Build a Vehicle Inspection Booking and Payment App

Tables: centers (name, location, capacity_per_slot, paystack_subaccount_code), inspection_slots (center_id, date, time, booked_count, capacity), inspections (owner_id, vehicle_id, center_id, slot_id, type, fee, status, paystack_ref, certificate_url), vehicles (owner_id, plate_number, make, model, year, color).

var INSPECTION_FEES = {
  annual_roadworthiness: 350000,  // NGN 3,500
  pre_purchase:          500000,  // NGN 5,000
  insurance_valuation:   250000,  // NGN 2,500
};

async function bookInspection(ownerEmail, ownerId, vehicleId, centerId, slotId, type) {
  var fee = INSPECTION_FEES[type];
  if (!fee) throw new Error('Invalid inspection type');

  var slot = await db.inspectionSlots.findById(slotId);
  if (slot.booked_count >= slot.capacity) throw new Error('Slot is fully booked');

  var reference = 'INSP-' + Date.now();
  var center = await db.centers.findById(centerId);

  var inspection = await db.inspections.create({
    owner_id: ownerId, vehicle_id: vehicleId, center_id: centerId, slot_id: slotId,
    type, fee, status: 'pending_payment', paystack_ref: reference,
  });

  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: ownerEmail, amount: fee, currency: 'NGN', reference,
      subaccount: center.paystack_subaccount_code, // center gets their share
      metadata: { inspection_id: inspection.id, vehicle_id: vehicleId, slot_id: slotId },
    }),
  });
  return (await res.json()).data.authorization_url;
}

// Webhook: confirm inspection slot
if (event.event === 'charge.success') {
  var meta = event.data.metadata;
  if (!meta.inspection_id) return res.sendStatus(200);

  await db.inspections.update(meta.inspection_id, { status: 'confirmed' });
  await db.inspectionSlots.increment(meta.slot_id, 'booked_count', 1);

  var inspection = await db.inspections.findById(meta.inspection_id);
  var vehicle = await db.vehicles.findById(meta.vehicle_id);
  var slot = await db.inspectionSlots.findById(meta.slot_id);
  await sendBookingConfirmation(inspection.owner_id, vehicle.plate_number, slot.date, slot.time);
}

// Inspector submits results via inspector app
async function submitInspectionResult(inspectorId, inspectionId, result, findings, mileage) {
  var inspection = await db.inspections.findById(inspectionId);
  var vehicle = await db.vehicles.findById(inspection.vehicle_id);
  var owner = await db.owners.findById(inspection.owner_id);

  await db.inspections.update(inspectionId, {
    status: result === 'pass' ? 'passed' : 'failed',
    inspector_id: inspectorId,
    findings: findings,
    inspected_at: new Date(),
    mileage_at_inspection: mileage,
  });

  if (result === 'pass') {
    // Generate certificate with unique verification code
    var certCode = 'CERT-' + vehicle.plate_number + '-' + new Date().getFullYear() + '-' + Math.random().toString(36).slice(2, 8).toUpperCase();
    var validUntil = new Date();
    validUntil.setFullYear(validUntil.getFullYear() + 1); // 1-year certificate

    var certificateUrl = await generateCertificatePdf({
      inspectionId, vehicle, owner, certCode, validUntil, mileage,
    });

    await db.inspections.update(inspectionId, {
      certificate_url: certificateUrl,
      certificate_code: certCode,
      certificate_valid_until: validUntil,
    });
    await sendCertificateEmail(owner.email, owner.name, vehicle.plate_number, certificateUrl);
  } else {
    // Failed inspection — send remediation report
    await sendFailureReport(owner.email, vehicle.plate_number, findings);
  }
}

// Public certificate verification (for police/insurers)
async function verifyCertificate(certCode) {
  var inspection = await db.inspections.findByCertCode(certCode);
  if (!inspection) return { valid: false };
  return {
    valid: new Date() < new Date(inspection.certificate_valid_until),
    plate_number: inspection.vehicle.plate_number,
    result: inspection.status,
    valid_until: inspection.certificate_valid_until,
  };
}

See build a barbershop appointment and payment app for a simpler slot booking with deposit pattern without the certificate generation component.

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