feat: add RabbitMQ worker, contracts, usage UI in channels screen

- Add HrynCo.NotificationService.Contracts project with SendEmailMessage and NotificationResultMessage
- Add SendEmailConsumer (RabbitMQ worker) with reply-to pattern via CorrelationContext.ReplyTo
- Add SendEmailHandler owning SMTP send + usage increment as business logic
- Add GetChannelUsageSummaryHandler with single DB query via navigation property
- Merge usage stats inline into channels list (daily/monthly with progress bars)
- Refactor AdminChannelsController.Index to use GetChannelUsageSummaryQuery
- Add RabbitMQ service to docker-compose files
- Remove dead AdminChannelUsageController, ChannelUsageViewModel, ChannelUsageSummary

Ref: IT-628

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Directory.Packages.props

@@ -30,7 +30,7 @@
 
         <!-- HrynCo shared packages -->
         <PackageVersion Include="HrynCo.Common" Version="1.0.0" />
-        <PackageVersion Include="HrynCo.RabbitMq" Version="1.0.11" />
+        <PackageVersion Include="HrynCo.RabbitMq" Version="1.0.14" />
 
         <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
         <PackageVersion Include="coverlet.collector" Version="6.0.4" />

HrynCo.NotificationService.Contracts/HrynCo.NotificationService.Contracts.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="HrynCo.RabbitMq" />
+  </ItemGroup>
+
+</Project>

HrynCo.NotificationService.Contracts/Messages/NotificationResultData.cs

@@ -0,0 +1,14 @@
+namespace HrynCo.NotificationService.Contracts.Messages;
+
+public record NotificationResultData
+{
+    public required string ServiceName { get; init; }
+    public required string RecipientEmail { get; init; }
+    public required string TemplateKey { get; init; }
+    public required DateTimeOffset Timestamp { get; init; }
+
+    /// <summary>Null when delivery succeeded; contains error details on failure.</summary>
+    public string? ErrorMessage { get; init; }
+
+    public bool IsSuccess => ErrorMessage is null;
+}

HrynCo.NotificationService.Contracts/Messages/NotificationResultMessage.cs

@@ -0,0 +1,9 @@
+namespace HrynCo.NotificationService.Contracts.Messages;
+
+using Hrynco.RabbitMq;
+
+public record NotificationResultMessage : IRabbitMqMessage<NotificationResultData>
+{
+    public CorrelationContext CorrelationContext { get; set; } = null!;
+    public NotificationResultData Data { get; set; } = null!;
+}

HrynCo.NotificationService.Contracts/Messages/SendEmailMessage.cs

@@ -0,0 +1,9 @@
+namespace HrynCo.NotificationService.Contracts.Messages;
+
+using Hrynco.RabbitMq;
+
+public record SendEmailMessage : IRabbitMqMessage<SendEmailMessageData>
+{
+    public CorrelationContext CorrelationContext { get; set; } = default!;
+    public SendEmailMessageData Data { get; set; } = default!;
+}

HrynCo.NotificationService.Contracts/Messages/SendEmailMessageData.cs

@@ -0,0 +1,11 @@
+namespace HrynCo.NotificationService.Contracts.Messages;
+
+public record SendEmailMessageData
+{
+    public required string ServiceName { get; init; }
+    public required string TemplateKey { get; init; }
+    public required string RecipientEmail { get; init; }
+    public required string RecipientName { get; init; }
+    public required IReadOnlyDictionary<string, string> Variables { get; init; }
+    public string? LanguageCode { get; init; }
+}

HrynCo.NotificationService.DAL.Abstract/Providers/ChannelWithUsage.cs

@@ -0,0 +1,6 @@
+namespace HrynCo.NotificationService.DAL.Abstract.Providers;
+
+public record ChannelWithUsage(
+    EmailChannel Channel,
+    int DailySent,
+    int MonthlySent);

HrynCo.NotificationService.DAL.Abstract/Repositories/IEmailChannelRepository.cs

@@ -7,6 +7,7 @@ public interface IEmailChannelRepository
     Task<IReadOnlyList<EmailChannel>> GetAllAsync(CancellationToken ct = default);
     Task<IReadOnlyList<EmailChannel>> GetByServiceAsync(string serviceName, CancellationToken ct = default);
     Task<EmailChannel?> GetByIdAsync(Guid id, CancellationToken ct = default);
+    Task<IReadOnlyList<ChannelWithUsage>> GetAllWithUsageSummaryAsync(DateOnly today, CancellationToken ct = default);
     Task AddAsync(EmailChannel channel, CancellationToken ct = default);
     Task UpdateAsync(EmailChannel channel, CancellationToken ct = default);
     Task DeleteAsync(EmailChannel channel, CancellationToken ct = default);

HrynCo.NotificationService.DAL.Abstract/Repositories/IEmailChannelUsageRepository.cs

