using System.Text;
using BakeryErp.Infrastructure.Database;

namespace BakeryErp.Infrastructure.Repositories;

public sealed class ReportCenterRepository
{
    private readonly DatabaseOptions _options;

    public ReportCenterRepository(DatabaseOptions options)
    {
        _options = options;
    }

    public IReadOnlyList<LocalReportDefinition> List()
    {
        return LocalDataStoreFile.Load(_options)
            .ReportDefinitions
            .OrderBy(static report => report.ReportCategory)
            .ThenBy(static report => report.ReportCode)
            .ToList();
    }

    public LocalReportDefinition? Find(Guid id)
    {
        return LocalDataStoreFile.Load(_options)
            .ReportDefinitions
            .FirstOrDefault(report => report.Id == id);
    }

    public ReportCenterSummary GetSummary()
    {
        var store = LocalDataStoreFile.Load(_options);
        return new ReportCenterSummary(
            store.ReportDefinitions.Count,
            store.ReportDefinitions.Count(static report => report.Status == LocalReportStatus.PendingApproval),
            store.ReportDefinitions.Count(static report => report.Status == LocalReportStatus.Approved),
            store.StockBalances.Count,
            store.PurchaseOrders.Count,
            store.PettyCashTransactions.Count,
            store.TransferOrders.Count,
            store.StoreReturns.Count);
    }

    public SaveReportDefinitionResult Save(LocalReportDefinition report)
    {
        var store = LocalDataStoreFile.Load(_options);
        var reportCode = report.ReportCode.Trim().ToUpperInvariant();

        if (string.IsNullOrWhiteSpace(reportCode) ||
            string.IsNullOrWhiteSpace(report.ReportName) ||
            string.IsNullOrWhiteSpace(report.ReportCategory))
        {
            return SaveReportDefinitionResult.ValidationError("報表代號、名稱與分類為必填。");
        }

        var duplicatedCode = store.ReportDefinitions.Any(existing =>
            existing.Id != report.Id &&
            string.Equals(existing.ReportCode, reportCode, StringComparison.OrdinalIgnoreCase));
        if (duplicatedCode)
        {
            return SaveReportDefinitionResult.ValidationError("報表代號已存在，請改用其他代號。");
        }

        var existingReport = store.ReportDefinitions.FirstOrDefault(existing => existing.Id == report.Id);
        if (existingReport is null)
        {
            report.Id = report.Id == Guid.Empty ? Guid.NewGuid() : report.Id;
            report.ReportCode = reportCode;
            report.ReportName = report.ReportName.Trim();
            report.ReportCategory = report.ReportCategory.Trim();
            report.Description = BlankToNull(report.Description);
            report.Status = LocalReportStatus.PendingApproval;
            report.CreatedAt = DateTime.UtcNow;
            store.ReportDefinitions.Add(report);
        }
        else
        {
            if (existingReport.Status == LocalReportStatus.Approved)
            {
                return SaveReportDefinitionResult.ValidationError("已審核報表不可編輯。");
            }

            existingReport.ReportCode = reportCode;
            existingReport.ReportName = report.ReportName.Trim();
            existingReport.ReportCategory = report.ReportCategory.Trim();
            existingReport.Description = BlankToNull(report.Description);
            existingReport.Status = LocalReportStatus.PendingApproval;
            existingReport.UpdatedAt = DateTime.UtcNow;
        }

        LocalDataStoreFile.Save(_options, store);
        return SaveReportDefinitionResult.Success();
    }

    public void Approve(Guid id)
    {
        Update(id, report =>
        {
            report.Status = LocalReportStatus.Approved;
            report.ApprovedAt = DateTime.UtcNow;
        });
    }

    public void Cancel(Guid id)
    {
        Update(id, report => report.Status = LocalReportStatus.Cancelled);
    }

    public CsvExport Export(string reportCode)
    {
        var store = LocalDataStoreFile.Load(_options);
        return reportCode.ToUpperInvariant() switch
        {
            "RPT-INVENTORY" => ExportInventory(store),
            "RPT-PURCHASE" => ExportPurchases(store),
            "RPT-PETTYCASH" => ExportPettyCash(store),
            "RPT-TRANSFERS" => ExportTransfers(store),
            "RPT-RETURNS" => ExportReturns(store),
            _ => ExportReportDefinitions(store)
        };
    }

    public static string GetStatusName(LocalReportStatus status)
    {
        return status switch
        {
            LocalReportStatus.Draft => "草稿",
            LocalReportStatus.PendingApproval => "待審核",
            LocalReportStatus.Approved => "已審核",
            LocalReportStatus.Cancelled => "已取消",
            _ => status.ToString()
        };
    }

