCatalogItemId"/>
    /// that match a catalog row by Manufacturer + ManufacturerPartNumber (the catalog SKU), sets the
    /// FK, and applies the catalog price/product data. Only links on a confident match (exact SKU,
    /// matching vendor, or a single unambiguous candidate) so it never mis-links. Returns the count
    /// newly linked. This backfills items created before linking existed, on every environment, with
    /// no manual step.
    /// </summary>
    private async Task<int> LinkUnlinkedInventoryAsync()
    {
        var unlinked = (await _unitOfWork.InventoryItems.FindAsync(
            i => i.PowderCatalogItemId == null
                 && i.Manufacturer != null && i.Manufacturer != ""
                 && i.ManufacturerPartNumber != null && i.ManufacturerPartNumber != "",
            ignoreQueryFilters: true)).ToList();
        if (unlinked.Count == 0)
            return 0;

        var partNumbers = unlinked.Select(i => i.ManufacturerPartNumber!).Distinct().ToList();
        var bySku = (await _unitOfWork.PowderCatalog.FindAsync(p => partNumbers.Contains(p.Sku)))
            .GroupBy(c => c.Sku, StringComparer.OrdinalIgnoreCase)
            .ToDictionary(g => g.Key, g => g.ToList(), StringComparer.OrdinalIgnoreCase);
        if (bySku.Count == 0)
            return 0;

        var linked = 0;
        foreach (var inv in unlinked)
        {
            if (!bySku.TryGetValue(inv.ManufacturerPartNumber!, out var candidates))
                continue;

            var mfr = inv.Manufacturer!.Trim().ToLower();
            var match = candidates.FirstOrDefault(c => c.VendorName.ToLower().Contains(mfr))
                        ?? (candidates.Count == 1 ? candidates[0] : null);
            if (match == null)
                continue;

            inv.PowderCatalogItemId = match.Id;
            ApplyCatalogToLinkedInventory(inv, match);
            await _unitOfWork.InventoryItems.UpdateAsync(inv);
            linked++;
        }

        if (linked > 0)
            await _unitOfWork.CompleteAsync();

        return linked;
    }

    /// <summary>
    /// Refreshes every tenant inventory item linked to a powder catalog row (across all companies)
    /// with the catalog's current list price and product data. Sets
    /// <see cref="InventoryItem.CatalogReferencePrice"/> (the QUOTING price) and product spec/doc
    /// fields, but NEVER the cost basis (UnitCost/AverageCost/LastPurchasePrice), quantity, notes,
    /// image, location, or stock levels — those are tenant-owned. EF persists only items that
    /// actually changed, so this is a cheap no-op when nothing moved. Returns the number updated.
    /// </summary>
    private async Task<int> RefreshLinkedInventoryAsync()
    {
        var linked = (await _unitOfWork.InventoryItems.FindAsync(
            i => i.PowderCatalogItemId != null, ignoreQueryFilters: true)).ToList();
        if (linked.Count == 0)
            return 0;

        var catalogIds = linked.Select(i => i.PowderCatalogItemId!.Value).Distinct().ToList();
        var catalogById = (await _unitOfWork.PowderCatalog.FindAsync(p => catalogIds.Contains(p.Id)))
            .ToDictionary(p => p.Id);

        var updated = 0;
        foreach (var inv in linked)
        {
            if (!catalogById.TryGetValue(inv.PowderCatalogItemId!.Value, out var cat))
                continue;

            if (ApplyCatalogToLinkedInventory(inv, cat))
            {
                await _unitOfWork.InventoryItems.UpdateAsync(inv);
                updated++;
            }
        }

        if (updated > 0)
            await _unitOfWork.CompleteAsync();

        return updated;
    }

    /// <summary>
    /// Applies the catalog's current price and product data onto a linked inventory item, returning
    /// true if anything changed. Sets the quoting reference price (only when the catalog has a real
    /// price &gt; 0) and refreshes product/spec fields where the catalog has a value — never erasing
    /// tenant data with catalog nulls, and never touching cost basis, quantity, notes, image, or
    /// stock levels.
    /// </summary>
    private static bool ApplyCatalogToLinkedInventory(InventoryItem inv, PowderCatalogItem cat)
    {
        var changed = false;

        // Quoting price (the point of this): keep the current catalog list price, separate from cost.
        if (cat.UnitPrice > 0 && inv.CatalogReferencePrice != cat.UnitPrice)
        {
            inv.CatalogReferencePrice = cat.UnitPrice;
            inv.CatalogPriceUpdatedAt = DateTime.UtcNow;
            changed = true;
        }

        // Product data — refresh from the catalog where it has a value (catalog is authoritative on
        // these); do not null out a tenant value the catalog doesn't carry.
        changed |= SetStrIfCatalogHas(() => inv.Description, v => inv.Description = v, cat.Description);
        changed |= SetStrIfCatalogHas(() => inv.Finish, v => inv.Finish = v, cat.Finish);
        changed |= SetStrIfCatalogHas(() => inv.ColorFamilies, v => inv.ColorFamilies = v, cat.ColorFamilies);
        changed |= SetStrIfCatalogHas(() => inv.SdsUrl, v => inv.SdsUrl = v, cat.SdsUrl);
        changed |= SetStrIfCatalogHas(() => inv.TdsUrl, v => inv.TdsUrl = v, cat.TdsUrl);
        changed |= SetStrIfCatalogHas(() => inv.SpecPageUrl, v => inv.SpecPageUrl = v, cat.ProductUrl);

