Retention and abandonment automation for D2C, retail and consumer brands.

// Cart abandonment: WhatsApp first, email fallback, no incentive until step 3.
// Fires from your cart's webhook — no polling, no cron.

import { addHours, differenceInMinutes } from 'date-fns';
import { sendWhatsAppTemplate, sendEmail } from './messaging';
import { getOrderForCart } from './orders';

type CartEvent = {
  cartId: string;
  customerId: string;
  channel: 'whatsapp' | 'email' | 'both';
  optedInAt: Date | null;      // WhatsApp opt-in timestamp
  abandonedAt: Date;
  cartValueInr: number;
};

const STEPS = [
  { after: '30m',  key: 'nudge_reminder',   incentive: null,             channelPref: 'whatsapp' },
  { after: '4h',   key: 'nudge_question',   incentive: null,             channelPref: 'whatsapp' },
  { after: '24h',  key: 'nudge_email',      incentive: null,             channelPref: 'email'    },
  { after: '48h',  key: 'nudge_incentive',  incentive: 'FLAT10',         channelPref: 'both'     },
] as const;

export async function scheduleAbandonmentFlow(event: CartEvent) {
  for (const step of STEPS) {
    const fireAt = addHours(event.abandonedAt, parseHours(step.after));
    await enqueue({ cartId: event.cartId, stepKey: step.key, fireAt });
  }
}

// The worker that picks up each scheduled step.
export async function runStep({ cartId, stepKey }: { cartId: string; stepKey: string }) {
  const step = STEPS.find((s) => s.key === stepKey);
  if (!step) return;

  // Cheapest correctness check — did they buy in the meantime?
  const order = await getOrderForCart(cartId);
  if (order) return { skipped: 'already_purchased' };

  const cart = await loadCart(cartId);
  if (cart.recovered || cart.expired) return { skipped: 'cart_state' };

  // Respect opt-in — WhatsApp without consent is a channel-killing move.
  const canWhatsApp = Boolean(cart.customer.optedInAt);
  const channel = pickChannel(step.channelPref, canWhatsApp);

  if (channel === 'whatsapp') {
    await sendWhatsAppTemplate(cart.customer.phone, stepKey, {
      first_name: cart.customer.firstName,
      cart_link: cart.recoveryUrl,
      incentive_code: step.incentive ?? '',
    });
  } else if (channel === 'email') {
    await sendEmail(cart.customer.email, {
      template: stepKey,
      vars: { cart, incentive: step.incentive },
    });
  }
  return { sent: channel, stepKey };
}

function pickChannel(pref: 'whatsapp' | 'email' | 'both', canWA: boolean) {
  if (pref === 'whatsapp') return canWA ? 'whatsapp' : 'email';
  if (pref === 'email')    return 'email';
  return canWA ? 'whatsapp' : 'email';
}

// ...enqueue/loadCart/parseHours are your queue (BullMQ, SQS, Cloud Tasks)
// and data layer of choice. Keep the retention logic itself platform-free.