using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Infrastructure;
using Prefab.Data.Entities;
using Prefab.Domain.Common;
using Prefab.Handler;
using System.Reflection;

namespace Prefab.Data;

public abstract class PrefabDb(DbContextOptions options, IHandlerContextAccessor accessor)
    : DbContext(options)
{
    /// <summary>
    /// Exposes the database facade for provider-specific operations.
    /// </summary>
    public new DatabaseFacade Database => base.Database;

    /// <summary>
    /// Applies Prefab conventions in addition to consumer-provided model configuration.
    /// </summary>
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        modelBuilder.ApplyConfigurationsFromAssembly(typeof(IPrefabDb).Assembly);

        PrefabOnModelCreating(modelBuilder);
        modelBuilder.IgnoreDomainEvents();
    }

    /// <summary>
    /// Allows derived contexts to extend model configuration.
    /// </summary>
    /// <param name="builder">The model builder supplied by EF Core.</param>
    protected abstract void PrefabOnModelCreating(ModelBuilder builder);

    /// <summary>
    /// Applies Prefab defaults followed by consumer configuration hooks.
    /// </summary>
    /// <param name="optionsBuilder">The options builder used to configure the context.</param>
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        PrefabOnConfiguring(optionsBuilder);
    }

    /// <summary>
    /// Allows derived contexts to customise provider-specific options.
    /// </summary>
    /// <param name="optionsBuilder">The options builder supplied by EF Core.</param>
    protected abstract void PrefabOnConfiguring(DbContextOptionsBuilder optionsBuilder);

    /// <summary>
    /// Persists changes to the database while executing auditing and outbox processing.
    /// </summary>
    public override int SaveChanges() => SaveChangesAsync().ConfigureAwait(false).GetAwaiter().GetResult();

    /// <summary>
    /// Persists changes to the database while executing auditing and outbox processing.
    /// </summary>
    /// <param name="cancellationToken">Token used to cancel the save operation.</param>
    public override async Task<int> SaveChangesAsync(CancellationToken cancellationToken = new())
    {
        var now = DateTimeOffset.UtcNow;
        var correlationId = Guid.TryParse(accessor?.Current?.CorrelationId, out var parsedCorrelationId)
            ? parsedCorrelationId
            : Guid.Empty;

        var auditEntitiesCache = new Dictionary<Type, bool>();
        var propertiesCache = new Dictionary<Type, (PropertyInfo? CreatedBy, PropertyInfo? CreatedOn, PropertyInfo? ModifiedBy, PropertyInfo? ModifiedOn)>();
        var auditEntries = new List<Microsoft.EntityFrameworkCore.ChangeTracking.EntityEntry>();

        foreach (var entry in ChangeTracker.Entries())
        {
            var entityType = entry.Entity.GetType();
            if (!auditEntitiesCache.TryGetValue(entityType, out var entityIsAuditable))
            {
                entityIsAuditable = entityType.GetInterfaces()
                    .Any(i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof(IEntityWithAudit<>));
                auditEntitiesCache[entityType] = entityIsAuditable;
            }

            if (!entityIsAuditable)
            {
                continue;
            }

            if (!propertiesCache.TryGetValue(entityType, out var props))
            {
                props = (
                    CreatedBy: entityType.GetProperty(nameof(IAudit.CreatedBy)),
                    CreatedOn: entityType.GetProperty(nameof(IAudit.CreatedOn)),
                    ModifiedBy: entityType.GetProperty(nameof(IAudit.LastModifiedBy)),
                    ModifiedOn: entityType.GetProperty(nameof(IAudit.LastModifiedOn))
                );
                propertiesCache[entityType] = props;
            }

            switch (entry.State)
            {
                case EntityState.Added:
                    props.CreatedBy?.SetValue(entry.Entity, props.CreatedBy.GetValue(entry.Entity) ?? accessor?.Current?.UserId);
                    props.CreatedOn?.SetValue(entry.Entity, now);
                    auditEntries.Add(entry);
                    break;
                case EntityState.Modified:
                    props.ModifiedBy?.SetValue(entry.Entity, accessor?.Current?.UserId ?? accessor?.Current?.UserId);
                    props.ModifiedOn?.SetValue(entry.Entity, now);
                    auditEntries.Add(entry);
                    break;
                case EntityState.Deleted:
                    if (TrySoftDelete(entry, props, accessor?.Current?.UserId, now))
                    {
                        entry.State = EntityState.Modified;
                        auditEntries.Add(entry);
                    }
                    break;
            }
        }

