using System.Globalization;
using System.IO;
using System.Text.Json.Nodes;
using Microsoft.Data.SqlClient;

namespace InvoiceParser.Src;

// Ports of the small read endpoints: vendors.asp, polist.asp, podetail.asp,
// newproduct.asp, archive.asp (list/detail/getfile), pending_stats.asp.
public class DataService
{
    private readonly Db _db;
    private readonly AppConfig _cfg;
    private readonly TablesConfig _t;

    public DataService(Db db, AppConfig cfg)
    {
        _db = db;
        _cfg = cfg;
        _t = cfg.Tables;
    }

    public JsonArray Vendors()
    {
        var arr = new JsonArray();
        using var conn = _db.Open();
        using var cmd = conn.CreateCommand();
        cmd.CommandText =
            $"SELECT {_t.VendorIdCol}, {_t.VendorNameCol} FROM {_t.VendorTable} ORDER BY {_t.VendorNameCol}";
        using var r = cmd.ExecuteReader();
        while (r.Read())
            arr.Add(new JsonObject
            {
                ["id"] = Convert.ToString(r.GetValue(0)),
                ["name"] = Convert.ToString(r.GetValue(1))
            });
        return arr;
    }

    public JsonArray PoList()
    {
        var arr = new JsonArray();
        try
        {
            using var conn = _db.Open();
            using var cmd = conn.CreateCommand();
            cmd.CommandText =
                "SELECT TOP 500 h.PONumber, CONVERT(VARCHAR(10), h.PODate, 120) AS PODate," +
                $" ISNULL(v.{_t.VendorNameCol},'') AS VendorName" +
                $" FROM {_t.PoHeaderTable} h" +
                $" LEFT JOIN {_t.VendorTable} v ON v.{_t.VendorIdCol} = h.Vendor" +
                " ORDER BY h.PONumber DESC";
            using var r = cmd.ExecuteReader();
            while (r.Read())
                arr.Add(new JsonObject
                {
                    ["po_number"] = Db.GetStr(r, "PONumber") ?? "",
                    ["po_date"] = Db.GetStr(r, "PODate") ?? "",
                    ["vendor_name"] = Db.GetStr(r, "VendorName") ?? ""
                });
        }
        catch { /* PO tables are optional - mirror polist.asp returning [] */ }
        return arr;
    }

    public JsonArray PoDetail(string poNumber)
    {
        var arr = new JsonArray();
        if (poNumber == "") return arr;
        try
        {
            using var conn = _db.Open();
            using var cmd = conn.CreateCommand();
            cmd.CommandText =
                "SELECT UPC, Cert_code, Description, Cost, Total, QuantityCase, QuantityPieces, Size, UnitOfMeasure" +
                $" FROM {_t.PoDetailTable} WHERE PONumber = @po ORDER BY UPC";
            cmd.Parameters.AddWithValue("@po", poNumber);
            using var r = cmd.ExecuteReader();
            while (r.Read())
                arr.Add(new JsonObject
                {
                    ["upc"] = Db.GetStr(r, "UPC") ?? "",
                    ["cert_code"] = Db.GetStr(r, "Cert_code") ?? "",
                    ["description"] = Db.GetStr(r, "Description") ?? "",
                    ["cost"] = Db.GetNum(r, "Cost"),
                    ["qty"] = Db.GetNum(r, "QuantityCase"),
                    ["qty_pieces"] = Db.GetNum(r, "QuantityPieces"),
                    ["size"] = Db.GetStr(r, "Size") ?? "",
                    ["uom"] = Db.GetStr(r, "UnitOfMeasure") ?? ""
                });
        }
        catch { }
        return arr;
    }

