feat: add class discounts, frontend visibility, and public listing

Add hasDiscount, freeSpots, and showOnFrontend on classes with a public get-all endpoint and richer notification user populate.

components/classes/classService.js

@@ -18,6 +18,28 @@ const applyScheduleFields = (payload, body) => {
   return payload;
 };
 
+const CLASS_LIST_FIELDS = 'name course professor students capacity tuitionFee hasDiscount discount freeSpots showOnFrontend startDate endDate days startTime endTime isActive adminNotes createdAt updatedAt';
+
+const normalizePricingFields = (body = {}) => {
+  const tuitionFee = Math.max(0, Number(body.tuitionFee) || 0);
+  const hasDiscount = Boolean(body.hasDiscount);
+  const discount = hasDiscount
+    ? Math.min(Math.max(0, Number(body.discount) || 0), tuitionFee)
+    : 0;
+  return { tuitionFee, hasDiscount, discount };
+};
+
+const enrichClassForDisplay = (cls) => {
+  const tuitionFee = cls.tuitionFee || 0;
+  const discount = cls.hasDiscount ? (cls.discount || 0) : 0;
+  const finalTuitionFee = Math.max(0, tuitionFee - discount);
+  let daysUntilStart = null;
+  if (cls.startDate) {
+    daysUntilStart = Math.ceil((new Date(cls.startDate).getTime() - Date.now()) / (1000 * 60 * 60 * 24));
+  }
+  return { ...cls, finalTuitionFee, daysUntilStart };
+};
+
 const getAll = async (query) => {
   const page = parseInt(query.page) || 1;
   const limit = Math.min(parseInt(query.limit) || 20, 200);
@@ -34,14 +56,14 @@ const getAll = async (query) => {
 
   const [items, total] = await Promise.all([
     Class.find(filter)
-      .select('name course professor students capacity tuitionFee startDate endDate days startTime endTime isActive adminNotes createdAt updatedAt')
+      .select(CLASS_LIST_FIELDS)
       .populate({ path: 'course', select: 'title type price' })
       .populate({ path: 'professor', select: 'name surname' })
       .skip(skip).limit(limit).sort({ createdAt: -1 }).lean(),
     Class.countDocuments(filter)
   ]);
 
-  return { data: items, meta: calculateMeta(total, page, limit) };
+  return { data: items.map(enrichClassForDisplay), meta: calculateMeta(total, page, limit) };
 };
 
 const getOne = async (id) => {
@@ -51,22 +73,32 @@ const getOne = async (id) => {
       .populate({ path: 'students', select: 'name phoneNumber gender' })
     .lean();
   if (!cls) throw new AppError('CLASS_NOT_FOUND');
-  return cls;
+  return enrichClassForDisplay(cls);
 };
 
 const create = async (body) => {
-  const payload = applyScheduleFields({ ...body }, body);
+  const payload = applyScheduleFields({ ...body, ...normalizePricingFields(body) }, body);
+  if (body.freeSpots === '' || body.freeSpots === null || body.freeSpots === undefined) {
+    payload.freeSpots = null;
+  } else {
+    payload.freeSpots = Math.max(0, Number(body.freeSpots) || 0);
+  }
   const cls = await Class.create(payload);
   return getOne(cls._id);
 };
 
 const update = async (id, body) => {
-  const payload = applyScheduleFields({ ...body }, body);
+  const payload = applyScheduleFields({ ...body, ...normalizePricingFields(body) }, body);
+  if (body.freeSpots === '' || body.freeSpots === null) {
+    payload.freeSpots = null;
+  } else if (body.freeSpots !== undefined) {
+    payload.freeSpots = Math.max(0, Number(body.freeSpots) || 0);
+  }
   const cls = await Class.findByIdAndUpdate(id, payload, { new: true, runValidators: true })
     .populate({ path: 'course', select: 'title' })
     .lean();
   if (!cls) throw new AppError('CLASS_NOT_FOUND');
-  return cls;
+  return enrichClassForDisplay(cls);
 };
 
 const remove = async (id) => {
@@ -144,7 +176,30 @@ const getMyClasses = async (userId, query = {}) => {
     Class.countDocuments(filter)
   ]);
 
-  return { data: items, meta: calculateMeta(total, page, limit) };
+  return { data: items.map(enrichClassForDisplay), meta: calculateMeta(total, page, limit) };
 };
 
-module.exports = { getAll, getOne, create, update, remove, registerUsers, removeUser, getMyClasses };
+const getPublicClasses = async (query = {}) => {
+  const page = parseInt(query.page) || 1;
+  const limit = Math.min(parseInt(query.limit) || 50, 200);
+  const skip = (page - 1) * limit;
+
+  const filter = {
+    isActive: { $ne: false },
+    showOnFrontend: { $ne: false }
+  };
+  if (query.courseId) filter.course = query.courseId;
+
+  const [items, total] = await Promise.all([
+    Class.find(filter)
+      .select('name course professor capacity tuitionFee hasDiscount discount freeSpots startDate endDate days startTime endTime')
+      .populate({ path: 'course', select: 'title type description' })
+      .populate({ path: 'professor', select: 'name surname' })
+      .skip(skip).limit(limit).sort({ startDate: 1, createdAt: -1 }).lean(),
+    Class.countDocuments(filter)
+  ]);
+
+  return { data: items.map(enrichClassForDisplay), meta: calculateMeta(total, page, limit) };
+};
+
+module.exports = { getAll, getOne, create, update, remove, registerUsers, removeUser, getMyClasses, getPublicClasses };