interface UserData {
  em?: string;
  client_user_agent?: string;
  client_ip_address?: string;
}

interface CustomData {
  location?: string;
}

interface MetaPixelEvent {
  event_name: string;
  event_time: number;
  event_source_url: string;
  action_source: string;
  user_data: UserData;
  custom_data?: CustomData;
  event_id: string;
}

interface MetaPixelPayload {
  data: MetaPixelEvent[];
  access_token: string;
}

async function hashEmail(email: string): Promise<string> {
  const encoder = new TextEncoder();
  const data = encoder.encode(email.toLowerCase().trim());
  const hashBuffer = await crypto.subtle.digest('SHA-256', data);
  const hashArray = Array.from(new Uint8Array(hashBuffer));
  return hashArray.map(byte => byte.toString(16).padStart(2, '0')).join('');
}

function generateEventId(): string {
  const array = new Uint8Array(16);
  crypto.getRandomValues(array);
  return Array.from(array, byte => byte.toString(16).padStart(2, '0')).join('');
}

export async function sendCompleteRegistrationEvent(
  email: string,
  eventSourceUrl: string,
  userAgent?: string,
  clientIpAddress?: string,
  location?: string
): Promise<boolean> {
  try {
    const pixelId = process.env.META_PIXEL_ID || import.meta.env.META_PIXEL_ID;
    const accessToken =
      process.env.META_PIXEL_ACCESS_TOKEN || import.meta.env.META_PIXEL_ACCESS_TOKEN;

    if (!pixelId || !accessToken) {
      return false;
    }

    const userData: UserData = {
      em: await hashEmail(email),
    };

    if (userAgent) {
      userData.client_user_agent = userAgent;
    }

    if (clientIpAddress) {
      userData.client_ip_address = clientIpAddress;
    }

    const customData: CustomData = {};
    if (location) {
      customData.location = location;
    }

    const event: MetaPixelEvent = {
      event_name: 'CompleteRegistration',
      event_time: Math.floor(Date.now() / 1000),
      event_source_url: eventSourceUrl,
      action_source: 'website',
      user_data: userData,
      event_id: generateEventId(),
    };

    if (Object.keys(customData).length > 0) {
      event.custom_data = customData;
    }

    const payload: MetaPixelPayload = {
      data: [event],
      access_token: accessToken,
    };

    const response = await fetch(`https://graph.facebook.com/v21.0/${pixelId}/events`, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify(payload),
    });

    if (!response.ok) {
      return false;
    }

    return true;
  } catch (error) {
    return false;
  }
}