    public JsonArray Departments()
    {
        var arr = new JsonArray();
        using var conn = _db.Open();
        using var cmd = conn.CreateCommand();
        // dept_tax / dept_fs drive the tax + food stamp defaults on new products,
        // the same way newitem/product-edit-processor.asp seeds them.
        // dept_sub = 0 only. Departments is keyed on (dept_no, dept_sub), but
        // Products.department stores a bare dept_no - there is no way to point a
        // product at a sub-department. Without this filter dept_no 1 returns two
        // rows (GROCERY-NO TAX sub 0, GROCERY TAXABLE sub 1) that collide on the
        // same option value, and the second one silently wins the tax/fs lookup.
        // sql_GetAllDepartments() in swapps includes/SiteSQL.asp filters the same way.
        cmd.CommandText =
            $"SELECT dept_no, dept_name, ISNULL(dept_tax,0) AS dept_tax, ISNULL(dept_fs,0) AS dept_fs " +
            $"FROM {_t.DepartmentsTable} WHERE dept_sub = 0 ORDER BY dept_name";
        using var r = cmd.ExecuteReader();
        while (r.Read())
            arr.Add(new JsonObject
            {
                ["id"] = Convert.ToInt64(r.GetValue(0)),
                ["name"] = Convert.ToString(r.GetValue(1)),
                ["tax"] = Convert.ToInt32(r.GetValue(2)) != 0 ? 1 : 0,
                ["fs"] = Convert.ToInt32(r.GetValue(3)) != 0 ? 1 : 0
            });
        return arr;
    }

    public JsonObject CreateProduct(string upcRaw, string desc, string price, string deptId,
                                    string cost, string itemCode, string tax, string foodstamp,
                                    string scale, string wicable, string pack, string size,
                                    string vendorId, string invoiceNum)
    {
        var rawDigits = Util.CleanDigits(upcRaw);
        var upc = Util.NormalizeUpcForStorage(rawDigits);
        desc = Truncate(desc.Trim(), 30);
        itemCode = Truncate(itemCode.Trim(), 15);
        size = Truncate(size.Trim(), 9);

        if (rawDigits == "" || rawDigits.Replace("0", "") == "" || rawDigits.Length > 13 || desc == "")
            return Fail("UPC, Description, and Price are required");

        // Department drives tax, foodstamp, attributes and validage, so a blank
        // one silently produces an untaxed, un-carded item. product-edit-processor.asp
        // rejects it for the same reason.
        if (!long.TryParse(deptId, out var deptNo) || deptNo <= 0)
            return Fail("Department is required");

        // Price takes either a plain amount or the POS group form "n/total"
        // ("2/5.00" = 2 for $5.00), the syntax product-edit-processor.asp parses.
        // Group pricing leaves normal_price NULL and carries the price in
        // groupprice/quantity - 898 active products are stored that way.
        int priceMethod = 0;
        double normalPrice = 0, groupPrice = 0;
        long groupQty = 0;
        price = price.Trim();
        var slash = price.IndexOf('/');
        if (slash >= 0)
        {
            var qtyPart = price[..slash].Trim();
            var amtPart = price[(slash + 1)..].Trim();
            if (!long.TryParse(qtyPart, NumberStyles.Integer, CultureInfo.InvariantCulture, out groupQty) ||
                groupQty <= 0 || groupQty > short.MaxValue)
                return Fail("Group price quantity must be a whole number from 1 to 32767 (e.g. 2/5.00)");
            if (!double.TryParse(amtPart, NumberStyles.Any, CultureInfo.InvariantCulture, out groupPrice) ||
                groupPrice <= 0)
                return Fail("Group price amount must be greater than zero (e.g. 2/5.00)");
            priceMethod = 1;
        }
        else
        {
            if (!double.TryParse(price, NumberStyles.Any, CultureInfo.InvariantCulture, out normalPrice))
                return Fail("UPC, Description, and Price are required");
            if (normalPrice < 0) return Fail("Price cannot be negative");
        }

        double dCost = 0;
        if (double.TryParse(cost, NumberStyles.Any, CultureInfo.InvariantCulture, out var c)) dCost = c;
        if (dCost < 0) return Fail("Cost cannot be negative");

        using var conn = _db.Open();

        using (var check = conn.CreateCommand())
        {
            check.CommandText = $"SELECT TOP 1 description FROM {_t.ProductsTable} WHERE upc = @upc";
            check.Parameters.AddWithValue("@upc", upc);
            var existing = check.ExecuteScalar();
            if (existing != null) return Fail("UPC already exists: " + existing);
        }

