Refactor email repository and query handling

Replaced `IMailRepository` with `IReceivedEmailRepository` to improve modularity and functionality. Updated `IReceivedEmailRepository` to make the `EmailAccount` parameter optional in the `FindAsync` method.

Added `ReceivedEmailRepository` with advanced filtering capabilities, including account, flags, text, UID, date, and recipient filters. Implemented deferred materialization for recipient filtering due to EF Core limitations.

Registered `IReceivedEmailRepository` in dependency injection. Updated `ReadEmailQueryHandler` to use the new repository. Improved query performance by applying filters conditionally.

src/core/DigitalData.MessagingService.Application/Common/Interfaces/Repositories/IReceivedEmailRepository.cs

@@ -6,6 +6,6 @@ namespace DigitalData.MessagingService.Application.Common.Interfaces.Repositorie
 
 public interface IReceivedEmailRepository : IRepository<ReceivedEmail>
 {
-    public Task<IEnumerable<ReceivedEmail>> FindAsync(MailSearchFilter mailSearchFilter, EmailAccount accountQuery, CancellationToken cancellationToken = default);
+    public Task<IEnumerable<ReceivedEmail>> FindAsync(MailSearchFilter mailSearchFilter, EmailAccount? accountQuery = null, CancellationToken cancellationToken = default);
 }
 #endif

src/core/DigitalData.MessagingService.Application/EmailReceiving/Queries/ReadEmailQuery.cs

@@ -28,7 +28,7 @@ public record ReadEmailQuery : IRequest<IEnumerable<ReceivedEmailDto>>
     public MailSearchFilter Mail { get; init; } = new();
 }
 
-public class ReadEmailQueryHandler(IMapper Mapper, ILogger<ReadEmailQueryHandler> Logger, IRepository<EmailAccount> EmailAccountRepo, IMailRepository MailRepo) : IRequestHandler<ReadEmailQuery, IEnumerable<ReceivedEmailDto>>
+public class ReadEmailQueryHandler(IMapper Mapper, ILogger<ReadEmailQueryHandler> Logger, IRepository<EmailAccount> EmailAccountRepo, IReceivedEmailRepository MailRepo) : IRequestHandler<ReadEmailQuery, IEnumerable<ReceivedEmailDto>>
 {
     public async Task<IEnumerable<ReceivedEmailDto>> Handle(ReadEmailQuery request, CancellationToken cancellationToken)
     {

src/infrastructure/DigitalData.MessagingService.Infrastructure/DependencyInjection.cs

@@ -66,6 +66,8 @@ public static class DependencyInjection
 
         services.AddScoped(typeof(IRepository<>), typeof(Repository<>));
 
+        services.AddScoped<IReceivedEmailRepository, ReceivedEmailRepository>();
+
         // AutoMapper - Register entity self-mappings (T -> T) for generic repository
         services.AddAutoMapper(config => config.AddMaps(typeof(EntitySelfMappingProfile).Assembly));
 

src/infrastructure/DigitalData.MessagingService.Infrastructure/Repositories/ReceivedEmailRepository.cs

@@ -0,0 +1,83 @@
+using AutoMapper;
+using DigitalData.MessagingService.Application.Common.Dto.MailSearch;
+using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
+using DigitalData.MessagingService.Domain.Entities;
+using DigitalData.MessagingService.Infrastructure.Persistence;
+using Microsoft.EntityFrameworkCore;
+
+namespace DigitalData.MessagingService.Infrastructure.Repositories;
+
+public class ReceivedEmailRepository(MessagingServiceDbContext Context, IMapper Mapper) : Repository<ReceivedEmail>(Context, Mapper), IReceivedEmailRepository
+{
+    public async Task<IEnumerable<ReceivedEmail>> FindAsync(MailSearchFilter mailSearchFilter, EmailAccount? accountQuery = null, CancellationToken cancellationToken = default)
+    {
+        IQueryable<ReceivedEmail> query = DbSet;
+
+        // ── Account filter ─────────────────────────────────────────────────────
+        if (accountQuery is not null)
+            query = query.Where(x => x.AccountId == accountQuery.Id);
+
+        // ── Flag filters ───────────────────────────────────────────────────────
+        if (mailSearchFilter.UnseenOnly)
+            query = query.Where(x => !x.IsSeen);
+
+        // ── Text filters ───────────────────────────────────────────────────────
+        if (!string.IsNullOrWhiteSpace(mailSearchFilter.SubjectContains))
+            query = query.Where(x => x.Subject.Contains(mailSearchFilter.SubjectContains));
+
+        if (!string.IsNullOrWhiteSpace(mailSearchFilter.SenderContains))
+            query = query.Where(x => x.From.Contains(mailSearchFilter.SenderContains));
+
+        if (!string.IsNullOrWhiteSpace(mailSearchFilter.BodyContains))
+            query = query.Where(x => x.TextBody.Contains(mailSearchFilter.BodyContains)
+                                  || x.HtmlBody.Contains(mailSearchFilter.BodyContains));
+
+        // ── UID filter ─────────────────────────────────────────────────────────
+        if (mailSearchFilter.Uid is { } uid)
+        {
+            if (uid.Absolute.HasValue)
+                query = query.Where(x => x.Uid == uid.Absolute.Value);
+            else
+            {
+                if (uid.Min.HasValue)
+                    query = query.Where(x => x.Uid >= uid.Min.Value);
+                if (uid.Max.HasValue)
+                    query = query.Where(x => x.Uid <= uid.Max.Value);
+            }
+        }
+
+        // ── Date filter ────────────────────────────────────────────────────────
+        if (mailSearchFilter.Date is { } date)
+        {
+            if (date.After.HasValue)
+                query = query.Where(x => x.Date >= date.After.Value);
+            if (date.Before.HasValue)
+                query = query.Where(x => x.Date <= date.Before.Value);
+        }
+
+        // ── Attachments ────────────────────────────────────────────────────────
+        if (mailSearchFilter.WithAttachments)
+            query = query.Include(x => x.Attachments);
+
+        // ── Sort ───────────────────────────────────────────────────────────────
+        query = mailSearchFilter.SortOrder == MailSortOrder.OldestFirst
+            ? query.OrderBy(x => x.Date)
+            : query.OrderByDescending(x => x.Date);
+
+        // ── Limit ──────────────────────────────────────────────────────────────
+        if (mailSearchFilter.MaxCount.HasValue)
+            query = query.Take(mailSearchFilter.MaxCount.Value);
+
+        // ── RecipientContains: To/Cc are IEnumerable<string> (nvarchar(max)) ──
+        // EF Core cannot translate collection predicates on these columns to SQL.
+        // Materialization is deferred until after other DB-side filters narrow the set.
+        var results = await query.ToListAsync(cancellationToken);
+
+        if (!string.IsNullOrWhiteSpace(mailSearchFilter.RecipientContains))
+            results = [.. results
+                .Where(x => x.To.Any(t => t.Contains(mailSearchFilter.RecipientContains, StringComparison.OrdinalIgnoreCase))
+                          || x.Cc.Any(c => c.Contains(mailSearchFilter.RecipientContains, StringComparison.OrdinalIgnoreCase)))];
+
+        return results;
+    }
+}