import * as crypto from 'crypto';

const BASE_URL = 'https://graph.facebook.com/v21.0';
const PIXEL_ID = process.env.META_PIXEL_ID;
const ACCESS_TOKEN = process.env.META_ACCESS_TOKEN;

function hashValue(value: string): string {
  return crypto.createHash('sha256').update(value.trim().toLowerCase()).digest('hex');
}

interface UserData {
  email?: string;
  ip?: string;
  userAgent?: string;
  fbc?: string;
  fbp?: string;
}

interface ConversionEvent {
  eventName: 'CompleteRegistration' | 'Purchase' | 'ViewContent' | 'Lead' | 'InitiateCheckout';
  eventTime?: number;
  eventSourceUrl?: string;
  userData: UserData;
  customData?: Record<string, unknown>;
}

export async function sendConversionEvent(event: ConversionEvent): Promise<void> {
  if (!PIXEL_ID || !ACCESS_TOKEN) {
    return;
  }

  const hashedUserData: Record<string, string> = {};
  if (event.userData.email) hashedUserData.em = hashValue(event.userData.email);
  if (event.userData.ip) hashedUserData.client_ip_address = event.userData.ip;
  if (event.userData.userAgent) hashedUserData.client_user_agent = event.userData.userAgent;
  if (event.userData.fbc) hashedUserData.fbc = event.userData.fbc;
  if (event.userData.fbp) hashedUserData.fbp = event.userData.fbp;

  const payload = {
    data: [
      {
        event_name: event.eventName,
        event_time: event.eventTime ?? Math.floor(Date.now() / 1000),
        event_source_url: event.eventSourceUrl ?? process.env.NEXT_PUBLIC_APP_URL,
        action_source: 'website',
        user_data: hashedUserData,
        custom_data: event.customData ?? {},
      },
    ],
  };

  try {
    const res = await fetch(`${BASE_URL}/${PIXEL_ID}/events?access_token=${ACCESS_TOKEN}`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(payload),
    });

    if (!res.ok) {
      const err = await res.json();
      console.error('[Meta CAPI] Error:', err);
    }
  } catch (error) {
    console.error('[Meta CAPI] Network error:', error);
  }
}

export { hashValue };