        // Age restriction is inherited from the department, exactly as
        // newitem/product-edit-processor.asp does it: a department flagged in
        // attributes passes its validage down and marks the product as carded.
        // Nothing in this UI exposes these, so missing them would quietly create
        // beer and tobacco items that never prompt at the register.
        int attributes = 0, validAge = 0;
        using (var dept = conn.CreateCommand())
        {
            dept.CommandText =
                $"SELECT TOP 1 ISNULL(attributes,0) AS attributes, ISNULL(validage,0) AS validage " +
                $"FROM {_t.DepartmentsTable} WHERE dept_no = @dept AND dept_sub = 0";
            dept.Parameters.AddWithValue("@dept", deptNo);
            using var dr = dept.ExecuteReader();
            if (dr.Read() && (Convert.ToInt32(dr.GetValue(0)) & 1) != 0)
            {
                attributes = 2;
                validAge = Convert.ToInt32(dr.GetValue(1));
            }
        }

        using var cmd = conn.CreateCommand();
        cmd.CommandText =
            $"INSERT INTO {_t.ProductsTable} " +
            "(upc,cert_code,description,cost,normal_price,pricemethod,groupprice,quantity," +
            "special_price,specialcost,specialpricemethod,specialgroupprice,specialquantity," +
            "start_date,end_date,target_margin,department,section,vendor,pack,size,tax," +
            "foodstamp,scale,dsd,upc_link,mixmatchcode,modified,cost_modified,active,advertised," +
            "whomodified,picture_name,longdescription,seconddescription,tareweight,discount," +
            "unitofmeasure,effectiveschedule,wicable,validage,deleted,currentbatchno,maxdiscount," +
            "attributes,QualifiedPercent,QualifiedFlatAmount,TOB,Created,CreatedBy,Points," +
            "groupprice2,quantity2,groupprice3,quantity3,groupprice4,quantity4,groupprice5,quantity5," +
            "Specialgroupprice2,Specialquantity2,Specialgroupprice3,Specialquantity3," +
            "Specialgroupprice4,Specialquantity4,Specialgroupprice5,Specialquantity5," +
            "StartTime,EndTime,LookupRanking,FSACategory,CGID,CGPurchaseRequired,PLU,IsLotto) " +
            "VALUES (" +
            "@upc,@cert,@desc,@cost,@price," +
            "@pricemethod,@groupprice,@quantity,NULL,NULL,NULL,NULL,NULL,NULL,NULL,0," +
            "@dept,NULL,@vendor,@pack,@size,@tax,@foodstamp,@scale," +
            "0,NULL,NULL,getdate(),getdate(),1,0," +
            "'111',NULL,NULL,NULL,NULL,0,NULL,NULL,@wicable," +
            "@validage,0,NULL,0,@attributes,NULL,NULL,NULL,getdate(),111,0," +
            "NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL," +
            "NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL," +
            "NULL,NULL,NULL,NULL,NULL,NULL,NULL,0)";
        cmd.Parameters.AddWithValue("@upc", upc);
        cmd.Parameters.AddWithValue("@cert", itemCode == "" ? DBNull.Value : itemCode);
        cmd.Parameters.AddWithValue("@desc", desc);
        cmd.Parameters.AddWithValue("@cost", dCost);
        cmd.Parameters.AddWithValue("@price", priceMethod == 1 ? DBNull.Value : normalPrice);
        cmd.Parameters.AddWithValue("@pricemethod", priceMethod);
        cmd.Parameters.AddWithValue("@groupprice", priceMethod == 1 ? groupPrice : DBNull.Value);
        cmd.Parameters.AddWithValue("@quantity", priceMethod == 1 ? groupQty : DBNull.Value);
        cmd.Parameters.AddWithValue("@dept", deptNo);
        // Only the vendor picked on the review header - no vendor means NULL, not 0.
        cmd.Parameters.AddWithValue("@vendor",
            vendorId.Trim() == "" ? DBNull.Value : vendorId.Trim());
        cmd.Parameters.AddWithValue("@validage", validAge);
        cmd.Parameters.AddWithValue("@attributes", attributes);
        cmd.Parameters.AddWithValue("@pack",
            double.TryParse(pack, NumberStyles.Any, CultureInfo.InvariantCulture, out var p) ? p : DBNull.Value);
        cmd.Parameters.AddWithValue("@size", size == "" ? DBNull.Value : size);
        cmd.Parameters.AddWithValue("@tax", tax == "1" ? 1 : 0);
        cmd.Parameters.AddWithValue("@foodstamp", foodstamp == "1" ? 1 : 0);
        cmd.Parameters.AddWithValue("@scale", scale == "1" ? 1 : 0);
        cmd.Parameters.AddWithValue("@wicable", wicable == "1" ? 1 : 0);

        try { cmd.ExecuteNonQuery(); }
        catch (Exception ex) { return Fail(ex.Message); }

