import { NextResponse } from 'next/server';
import { createServiceClient, createServerSupabaseClient } from '@/lib/supabase/server';
import QRCode from 'qrcode';
import ExcelJS from 'exceljs';

const BASE_URL = process.env.NEXT_PUBLIC_BASE_URL || 'https://gemeindeportal.vercel.app';

export async function GET() {
  try {
    // Auth check
    const authClient = await createServerSupabaseClient();
    const { data: { user } } = await authClient.auth.getUser();

    if (!user) {
      return NextResponse.json({ error: 'Nicht authentifiziert.' }, { status: 401 });
    }

    const supabase = createServiceClient();

    const { data: zaehler, error } = await supabase
      .from('wasserzaehler')
      .select('*')
      .order('kundennummer', { ascending: true });

    if (error || !zaehler || zaehler.length === 0) {
      return NextResponse.json(
        { error: 'Keine Wasserzähler gefunden.' },
        { status: 404 }
      );
    }

    // Create workbook
    const workbook = new ExcelJS.Workbook();
    workbook.creator = 'Gemeindeportal';
    workbook.created = new Date();

    // --- Sheet 1: Übersicht (Tabelle mit allen Kunden) ---
    const listSheet = workbook.addWorksheet('Übersicht', {
      pageSetup: {
        paperSize: 9, // A4
        orientation: 'landscape',
        fitToPage: true,
        fitToWidth: 1,
        fitToHeight: 0,
      },
    });

    listSheet.columns = [
      { header: 'Kundennummer', key: 'kundennummer', width: 18 },
      { header: 'Zählernummer', key: 'zaehlernummer', width: 18 },
      { header: 'Name', key: 'name', width: 28 },
      { header: 'Adresse', key: 'adresse', width: 30 },
      { header: 'Letzter Stand (m³)', key: 'stand', width: 18 },
      { header: 'QR-Code URL', key: 'url', width: 55 },
    ];

    // Header styling
    const headerRow = listSheet.getRow(1);
    headerRow.font = { bold: true, size: 11 };
    headerRow.fill = {
      type: 'pattern',
      pattern: 'solid',
      fgColor: { argb: 'FF0D2B4E' },
    };
    headerRow.font = { bold: true, size: 11, color: { argb: 'FFFFFFFF' } };
    headerRow.alignment = { vertical: 'middle' };
    headerRow.height = 28;

    for (const z of zaehler) {
      const url = `${BASE_URL}/wasserzaehler?token=${z.access_token}`;
      listSheet.addRow({
        kundennummer: z.kundennummer || '',
        zaehlernummer: z.zaehlernummer,
        name: z.haushalt_name,
        adresse: z.adresse || '',
        stand: z.alter_stand,
        url,
      });
    }

    // Auto-filter
    listSheet.autoFilter = {
      from: { row: 1, column: 1 },
      to: { row: zaehler.length + 1, column: 6 },
    };

    // --- Sheet 2+: Ein Blatt pro Kunde mit QR-Code (Druckseiten) ---
    for (let i = 0; i < zaehler.length; i++) {
      const z = zaehler[i];
      const url = `${BASE_URL}/wasserzaehler?token=${z.access_token}`;

      // Generate QR code as PNG buffer
      const qrBuffer = await QRCode.toBuffer(url, {
        width: 400,
        margin: 2,
        errorCorrectionLevel: 'M',
        type: 'png',
      });

      const sheetName = `${z.kundennummer || `Kunde ${i + 1}`}`.slice(0, 31);
      const sheet = workbook.addWorksheet(sheetName, {
        pageSetup: {
          paperSize: 9, // A4
          orientation: 'portrait',
          horizontalCentered: true,
          verticalCentered: true,
          margins: {
            left: 0.7,
            right: 0.7,
            top: 1.0,
            bottom: 1.0,
            header: 0.3,
            footer: 0.3,
          },
        },
      });

      // Set column widths
      sheet.getColumn(1).width = 5;
      sheet.getColumn(2).width = 25;
      sheet.getColumn(3).width = 35;
      sheet.getColumn(4).width = 5;

      // Title
      sheet.mergeCells('B2:C2');
      const titleCell = sheet.getCell('B2');
      titleCell.value = 'Gemeindeamt Weißkirchen an der Traun';
      titleCell.font = { bold: true, size: 16, color: { argb: 'FF0D2B4E' } };
      titleCell.alignment = { horizontal: 'center', vertical: 'middle' };
      sheet.getRow(2).height = 30;

