using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;
using ZB.MOM.WW.CBDDC.Core.Storage;
using ZB.MOM.WW.CBDDC.Persistence.Surreal;

namespace ZB.MOM.WW.CBDDC.Persistence.Lmdb;

/// <summary>
///     Extension methods for adding the LMDB oplog provider and migration feature flags.
/// </summary>
public static class CBDDCLmdbOplogExtensions
{
    /// <summary>
    ///     Registers LMDB oplog services and replaces <see cref="IOplogStore" /> with a feature-flag migration router.
    /// </summary>
    /// <param name="services">The service collection.</param>
    /// <param name="optionsFactory">Factory creating LMDB environment options.</param>
    /// <param name="configureFlags">Optional migration feature-flag configuration.</param>
    /// <returns>The service collection.</returns>
    public static IServiceCollection AddCBDDCLmdbOplog(
        this IServiceCollection services,
        Func<IServiceProvider, LmdbOplogOptions> optionsFactory,
        Action<LmdbOplogFeatureFlags>? configureFlags = null)
    {
        if (services == null) throw new ArgumentNullException(nameof(services));
        if (optionsFactory == null) throw new ArgumentNullException(nameof(optionsFactory));

        services.TryAddSingleton(optionsFactory);

        var flags = new LmdbOplogFeatureFlags
        {
            UseLmdbOplog = true,
            DualWriteOplog = true,
            PreferLmdbReads = false,
            EnableReadShadowValidation = false
        };
        configureFlags?.Invoke(flags);
        services.TryAddSingleton(flags);

        services.TryAddSingleton<OplogMigrationTelemetry>();
        services.TryAddSingleton<LmdbOplogStore>();

        bool surrealRegistered = services.Any(descriptor => descriptor.ServiceType == typeof(SurrealOplogStore));
        if (surrealRegistered)
        {
            services.TryAddSingleton<LmdbOplogBackfillTool>();
            services.Replace(ServiceDescriptor.Singleton<IOplogStore, FeatureFlagOplogStore>());
        }
        else
            services.Replace(ServiceDescriptor.Singleton<IOplogStore>(sp => sp.GetRequiredService<LmdbOplogStore>()));

        return services;
    }
}