        // Hand back the effective shelf retail so the row's margin is right
        // immediately - for a group price that is the per-unit slice, not the total.
        var retail = priceMethod == 1 ? groupPrice / groupQty : normalPrice;

        // Change log. The product already exists, so a failed log row is only warned.
        try
        {
            using var log = conn.CreateCommand();
            log.CommandText =
                $"IF OBJECT_ID(@tbl) IS NOT NULL INSERT INTO {_t.ProductChangesTable} " +
                "(ChangeType, UPC, Description, Vendor, InvoiceNumber, NewCost, Retail, Pack, EmpNo) " +
                "VALUES ('NEW', @upc, @desc, @vendor, @inv, @cost, @retail, @pack, @emp)";
            log.Parameters.AddWithValue("@tbl", _t.ProductChangesTable);
            log.Parameters.AddWithValue("@upc", upc);
            log.Parameters.AddWithValue("@desc", desc);
            log.Parameters.AddWithValue("@vendor", vendorId.Trim() == "" ? DBNull.Value : vendorId.Trim());
            log.Parameters.AddWithValue("@inv", invoiceNum.Trim() == "" ? DBNull.Value : Truncate(invoiceNum.Trim(), 100));
            log.Parameters.AddWithValue("@cost", dCost);
            log.Parameters.AddWithValue("@retail", retail);
            log.Parameters.AddWithValue("@pack", cmd.Parameters["@pack"].Value);
            log.Parameters.AddWithValue("@emp", _cfg.ReceiverEmpNo);
            log.ExecuteNonQuery();
        }
        catch (Exception ex)
        {
            Log.Warn("changes", $"new product {upc} not logged: {ex.Message}");
        }

        return new JsonObject
        {
            ["success"] = true,
            ["upc"] = upc,
            ["description"] = desc,
            ["retail"] = retail
        };
    }

    // ---- change log ----

    public JsonArray ProductChanges(string dateFrom, string dateTo, string type)
    {
        var arr = new JsonArray();
        using var conn = _db.Open();
        using var cmd = conn.CreateCommand();

        var where = " WHERE 1=1";
        // Typed DateTime parameters: 'yyyy-MM-dd' text is DATEFORMAT dependent.
        if (Util.IsIsoDate(dateFrom))
        {
            where += " AND c.ChangeDate >= @dateFrom";
            cmd.Parameters.AddWithValue("@dateFrom", DateTime.ParseExact(dateFrom, "yyyy-MM-dd", CultureInfo.InvariantCulture));
        }
        if (Util.IsIsoDate(dateTo))
        {
            where += " AND c.ChangeDate < @dateTo";
            cmd.Parameters.AddWithValue("@dateTo", DateTime.ParseExact(dateTo, "yyyy-MM-dd", CultureInfo.InvariantCulture).AddDays(1));
        }
        if (type == "NEW" || type == "COST")
        {
            where += " AND c.ChangeType = @type";
            cmd.Parameters.AddWithValue("@type", type);
        }

        cmd.CommandText =
            "SELECT TOP 2000 CONVERT(VARCHAR(19), c.ChangeDate, 120) AS ChangeDate, c.ChangeType, c.UPC, c.Description," +
            " c.Vendor, c.InvoiceNumber, c.PONumber, c.BatchNo, c.OldCost, c.NewCost, c.Retail, c.Pack," +
            $" ISNULL(v.{_t.VendorNameCol},'') AS VendorName" +
            $" FROM {_t.ProductChangesTable} c" +
            $" LEFT JOIN {_t.VendorTable} v ON v.{_t.VendorIdCol} = c.Vendor" +
            where +
            " ORDER BY c.ChangeDate DESC, c.ChangeID DESC";

