import { NextRequest, NextResponse } from 'next/server';

export async function POST(req: NextRequest) {
  try {
    const {
      campaignName,
      subject,
      htmlContent,
      scheduledAt,
      updateExisting = false,
      existingCampaignId
    } = await req.json();

    if (!htmlContent) {
      return NextResponse.json(
        { error: 'Chýba povinné pole htmlContent.' },
        { status: 400 }
      );
    }

    const apiKey = process.env.BREVO_API_KEY;
    const senderName = process.env.BREVO_SENDER_NAME || 'Jakub Hostačný (COOP Newsletter)';
    const senderEmail = process.env.BREVO_SENDER_EMAIL || 'tomas.rafay@jandl.sk';

    if (!apiKey) {
      return NextResponse.json(
        { error: 'BREVO_API_KEY nie je nakonfigurovaný na serveri.' },
        { status: 500 }
      );
    }

    // 1. Ak je zadané updateExisting a máme existujúce ID, skúsime aktualizovať existujúcu kampaň
    if (updateExisting && existingCampaignId) {
      const updatePayload: any = {
        name: campaignName,
        subject: subject,
        sender: {
          name: senderName,
          email: senderEmail
        },
        htmlContent: htmlContent
      };

      if (scheduledAt) {
        updatePayload.scheduledAt = scheduledAt;
      }

      const updateRes = await fetch(
        `https://api.brevo.com/v3/emailCampaigns/${encodeURIComponent(existingCampaignId)}`,
        {
          method: 'PUT',
          headers: {
            'accept': 'application/json',
            'content-type': 'application/json',
            'api-key': apiKey
          },
          body: JSON.stringify(updatePayload)
        }
      );

      if (updateRes.ok || updateRes.status === 204) {
        return NextResponse.json({
          success: true,
          updated: true,
          campaignId: Number(existingCampaignId),
          brevoUrl: 'https://app.brevo.com/campaigns/listing',
          brevoListingUrl: 'https://app.brevo.com/campaigns/listing',
          message: 'Kampaň bola úspešne aktualizovaná v Brevo!'
        });
      }

      // Ak aktualizácia zlyhala (napr. kampaň už bola odoslaná alebo neexistuje), vytvoríme novú
      console.warn(`Update failed on campaign ${existingCampaignId}, creating a new one instead.`);
    }

    // 2. Vytvorenie novej kampane v Brevo
    const createPayload: any = {
      name: campaignName || 'COOP Jednota Newsletter',
      subject: subject || 'COOP Jednota Newsletter',
      sender: {
        name: senderName,
        email: senderEmail
      },
      type: 'classic',
      htmlContent: htmlContent
    };

    if (scheduledAt) {
      createPayload.scheduledAt = scheduledAt;
    }

    const brevoRes = await fetch('https://api.brevo.com/v3/emailCampaigns', {
      method: 'POST',
      headers: {
        'accept': 'application/json',
        'content-type': 'application/json',
        'api-key': apiKey
      },
      body: JSON.stringify(createPayload)
    });

    const data = await brevoRes.json();

    if (!brevoRes.ok) {
      console.error('Brevo API error:', data);
      return NextResponse.json(
        { error: data.message || 'Chyba pri vytváraní kampane v Brevo', details: data },
        { status: brevoRes.status }
      );
    }

    return NextResponse.json({
      success: true,
      updated: false,
      campaignId: data.id,
      brevoUrl: 'https://app.brevo.com/campaigns/listing',
      brevoListingUrl: 'https://app.brevo.com/campaigns/listing',
      message: 'Kampaň bola úspešne vytvorená v Brevo!'
    });
  } catch (error: any) {
    console.error('Export to Brevo error:', error);
    return NextResponse.json(
      { error: error.message || 'Interná chyba servera' },
      { status: 500 }
    );
  }
}