From ba59e00006efa9d8edaacf3c0a5b2cd649eae155 Mon Sep 17 00:00:00 2001
From: Ahmedscreativeverse <olugbasaahmed@gmail.com>
Date: Thu, 23 Apr 2026 20:13:53 +0100
Subject: [PATCH] Implement pagination limits and validation tests for DTOs

---
 README.md                             |  2 ++
 src/common/constants/app.constants.ts |  2 +-
 src/common/dto/pagination.dto.spec.ts | 41 +++++++++++++++++++++++++++
 src/common/dto/pagination.dto.ts      | 11 ++++---
 src/common/utils/pagination.util.ts   |  7 +++--
 5 files changed, 56 insertions(+), 7 deletions(-)
 create mode 100644 src/common/dto/pagination.dto.spec.ts

diff --git a/README.md b/README.md
index dba241b4..cfa94f32 100644
--- a/README.md
+++ b/README.md
@@ -11,6 +11,8 @@
 
 This is the **NestJS** backend powering TeachLink — offering APIs, authentication, user management, notifications, and knowledge monetization features.
 
+- Pagination is limited to a maximum page size of **100** items per request.
+
 ---
 
 ## 🔁 CI / Testing
diff --git a/src/common/constants/app.constants.ts b/src/common/constants/app.constants.ts
index b1a4858a..07bd4241 100644
--- a/src/common/constants/app.constants.ts
+++ b/src/common/constants/app.constants.ts
@@ -9,7 +9,7 @@ export const APP_CONSTANTS = {
 
   // Pagination defaults
   DEFAULT_PAGE_SIZE: 10,
-  MAX_PAGE_SIZE: 100,
+  MAX_PAGE_SIZE: 100, // Max items allowed per page for paginated API responses
 
   // Status values
   COURSE_STATUS: {
diff --git a/src/common/dto/pagination.dto.spec.ts b/src/common/dto/pagination.dto.spec.ts
new file mode 100644
index 00000000..596cd092
--- /dev/null
+++ b/src/common/dto/pagination.dto.spec.ts
@@ -0,0 +1,41 @@
+import { validateSync } from 'class-validator';
+import { PaginationQueryDto, CursorPaginationQueryDto } from './pagination.dto';
+import { APP_CONSTANTS } from '../constants/app.constants';
+
+describe('Pagination DTO validation', () => {
+  const { DEFAULT_PAGE_SIZE, MAX_PAGE_SIZE } = APP_CONSTANTS;
+
+  it('uses the default page size when no limit is provided', () => {
+    const dto = new PaginationQueryDto();
+    const errors = validateSync(dto);
+
+    expect(errors).toHaveLength(0);
+    expect(dto.limit).toBe(DEFAULT_PAGE_SIZE);
+  });
+
+  it('accepts a limit equal to the maximum page size', () => {
+    const dto = new PaginationQueryDto();
+    dto.limit = MAX_PAGE_SIZE;
+    const errors = validateSync(dto);
+
+    expect(errors).toHaveLength(0);
+  });
+
+  it('rejects a limit greater than the maximum page size', () => {
+    const dto = new PaginationQueryDto();
+    dto.limit = MAX_PAGE_SIZE + 1;
+    const errors = validateSync(dto);
+
+    expect(errors).toHaveLength(1);
+    expect(errors[0].constraints).toHaveProperty('max');
+  });
+
+  it('validates cursor pagination limit against the same maximum', () => {
+    const dto = new CursorPaginationQueryDto();
+    dto.limit = MAX_PAGE_SIZE + 1;
+    const errors = validateSync(dto);
+
+    expect(errors).toHaveLength(1);
+    expect(errors[0].constraints).toHaveProperty('max');
+  });
+});
diff --git a/src/common/dto/pagination.dto.ts b/src/common/dto/pagination.dto.ts
index 6f2dacca..dec54571 100644
--- a/src/common/dto/pagination.dto.ts
+++ b/src/common/dto/pagination.dto.ts
@@ -1,5 +1,8 @@
 import { IsOptional, IsInt, Min, Max, IsString, IsIn, IsNumber } from 'class-validator';
 import { Type } from 'class-transformer';
+import { APP_CONSTANTS } from '../constants/app.constants';
+
+const { DEFAULT_PAGE_SIZE, MAX_PAGE_SIZE } = APP_CONSTANTS;
 
 export enum SortOrder {
   ASC = 'ASC',
@@ -23,9 +26,9 @@ export class PaginationQueryDto {
   @Type(() => Number)
   @IsInt()
   @Min(1)
-  @Max(100)
+  @Max(MAX_PAGE_SIZE, { message: `Page size cannot exceed ${MAX_PAGE_SIZE}` })
   @IsNumber()
-  limit?: number = 10;
+  limit?: number = DEFAULT_PAGE_SIZE;
 
   @IsOptional()
   @IsString()
@@ -49,8 +52,8 @@ export class CursorPaginationQueryDto {
   @Type(() => Number)
   @IsInt()
   @Min(1)
-  @Max(100)
-  limit?: number = 10;
+  @Max(MAX_PAGE_SIZE, { message: `Page size cannot exceed ${MAX_PAGE_SIZE}` })
+  limit?: number = DEFAULT_PAGE_SIZE;
 
   @IsOptional()
   @IsString()
diff --git a/src/common/utils/pagination.util.ts b/src/common/utils/pagination.util.ts
index 0b64a23c..4599c312 100644
--- a/src/common/utils/pagination.util.ts
+++ b/src/common/utils/pagination.util.ts
@@ -6,6 +6,9 @@ import {
   CursorPaginationQueryDto,
   CursorDirection,
 } from '../dto/pagination.dto';
+import { APP_CONSTANTS } from '../constants/app.constants';
+
+const { DEFAULT_PAGE_SIZE } = APP_CONSTANTS;
 
 export interface PaginatedResponse<T> {
   data: T[];
@@ -34,7 +37,7 @@ export async function paginate<T>(
   options: PaginationQueryDto,
 ): Promise<PaginatedResponse<T>> {
   const page = options.page || 1;
-  const limit = options.limit || 10;
+  const limit = options.limit || DEFAULT_PAGE_SIZE;
   const skip = (page - 1) * limit;
 
   // Apply sorting
@@ -116,7 +119,7 @@ export async function paginateWithCursor<T extends Record<string, any>>(
   queryBuilder: SelectQueryBuilder<T>,
   options: CursorPaginationQueryDto,
 ): Promise<CursorPaginatedResponse<T>> {
-  const limit = options.limit || 10;
+  const limit = options.limit || DEFAULT_PAGE_SIZE;
   const sortBy = options.sortBy || 'createdAt';
   const order = options.order || SortOrder.DESC;
   const direction = options.direction || CursorDirection.FORWARD;