import type { VercelRequest, VercelResponse } from '@vercel/node';
import { createClient } from '@supabase/supabase-js';
import Papa from 'papaparse';

const supabase = createClient(
  process.env.SUPABASE_URL || '',
  process.env.SUPABASE_SERVICE_KEY || ''
);

function parseEUNumber(val: string | undefined | null): number | null {
  if (!val || val.trim() === '') return null;
  const cleaned = val.replace(/\./g, '').replace(',', '.');
  const num = parseFloat(cleaned);
  return isNaN(num) ? null : num;
}

function parseIntSafe(val: string | undefined | null): number | null {
  if (!val || val.trim() === '') return null;
  const cleaned = val.replace(/\./g, '').replace(',', '.');
  const num = parseInt(cleaned, 10);
  return isNaN(num) ? null : num;
}

interface CSVRow {
  [key: string]: string;
}

export default async function handler(req: VercelRequest, res: VercelResponse) {
  res.setHeader('Access-Control-Allow-Origin', '*');
  res.setHeader('Access-Control-Allow-Methods', 'POST, OPTIONS');
  res.setHeader('Access-Control-Allow-Headers', 'Content-Type');

  if (req.method === 'OPTIONS') return res.status(200).end();
  if (req.method !== 'POST') return res.status(405).json({ error: 'Method not allowed' });

  try {
    const csvText = typeof req.body === 'string' ? req.body : req.body?.toString() || '';

    if (!csvText.trim()) {
      return res.status(400).json({ error: 'Empty CSV body' });
    }

    const parsed = Papa.parse<CSVRow>(csvText, {
      header: true,
      skipEmptyLines: true,
    });

    if (parsed.errors.length > 0) {
      console.error('[upload-vendor-data] Parse errors:', parsed.errors.slice(0, 5));
    }

    const rows = parsed.data
      .filter(row => row['Date'] && row['Market'] && row['ASIN'])
      .map(row => ({
        date: row['Date'],
        market: row['Market'],
        asin: row['ASIN'],
        product_title: row['Product Title'] || null,
        tags: row['Tags'] || null,
        bsr_top_rank: parseIntSafe(row['Top Level Category (Rank)']),
        bsr_top_category: row['Top Level Category (Name)'] || null,
        bsr_detail_rank: parseIntSafe(row['Detail Level Category (Rank)']),
        bsr_detail_category: row['Detail Level Category (Name)'] || null,
        avg_rating: parseEUNumber(row['Average Rating']),
        num_reviews: parseIntSafe(row['Number of Reviews']),
        buybox_owner: row['Buybox Seller Name'] || null,
        buybox_price: parseEUNumber(row['Buybox Price']),
        amazon_has_buybox: row['Amazon Has Buybox'] === '1',
        glance_views: parseIntSafe(row['Glance Views']),
      }));

    if (rows.length === 0) {
      return res.status(400).json({ error: 'No valid rows found in CSV' });
    }

    // Upsert in batches of 500
    const BATCH_SIZE = 500;
    let totalUpserted = 0;

    for (let i = 0; i < rows.length; i += BATCH_SIZE) {
      const batch = rows.slice(i, i + BATCH_SIZE);
      const { error } = await supabase
        .from('vendor_daily_data')
        .upsert(batch, { onConflict: 'date,market,asin' });

      if (error) {
        console.error('[upload-vendor-data] Upsert error at batch', i, error);
        throw error;
      }
      totalUpserted += batch.length;
    }

    console.log(`[upload-vendor-data] Successfully upserted ${totalUpserted} rows`);

    res.status(200).json({
      success: true,
      rowsParsed: parsed.data.length,
      rowsUpserted: totalUpserted,
    });
  } catch (error: any) {
    console.error('[upload-vendor-data] Error:', error);
    res.status(500).json({ error: error.message });
  }
}