        if (cat.CureTemperatureF.HasValue && inv.CureTemperatureF != cat.CureTemperatureF)
        { inv.CureTemperatureF = cat.CureTemperatureF; changed = true; }
        if (cat.CureTimeMinutes.HasValue && inv.CureTimeMinutes != cat.CureTimeMinutes)
        { inv.CureTimeMinutes = cat.CureTimeMinutes; changed = true; }
        if (cat.CoverageSqFtPerLb.HasValue && inv.CoverageSqFtPerLb != cat.CoverageSqFtPerLb)
        { inv.CoverageSqFtPerLb = cat.CoverageSqFtPerLb; changed = true; }
        if (cat.SpecificGravity.HasValue && inv.SpecificGravity != cat.SpecificGravity)
        { inv.SpecificGravity = cat.SpecificGravity; changed = true; }
        if (cat.TransferEfficiency.HasValue && inv.TransferEfficiency != cat.TransferEfficiency)
        { inv.TransferEfficiency = cat.TransferEfficiency; changed = true; }
        if (cat.RequiresClearCoat == true && !inv.RequiresClearCoat)
        { inv.RequiresClearCoat = true; changed = true; }

        return changed;
    }

    /// <summary>Sets a string property from the catalog only when the catalog value is non-blank and differs.</summary>
    private static bool SetStrIfCatalogHas(Func<string?> get, Action<string?> set, string? catalogValue)
    {
        if (!string.IsNullOrWhiteSpace(catalogValue) && !string.Equals(get(), catalogValue, StringComparison.Ordinal))
        {
            set(catalogValue);
            return true;
        }
        return false;
    }

    private static string KeyOf(PowderCatalogItem p) => $"{p.VendorName}|{p.Sku}";

    /// <summary>
    /// Copies feed-sourced fields from <paramref name="src"/> onto <paramref name="dest"/> and
    /// returns true if anything changed. Deliberately leaves enrichment fields (SpecificGravity,
    /// CoverageSqFtPerLb, TransferEfficiency, Finish) and lifecycle flags untouched — those are
    /// owned by lazy TDS/AI enrichment and the discontinuation sweep, not the feed.
    /// </summary>
    private static bool ApplyFeedFields(PowderCatalogItem dest, PowderCatalogItem src)
    {
        var changed = false;

        changed |= Set(() => dest.ColorName, v => dest.ColorName = v, src.ColorName);
        changed |= Set(() => dest.Description, v => dest.Description = v, src.Description);
        changed |= src.UnitPrice > 0 && dest.UnitPrice != src.UnitPrice && Assign(() => dest.UnitPrice = src.UnitPrice);
        changed |= Set(() => dest.PriceTiersJson, v => dest.PriceTiersJson = v, src.PriceTiersJson);
        changed |= Set(() => dest.ImageUrl, v => dest.ImageUrl = v, src.ImageUrl);
        changed |= Set(() => dest.SdsUrl, v => dest.SdsUrl = v, src.SdsUrl);
        changed |= Set(() => dest.TdsUrl, v => dest.TdsUrl = v, src.TdsUrl);
        changed |= Set(() => dest.ApplicationGuideUrl, v => dest.ApplicationGuideUrl = v, src.ApplicationGuideUrl);
        changed |= Set(() => dest.ProductUrl, v => dest.ProductUrl = v, src.ProductUrl);
        changed |= Set(() => dest.ChemistryType, v => dest.ChemistryType = v, src.ChemistryType);
        changed |= Set(() => dest.MilThickness, v => dest.MilThickness = v, src.MilThickness);
        changed |= Set(() => dest.CureScheduleText, v => dest.CureScheduleText = v, src.CureScheduleText);
        changed |= Set(() => dest.CureCurvesJson, v => dest.CureCurvesJson = v, src.CureCurvesJson);
        changed |= src.CureTemperatureF.HasValue && dest.CureTemperatureF != src.CureTemperatureF && Assign(() => dest.CureTemperatureF = src.CureTemperatureF);
        changed |= src.CureTimeMinutes.HasValue && dest.CureTimeMinutes != src.CureTimeMinutes && Assign(() => dest.CureTimeMinutes = src.CureTimeMinutes);
        changed |= src.RequiresClearCoat.HasValue && dest.RequiresClearCoat != src.RequiresClearCoat && Assign(() => dest.RequiresClearCoat = src.RequiresClearCoat);
        changed |= Set(() => dest.ColorFamilies, v => dest.ColorFamilies = v, src.ColorFamilies);
        changed |= Set(() => dest.FormulationChanges, v => dest.FormulationChanges = v, src.FormulationChanges);
        changed |= Set(() => dest.Category, v => dest.Category = v, src.Category);
        changed |= Set(() => dest.Source, v => dest.Source = v, src.Source);

        return changed;
    }

    /// <summary>
    /// Sets a nullable-string property when the feed provides a non-blank value that differs.
    /// Merge semantics: a blank incoming value is ignored, so a partial feed (e.g. the Prismatic
    /// file import, which omits cure/chemistry) never nulls out existing data.
    /// </summary>
    private static bool Set(Func<string?> get, Action<string?> set, string? newValue)
    {
        if (string.IsNullOrWhiteSpace(newValue))
            return false;
        if (!string.Equals(get(), newValue, StringComparison.Ordinal))
        {
            set(newValue);
            return true;
        }
        return false;
    }

    /// <summary>Helper so a value assignment can participate in a boolean OR chain.</summary>
    private static bool Assign(Action assign)
    {
        assign();
        return true;
    }
}