@@ -1,5 +1,3 @@
-using HrynCo.NotificationService.DAL.Abstract.Providers;
-
 namespace HrynCo.NotificationService.DAL.Abstract.Repositories;
 
 public interface IEmailChannelUsageRepository

HrynCo.NotificationService.DAL.EF/Configurations/EmailChannelEntityConfiguration.cs

@@ -35,5 +35,9 @@ internal class EmailChannelEntityConfiguration : IEntityTypeConfiguration<EmailC
         builder.Property(x => x.IsActive).HasColumnName("is_active");
         builder.Property(x => x.Created).HasColumnName("created");
         builder.Property(x => x.Updated).HasColumnName("updated");
+
+        builder.HasMany(x => x.UsageRecords)
+            .WithOne()
+            .HasForeignKey(u => u.ProviderId);
     }
 }

HrynCo.NotificationService.DAL.EF/Entities/EmailChannelEntity.cs

@@ -19,4 +19,6 @@ internal class EmailChannelEntity : Entity
     public int? MonthlyLimit { get; set; }
     public int WarnThresholdPercent { get; set; }
     public bool IsActive { get; set; }
+
+    public ICollection<EmailChannelUsageEntity> UsageRecords { get; set; } = [];
 }

HrynCo.NotificationService.DAL.EF/Repositories/EmailChannelRepository.cs

@@ -35,6 +35,30 @@ internal sealed class EmailChannelRepository : EfRepository<EmailChannelEntity>,
         return entities.Select(MapToDomain).ToList();
     }
 
+    public async Task<IReadOnlyList<ChannelWithUsage>> GetAllWithUsageSummaryAsync(
+        DateOnly today, CancellationToken ct = default)
+    {
+        var rows = await DbSet
+            .AsNoTracking()
+            .OrderBy(c => c.ServiceName)
+            .ThenBy(c => c.Priority)
+            .Select(c => new
+            {
+                Channel = c,
+                DailySent = c.UsageRecords
+                    .Where(u => u.Date == today)
+                    .Sum(u => (int?)u.SentCount) ?? 0,
+                MonthlySent = c.UsageRecords
+                    .Where(u => u.Date.Year == today.Year && u.Date.Month == today.Month)
+                    .Sum(u => (int?)u.SentCount) ?? 0
+            })
+            .ToListAsync(ct);
+
+        return rows
+            .Select(r => new ChannelWithUsage(MapToDomain(r.Channel), r.DailySent, r.MonthlySent))
+            .ToList();
+    }
+
     public async Task<EmailChannel?> GetByIdAsync(Guid id, CancellationToken ct = default)
     {
         EmailChannelEntity? entity = await DbSet.AsNoTracking().FirstOrDefaultAsync(x => x.Id == id, ct);

HrynCo.NotificationService.Services/EmailChannels/GetUsageSummary/GetChannelUsageSummaryHandler.cs

@@ -0,0 +1,45 @@
+using HrynCo.NotificationService.DAL.Abstract;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.Services.Core;
+using HrynCo.NotificationService.Services.Logging;
+using static HrynCo.NotificationService.Services.Core.ServiceResultHelper;
+
+namespace HrynCo.NotificationService.Services.EmailChannels.GetUsageSummary;
+
+internal sealed class GetChannelUsageSummaryHandler
+    : RequestHandler<GetChannelUsageSummaryQuery, ServiceResult<IReadOnlyList<ChannelUsageEntry>>>
+{
+    private readonly IEmailChannelRepository _channelsRepository;
+
+    public GetChannelUsageSummaryHandler(
+        IContextualSerilogLogger<GetChannelUsageSummaryQuery> logger,
+        IUnitOfWork unitOfWork,
+        IEmailChannelRepository channelsRepository)
+        : base(logger, unitOfWork)
+    {
+        _channelsRepository = channelsRepository;
+    }
+
+    protected override async Task<ServiceResult<IReadOnlyList<ChannelUsageEntry>>> DoOnHandle(
+        GetChannelUsageSummaryQuery request, CancellationToken cancellationToken)
+    {
+        var today = DateOnly.FromDateTime(DateTime.UtcNow);
+
+        var rows = await _channelsRepository.GetAllWithUsageSummaryAsync(today, cancellationToken);
+
+        var entries = rows
+            .Select(r => new ChannelUsageEntry(
+                ChannelId:    r.Channel.Id,
+                ServiceName:  r.Channel.ServiceName,
+                ChannelType:  r.Channel.EmailChannelType.ToString(),
+                IsActive:     r.Channel.IsActive,
+                Priority:     r.Channel.Priority,
+                DailyLimit:   r.Channel.DailyLimit,
+                MonthlyLimit: r.Channel.MonthlyLimit,
+                DailySent:    r.DailySent,
+                MonthlySent:  r.MonthlySent))
+            .ToList();
+
+        return Success<IReadOnlyList<ChannelUsageEntry>>(entries);
+    }
+}

