Build a Farmers Market Ordering Platform

Tables: farmers (name, phone, bank_code, account_number, paystack_subaccount_code), products (farmer_id, name, unit, price_per_unit, stock_qty), orders (customer_id, status, total, paystack_ref), order_items (order_id, product_id, farmer_id, qty, unit_price, subtotal).

async function checkout(customerEmail, customerId, cartItems) {
  var total = cartItems.reduce(function(sum, item) { return sum + (item.qty * item.unit_price); }, 0);
  var reference = 'FARM-' + Date.now();

  // Group items by farmer for split calculation
  var farmerTotals = {};
  for (var item of cartItems) {
    if (!farmerTotals[item.farmer_id]) farmerTotals[item.farmer_id] = 0;
    farmerTotals[item.farmer_id] += item.qty * item.unit_price;
  }

  var order = await db.orders.create({
    customer_id: customerId, status: 'pending', total, paystack_ref: reference,
  });
  for (var item of cartItems) {
    await db.orderItems.create({ ...item, order_id: order.id });
  }

  var res = await fetch('https://api.paystack.co/transaction/initialize', {
    method: 'POST',
    headers: { Authorization: 'Bearer ' + process.env.PAYSTACK_SECRET_KEY, 'Content-Type': 'application/json' },
    body: JSON.stringify({
      email: customerEmail,
      amount: total,
      currency: 'NGN',
      reference,
      metadata: { order_id: order.id, customer_id: customerId, farmer_totals: farmerTotals },
    }),
  });
  return (await res.json()).data.authorization_url;
}

// Webhook: confirm order and pay each farmer
if (event.event === 'charge.success') {
  var meta = event.data.metadata;
  if (!meta.order_id) return res.sendStatus(200);

  await db.orders.update(meta.order_id, { status: 'confirmed' });

  // Pay each farmer their share via Transfers
  var farmerTotals = meta.farmer_totals;
  for (var farmerId of Object.keys(farmerTotals)) {
    var farmer = await db.farmers.findById(farmerId);
    var platformFee = Math.floor(farmerTotals[farmerId] * 0.10); // 10% platform fee
    var payout = farmerTotals[farmerId] - platformFee;

    await fetch('https://api.paystack.co/transfer', {
      method: 'POST',
      headers: { Authorization: 'Bearer ' + process.env.PAYSTACK_SECRET_KEY, 'Content-Type': 'application/json' },
      body: JSON.stringify({
        source: 'balance', amount: payout,
        recipient: farmer.paystack_recipient_code,
        reason: 'Order #' + meta.order_id + ' payout',
      }),
    });

    // Notify farmer of new order
    await sendOrderNotification(farmer.phone, meta.order_id, farmerTotals[farmerId] / 100);
  }
}

// Reduce stock on order confirmation
async function reduceStock(orderId) {
  var items = await db.orderItems.findByOrder(orderId);
  for (var item of items) {
    var product = await db.products.findById(item.product_id);
    if (product.stock_qty < item.qty) {
      // Out of stock after payment — refund this item and notify
      await refundOrderItem(item);
      continue;
    }
    await db.products.update(item.product_id, { stock_qty: product.stock_qty - item.qty });
  }
}

// Delivery: aggregate order by delivery zone
async function assignDeliveryDriver(orderId) {
  var order = await db.orders.findById(orderId);
  var customer = await db.customers.findById(order.customer_id);
  var driver = await db.drivers.findAvailableInZone(customer.delivery_zone);

  await db.orders.update(orderId, { driver_id: driver.id, status: 'out_for_delivery' });
  await sendSMS(driver.phone, 'New order ' + orderId + ' for delivery to ' + customer.address);
  await sendSMS(customer.phone, 'Your order is on its way! Driver: ' + driver.name + ' — ' + driver.phone);
}

// Cron: weekly farmer reconciliation report
async function sendFarmerWeeklyReport(farmerId) {
  var weekStart = new Date();
  weekStart.setDate(weekStart.getDate() - 7);
  var items = await db.orderItems.findByFarmerAndPeriod(farmerId, weekStart, new Date());
  var totalEarned = items.reduce(function(sum, i) { return sum + i.subtotal; }, 0);
  var farmer = await db.farmers.findById(farmerId);
  await sendFarmerReport(farmer.phone, totalEarned / 100, items.length);
}

See build a grocery delivery app with rider payouts for a related model focused on rider-based delivery and per-delivery payouts.

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