src/api/SIGCM2.Application/Abstractions/ICommandHandler.cs

@@ -0,0 +1,6 @@
+namespace SIGCM2.Application.Abstractions;
+
+public interface ICommandHandler<TCommand, TResult>
+{
+    Task<TResult> Handle(TCommand command);
+}

src/api/SIGCM2.Application/Abstractions/IDispatcher.cs

@@ -0,0 +1,6 @@
+namespace SIGCM2.Application.Abstractions;
+
+public interface IDispatcher
+{
+    Task<TResult> Send<TCommand, TResult>(TCommand command);
+}

src/api/SIGCM2.Application/Abstractions/IQueryHandler.cs

@@ -0,0 +1,6 @@
+namespace SIGCM2.Application.Abstractions;
+
+public interface IQueryHandler<TQuery, TResult>
+{
+    Task<TResult> Handle(TQuery query);
+}

src/api/SIGCM2.Application/Abstractions/Persistence/IUsuarioRepository.cs

@@ -0,0 +1,8 @@
+using SIGCM2.Domain.Entities;
+
+namespace SIGCM2.Application.Abstractions.Persistence;
+
+public interface IUsuarioRepository
+{
+    Task<Usuario?> GetByUsernameAsync(string username);
+}

src/api/SIGCM2.Application/Abstractions/Security/IJwtService.cs

@@ -0,0 +1,8 @@
+using SIGCM2.Domain.Entities;
+
+namespace SIGCM2.Application.Abstractions.Security;
+
+public interface IJwtService
+{
+    string GenerateAccessToken(Usuario usuario);
+}

src/api/SIGCM2.Application/Abstractions/Security/IPasswordHasher.cs

@@ -0,0 +1,7 @@
+namespace SIGCM2.Application.Abstractions.Security;
+
+public interface IPasswordHasher
+{
+    bool Verify(string plainPassword, string hash);
+    string Hash(string plainPassword);
+}

src/api/SIGCM2.Application/Auth/Login/LoginCommand.cs

@@ -0,0 +1,3 @@
+namespace SIGCM2.Application.Auth.Login;
+
+public sealed record LoginCommand(string Username, string Password);

src/api/SIGCM2.Application/Auth/Login/LoginCommandHandler.cs

@@ -0,0 +1,54 @@
+using System.Text.Json;
+using SIGCM2.Application.Abstractions;
+using SIGCM2.Application.Abstractions.Persistence;
+using SIGCM2.Application.Abstractions.Security;
+using SIGCM2.Domain.Exceptions;
+
+namespace SIGCM2.Application.Auth.Login;
+
+public sealed class LoginCommandHandler : ICommandHandler<LoginCommand, LoginResponseDto>
+{
+    private readonly IUsuarioRepository _repository;
+    private readonly IPasswordHasher _hasher;
+    private readonly IJwtService _jwtService;
+
+    public LoginCommandHandler(
+        IUsuarioRepository repository,
+        IPasswordHasher hasher,
+        IJwtService jwtService)
+    {
+        _repository = repository;
+        _hasher = hasher;
+        _jwtService = jwtService;
+    }
+
+    public async Task<LoginResponseDto> Handle(LoginCommand command)
+    {
+        var usuario = await _repository.GetByUsernameAsync(command.Username);
+
+        // Deliberately vague — never reveal which check failed
+        if (usuario is null || !usuario.Activo)
+            throw new InvalidCredentialsException();
+
+        if (!_hasher.Verify(command.Password, usuario.PasswordHash))
+            throw new InvalidCredentialsException();
+
+        var accessToken = _jwtService.GenerateAccessToken(usuario);
+        var refreshToken = Guid.NewGuid().ToString("N"); // opaque, not persisted in UDT-001
+
+        var permisos = JsonSerializer.Deserialize<string[]>(usuario.PermisosJson)
+                       ?? Array.Empty<string>();
+
+        return new LoginResponseDto(
+            AccessToken: accessToken,
+            RefreshToken: refreshToken,
+            ExpiresIn: 3600,
+            Usuario: new UsuarioDto(
+                Id: usuario.Id,
+                Nombre: $"{usuario.Nombre} {usuario.Apellido}".Trim(),
+                Rol: usuario.Rol,
+                Permisos: permisos
+            )
+        );
+    }
+}

src/api/SIGCM2.Application/Auth/Login/LoginCommandValidator.cs

@@ -0,0 +1,17 @@
+using FluentValidation;
+
+namespace SIGCM2.Application.Auth.Login;
+
+public sealed class LoginCommandValidator : AbstractValidator<LoginCommand>
+{
+    public LoginCommandValidator()
+    {
+        RuleFor(x => x.Username)
+            .NotEmpty()
+            .WithMessage("El nombre de usuario es requerido.");
+
+        RuleFor(x => x.Password)
+            .NotEmpty()
+            .WithMessage("La contraseña es requerida.");
+    }
+}

src/api/SIGCM2.Application/Auth/Login/LoginResponseDto.cs

@@ -0,0 +1,15 @@
+namespace SIGCM2.Application.Auth.Login;
+
+public sealed record LoginResponseDto(
+    string AccessToken,
+    string RefreshToken,
+    int ExpiresIn,
+    UsuarioDto Usuario
+);
+
+public sealed record UsuarioDto(
+    int Id,
+    string Nombre,
+    string Rol,
+    string[] Permisos
+);

src/api/SIGCM2.Application/DependencyInjection.cs

@@ -0,0 +1,20 @@
+using FluentValidation;
+using Microsoft.Extensions.DependencyInjection;
+using SIGCM2.Application.Abstractions;
+using SIGCM2.Application.Auth.Login;
+
+namespace SIGCM2.Application;
+
+public static class DependencyInjection
+{
+    public static IServiceCollection AddApplication(this IServiceCollection services)
+    {
+        // Register command handlers
+        services.AddScoped<ICommandHandler<LoginCommand, LoginResponseDto>, LoginCommandHandler>();
+
+        // Register FluentValidation validators from this assembly
+        services.AddValidatorsFromAssemblyContaining<LoginCommandValidator>();
+
+        return services;
+    }
+}

src/api/SIGCM2.Application/SIGCM2.Application.csproj

@@ -0,0 +1,18 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <RootNamespace>SIGCM2.Application</RootNamespace>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="FluentValidation.AspNetCore" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\SIGCM2.Domain\SIGCM2.Domain.csproj" />
+  </ItemGroup>
+
+</Project>