        using var r = cmd.ExecuteReader();
        while (r.Read())
            arr.Add(new JsonObject
            {
                ["date"] = Db.GetStr(r, "ChangeDate") ?? "",
                ["type"] = Db.GetStr(r, "ChangeType") ?? "",
                ["upc"] = Db.GetStr(r, "UPC") ?? "",
                ["description"] = Db.GetStr(r, "Description") ?? "",
                ["vendor"] = Db.GetStr(r, "Vendor") ?? "",
                ["vendor_name"] = Db.GetStr(r, "VendorName") ?? "",
                ["invoice_number"] = Db.GetStr(r, "InvoiceNumber") ?? "",
                ["po_number"] = Db.GetStr(r, "PONumber") ?? "",
                ["batch_no"] = Db.GetStr(r, "BatchNo") ?? "",
                ["old_cost"] = Db.GetNum(r, "OldCost"),
                ["new_cost"] = Db.GetNum(r, "NewCost"),
                ["retail"] = Db.GetNum(r, "Retail"),
                ["pack"] = Db.GetNum(r, "Pack")
            });
        return arr;
    }

    // ---- archive ----

    public JsonArray ArchiveList(string vendor, string inv, string po, string dateFrom,
                                 string dateTo, string amtMin, string amtMax, string product)
    {
        var arr = new JsonArray();
        using var conn = _db.Open();
        using var cmd = conn.CreateCommand();

        var where = " WHERE 1=1";
        if (vendor != "")
        {
            where += " AND h.Vendor = @vendor";
            cmd.Parameters.AddWithValue("@vendor", vendor);
        }
        if (inv != "")
        {
            where += " AND h.InvoiceNumber LIKE @inv";
            cmd.Parameters.AddWithValue("@inv", "%" + Util.EscapeLike(Truncate(inv, 30)) + "%");
        }
        if (po != "")
        {
            where += " AND h.PONumber LIKE @po";
            cmd.Parameters.AddWithValue("@po", "%" + Util.EscapeLike(Truncate(po, 30)) + "%");
        }
        // Typed DateTime parameters: 'yyyy-MM-dd' text is DATEFORMAT dependent.
        if (Util.IsIsoDate(dateFrom))
        {
            where += " AND h.InvoiceDate >= @dateFrom";
            cmd.Parameters.AddWithValue("@dateFrom", DateTime.ParseExact(dateFrom, "yyyy-MM-dd", CultureInfo.InvariantCulture));
        }
        if (Util.IsIsoDate(dateTo))
        {
            where += " AND h.InvoiceDate < @dateTo";
            cmd.Parameters.AddWithValue("@dateTo", DateTime.ParseExact(dateTo, "yyyy-MM-dd", CultureInfo.InvariantCulture).AddDays(1));
        }
        if (amtMin != "" && double.TryParse(amtMin, NumberStyles.Any, CultureInfo.InvariantCulture, out var mn))
        {
            where += " AND ISNULL(h.VendorTotal,0) >= @amtMin";
            cmd.Parameters.AddWithValue("@amtMin", mn);
        }
        if (amtMax != "" && double.TryParse(amtMax, NumberStyles.Any, CultureInfo.InvariantCulture, out var mx))
        {
            where += " AND ISNULL(h.VendorTotal,0) <= @amtMax";
            cmd.Parameters.AddWithValue("@amtMax", mx);
        }
        if (product != "")
        {
            where += $" AND EXISTS (SELECT 1 FROM {_t.InvoiceDetailTable} d" +
                     " WHERE d.PONumber = h.PONumber" +
                     " AND (d.UPC LIKE @product OR d.Cert_code LIKE @product OR d.Description LIKE @product))";
            cmd.Parameters.AddWithValue("@product", "%" + Util.EscapeLike(Truncate(product, 80)) + "%");
        }

        cmd.CommandText =
            "SELECT TOP 500 h.InvoiceNumber, CONVERT(VARCHAR(10), h.InvoiceDate, 120) AS InvDate," +
            " h.Vendor, ISNULL(h.VendorTotal,0) AS VendorTotal," +
            $" ISNULL(v.{_t.VendorNameCol},'Unknown') AS VendorName" +
            $" FROM {_t.InvoiceHeaderTable} h" +
            $" LEFT JOIN {_t.VendorTable} v ON v.{_t.VendorIdCol} = h.Vendor" +
            where +
            " ORDER BY h.InvoiceDate DESC, h.InvoiceNumber DESC";