HrynCo.NotificationService.Services/EmailChannels/GetUsageSummary/GetChannelUsageSummaryQuery.cs

@@ -0,0 +1,19 @@
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.Services.Core;
+using MediatR;
+
+namespace HrynCo.NotificationService.Services.EmailChannels.GetUsageSummary;
+
+public sealed record GetChannelUsageSummaryQuery
+    : IRequest<ServiceResult<IReadOnlyList<ChannelUsageEntry>>>;
+
+public sealed record ChannelUsageEntry(
+    Guid ChannelId,
+    string ServiceName,
+    string ChannelType,
+    bool IsActive,
+    int Priority,
+    int? DailyLimit,
+    int? MonthlyLimit,
+    int DailySent,
+    int MonthlySent);

HrynCo.NotificationService.Services/EmailChannels/Send/SendEmailCommand.cs

@@ -0,0 +1,17 @@
+using HrynCo.NotificationService.Services.Core;
+using MediatR;
+
+namespace HrynCo.NotificationService.Services.EmailChannels.Send;
+
+/// <summary>
+/// Sends an email via the channel associated with the given channel ID,
+/// then increments the usage counter for that channel.
+/// </summary>
+public sealed record SendEmailCommand(
+    Guid ChannelId,
+    string RecipientEmail,
+    string RecipientName,
+    string Subject,
+    string HtmlBody,
+    string? TextBody
+) : IRequest<ServiceResult<Core.Unit>>;

HrynCo.NotificationService.Services/EmailChannels/Send/SendEmailHandler.cs

@@ -0,0 +1,80 @@
+using System.Net;
+using System.Net.Mail;
+using HrynCo.NotificationService.DAL.Abstract;
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.Services.Core;
+using HrynCo.NotificationService.Services.Logging;
+using static HrynCo.NotificationService.Services.Core.ServiceResultHelper;
+
+namespace HrynCo.NotificationService.Services.EmailChannels.Send;
+
+internal sealed class SendEmailHandler
+    : RequestHandler<SendEmailCommand, ServiceResult<Core.Unit>>
+{
+    private readonly IEmailChannelRepository _channels;
+    private readonly IEmailChannelUsageRepository _usage;
+
+    public SendEmailHandler(
+        IContextualSerilogLogger<SendEmailCommand> logger,
+        IUnitOfWork unitOfWork,
+        IEmailChannelRepository channels,
+        IEmailChannelUsageRepository usage)
+        : base(logger, unitOfWork)
+    {
+        _channels = channels;
+        _usage = usage;
+    }
+
+    protected override async Task<ServiceResult<Core.Unit>> DoOnHandle(
+        SendEmailCommand request, CancellationToken cancellationToken)
+    {
+        var channel = await _channels.GetByIdAsync(request.ChannelId, cancellationToken);
+        if (channel is null)
+            return Failure<Core.Unit>($"Channel '{request.ChannelId}' not found.");
+
+        if (channel.Settings is not SmtpChannelSettings smtp)
+            return Failure<Core.Unit>($"Channel type '{channel.EmailChannelType}' is not supported for sending.");
+
+        try
+        {
+            using var client = new SmtpClient(smtp.Host, smtp.Port)
+            {
+                EnableSsl = smtp.UseSsl,
+                Credentials = string.IsNullOrWhiteSpace(smtp.Username)
+                    ? null
+                    : new NetworkCredential(smtp.Username, smtp.Password)
+            };
+
+            using var mail = new MailMessage
+            {
+                From = new MailAddress(smtp.FromEmail, smtp.FromName),
+                Subject = request.Subject,
+                Body = request.HtmlBody,
+                IsBodyHtml = true
+            };
+
+            if (!string.IsNullOrWhiteSpace(request.TextBody))
+            {
+                var plain = AlternateView.CreateAlternateViewFromString(request.TextBody, null, "text/plain");
+                mail.AlternateViews.Add(plain);
+            }
+
+            mail.To.Add(new MailAddress(request.RecipientEmail, request.RecipientName));
+
+            await client.SendMailAsync(mail, cancellationToken);
+        }
+        catch (Exception ex)
+        {
+            Logger.Error(ex, "SMTP send failed for channel {ChannelId}", request.ChannelId);
+            return Failure<Core.Unit>(ex.Message);
+        }
+
+        await _usage.IncrementUsageAsync(
+            request.ChannelId,
+            DateOnly.FromDateTime(DateTime.UtcNow),
+            cancellationToken);
+
+        return Success(Unit.Value);
+    }
+}

