academia/src/backend/Application/Students/Commands/CreateStudentCommand.cs

namespace Application.Students.Commands;

using System.Security.Cryptography;
using Application.Auth;
using Application.Students.DTOs;
using Domain.Entities;
using Domain.Ports.Repositories;
using Domain.ValueObjects;
using MediatR;
using Microsoft.Extensions.Configuration;

public record CreateStudentCommand(string Name, string Email, string? BaseUrl = null)
    : IRequest<CreateStudentResult>;

public class CreateStudentHandler(
    IStudentRepository studentRepository,
    IPasswordService passwordService,
    IUnitOfWork unitOfWork,
    IConfiguration configuration)
    : IRequestHandler<CreateStudentCommand, CreateStudentResult>
{
    private static readonly TimeSpan ActivationExpiration = TimeSpan.FromHours(48);

    public async Task<CreateStudentResult> Handle(CreateStudentCommand request, CancellationToken ct)
    {
        var email = Email.Create(request.Email);
        var student = new Student(request.Name, email);

        // Generate activation code
        var activationCode = GenerateActivationCode();
        var codeHash = passwordService.HashPassword(activationCode);
        student.SetActivationCode(codeHash, ActivationExpiration);

        studentRepository.Add(student);
        await unitOfWork.SaveChangesAsync(ct);

        var baseUrl = request.BaseUrl ?? configuration["App:BaseUrl"] ?? "http://localhost:4200";
        var activationUrl = $"{baseUrl}/activate?code={activationCode}";

        var studentDto = new StudentDto(student.Id, student.Name, student.Email.Value, 0, []);

        return new CreateStudentResult(
            studentDto,
            activationCode,
            activationUrl,
            student.ActivationExpiresAt!.Value);
    }

    private static string GenerateActivationCode()
    {
        const string chars = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
        var bytes = RandomNumberGenerator.GetBytes(12);
        return new string(bytes.Select(b => chars[b % chars.Length]).ToArray());
    }
}