      // Subtitle
      sheet.mergeCells('B3:C3');
      const subtitleCell = sheet.getCell('B3');
      subtitleCell.value = `Wasserzähler-Ablesung ${new Date().getFullYear()}`;
      subtitleCell.font = { size: 12, color: { argb: 'FF666666' } };
      subtitleCell.alignment = { horizontal: 'center', vertical: 'middle' };
      sheet.getRow(3).height = 22;

      // QR Code image — rows 5-20
      const imageId = workbook.addImage({
        buffer: qrBuffer as unknown as ExcelJS.Buffer,
        extension: 'png',
      });

      sheet.addImage(imageId, {
        tl: { col: 1.5, row: 5 },
        ext: { width: 250, height: 250 },
      });

      // Space for QR code
      for (let row = 5; row <= 20; row++) {
        sheet.getRow(row).height = 18;
      }

      // Customer info below QR code
      const infoStartRow = 22;

      // Kundennummer
      sheet.getCell(`B${infoStartRow}`).value = 'Kundennummer';
      sheet.getCell(`B${infoStartRow}`).font = { size: 10, color: { argb: 'FF999999' } };
      sheet.getCell(`B${infoStartRow}`).alignment = { horizontal: 'center' };
      sheet.mergeCells(`B${infoStartRow}:C${infoStartRow}`);

      sheet.getCell(`B${infoStartRow + 1}`).value = z.kundennummer || '—';
      sheet.getCell(`B${infoStartRow + 1}`).font = { bold: true, size: 22 };
      sheet.getCell(`B${infoStartRow + 1}`).alignment = { horizontal: 'center' };
      sheet.mergeCells(`B${infoStartRow + 1}:C${infoStartRow + 1}`);
      sheet.getRow(infoStartRow + 1).height = 32;

      // Zählernummer
      sheet.getCell(`B${infoStartRow + 3}`).value = 'Zählernummer';
      sheet.getCell(`B${infoStartRow + 3}`).font = { size: 10, color: { argb: 'FF999999' } };
      sheet.getCell(`B${infoStartRow + 3}`).alignment = { horizontal: 'center' };
      sheet.mergeCells(`B${infoStartRow + 3}:C${infoStartRow + 3}`);

      sheet.getCell(`B${infoStartRow + 4}`).value = z.zaehlernummer;
      sheet.getCell(`B${infoStartRow + 4}`).font = { bold: true, size: 16 };
      sheet.getCell(`B${infoStartRow + 4}`).alignment = { horizontal: 'center' };
      sheet.mergeCells(`B${infoStartRow + 4}:C${infoStartRow + 4}`);
      sheet.getRow(infoStartRow + 4).height = 26;

      // Instructions
      sheet.mergeCells(`B${infoStartRow + 7}:C${infoStartRow + 7}`);
      const instrCell = sheet.getCell(`B${infoStartRow + 7}`);
      instrCell.value = 'Scannen Sie den QR-Code mit Ihrem Smartphone';
      instrCell.font = { size: 11, color: { argb: 'FF666666' } };
      instrCell.alignment = { horizontal: 'center', wrapText: true };

      sheet.mergeCells(`B${infoStartRow + 8}:C${infoStartRow + 8}`);
      const instrCell2 = sheet.getCell(`B${infoStartRow + 8}`);
      instrCell2.value = 'um Ihren aktuellen Zählerstand zu melden.';
      instrCell2.font = { size: 11, color: { argb: 'FF666666' } };
      instrCell2.alignment = { horizontal: 'center', wrapText: true };

      // Border box around content
      for (let row = 1; row <= infoStartRow + 9; row++) {
        const r = sheet.getRow(row);
        r.getCell(2).border = { left: { style: 'thin', color: { argb: 'FFE0E0E0' } } };
        r.getCell(3).border = { right: { style: 'thin', color: { argb: 'FFE0E0E0' } } };
      }
    }

    // Generate buffer
    const buffer = await workbook.xlsx.writeBuffer();

    const filename = `wasserzaehler_qrcodes_${new Date().toISOString().split('T')[0]}.xlsx`;

    return new NextResponse(buffer, {
      status: 200,
      headers: {
        'Content-Type': 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
        'Content-Disposition': `attachment; filename="${filename}"`,
      },
    });
  } catch (err) {
    console.error('QR-Code Excel Error:', err);
    return NextResponse.json(
      { error: 'Interner Serverfehler.' },
      { status: 500 }
    );
  }
}