#nullable enable
using Baya.Application.Contracts.Common;
using Baya.Domain.Common;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Diagnostics;

namespace Baya.Infrastructure.Persistence.Interceptors;

/// <summary>
/// Stamps audit fields on every save: <c>CreatedAt</c>/<c>CreatedById</c> on insert and
/// <c>ModifiedAt</c>/<c>ModifiedById</c> on update, sourcing time from <see cref="IDateTimeProvider"/>
/// and the acting user from <see cref="ICurrentUser"/>. Handlers never set these fields.
/// This is the extension point backend-phase-1 builds on to also write append-only audit-log rows.
/// </summary>
public sealed class AuditFieldInterceptor(ICurrentUser currentUser, IDateTimeProvider dateTimeProvider)
    : SaveChangesInterceptor
{
    public override InterceptionResult<int> SavingChanges(
        DbContextEventData eventData,
        InterceptionResult<int> result)
    {
        Stamp(eventData.Context);
        return base.SavingChanges(eventData, result);
    }

    public override ValueTask<InterceptionResult<int>> SavingChangesAsync(
        DbContextEventData eventData,
        InterceptionResult<int> result,
        CancellationToken cancellationToken = default)
    {
        Stamp(eventData.Context);
        return base.SavingChangesAsync(eventData, result, cancellationToken);
    }

    private void Stamp(DbContext? context)
    {
        if (context is null)
            return;

        var now = dateTimeProvider.UtcNow;
        var userId = currentUser.UserId;

        foreach (var entry in context.ChangeTracker.Entries<ITimeModification>())
        {
            switch (entry.State)
            {
                case EntityState.Added:
                    entry.Entity.CreatedAt = now;
                    entry.Entity.ModifiedAt = now;
                    if (entry.Entity is IAuditableEntity addedAuditable)
                    {
                        addedAuditable.CreatedById = userId;
                        addedAuditable.ModifiedById = userId;
                    }

                    break;

                case EntityState.Modified:
                    entry.Entity.ModifiedAt = now;
                    if (entry.Entity is IAuditableEntity modifiedAuditable)
                        modifiedAuditable.ModifiedById = userId;

                    break;
            }
        }
    }
}