HrynCo.NotificationService.Web/Controllers/Admin/AdminChannelsController.cs

@@ -1,36 +1,30 @@
 using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
 using HrynCo.NotificationService.Services.EmailChannels.Create;
 using HrynCo.NotificationService.Services.EmailChannels.Delete;
 using HrynCo.NotificationService.Services.EmailChannels.Get;
-using HrynCo.NotificationService.Services.EmailChannels.GetAll;
+using HrynCo.NotificationService.Services.EmailChannels.GetUsageSummary;
+using HrynCo.NotificationService.Services.EmailChannels.Send;
 using HrynCo.NotificationService.Services.EmailChannels.Update;
 using HrynCo.NotificationService.Web.Controllers.Admin.ViewModels;
 using MediatR;
 using Microsoft.AspNetCore.Mvc;
-using System.Net;
-using System.Net.Mail;
 
 namespace HrynCo.NotificationService.Web.Controllers.Admin;
 
 [Route("admin/channels")]
-public class AdminChannelsController : Controller
+public class AdminChannelsController(IMediator mediator) : Controller
 {
-    private readonly IMediator _mediator;
-
-    public AdminChannelsController(IMediator mediator)
-    {
-        _mediator = mediator;
-    }
 
     // GET /admin/channels
     [HttpGet("")]
     public async Task<IActionResult> Index(CancellationToken ct)
     {
-        var result = await _mediator.Send(new GetAllEmailChannelsQuery(), ct);
+        var result = await mediator.Send(new GetChannelUsageSummaryQuery(), ct);
         if (!result.IsSuccess)
         {
             ModelState.AddModelError("", result.Error?.Message ?? "Failed to load channels.");
-            return View(Array.Empty<EmailChannel>());
+            return View(Array.Empty<ChannelUsageEntry>());
         }
 
         return View(result.Result);
@@ -47,7 +41,7 @@ public class AdminChannelsController : Controller
     [HttpGet("{id:guid}")]
     public async Task<IActionResult> Edit(Guid id, CancellationToken ct)
     {
-        var result = await _mediator.Send(new GetEmailChannelQuery(id), ct);
+        var result = await mediator.Send(new GetEmailChannelQuery(id), ct);
         if (!result.IsSuccess || result.Result is null)
             return NotFound();
 
@@ -110,7 +104,7 @@ public class AdminChannelsController : Controller
                 model.WarnThresholdPercent,
                 model.IsActive);
 
-            var result = await _mediator.Send(command, ct);
+            var result = await mediator.Send(command, ct);
             if (!result.IsSuccess)
             {
                 ModelState.AddModelError("", result.Error?.Message ?? "Failed to create channel.");
@@ -128,7 +122,7 @@ public class AdminChannelsController : Controller
                 model.WarnThresholdPercent,
                 model.IsActive);
 
-            var result = await _mediator.Send(command, ct);
+            var result = await mediator.Send(command, ct);
             if (!result.IsSuccess)
             {
                 ModelState.AddModelError("", result.Error?.Message ?? "Failed to update channel.");
@@ -143,40 +137,21 @@ public class AdminChannelsController : Controller
     [HttpPost("{id:guid}/test")]
     public async Task<IActionResult> Test(Guid id, [FromBody] TestChannelRequest request, CancellationToken ct)
     {
-        var result = await _mediator.Send(new GetEmailChannelQuery(id), ct);
+        var channelResult = await mediator.Send(new GetEmailChannelQuery(id), ct);
-        if (!result.IsSuccess || result.Result is null)
+        if (!channelResult.IsSuccess || channelResult.Result is null)
             return NotFound(new { success = false, message = "Channel not found." });
 
-        if (result.Result.Settings is not SmtpChannelSettings smtp)
+        var channel = channelResult.Result;
-            return BadRequest(new { success = false, message = "Only SMTP channels are supported." });
+        var subject = "✅ Test email from Notification Service";
+        var body = $"This is a test email sent from the Notification Service admin panel.\n\nChannel: {channel.ServiceName}";
 
-        try
+        var sendResult = await mediator.Send(
-        {
+            new SendEmailCommand(id, request.ToEmail, request.ToEmail, subject, body, null), ct);
-            using var client = new SmtpClient(smtp.Host, smtp.Port)
-            {
-                EnableSsl = smtp.UseSsl,
-                Credentials = string.IsNullOrWhiteSpace(smtp.Username)
-                    ? null
-                    : new NetworkCredential(smtp.Username, smtp.Password)
-            };
 
-            var message = new MailMessage
+        if (!sendResult.IsSuccess)
-            {
+            return Ok(new { success = false, message = sendResult.Error?.Message });
-                From = new MailAddress(smtp.FromEmail, smtp.FromName),
-                Subject = "✅ Test email from Notification Service",
-                Body = $"This is a test email sent from the Notification Service admin panel.\n\nChannel: {result.Result.ServiceName}\nHost: {smtp.Host}:{smtp.Port}",
-                IsBodyHtml = false
-            };
-            message.To.Add(request.ToEmail);
 
-            await client.SendMailAsync(message, ct);
+        return Ok(new { success = true, message = $"Test email sent to {request.ToEmail}." });
-
-            return Ok(new { success = true, message = $"Test email sent to {request.ToEmail}." });
-        }
-        catch (Exception ex)
-        {
-            return Ok(new { success = false, message = ex.Message });
-        }
     }
 
