import { NextRequest, NextResponse } from 'next/server';
import * as XLSX from 'xlsx';
import supabase from '@/lib/db';

// POST - Upload dan proses file Excel/CSV untuk data dosen
export async function POST(request: NextRequest) {
  try {
    // Ambil data formulir dari request
    const formData = await request.formData();
    const file = formData.get('file') as File;

    if (!file) {
      return NextResponse.json(
        { message: 'File is required' },
        { status: 400 }
      );
    }

    // Validasi tipe file (Excel atau CSV)
    const allowedTypes = [
      'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet', // .xlsx
      'application/vnd.ms-excel', // .xls
      'text/csv' // .csv
    ];

    if (!allowedTypes.includes(file.type)) {
      return NextResponse.json(
        { message: 'File type not supported. Please upload Excel (.xlsx, .xls) or CSV file.' },
        { status: 400 }
      );
    }

    // Baca file sebagai buffer
    const buffer = Buffer.from(await file.arrayBuffer());
    
    // Parse file menggunakan XLSX
    const workbook = XLSX.read(buffer, { type: 'buffer' });
    const sheetName = workbook.SheetNames[0];
    const worksheet = workbook.Sheets[sheetName];
    
    // Konversi ke JSON
    const jsonData = XLSX.utils.sheet_to_json(worksheet, { header: 1 });
    
    if (jsonData.length === 0) {
      return NextResponse.json(
        { message: 'File is empty' },
        { status: 400 }
      );
    }

    // Ambil header dari baris pertama
    const headers = jsonData[0] as string[];
    const dataRows = jsonData.slice(1);

    // Validasi header yang diperlukan
    const requiredHeaders = ['nama_dosen', 'nip'];
    const missingHeaders = requiredHeaders.filter(header => 
      !headers.some(h => h && h.toString().toLowerCase().includes(header.toLowerCase()))
    );

    if (missingHeaders.length > 0) {
      return NextResponse.json(
        { message: `Missing required columns: ${missingHeaders.join(', ')}` },
        { status: 400 }
      );
    }

    // Mapping index kolom
    const getColumnIndex = (headerName: string) => {
      return headers.findIndex(h => h && h.toString().toLowerCase().includes(headerName.toLowerCase()));
    };

    const nama_dosenIndex = getColumnIndex('nama_dosen');
    const nipIndex = getColumnIndex('nip');

    // Proses setiap baris data
    const results = {
      success: 0,
      failed: 0,
      errors: [] as string[]
    };

    for (let i = 0; i < dataRows.length; i++) {
      const row = dataRows[i] as any[];
      const rowNumber = i + 2; // +2 karena index dimulai dari 0 dan ada header

      try {
        // Ekstrak data dari row
        const nama_dosen = row[nama_dosenIndex]?.toString().trim();
        const nip = row[nipIndex]?.toString().trim();

        // Validasi data yang diperlukan
        if (!nama_dosen || !nip) {
          results.failed++;
          results.errors.push(`Row ${rowNumber}: Missing required data (nama_dosen or nip)`);
          continue;
        }

        // Validasi panjang NIP
        if (nip.length !== 18) {
          results.failed++;
          results.errors.push(`Row ${rowNumber}: NIP harus terdiri dari 18 karakter`);
          continue;
        }

        // Cek apakah NIP sudah ada
        const { data: existingDosen, error: checkError } = await supabase
          .from('dosen')
          .select('nip')
          .eq('nip', nip)
          .single();

        if (!checkError && existingDosen) {
          // Update data yang sudah ada
          const { error: updateError } = await supabase
            .from('dosen')
            .update({
              nama_dosen
            })
            .eq('nip', nip);

          if (updateError) {
            results.failed++;
            results.errors.push(`Row ${rowNumber}: Error updating dosen with NIP ${nip}: ${updateError.message}`);
            continue;
          }
        } else {
          // Insert data baru
          const { error: insertError } = await supabase
            .from('dosen')
            .insert({
              nama_dosen,
              nip
            });

          if (insertError) {
            results.failed++;
            results.errors.push(`Row ${rowNumber}: Error inserting dosen with NIP ${nip}: ${insertError.message}`);
            continue;
          }
        }

        results.success++;
      } catch (error) {
        results.failed++;
        results.errors.push(`Row ${rowNumber}: Unexpected error: ${error}`);
      }
    }

    return NextResponse.json({
      message: `Upload completed. Success: ${results.success}, Failed: ${results.failed}`,
      details: {
        totalRows: dataRows.length,
        successCount: results.success,
        failedCount: results.failed,
        errors: results.errors
      }
    });

  } catch (error) {
    console.error('Error processing file:', error);
    return NextResponse.json(
      { message: 'Error processing file' },
      { status: 500 }
    );
  }
}