        using var r = cmd.ExecuteReader();
        while (r.Read())
            arr.Add(new JsonObject
            {
                ["invoice_number"] = Db.GetStr(r, "InvoiceNumber") ?? "",
                ["invoice_date"] = Db.GetStr(r, "InvDate") ?? "",
                ["vendor"] = Db.GetStr(r, "Vendor") ?? "",
                ["vendor_total"] = Db.GetNum(r, "VendorTotal"),
                ["vendor_name"] = Db.GetStr(r, "VendorName") ?? ""
            });
        return arr;
    }

    public JsonObject ArchiveDetail(string inv, string vendor)
    {
        if (inv == "" || vendor == "")
            return new JsonObject { ["error"] = "Missing parameters" };

        using var conn = _db.Open();

        JsonObject header;
        using (var cmd = conn.CreateCommand())
        {
            cmd.CommandText =
                "SELECT TOP 1 h.InvoiceNumber, CONVERT(VARCHAR(10), h.InvoiceDate, 120) AS InvDate," +
                " ISNULL(h.PONumber,'') AS PONumber, ISNULL(h.VendorTotal,0) AS VendorTotal," +
                $" ISNULL(v.{_t.VendorNameCol},'') AS VendorName" +
                $" FROM {_t.InvoiceHeaderTable} h" +
                $" LEFT JOIN {_t.VendorTable} v ON v.{_t.VendorIdCol} = h.Vendor" +
                " WHERE h.InvoiceNumber = @inv AND h.Vendor = @vendor" +
                " ORDER BY h.InvoiceDate DESC";
            cmd.Parameters.AddWithValue("@inv", inv);
            cmd.Parameters.AddWithValue("@vendor", vendor);
            using var r = cmd.ExecuteReader();
            if (!r.Read()) return new JsonObject { ["error"] = "Invoice not found" };
            header = new JsonObject
            {
                ["invoice_number"] = Db.GetStr(r, "InvoiceNumber") ?? "",
                ["invoice_date"] = Db.GetStr(r, "InvDate") ?? "",
                ["po_number"] = Db.GetStr(r, "PONumber") ?? "",
                ["vendor_total"] = Db.GetNum(r, "VendorTotal"),
                ["vendor_name"] = Db.GetStr(r, "VendorName") ?? ""
            };
        }

        // Line items come back in the order they were entered, the same order
        // the review screen shows them in, not sorted by UPC. The detail table
        // has no line number column, so its identity column is the insertion
        // order; without one there is nothing to recover and UPC is the only
        // stable fallback.
        var orderBy = DetailOrderColumn(conn);

        var items = new JsonArray();
        using (var cmd = conn.CreateCommand())
        {
            cmd.CommandText =
                "SELECT d.UPC, d.Cert_code, d.Description, d.Cost, d.Total, d.QuantityCase, d.Size, d.UnitOfMeasure" +
                $" FROM {_t.InvoiceDetailTable} d" +
                $" JOIN {_t.InvoiceHeaderTable} h ON h.PONumber = d.PONumber" +
                $" WHERE h.InvoiceNumber = @inv AND h.Vendor = @vendor ORDER BY d.[{orderBy}]";
            cmd.Parameters.AddWithValue("@inv", inv);
            cmd.Parameters.AddWithValue("@vendor", vendor);
            using var r = cmd.ExecuteReader();
            while (r.Read())
                items.Add(new JsonObject
                {
                    ["upc"] = Db.GetStr(r, "UPC") ?? "",
                    ["cert"] = Db.GetStr(r, "Cert_code") ?? "",
                    ["desc"] = Db.GetStr(r, "Description") ?? "",
                    ["cost"] = Db.GetNum(r, "Cost"),
                    ["total"] = Db.GetNum(r, "Total"),
                    ["qty"] = Db.GetNum(r, "QuantityCase"),
                    ["size"] = Db.GetStr(r, "Size") ?? "",
                    ["uom"] = Db.GetStr(r, "UnitOfMeasure") ?? ""
                });
        }

        header["items"] = items;
        header["batch"] = ArchiveBatch(conn, inv, vendor);
        return header;
    }