     // POST /admin/channels/{id}/delete
@@ -184,7 +159,7 @@ public class AdminChannelsController : Controller
     [ValidateAntiForgeryToken]
     public async Task<IActionResult> Delete(Guid id, CancellationToken ct)
     {
-        await _mediator.Send(new DeleteEmailChannelCommand(id), ct);
+        await mediator.Send(new DeleteEmailChannelCommand(id), ct);
         return RedirectToAction(nameof(Index));
     }
 }

HrynCo.NotificationService.Web/Views/AdminChannels/Index.cshtml

@@ -1,5 +1,5 @@
-@using HrynCo.NotificationService.DAL.Abstract.Providers
+@using HrynCo.NotificationService.Services.EmailChannels.GetUsageSummary
-@model IReadOnlyList<EmailChannel>
+@model IReadOnlyList<ChannelUsageEntry>
 @{
     ViewData["Title"] = "Email Channels";
 }
@@ -40,12 +40,12 @@ else
             <table class="table table-hover table-sm mb-0">
                 <thead class="table-dark">
                     <tr>
-                        <th>Service Name</th>
+                        <th>Service</th>
                         <th>Type</th>
                         <th>Priority</th>
                         <th>Status</th>
-                        <th>Daily Limit</th>
+                        <th>Today</th>
-                        <th>Monthly Limit</th>
+                        <th>This Month</th>
                         <th class="text-end">Actions</th>
                     </tr>
                 </thead>
@@ -54,7 +54,7 @@ else
                     {
                         <tr>
                             <td>@c.ServiceName</td>
-                            <td>@c.EmailChannelType</td>
+                            <td>@c.ChannelType</td>
                             <td>@c.Priority</td>
                             <td>
                                 @if (c.IsActive)
@@ -66,15 +66,53 @@ else
                                     <span class="badge bg-secondary text-muted">Inactive</span>
                                 }
                             </td>
-                            <td>@(c.DailyLimit.HasValue ? c.DailyLimit.ToString() : "—")</td>
+                            <td style="min-width:130px">
-                            <td>@(c.MonthlyLimit.HasValue ? c.MonthlyLimit.ToString() : "—")</td>
+                                @{
+                                    var dailyLabel = c.DailyLimit.HasValue ? $"{c.DailySent} / {c.DailyLimit}" : c.DailySent.ToString();
+                                }
+                                @if (c.DailyLimit.HasValue && c.DailyLimit > 0)
+                                {
+                                    var pct = Math.Min((double)c.DailySent / c.DailyLimit.Value * 100, 100);
+                                    var color = pct >= 100 ? "danger" : pct >= 90 ? "warning" : "success";
+                                    <div class="d-flex align-items-center gap-2">
+                                        <div class="progress flex-grow-1" style="height:6px; min-width:60px">
+                                            <div class="progress-bar bg-@color" style="width:@pct.ToString("F0")%"></div>
+                                        </div>
+                                        <small class="text-nowrap text-muted">@dailyLabel</small>
+                                    </div>
+                                }
+                                else
+                                {
+                                    <small class="text-muted">@dailyLabel</small>
+                                }
+                            </td>
+                            <td style="min-width:130px">
+                                @{
+                                    var monthlyLabel = c.MonthlyLimit.HasValue ? $"{c.MonthlySent} / {c.MonthlyLimit}" : c.MonthlySent.ToString();
+                                }
+                                @if (c.MonthlyLimit.HasValue && c.MonthlyLimit > 0)
+                                {
+                                    var pct = Math.Min((double)c.MonthlySent / c.MonthlyLimit.Value * 100, 100);
+                                    var color = pct >= 100 ? "danger" : pct >= 90 ? "warning" : "success";
+                                    <div class="d-flex align-items-center gap-2">
+                                        <div class="progress flex-grow-1" style="height:6px; min-width:60px">
+                                            <div class="progress-bar bg-@color" style="width:@pct.ToString("F0")%"></div>
+                                        </div>
+                                        <small class="text-nowrap text-muted">@monthlyLabel</small>
+                                    </div>
+                                }
+                                else
+                                {
+                                    <small class="text-muted">@monthlyLabel</small>
+                                }
+                            </td>
                             <td class="text-end">
-                                <a href="/admin/channels/@c.Id"
+                                <a href="/admin/channels/@c.ChannelId"
                                    class="btn btn-sm btn-outline-primary me-1">
                                     <i class="bi bi-pencil"></i> Edit
                                 </a>
                                 <form method="post"
-                                      action="/admin/channels/@c.Id/delete"
+                                      action="/admin/channels/@c.ChannelId/delete"
                                       class="d-inline">
                                     @Html.AntiForgeryToken()
                                     <button type="submit"

