using System;
using System.Threading;
using System.Threading.Tasks;
using GB5Shared.DTO.Framework.Login;
using GB5Shared.DTO.Promotion;
using Microsoft.Extensions.DependencyInjection;

namespace GB5Shared.Promotion
{
    // ============================================================
    // PromotionBridgeService — the shared server-side logic behind every module's own
    // three PromotionBridge endpoints (ExportForPromotion/ValidateForPromotion/ImportPromoted).
    //
    // Deliberately entity-agnostic: it just resolves the locally-registered IPromotableEntity for
    // a given EntityTypeCode (the module's own keyed DI — e.g. TMSModule.Register() keys
    // TrainingProgrammePromotionAdapter under "TRAININGPROGRAMME") and calls it, exactly the same
    // resolution PromotionBLL already performs in-process for GB5Framework's own entities. Each
    // owning module gets three thin FastEndpoints that call these three methods — see
    // PromotionBridgeDTOs.cs for why this exists instead of a direct BLL reference.
    // ============================================================
    public static class PromotionBridgeService
    {
        public static async Task<PromotionBundleDTO> ExportAsync(
            IServiceProvider serviceProvider, string entityTypeCode, int originEntityId,
            LoginDTO login, CancellationToken ct)
        {
            var entity = Resolve(serviceProvider, entityTypeCode);
            return await entity.ExportForPromotionAsync(originEntityId, login, ct).ConfigureAwait(false);
        }

        public static async Task<PromotionValidationResultDTO> ValidateAsync(
            IServiceProvider serviceProvider, PromotionBundleDTO bundle, CancellationToken ct)
        {
            var entity = Resolve(serviceProvider, bundle.EntityTypeCode);
            return await entity.ValidateForPromotionAsync(bundle, ct).ConfigureAwait(false);
        }

        public static async Task<int> ImportAsync(
            IServiceProvider serviceProvider, PromotionBundleDTO bundle, byte destinationSourceType,
            int? existingDestinationId, LoginDTO login, CancellationToken ct)
        {
            var entity = Resolve(serviceProvider, bundle.EntityTypeCode);
            return await entity.ImportPromotedAsync(bundle, destinationSourceType, existingDestinationId, login, ct)
                .ConfigureAwait(false);
        }

        private static IPromotableEntity Resolve(IServiceProvider serviceProvider, string entityTypeCode)
        {
            if (string.IsNullOrWhiteSpace(entityTypeCode))
                throw new InvalidOperationException("EntityTypeCode is required.");

            return serviceProvider.GetKeyedService<IPromotableEntity>(entityTypeCode)
                ?? throw new InvalidOperationException(
                    $"No IPromotableEntity registered locally for EntityTypeCode '{entityTypeCode}'.");
        }
    }
}