Add GetTodoByIdQuery

JixMinApi/Features/Todo/Extensions.cs

@@ -7,7 +7,7 @@ public static TodoDto ToDto(this Todo model)
         return new TodoDto(model.Id, model.Name, model.IsComplete);
     }
 
-    public static List<TodoDto> ToDto(this IList<Todo> model)
+    public static List<TodoDto> ToDto(this IEnumerable<Todo> model)
     {
         var result = new List<TodoDto>();
         foreach (var item in model)

JixMinApi/Features/Todo/Queries/GetTodoByIdQuery.cs

@@ -0,0 +1,49 @@
+using FluentValidation;
+using FluentValidation.Results;
+using JixMinApi.Features.Todo.Commands;
+using MediatR;
+using Microsoft.EntityFrameworkCore;
+
+namespace JixMinApi.Features.Todo.Queries;
+
+public record GetTodoByIdQuery(Guid Id) :IRequest<Result<TodoDto>>;
+
+public sealed class GetTodoByIdQueryValidator
+    : AbstractValidator<GetTodoByIdQuery>
+{
+    public GetTodoByIdQueryValidator()
+    {
+        RuleFor(query => query.Id)
+            .NotNull()
+            .NotEmpty();
+    }
+}
+
+public class GetTodoByIdQueryHandler : IRequestHandler<GetTodoByIdQuery, Result<TodoDto>>
+{
+    private readonly TodoDb _db;
+    private readonly ILogger<GetTodoByIdQueryHandler> _logger;
+
+    public GetTodoByIdQueryHandler(TodoDb db, ILogger<GetTodoByIdQueryHandler> logger) => (_db, _logger) = (db, logger);
+
+    public async Task<Result<TodoDto>> Handle(GetTodoByIdQuery request, CancellationToken cancellationToken)
+    {
+        // validate
+        var validator = new GetTodoByIdQueryValidator();
+        ValidationResult validationResult = validator.Validate(request);
+
+        if (!validationResult.IsValid)
+        {
+            var errors = validationResult.Errors.Select(e => new KeyValuePair<string, string>(e.PropertyName, e.ErrorMessage));
+            return new Result<TodoDto>(errors);
+        }
+
+        _logger.LogDebug($"Start query");
+        Todo? todo = await _db.Todos
+            .AsNoTracking()
+            .FirstOrDefaultAsync(x => x.Id == request.Id, cancellationToken: cancellationToken);
+        _logger.LogDebug($"End query");
+
+        return new Result<TodoDto>(todo?.ToDto());
+    }
+}

JixMinApi/Features/Todo/Result.cs

@@ -21,6 +21,13 @@ public Result(string field, string validationErrorMessage)
     {
         Errors = [new(field, validationErrorMessage)];
     }
+
+    // TODO: using NotFound still Result.IsSuccess to true, will lead to bugs
+    public static Result<T> NotFound<T>()
+    {
+        T val = default(T);
+        return new Result<T>(val);
+    }
 }
 
 public static class ResultExtensions

JixMinApi/Features/Todo/TodoEndpoints.cs

@@ -63,24 +63,19 @@ public static async Task<Ok<TodoDto[]>> GetAllTodosAsync(IMediator mediator)
     /// </summary>
     public static async Task<Results<ValidationProblem, NotFound, Ok<TodoDto>>> GetTodoByIdAsync(Guid id, IMediator mediator)
     {
-        if (id == Guid.Empty)
+        var result = await mediator.Send(new GetTodoByIdQuery(id));
+
+        if (!result.IsSuccess)
         {
-            var errors = new Dictionary<string, string[]>
-            {
-                ["id"] = ["id parameter must not be an empty guid."],
-            };
-            return TypedResults.ValidationProblem(errors);
+            return TypedResults.ValidationProblem(result.Errors.ToErrorDictionary());
         }
 
-        var todos = await mediator.Send(new GetAllTodosQuery());
-        var todo = todos.FirstOrDefault(t => t.Id == id);
-
-        if (todo is null)
+        if (result.Value is null)
         {
             return TypedResults.NotFound();
         }
 
-        return TypedResults.Ok(todo);
+        return TypedResults.Ok(result.Value);
     }
 
     /// <summary>

JixMinApiTests/Features/Todo/TodoEndpointsTests.cs

@@ -2,6 +2,7 @@
 using MediatR;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.HttpResults;
+using Microsoft.AspNetCore.Mvc;
 using Moq;
 using Xunit;
 using Assert = Xunit.Assert;
@@ -20,6 +21,8 @@ public async Task GetTodoByIdAsync_Returns_BadRequest_When_Id_Is_Empty()
         {
             ["id"] = ["id parameter must not be an empty guid."],
         };
+        mediatorMock.Setup(m => m.Send(It.IsAny<GetTodoByIdQuery>(), CancellationToken.None))
+            .ReturnsAsync(new Result<TodoDto>("id", "id parameter must not be an empty guid."));
 
         // Act
         var response = await TodoEndpoints.GetTodoByIdAsync(emptyId, mediatorMock.Object);
@@ -42,8 +45,8 @@ public async Task GetTodoByIdAsync_Returns_NotFound_When_Todo_Not_Found()
         // Arrange
         var mediatorMock = new Mock<IMediator>();
         var nonExistentId = Guid.NewGuid(); // Assuming this id doesn't exist
-        mediatorMock.Setup(m => m.Send(It.IsAny<GetAllTodosQuery>(), CancellationToken.None))
-            .ReturnsAsync(new List<TodoDto>());
+        mediatorMock.Setup(m => m.Send(It.IsAny<GetTodoByIdQuery>(), CancellationToken.None))
+            .ReturnsAsync(Result<TodoDto>.NotFound<TodoDto>());
 
         // Act
         var response = await TodoEndpoints.GetTodoByIdAsync(nonExistentId, mediatorMock.Object);
@@ -64,10 +67,8 @@ public async Task GetTodoByIdAsync_Returns_Ok_When_Todo_Found()
         var existingId = Guid.NewGuid(); // Assuming this id exists
         var todoDto = new TodoDto(existingId, "Test name", false); // Assuming todo with this id exists
 
-        mediatorMock.Setup(m => m.Send(It.IsAny<GetAllTodosQuery>(), CancellationToken.None))
-            .ReturnsAsync(new List<TodoDto>() {
-                todoDto
-            });
+        mediatorMock.Setup(m => m.Send(It.IsAny<GetTodoByIdQuery>(), CancellationToken.None))
+            .ReturnsAsync(new Result<TodoDto>(todoDto));
 
         // Act
         var response = await TodoEndpoints.GetTodoByIdAsync(existingId, mediatorMock.Object);