HrynCo.NotificationService.Worker/AppSettings.cs

@@ -1,3 +1,5 @@
+using Hrynco.RabbitMq;
+
 namespace HrynCo.NotificationService.Worker;
 
 public sealed class AppSettings
@@ -5,4 +7,5 @@ public sealed class AppSettings
     public const string SectionName = "App";
 
     public string ConnectionString { get; init; } = string.Empty;
+    public RabbitMqSettings RabbitMq { get; init; } = null!;
 }

HrynCo.NotificationService.Worker/HrynCo.NotificationService.Worker.csproj

@@ -9,6 +9,8 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.Hosting" />
+    <PackageReference Include="HrynCo.RabbitMq" />
+    <PackageReference Include="MediatR" />
     <PackageReference Include="Serilog.Extensions.Hosting" />
     <PackageReference Include="Serilog.Settings.Configuration" />
     <PackageReference Include="Serilog.Sinks.Console" />
@@ -16,6 +18,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <ProjectReference Include="..\HrynCo.NotificationService.Contracts\HrynCo.NotificationService.Contracts.csproj" />
     <ProjectReference Include="..\HrynCo.NotificationService.Services\HrynCo.NotificationService.Services.csproj" />
     <ProjectReference Include="..\HrynCo.NotificationService.DAL.EF\HrynCo.NotificationService.DAL.EF.csproj" />
   </ItemGroup>

HrynCo.NotificationService.Worker/Program.cs

@@ -1,6 +1,8 @@
 using HrynCo.NotificationService.DAL.EF;
 using HrynCo.NotificationService.Services;
 using HrynCo.NotificationService.Worker;
+using Hrynco.RabbitMq;
+using Microsoft.Extensions.Options;
 
 var builder = Host.CreateApplicationBuilder(args);
 
@@ -13,7 +15,11 @@ var appSettings = builder.Configuration
 builder.Services.AddSingleton(appSettings);
 builder.Services.AddNotificationDataAccess(appSettings.ConnectionString);
 builder.Services.AddNotificationServices();
-builder.Services.AddHostedService<Worker>();
+
+builder.Services.Configure<RabbitMqSettings>(
+    builder.Configuration.GetSection($"{AppSettings.SectionName}:RabbitMq"));
+
+builder.Services.AddHostedService<SendEmailConsumer>();
 
 var host = builder.Build();
 host.Run();

HrynCo.NotificationService.Worker/RenderedEmail.cs

@@ -0,0 +1,3 @@
+namespace HrynCo.NotificationService.Worker;
+
+public record RenderedEmail(string Subject, string HtmlBody, string TextBody);