        foreach (var entry in auditEntries)
        {
            var audit = new AuditLog
            {
                CorrelationId = correlationId,
                Entity = entry.Entity.GetType().Name,
                State = entry.State.ToString(),
                CreatedBy = Guid.TryParse(accessor?.Current?.UserId, out var userId) ? userId : Guid.Empty,
                CreatedOn = now,
                Items = new List<AuditLogItem>()
            };

            foreach (var prop in entry.Properties)
            {
                if (entry.State == EntityState.Modified && !prop.IsModified)
                {
                    continue;
                }

                var oldVal = entry.State == EntityState.Modified ? prop.OriginalValue?.ToString() : null;
                var newVal = prop.CurrentValue?.ToString();
                audit.Items.Add(new AuditLogItem
                {
                    Property = prop.Metadata.Name,
                    OldValue = oldVal,
                    NewValue = newVal
                });
            }

            AuditLogs.Add(audit);
        }

        var domainEventEntities = ChangeTracker
            .Entries<IHasDomainEvents>()
            .Where(e => e.Entity.Events.Count > 0)
            .Select(e => e.Entity)
            .ToList();

        if (domainEventEntities.Count > 0)
        {
            var domainEvents = domainEventEntities.SelectMany(e => e.Events).ToList();
            foreach (var ev in domainEvents)
            {
                //Outbox.Add(Prefab.Queuing.Domain.Outbox.New(ev));
            }

            domainEventEntities.ForEach(e => e.ClearEvents());
        }

        return await base.SaveChangesAsync(cancellationToken);
    }

    private static bool TrySoftDelete(
        Microsoft.EntityFrameworkCore.ChangeTracking.EntityEntry entry,
        (PropertyInfo? CreatedBy, PropertyInfo? CreatedOn, PropertyInfo? ModifiedBy, PropertyInfo? ModifiedOn) props,
        string? userId,
        DateTimeOffset deletedOn)
    {
        var entityType = entry.Entity.GetType();
        var supportsSoftDelete = entityType.GetInterfaces()
            .Any(i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof(IEntityWithAuditAndStatus<>));

        if (!supportsSoftDelete)
        {
            return false;
        }

        var deletedOnProp = entityType.GetProperty(nameof(EntityWithAuditAndStatus<Guid>.DeletedOn));
        var deletedByProp = entityType.GetProperty(nameof(EntityWithAuditAndStatus<Guid>.DeletedBy));

        deletedOnProp?.SetValue(entry.Entity, deletedOn);
        if (deletedByProp is not null)
        {
            if (Guid.TryParse(userId, out var parsedUserId))
            {
                deletedByProp.SetValue(entry.Entity, parsedUserId);
            }
            else
            {
                deletedByProp.SetValue(entry.Entity, null);
            }
        }

        const string deletedOnPropertyName = nameof(EntityWithAuditAndStatus<Guid>.DeletedOn);
        if (entry.Metadata.FindProperty(deletedOnPropertyName) is not null)
        {
            entry.Property(deletedOnPropertyName).IsModified = true;
        }

        const string deletedByPropertyName = nameof(EntityWithAuditAndStatus<Guid>.DeletedBy);
        if (entry.Metadata.FindProperty(deletedByPropertyName) is not null)
        {
            entry.Property(deletedByPropertyName).IsModified = true;
        }

        props.ModifiedOn?.SetValue(entry.Entity, deletedOn);
        if (props.ModifiedBy is not null)
        {
            if (Guid.TryParse(userId, out var parsedUserId))
            {
                props.ModifiedBy.SetValue(entry.Entity, parsedUserId);
            }
            else
            {
                props.ModifiedBy.SetValue(entry.Entity, null);
            }
        }

        return true;
    }

    /// <summary>
    /// Gets the audit log set.
    /// </summary>
    public DbSet<AuditLog> AuditLogs { get; set; } = null!;

    /// <summary>
    /// Gets the audit log item set.
    /// </summary>
    public DbSet<AuditLogItem> AuditLogItems { get; set; } = null!;

    /// <summary>
    /// Gets the generic attribute set.
    /// </summary>
    public DbSet<GenericAttribute> GenericAttributes => Set<GenericAttribute>();

    /// <summary>
    /// Gets the seeder log set.
    /// </summary>
    public DbSet<SeederLog> SeederLogs => Set<SeederLog>();
}