KArtSell.Aegis/src/Modules/IdentityAccess/ManageIdentityAndRoles/Features/RegisterIdentity/RegisterIdentityEndpoint.cs

using FastEndpoints;
using KArtSell.BuildingBlocks.Data;
using KArtSell.BuildingBlocks.Reliability;
using KArtSell.Modules.IdentityAccess.ManageIdentityAndRoles.Events;
using Npgsql;
using System.Data;
using System.Text.Json;

namespace KArtSell.Modules.IdentityAccess.ManageIdentityAndRoles.Features.RegisterIdentity;

public sealed class RegisterIdentityEndpoint(
    IRegisterIdentitySql sql,
    IDbConnectionFactory connectionFactory,
    IOutboxWriter outboxWriter)
    : Endpoint<RegisterIdentityRequest, RegisterIdentityResponse>
{
    public override void Configure()
    {
        Post("/api/identities");
        AllowAnonymous();
    }

    public override async Task HandleAsync(RegisterIdentityRequest req, CancellationToken ct)
    {
        var email = req.Email?.Trim().ToLowerInvariant() ?? string.Empty;
        if (string.IsNullOrWhiteSpace(email) || !email.Contains('@'))
        {
            await SendErrorAsync(400, "Invalid email format", ct);
            return;
        }

        if (string.IsNullOrWhiteSpace(req.DisplayName) || req.DisplayName.Length > 255)
        {
            await SendErrorAsync(400, "Display name required, max 255 characters", ct);
            return;
        }

        var emailExists = await sql.EmailExistsAsync(email, ct);
        if (emailExists)
        {
            await SendErrorAsync(409, "Email already registered", ct);
            return;
        }

        var identityId = Guid.NewGuid();
        var correlationId = Guid.NewGuid().ToString();

        var conn = await connectionFactory.OpenAsync(ct) as NpgsqlConnection
            ?? throw new InvalidOperationException("Failed to open connection");

        await using (conn)
        {
            await using var transaction = await conn.BeginTransactionAsync(IsolationLevel.ReadCommitted, ct);

            try
            {
                var createdId = await sql.CreateIdentityAsync(conn, transaction, identityId, email, req.DisplayName, correlationId, ct);
                if (createdId == Guid.Empty)
                {
                    await SendErrorAsync(409, "Failed to create identity", ct);
                    return;
                }

                // Write IdentityCreated event to Outbox
                var identityCreatedEvent = new IdentityCreated
                {
                    IdentityId = createdId,
                    Email = email,
                    DisplayName = req.DisplayName,
                    CorrelationId = correlationId,
                    OccurredAt = DateTime.UtcNow
                };

                var payloadJson = JsonSerializer.Serialize(identityCreatedEvent);
                var outboxMessage = new OutboxMessage(
                    MessageId: Guid.NewGuid(),
                    EventType: nameof(IdentityCreated),
                    SchemaVersion: 1,
                    PayloadJson: payloadJson,
                    CorrelationId: correlationId,
                    OccurredAt: DateTimeOffset.UtcNow,
                    PayloadHash: ComputePayloadHash(payloadJson));

                await outboxWriter.AddAsync(conn, transaction, outboxMessage, ct);
                await transaction.CommitAsync(ct);

                var (id, returnedEmail, _, currentState) = await sql.GetIdentityAsync(createdId, ct);

                await Send.OkAsync(new RegisterIdentityResponse
                {
                    Id = id,
                    Email = returnedEmail,
                    State = currentState
                }, ct);
            }
            catch (Exception)
            {
                await transaction.RollbackAsync(ct);
                throw;
            }
        }
    }

    private async Task SendErrorAsync(int statusCode, string message, CancellationToken ct)
    {
        await Send.StatusCodeAsync(statusCode, ct);
    }

    private static string ComputePayloadHash(string payloadJson)
    {
        using var hasher = System.Security.Cryptography.SHA256.Create();
        var hash = hasher.ComputeHash(System.Text.Encoding.UTF8.GetBytes(payloadJson));
        return Convert.ToHexString(hash);
    }
}