    // The identity column of InvoiceDetail, discovered once. Installs differ on
    // its name (RECID, ID, DetailID...), and hard-coding a guess would break
    // every archive detail view on the ones that named it something else.
    private string? _detailOrderCol;

    private string DetailOrderColumn(SqlConnection conn)
    {
        if (_detailOrderCol != null) return _detailOrderCol;
        try
        {
            // sys.identity_columns is database-scoped. The detail table lives in
            // posinv while the connection is open on posbdat, so the probe has
            // to read the catalog view of the table's own database or it always
            // comes back empty and every archive falls back to UPC order.
            using var cmd = conn.CreateCommand();
            cmd.CommandText =
                $"SELECT TOP 1 c.name FROM {CatalogPrefix(_t.InvoiceDetailTable)}sys.identity_columns c " +
                $"WHERE c.object_id = OBJECT_ID(@t)";
            cmd.Parameters.AddWithValue("@t", _t.InvoiceDetailTable);
            _detailOrderCol = Convert.ToString(cmd.ExecuteScalar()) ?? "";
        }
        catch (Exception ex)
        {
            Log.Warn("archive", "identity column probe failed, ordering by UPC: " + ex.Message);
            _detailOrderCol = "";
        }
        if (_detailOrderCol == "")
        {
            Log.Info("archive", $"{_t.InvoiceDetailTable} has no identity column - ordering line items by UPC");
            _detailOrderCol = "UPC";
        }
        else Log.Info("archive", $"ordering line items by {_t.InvoiceDetailTable}.{_detailOrderCol}");
        return _detailOrderCol;
    }

    // "posinv.dbo.InvoiceDetail" -> "[posinv].", an unqualified name -> "" so
    // the catalog view resolves in the connection's own database.
    private static string CatalogPrefix(string qualified)
    {
        var parts = qualified.Split('.');
        return parts.Length >= 3 ? "[" + parts[^3].Trim('[', ']') + "]." : "";
    }

    // The price/cost batch this invoice produced, if any, plus its rows. Missing
    // batch tables are not an error - a store that does not use batches still
    // gets its archive.
    private JsonNode? ArchiveBatch(SqlConnection conn, string inv, string vendor)
    {
        if (!_cfg.Batch.Enabled) return null;
        try
        {
            var baseName = _cfg.Batch.NamePrefix + inv;
            JsonObject? head = null;
            using (var cmd = conn.CreateCommand())
            {
                // Two vendors can share an invoice number, so a collision is
                // parked as BatchNo_1; the description carries the vendor.
                cmd.CommandText =
                    "SELECT TOP 10 BatchNo, Description, CONVERT(VARCHAR(19), Created, 120) AS Created" +
                    $" FROM {_t.ProductBatchesHeaderTable}" +
                    " WHERE BatchNo = @exact OR BatchNo LIKE @like" +
                    " ORDER BY BatchNo";
                cmd.Parameters.AddWithValue("@exact", baseName);
                cmd.Parameters.AddWithValue("@like", Util.EscapeLike(baseName) + "[_]%");
                using var r = cmd.ExecuteReader();
                var rows = new List<JsonObject>();
                while (r.Read())
                    rows.Add(new JsonObject
                    {
                        ["batch_no"] = Db.GetStr(r, "BatchNo") ?? "",
                        ["description"] = Db.GetStr(r, "Description") ?? "",
                        ["created"] = Db.GetStr(r, "Created") ?? ""
                    });
                head = rows.FirstOrDefault(x => (x["description"]?.ToString() ?? "").Contains("vendor " + vendor))
                    ?? rows.FirstOrDefault(x => x["batch_no"]?.ToString() == baseName);
            }
            if (head == null) return null;