    private static CsvExport ExportInventory(LocalDataStore store)
    {
        var rows = store.StockBalances.Select(stock => new[]
        {
            stock.WarehouseName,
            stock.ItemSku,
            stock.ItemName,
            stock.QuantityOnHand.ToString("0.##"),
            stock.SafetyStockQuantity.ToString("0.##"),
            stock.Unit
        });
        return Csv("inventory-report.csv", ["倉庫", "品項代號", "品項名稱", "現有庫存", "安全庫存", "單位"], rows);
    }

    private static CsvExport ExportPurchases(LocalDataStore store)
    {
        var rows = store.PurchaseOrders.Select(order => new[]
        {
            order.OrderNumber,
            order.SupplierName,
            order.OrderDate.ToString("yyyy-MM-dd"),
            order.ItemName,
            order.Quantity.ToString("0.##"),
            order.UnitPrice.ToString("0.##"),
            order.LineAmount.ToString("0.##"),
            PurchaseRepository.GetStatusName(order.Status)
        });
        return Csv("purchase-report.csv", ["採購單號", "供應商", "日期", "品項", "數量", "單價", "金額", "狀態"], rows);
    }

    private static CsvExport ExportPettyCash(LocalDataStore store)
    {
        var rows = store.PettyCashTransactions.Select(transaction => new[]
        {
            transaction.TransactionNumber,
            transaction.StoreName,
            transaction.TransactionDate.ToString("yyyy-MM-dd"),
            PettyCashRepository.GetTransactionTypeName(transaction.TransactionType),
            transaction.ExpenseCategory,
            transaction.Amount.ToString("0.##"),
            PettyCashRepository.GetStatusName(transaction.Status)
        });
        return Csv("petty-cash-report.csv", ["單號", "門市", "日期", "類型", "分類", "金額", "狀態"], rows);
    }

    private static CsvExport ExportTransfers(LocalDataStore store)
    {
        var rows = store.TransferOrders.Select(order => new[]
        {
            order.TransferNumber,
            order.StoreName,
            order.ItemName,
            order.RequestedQuantity.ToString("0.##"),
            order.ShippedQuantity.ToString("0.##"),
            order.ReceivedQuantity.ToString("0.##"),
            order.DifferenceQuantity.ToString("0.##"),
            TransferRepository.GetStatusName(order.Status)
        });
        return Csv("transfer-report.csv", ["調撥單號", "門市", "品項", "叫貨", "出庫", "收貨", "差異", "狀態"], rows);
    }

    private static CsvExport ExportReturns(LocalDataStore store)
    {
        var rows = store.StoreReturns.Select(item => new[]
        {
            item.ReturnNumber,
            item.StoreName,
            item.ItemName,
            item.Quantity.ToString("0.##"),
            item.Reason,
            StoreReturnRepository.GetStatusName(item.Status),
            StoreReturnRepository.GetDispositionName(item.Disposition)
        });
        return Csv("store-return-report.csv", ["退貨單號", "門市", "品項", "數量", "原因", "狀態", "處理方式"], rows);
    }

    private static CsvExport ExportReportDefinitions(LocalDataStore store)
    {
        var rows = store.ReportDefinitions.Select(report => new[]
        {
            report.ReportCode,
            report.ReportName,
            report.ReportCategory,
            ReportCenterRepository.GetStatusName(report.Status)
        });
        return Csv("report-definitions.csv", ["報表代號", "報表名稱", "分類", "狀態"], rows);
    }

    private static CsvExport Csv(string fileName, IReadOnlyList<string> headers, IEnumerable<IReadOnlyList<string>> rows)
    {
        var builder = new StringBuilder();
        builder.AppendLine(string.Join(",", headers.Select(EscapeCsv)));
        foreach (var row in rows)
        {
            builder.AppendLine(string.Join(",", row.Select(EscapeCsv)));
        }

        return new CsvExport(fileName, "\uFEFF" + builder);
    }

    private static string EscapeCsv(string value)
    {
        var normalized = value.Replace("\"", "\"\"", StringComparison.Ordinal);
        return $"\"{normalized}\"";
    }

    private void Update(Guid id, Action<LocalReportDefinition> update)
    {
        var store = LocalDataStoreFile.Load(_options);
        var report = store.ReportDefinitions.FirstOrDefault(existing => existing.Id == id);
        if (report is null)
        {
            return;
        }

        update(report);
        report.UpdatedAt = DateTime.UtcNow;
        LocalDataStoreFile.Save(_options, store);
    }

    private static string? BlankToNull(string? value)
    {
        return string.IsNullOrWhiteSpace(value) ? null : value.Trim();
    }
}

public sealed record ReportCenterSummary(
    int ReportCount,
    int PendingApprovalCount,
    int ApprovedCount,
    int InventoryRows,
    int PurchaseRows,
    int PettyCashRows,
    int TransferRows,
    int ReturnRows);

public sealed record CsvExport(string FileName, string Content);

public sealed record SaveReportDefinitionResult(bool IsSuccess, string? ErrorMessage)
{
    public static SaveReportDefinitionResult Success() => new(true, null);
    public static SaveReportDefinitionResult ValidationError(string message) => new(false, message);
}