[FEAT] Fetch All Subscribers to Newsletter (Paginated)

src/Hng.Application.Test/Features/NewsLetterSubscription/GetPaginatedSubscribersHandlerTests.cs

@@ -0,0 +1,103 @@
+using AutoMapper;
+using Hng.Application.Features.NewsLetterSubscription.Dtos;
+using Hng.Application.Features.NewsLetterSubscription.Handlers;
+using Hng.Application.Features.NewsLetterSubscription.Queries;
+using Hng.Domain.Entities;
+using Hng.Infrastructure.Context;
+using Microsoft.EntityFrameworkCore;
+using Moq;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace Hng.Application.Test.NewsLetterSubscription
+{
+    public class GetPaginatedSubscribersHandlerTests
+    {
+        private readonly ApplicationDbContext _context;
+        private readonly IMapper _mapper;
+        private readonly GetPaginatedSubscribersHandler _handler;
+
+        public GetPaginatedSubscribersHandlerTests()
+        {
+            // Setup InMemory Database
+            var options = new DbContextOptionsBuilder<ApplicationDbContext>()
+                .UseInMemoryDatabase(databaseName: Guid.NewGuid().ToString()) // Unique DB for each test
+                .Options;
+
+            _context = new ApplicationDbContext(options);
+
+            // Seed data
+            _context.NewsLetterSubscribers.AddRange(
+                new() { Id = Guid.NewGuid(), Email = "[email protected]", LeftOn = null, CreatedAt = DateTime.UtcNow },
+                new() { Id = Guid.NewGuid(), Email = "[email protected]", LeftOn = null, CreatedAt = DateTime.UtcNow }
+            );
+            _context.SaveChanges();
+
+            // Mock AutoMapper
+            var config = new MapperConfiguration(cfg =>
+            {
+                cfg.CreateMap<Hng.Domain.Entities.NewsLetterSubscriber, NewsLetterSubscriptionDto>();
+            });
+
+            _mapper = config.CreateMapper();
+
+            // Initialize handler
+            _handler = new GetPaginatedSubscribersHandler(_context, _mapper);
+        }
+
+        [Fact]
+        public async Task Handle_ShouldReturnActiveSubscribers_WithPagination()
+        {
+            // Arrange
+            var query = new GetPaginatedSubscribersQuery { Page = 1, Limit = 10 };
+
+            // Act
+            var result = await _handler.Handle(query, CancellationToken.None);
+
+            // Assert
+            Assert.True(result.Success);
+            Assert.Equal(200, result.StatusCode);
+            Assert.Equal("Subscribers retrieved successfully", result.Message);
+            Assert.NotNull(result.Data);
+            Assert.NotEmpty(result.Data);
+            Assert.Equal(2, result.Pagination.Total); // Total should match seed data
+        }
+
+        [Fact]
+        public async Task Handle_ShouldReturnNoSubscribers_WhenNoneExist()
+        {
+            // Arrange
+            _context.NewsLetterSubscribers.RemoveRange(_context.NewsLetterSubscribers);
+            await _context.SaveChangesAsync();
+
+            var query = new GetPaginatedSubscribersQuery { Page = 1, Limit = 10 };
+
+            // Act
+            var result = await _handler.Handle(query, CancellationToken.None);
+
+            // Assert
+            Assert.False(result.Success);
+            Assert.Equal(404, result.StatusCode);
+            Assert.Equal("No subscribers found", result.Message);
+        }
+
+        [Fact]
+        public async Task Handle_ShouldReturn400_WhenInvalidPaginationParams()
+        {
+            // Arrange
+            var query = new GetPaginatedSubscribersQuery { Page = -1, Limit = 0 };
+
+            // Act
+            var result = await _handler.Handle(query, CancellationToken.None);
+
+            // Assert
+            Assert.False(result.Success);
+            Assert.Equal(400, result.StatusCode);
+            Assert.Equal("Invalid pagination parameters", result.Message);
+        }
+    }
+}

src/Hng.Application/Features/NewsLetterSubscription/Dtos/NewsLetterSubscriptionDto.cs