            var batchNo = head["batch_no"]!.ToString();
            var rowsOut = new JsonArray();
            using (var cmd = conn.CreateCommand())
            {
                // Retail is the shelf price off the product file, not off the
                // batch row - the batch only carries the new cost.
                cmd.CommandText =
                    "SELECT b.upc, b.cert_code, b.description, b.cost, b.pack, b.size," +
                    $" p.cost AS current_cost, {ProductSql.RetailFor("p")}" +
                    $" FROM {_t.ProductBatchesTable} b" +
                    $" LEFT JOIN {_t.ProductsTable} p ON p.upc = b.upc" +
                    " WHERE b.BatchNo = @b ORDER BY b.upc";
                cmd.Parameters.AddWithValue("@b", batchNo);
                using var r = cmd.ExecuteReader();
                while (r.Read())
                {
                    var cost = Db.GetNum(r, "cost");
                    var retail = Db.GetNum(r, "retail");
                    rowsOut.Add(new JsonObject
                    {
                        ["upc"] = Db.GetStr(r, "upc") ?? "",
                        ["cert"] = Db.GetStr(r, "cert_code") ?? "",
                        ["desc"] = Db.GetStr(r, "description") ?? "",
                        ["cost"] = cost,
                        ["current_cost"] = Db.GetNum(r, "current_cost"),
                        ["pack"] = Db.GetNum(r, "pack"),
                        ["size"] = Db.GetStr(r, "size") ?? "",
                        ["retail"] = retail,
                        ["margin"] = retail is > 0 && cost != null
                            ? (retail.Value - cost.Value) / retail.Value * 100
                            : (double?)null
                    });
                }
            }
            head["items"] = rowsOut;
            head["margin_threshold"] = _cfg.Batch.MarginThreshold;
            return head;
        }
        catch (Exception ex)
        {
            Log.Warn("archive", $"batch lookup for invoice {inv} failed: " + ex.Message);
            return null;
        }
    }

    // Locates the archived source file for an invoice, verifying the DB record exists.
    public string? ArchiveFile(string inv, string vendor, out string ext)
    {
        ext = "";
        if (inv == "" || vendor == "") return null;

        using (var conn = _db.Open())
        using (var cmd = conn.CreateCommand())
        {
            cmd.CommandText =
                $"SELECT TOP 1 InvoiceNumber FROM {_t.InvoiceHeaderTable} " +
                "WHERE InvoiceNumber = @inv AND Vendor = @vendor";
            cmd.Parameters.AddWithValue("@inv", inv);
            cmd.Parameters.AddWithValue("@vendor", vendor);
            if (cmd.ExecuteScalar() == null) return null;
        }

        var baseName = Util.SafeFileName(vendor) + "_" + Util.SafeFileName(inv);
        return Util.FindInvoiceFile(_cfg.ArchiveRoot, baseName, out ext);
    }

    // ---- dashboard stats (pending_stats.asp port) ----
    public JsonObject Stats(PendingStore store)
    {
        int queued = 0, processing = 0, parsed = 0, review = 0, editing = 0,
            error = 0, other = 0, total = 0, today = 0, pendingLines = 0;
        double pendingValue = 0;
        var todayStr = DateTime.UtcNow.ToString("yyyy-MM-dd");

        foreach (var item in store.List())
        {
            var state = store.ReadState(item.Id);
            if (state == null) continue;
            total++;
            switch (state["stage"]?.ToString() ?? "")
            {
                case "queued": case "queue": queued++; break;
                case "processing": processing++; break;
                case "parsed": parsed++; break;
                case "review": review++; break;
                case "editing": editing++; break;
                case "error": error++; break;
                default: other++; break;
            }
            var created = state["created_at"]?.ToString() ?? "";
            if (created.Length >= 10 && created[..10] == todayStr) today++;

            var totalStr = state["header"]?["invoice_total"]?.ToString() ?? "";
            if (double.TryParse(totalStr, NumberStyles.Any, CultureInfo.InvariantCulture, out var t))
                pendingValue += t;
            if (state["line_items"] is JsonArray li) pendingLines += li.Count;
        }

        int archived = Directory.Exists(_cfg.ArchiveRoot)
            ? Directory.GetFiles(_cfg.ArchiveRoot).Length : 0;

        return new JsonObject
        {
            ["queued"] = queued,
            ["processing"] = processing,
            ["parsed"] = parsed,
            ["review"] = review,
            ["editing"] = editing,
            ["error"] = error,
            ["total"] = total,
            ["ready"] = parsed,
            ["in_progress"] = review + editing,
            ["needs_parse"] = queued + processing,
            ["uploaded_today"] = today,
            ["archived"] = archived,
            ["pending_value"] = pendingValue,
            ["pending_lines"] = pendingLines
        };
    }

    private static string Truncate(string s, int n) => s.Length <= n ? s : s[..n];

    private static JsonObject Fail(string error) =>
        new() { ["success"] = false, ["error"] = error };
}