feat: implement handler to decrpyt message with symmetric key

Modules/Messages/src/Messages.Application/Messages/DTOs/ViewMessageDTO.cs

@@ -0,0 +1,15 @@
+using Backbone.BuildingBlocks.Application.Abstractions.Infrastructure.Mapping;
+using Backbone.DevelopmentKit.Identity.ValueObjects;
+using Backbone.Modules.Messages.Domain.Entities;
+using Backbone.Modules.Messages.Domain.Ids;
+
+namespace Backbone.Modules.Messages.Application.Messages.DTOs;
+
+public class ViewMessageDTO : IMapTo<Message>
+{
+    public MessageId Id { get; set; }
+
+    public DateTime CreatedAt { get; set; }
+
+    public string Body { get; set; }
+}

Modules/Messages/src/Messages.Application/Messages/Queries/ViewMessages/GetViewMessageQuery.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Backbone.Modules.Messages.Application.Messages.DTOs;
+using Backbone.Modules.Messages.Domain.Entities;
+using Backbone.Modules.Messages.Domain.Ids;
+using MediatR;
+
+namespace Backbone.Modules.Messages.Application.Messages.Queries.ViewMessages;
+
+public class GetViewMessageQuery : IRequest<ViewMessageDTO>
+{
+    public MessageId MessageId { get; set; }
+    public string SymmetricKey { get; set; }
+}

Modules/Messages/src/Messages.Application/Messages/Queries/ViewMessages/Handler.cs

@@ -0,0 +1,61 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using AutoMapper;
+using Backbone.BuildingBlocks.Application.Abstractions.Infrastructure.Mapping;
+using Backbone.BuildingBlocks.Application.Abstractions.Infrastructure.UserContext;
+using Backbone.Modules.Messages.Application.Infrastructure.Persistence.Repository;
+using Backbone.Modules.Messages.Application.Messages.DTOs;
+using Backbone.Modules.Messages.Application.Messages.Queries.GetMessage;
+using Backbone.Modules.Messages.Domain.Entities;
+using Backbone.Modules.Messages.Domain.Ids;
+using MediatR;
+using NSec.Cryptography;
+
+namespace Backbone.Modules.Messages.Application.Messages.Queries.ViewMessages;
+public class Handler : IRequestHandler<GetViewMessageQuery, ViewMessageDTO>
+{
+    private readonly IMessagesRepository _messagesRepository;
+    private readonly IMapper _mapper;
+    private readonly IUserContext _userContext;
+
+    public Handler()
+    {
+    }
+
+    public Handler(IMapper mapper)
+    {
+        _mapper = mapper;
+    }
+
+    public Handler(IUserContext userContext, IMapper mapper, IMessagesRepository messagesRepository)
+    {
+        _userContext = userContext;
+        _mapper = mapper;
+        _messagesRepository = messagesRepository;
+    }
+
+    public async Task<ViewMessageDTO> Handle(GetViewMessageQuery request, CancellationToken cancellationToken)
+    {
+        if (request.MessageId == null || request.SymmetricKey == null)
+        {
+            throw new NullReferenceException(nameof(request));
+        }
+
+        var message = await _messagesRepository.Find(request.MessageId, _userContext.GetAddress(), cancellationToken, track: true);
+
+        var decryptedBody = message.Decrypt(request.SymmetricKey);
+
+        // Create ViewMessageDTO object
+        var response = new ViewMessageDTO
+        {
+            Id = message.Id,
+            CreatedAt = message.CreatedAt,
+            Body = decryptedBody
+        };
+
+        return response;
+    }
+}