import ExcelJS from "exceljs";
import type { Response } from "express";

export interface RetailSaleExportRow {
  invoiceNo: string;
  invoiceDate: string;
  customer: string;
  itemsCount: number;
  paymentMode: string;
  subTotal: number | string;
  discount: number | string;
  grandTotal: number | string;
}

const COLUMNS: { header: string; key: keyof RetailSaleExportRow; width: number }[] = [
  { header: "Invoice No", key: "invoiceNo", width: 20 },
  { header: "Invoice Date", key: "invoiceDate", width: 16 },
  { header: "Customer Name", key: "customer", width: 26 },
  { header: "Items Count", key: "itemsCount", width: 14 },
  { header: "Payment Mode", key: "paymentMode", width: 16 },
  { header: "Sub Total", key: "subTotal", width: 14 },
  { header: "Discount", key: "discount", width: 12 },
  { header: "Grand Total", key: "grandTotal", width: 16 },
];

const NUMERIC_KEYS = new Set<keyof RetailSaleExportRow>([
  "itemsCount",
  "subTotal",
  "discount",
  "grandTotal",
]);

const HEADER_FILL: ExcelJS.Fill = {
  type: "pattern",
  pattern: "solid",
  fgColor: { argb: "FF15803D" }, // Emerald green
};

const HEADER_FONT: Partial<ExcelJS.Font> = {
  bold: true,
  color: { argb: "FFFFFFFF" },
  size: 11,
  name: "Calibri",
};

const TOTAL_FILL: ExcelJS.Fill = {
  type: "pattern",
  pattern: "solid",
  fgColor: { argb: "FFE8F5E9" },
};

const ALT_FILL: ExcelJS.Fill = {
  type: "pattern",
  pattern: "solid",
  fgColor: { argb: "FFF6F8FA" },
};

const NUM_FORMAT = "#,##0.00";
const BORDER_STYLE: Partial<ExcelJS.Border> = { style: "thin", color: { argb: "FFD1D5DB" } };
const CELL_BORDER: Partial<ExcelJS.Borders> = {
  top: BORDER_STYLE,
  left: BORDER_STYLE,
  bottom: BORDER_STYLE,
  right: BORDER_STYLE,
};

export async function generateRetailSaleExcel(
  rows: RetailSaleExportRow[],
  res: Response,
  filename = "retail-sales-report"
): Promise<void> {
  const workbook = new ExcelJS.Workbook();
  workbook.creator = "AVS System";
  workbook.created = new Date();

  const sheet = workbook.addWorksheet("Retail Sales Report", {
    pageSetup: {
      paperSize: 9,
      orientation: "landscape",
      fitToPage: true,
      fitToWidth: 1,
    },
    views: [{ state: "frozen", ySplit: 1 }],
  });

  sheet.columns = COLUMNS.map((col) => ({
    header: col.header,
    key: col.key,
    width: col.width,
  }));

  const headerRow = sheet.getRow(1);
  headerRow.height = 28;
  headerRow.eachCell((cell) => {
    cell.fill = HEADER_FILL;
    cell.font = HEADER_FONT;
    cell.alignment = { vertical: "middle", horizontal: "center", wrapText: false };
    cell.border = CELL_BORDER;
  });

  rows.forEach((rowData, idx) => {
    const row = sheet.addRow(rowData);
    row.height = 20;
    const isAlt = idx % 2 !== 0;
    row.eachCell({ includeEmpty: true }, (cell, colNumber) => {
      const colKey = COLUMNS[colNumber - 1]?.key;
      if (isAlt) cell.fill = ALT_FILL;
      if (colKey && NUMERIC_KEYS.has(colKey)) {
        const raw = cell.value;
        const num = raw !== null && raw !== undefined && raw !== "" ? Number(raw) : null;
        cell.value = num;
        if (colKey !== "itemsCount") {
          cell.numFmt = NUM_FORMAT;
        }
        cell.alignment = { vertical: "middle", horizontal: "right" };
      } else {
        cell.alignment = { vertical: "middle", horizontal: "left" };
      }
      cell.font = { name: "Calibri", size: 10 };
      cell.border = CELL_BORDER;
    });
  });

  if (rows.length > 0) {
    const dataStartRow = 2;
    const dataEndRow = rows.length + 1;

    const totalRow = sheet.addRow({
      invoiceNo: "TOTAL",
      invoiceDate: "",
      customer: "",
      itemsCount: { formula: `SUM(D${dataStartRow}:D${dataEndRow})` } as any,
      paymentMode: "",
      subTotal: { formula: `SUM(F${dataStartRow}:F${dataEndRow})` } as any,
      discount: { formula: `SUM(G${dataStartRow}:G${dataEndRow})` } as any,
      grandTotal: { formula: `SUM(H${dataStartRow}:H${dataEndRow})` } as any,
    });

    totalRow.height = 24;
    totalRow.eachCell({ includeEmpty: true }, (cell, colNumber) => {
      cell.fill = TOTAL_FILL;
      cell.font = { name: "Calibri", size: 10, bold: true };
      cell.border = CELL_BORDER;
      const colKey = COLUMNS[colNumber - 1]?.key;
      if (colKey && NUMERIC_KEYS.has(colKey)) {
        if (colKey !== "itemsCount") {
          cell.numFmt = NUM_FORMAT;
        }
        cell.alignment = { vertical: "middle", horizontal: "right" };
      } else {
        cell.alignment = { vertical: "middle", horizontal: "left" };
      }
    });
  }

  sheet.autoFilter = {
    from: { row: 1, column: 1 },
    to: { row: 1, column: COLUMNS.length },
  };

  const safeFilename = encodeURIComponent(filename);
  res.setHeader("Content-Type", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
  res.setHeader(
    "Content-Disposition",
    `attachment; filename="${safeFilename}.xlsx"; filename*=UTF-8''${safeFilename}.xlsx`
  );
  res.setHeader("Access-Control-Expose-Headers", "Content-Disposition");

  await workbook.xlsx.write(res);
  res.end();
}

export function mapRetailSaleToExportRow(item: any): RetailSaleExportRow {
  let invoiceDateStr = "";
  if (item.invoiceDate) {
    invoiceDateStr = new Date(item.invoiceDate as string).toISOString().slice(0, 10);
  }
  return {
    invoiceNo: item.invoiceNo ?? "",
    invoiceDate: invoiceDateStr,
    customer: item.walkInName ? `${item.walkInName}${item.walkInMobile ? ` (${item.walkInMobile})` : ""}` : "Walk-in Customer",
    itemsCount: Array.isArray(item.items) ? item.items.length : 0,
    paymentMode: item.paymentMode ?? "CASH",
    subTotal: Number(item.subTotal ?? 0),
    discount: Number(item.discount ?? 0),
    grandTotal: Number(item.grandTotal ?? 0),
  };
}