@@ -6,6 +6,7 @@ namespace Hng.Application.Features.NewsLetterSubscription.Dtos
 {
     public class NewsLetterSubscriptionDto
     {
+        public Guid Id { get; set; }
         [EmailAddress]
         public string Email { get; set; }
     }

src/Hng.Application/Features/NewsLetterSubscription/Dtos/PaginatedSubscribersResponseDto.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Hng.Application.Features.NewsLetterSubscription.Dtos
+{
+    public class PaginatedSubscribersResponseDto
+    {
+        public bool Success { get; set; }
+        public int StatusCode { get; set; }
+        public string Message { get; set; }
+        public IEnumerable<NewsLetterSubscriptionDto> Data { get; set; }
+        public PaginationMetadata Pagination { get; set; }
+    }
+
+    public class PaginationMetadata
+    {
+        public int Page { get; set; }
+        public int Limit { get; set; }
+        public int Total { get; set; }
+    }
+}

src/Hng.Application/Features/NewsLetterSubscription/Handlers/GetPaginatedSubscribersHandler.cs

@@ -0,0 +1,72 @@
+using AutoMapper;
+using Hng.Application.Features.NewsLetterSubscription.Dtos;
+using Hng.Application.Features.NewsLetterSubscription.Queries;
+using Hng.Infrastructure.Context;
+using MediatR;
+using Microsoft.EntityFrameworkCore;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Hng.Application.Features.NewsLetterSubscription.Handlers
+{
+    public class GetPaginatedSubscribersHandler : IRequestHandler<GetPaginatedSubscribersQuery, PaginatedSubscribersResponseDto>
+    {
+        private readonly ApplicationDbContext _context;
+        private readonly IMapper _mapper;
+
+        public GetPaginatedSubscribersHandler(ApplicationDbContext context, IMapper mapper)
+        {
+            _context = context;
+            _mapper = mapper;
+        }
+
+        public async Task<PaginatedSubscribersResponseDto> Handle(GetPaginatedSubscribersQuery request, CancellationToken cancellationToken)
+        {
+            if (request.Page <= 0 || request.Limit <= 0)
+            {
+                return new PaginatedSubscribersResponseDto
+                {
+                    Success = false,
+                    StatusCode = 400,
+                    Message = "Invalid pagination parameters"
+                };
+            }
+
+            var totalSubscribers = await _context.NewsLetterSubscribers.CountAsync(s => s.LeftOn == null, cancellationToken);
+            var subscribers = await _context.NewsLetterSubscribers
+                .Where(s => s.LeftOn == null)
+                .OrderByDescending(s => s.CreatedAt)
+                .Skip((request.Page - 1) * request.Limit)
+                .Take(request.Limit)
+                .ToListAsync(cancellationToken);
+
+            if (!subscribers.Any())
+            {
+                return new PaginatedSubscribersResponseDto
+                {
+                    Success = false,
+                    StatusCode = 404,
+                    Message = "No subscribers found"
+                };
+            }
+
+            return new PaginatedSubscribersResponseDto
+            {
+                Success = true,
+                StatusCode = 200,
+                Message = "Subscribers retrieved successfully",
+                Data = _mapper.Map<IEnumerable<NewsLetterSubscriptionDto>>(subscribers), // Keep Guid as Id
+                Pagination = new PaginationMetadata
+                {
+                    Page = request.Page,
+                    Limit = request.Limit,
+                    Total = totalSubscribers
+                }
+            };
+        }
+    }
+}
+

src/Hng.Application/Features/NewsLetterSubscription/Queries/GetPaginatedSubscribersQuery.cs

@@ -0,0 +1,16 @@
+using Hng.Application.Features.NewsLetterSubscription.Dtos;
+using MediatR;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Hng.Application.Features.NewsLetterSubscription.Queries
+{
+    public class GetPaginatedSubscribersQuery : IRequest<PaginatedSubscribersResponseDto>
+    {
+        public int Page { get; set; } = 1;
+        public int Limit { get; set; } = 10;
+    }
+}

src/Hng.Domain/Entities/NewsLetterSubscriber.cs

@@ -5,6 +5,8 @@ public class NewsLetterSubscriber : EntityBase
         public string Email { get; set; }
         public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
         public DateTime? LeftOn { get; set; }
+
         public bool IsDeleted { get; set; } = false;
+
     }
 }