HrynCo.NotificationService.Worker/SendEmailConsumer.cs

@@ -0,0 +1,174 @@
+namespace HrynCo.NotificationService.Worker;
+
+using System.Text;
+using System.Text.Json;
+using HrynCo.NotificationService.Contracts.Messages;
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.Services.EmailChannels.Send;
+using Hrynco.RabbitMq;
+using MediatR;
+using Microsoft.Extensions.Options;
+using RabbitMQ.Client;
+
+public sealed class SendEmailConsumer(
+    IOptionsMonitor<RabbitMqSettings> options,
+    IEmailChannelRepository channelRepository,
+    IEmailTemplateRepository templateRepository,
+    IEmailChannelUsageRepository usageRepository,
+    IMediator mediator,
+    AppSettings appSettings,
+    ILogger<SendEmailConsumer> logger)
+    : RabbitMqConsumerBase<SendEmailMessage, SendEmailMessageData>(options, logger)
+{
+    private const string IncomingQueue = "notification.send-email";
+
+    protected override string QueueName => IncomingQueue;
+
+    protected override async Task HandleMessageAsync(SendEmailMessage message, CancellationToken cancellationToken)
+    {
+        var data = message.Data;
+
+        logger.LogInformation(
+            "Processing SendEmail for service={Service} template={Template} recipient={Recipient} [CorrelationId={CorrelationId}]",
+            data.ServiceName, data.TemplateKey, data.RecipientEmail, message.CorrelationContext?.CorrelationId);
+
+        var channel = await ResolveChannelAsync(data.ServiceName, cancellationToken);
+        var template = await ResolveTemplateAsync(data.ServiceName, data.TemplateKey, data.LanguageCode, cancellationToken);
+
+        await EnforceLimitsAsync(channel, cancellationToken);
+
+        var rendered = RenderTemplate(template, data);
+
+        var sendResult = await mediator.Send(
+            new SendEmailCommand(channel.Id, data.RecipientEmail, data.RecipientName,
+                rendered.Subject, rendered.HtmlBody, rendered.TextBody),
+            cancellationToken);
+
+        if (!sendResult.IsSuccess)
+            throw new InvalidOperationException(sendResult.Error?.Message ?? "Send failed.");
+
+        logger.LogInformation(
+            "Email sent successfully service={Service} template={Template} recipient={Recipient}",
+            data.ServiceName, data.TemplateKey, data.RecipientEmail);
+
+        await PublishResultAsync(message.CorrelationContext, data, errorMessage: null, cancellationToken);
+    }
+
+    private async Task<EmailChannel> ResolveChannelAsync(string serviceName, CancellationToken ct)
+    {
+        var channels = await channelRepository.GetByServiceAsync(serviceName, ct);
+
+        return channels
+            .Where(c => c.IsActive)
+            .OrderBy(c => c.Priority)
+            .FirstOrDefault()
+            ?? throw new InvalidOperationException(
+                $"No active email channel found for service '{serviceName}'.");
+    }
+
+    private async Task<EmailTemplate> ResolveTemplateAsync(
+        string serviceName, string templateKey, string? languageCode, CancellationToken ct)
+    {
+        var lang = string.IsNullOrWhiteSpace(languageCode) ? "en" : languageCode;
+        var template = await templateRepository.GetAsync(serviceName, templateKey, lang, ct);
+
+        if (template is null && lang != "en")
+            template = await templateRepository.GetAsync(serviceName, templateKey, "en", ct);
+
+        return template
+            ?? throw new InvalidOperationException(
+                $"Template not found: service='{serviceName}' key='{templateKey}' language='{lang}'.");
+    }
+
+    private async Task EnforceLimitsAsync(EmailChannel channel, CancellationToken ct)
+    {
+        var today = DateOnly.FromDateTime(DateTime.UtcNow);
+
+        if (channel.DailyLimit.HasValue)
+        {
+            var daily = await usageRepository.GetDailyCountAsync(channel.Id, today, ct);
+            if (daily >= channel.DailyLimit.Value)
+                throw new InvalidOperationException(
+                    $"Channel '{channel.Id}' daily limit of {channel.DailyLimit.Value} reached ({daily} sent today).");
+        }
+
+        if (channel.MonthlyLimit.HasValue)
+        {
+            var monthly = await usageRepository.GetMonthlyCountAsync(channel.Id, today.Year, today.Month, ct);
+            if (monthly >= channel.MonthlyLimit.Value)
+                throw new InvalidOperationException(
+                    $"Channel '{channel.Id}' monthly limit of {channel.MonthlyLimit.Value} reached ({monthly} sent this month).");
+        }
+    }
+
+    private static RenderedEmail RenderTemplate(EmailTemplate template, SendEmailMessageData data)
+    {
+        return new RenderedEmail(
+            Interpolate(template.Subject, data.Variables),
+            Interpolate(template.HtmlBody, data.Variables),
+            Interpolate(template.TextBody, data.Variables));
+    }
+
+    private static string Interpolate(string text, IReadOnlyDictionary<string, string> variables)
+    {
+        var sb = new StringBuilder(text);
+        foreach (var (key, value) in variables)
+            sb.Replace($"{{{{{key}}}}}", value);
+        return sb.ToString();
+    }
+
+    private async Task PublishResultAsync(
+        CorrelationContext? correlationContext,
+        SendEmailMessageData data,
+        string? errorMessage,
+        CancellationToken ct)
+    {
+        var replyTo = correlationContext?.ReplyTo;
+        if (string.IsNullOrWhiteSpace(replyTo))
+            return;
+
+        try
+        {
+            var result = new NotificationResultMessage
+            {
+                CorrelationContext = (correlationContext ?? new CorrelationContext { CorrelationId = Guid.NewGuid().ToString() }) with { ReplyTo = null },
+                Data = new NotificationResultData
+                {
+                    ServiceName = data.ServiceName,
+                    RecipientEmail = data.RecipientEmail,
+                    TemplateKey = data.TemplateKey,
+                    Timestamp = DateTimeOffset.UtcNow,
+                    ErrorMessage = errorMessage
+                }
+            };
+
+            byte[] body = Encoding.UTF8.GetBytes(JsonSerializer.Serialize(result));
+
+            var factory = new ConnectionFactory
+            {
+                HostName = appSettings.RabbitMq.Host,
+                Port = appSettings.RabbitMq.Port,
+                UserName = appSettings.RabbitMq.User,
+                Password = appSettings.RabbitMq.Password,
+                VirtualHost = appSettings.RabbitMq.VirtualHost
+            };
+
+            await using var conn = await factory.CreateConnectionAsync(ct);
+            await using var ch = await conn.CreateChannelAsync(cancellationToken: ct);
+
+            await ch.QueueDeclareAsync(replyTo, durable: true, exclusive: false, autoDelete: false,
+                cancellationToken: ct);
+            await ch.BasicPublishAsync(exchange: string.Empty, routingKey: replyTo, body: body,
+                cancellationToken: ct);
+
+            logger.LogDebug("Result published to reply queue '{Queue}' [CorrelationId={CorrelationId}]",
+                replyTo, correlationContext?.CorrelationId);
+        }
+        catch (Exception ex)
+        {
+            logger.LogWarning(ex, "Failed to publish notification result to reply queue '{Queue}'", replyTo);
+        }
+    }
+}

HrynCo.NotificationService.Worker/Worker.cs

@@ -1,16 +0,0 @@
-namespace HrynCo.NotificationService.Worker;
-
-public class Worker(ILogger<Worker> logger) : BackgroundService
-{
-    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
-    {
-        while (!stoppingToken.IsCancellationRequested)
-        {
-            if (logger.IsEnabled(LogLevel.Information))
-            {
-                logger.LogInformation("Worker running at: {time}", DateTimeOffset.Now);
-            }
-            await Task.Delay(1000, stoppingToken);
-        }
-    }
-}

HrynCo.NotificationService.Worker/appsettings.json

@@ -1,6 +1,13 @@
 {
   "App": {
-    "ConnectionString": "Host=localhost;Port=5432;Database=notification_service;Username=postgres;Password=postgres"
+    "ConnectionString": "Host=localhost;Port=5432;Database=notification_service;Username=postgres;Password=postgres",
+    "RabbitMq": {
+      "Host": "localhost",
+      "Port": 5672,
+      "User": "guest",
+      "Password": "guest",
+      "VirtualHost": "/"
+    }
   },
   "Serilog": {
     "MinimumLevel": {

HrynCo.NotificationService.sln.DotSettings

@@ -0,0 +1,2 @@
+<wpf:ResourceDictionary xml:space="preserve" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:ss="urn:shemas-jetbrains-com:settings-storage-xaml" xmlns:wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=Hryn/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>

HrynCo.NotificationService.slnx

@@ -15,6 +15,7 @@
   <Project Path="HrynCo.NotificationService.Migrator/HrynCo.NotificationService.Migrator.csproj" />
   <Project Path="HrynCo.NotificationService.Web.IntegrationTests/HrynCo.NotificationService.Web.IntegrationTests.csproj" />
   <Project Path="HrynCo.NotificationService.Web/HrynCo.NotificationService.Web.csproj" />
+  <Project Path="HrynCo.NotificationService.Contracts/HrynCo.NotificationService.Contracts.csproj" />
   <Project Path="HrynCo.NotificationService.DAL.Abstract/HrynCo.NotificationService.DAL.Abstract.csproj" />
   <Project Path="HrynCo.NotificationService.DAL.EF/HrynCo.NotificationService.DAL.EF.csproj" />
   <Project Path="HrynCo.NotificationService.Services.Tests/HrynCo.NotificationService.Services.Tests.csproj" />

docker/environments/docker-compose.Development.yml

@@ -1,3 +1,5 @@
+name: hrynco-notification-service
+
 services:
   migrator:
     environment:
@@ -15,7 +17,29 @@ services:
     environment:
       - DOTNET_ENVIRONMENT=Development
       - App__ConnectionString=Host=db;Port=5432;Database=notification_service;Username=postgres;Password=postgres
+      - App__RabbitMq__Host=rabbitmq
+      - App__RabbitMq__User=guest
+      - App__RabbitMq__Password=guest
       - Serilog__WriteTo__1__Args__serverUrl=http://seq
+    depends_on:
+      rabbitmq:
+        condition: service_healthy
+
+  rabbitmq:
+    image: rabbitmq:4-management-alpine
+    environment:
+      RABBITMQ_DEFAULT_USER: guest
+      RABBITMQ_DEFAULT_PASS: guest
+    ports:
+      - "5672:5672"
+      - "15672:15672"
+    healthcheck:
+      test: ["CMD", "rabbitmq-diagnostics", "ping"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+    volumes:
+      - notification_rabbitmq:/var/lib/rabbitmq
 
   db:
     image: postgres:17
@@ -41,3 +65,4 @@ services:
 volumes:
   notification_db:
   notification_seq:
+  notification_rabbitmq:

docker/environments/docker-compose.yml

@@ -1,3 +1,5 @@
+name: hrynco-notification-service
+
 services:
   migrator:
     build:
@@ -30,8 +32,24 @@ services:
     environment:
       - DOTNET_ENVIRONMENT=Production
       - App__ConnectionString=${CONNECTION_STRING}
+      - App__RabbitMq__Host=rabbitmq
+      - App__RabbitMq__User=${RABBITMQ_USER:-guest}
+      - App__RabbitMq__Password=${RABBITMQ_PASSWORD:-guest}
     depends_on:
       db:
         condition: service_started
       migrator:
         condition: service_completed_successfully
+      rabbitmq:
+        condition: service_healthy
+
+  rabbitmq:
+    image: rabbitmq:4-management-alpine
+    environment:
+      RABBITMQ_DEFAULT_USER: ${RABBITMQ_USER:-guest}
+      RABBITMQ_DEFAULT_PASS: ${RABBITMQ_PASSWORD:-guest}
+    healthcheck:
+      test: ["CMD", "rabbitmq-diagnostics", "ping"]
+      interval: 10s
+      timeout: 5s
+      retries: 5