using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using GB5Shared.DTO.Framework.Login;
using GB5Shared.DTO.Qualifier;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

namespace GB5Shared.GOP.Qualifier.Executors
{
    // ============================================================
    // ServiceExecutor — ExecutionMode 3 (IQualifierService registry)
    //
    // Dispatches to a feature-module-registered IQualifierService
    // keyed by SnapshotMethod.ServiceCode.
    //
    // Feature modules register their services as:
    //   services.AddKeyedScoped<IQualifierService, MyService>("MY_SERVICE_CODE");
    //
    // If no service is registered for the given ServiceCode, an
    // Error finding is emitted (this is a configuration error).
    // ============================================================
    public class ServiceExecutor : IQualifierMethodExecutor
    {
        private readonly IServiceProvider        _ServiceProvider;
        private readonly ILogger<ServiceExecutor> _Logger;

        public ServiceExecutor(
            IServiceProvider         serviceProvider,
            ILogger<ServiceExecutor> logger)
        {
            _ServiceProvider = serviceProvider;
            _Logger          = logger;
        }

        public string ExecutionModeKey => "Service";

        public async Task<IReadOnlyList<QualifierFinding>> ExecuteAsync(
            SnapshotMethod            method,
            QualifierExecutionContext ctx,
            LoginDTO                  loginDTO,
            CancellationToken         ct)
        {
            if (string.IsNullOrWhiteSpace(method.ServiceCode))
            {
                return
                [
                    new QualifierFinding
                    {
                        Severity      = FindingSeverity.Error,
                        Code          = "SERVICE_CODE_MISSING",
                        Message       = $"Method {method.QualifierMethodId} has ExecutionMode=Service but no ServiceCode.",
                        QualifierId   = 0,
                        QualifierCode = string.Empty
                    }
                ];
            }

            var service = _ServiceProvider.GetKeyedService<IQualifierService>(method.ServiceCode);
            if (service is null)
            {
                _Logger.LogError(
                    "ServiceExecutor: no IQualifierService registered for ServiceCode '{ServiceCode}'",
                    method.ServiceCode);

                return
                [
                    new QualifierFinding
                    {
                        Severity      = FindingSeverity.Error,
                        Code          = "SERVICE_NOT_REGISTERED",
                        Message       = $"No IQualifierService registered for ServiceCode '{method.ServiceCode}'.",
                        QualifierId   = 0,
                        QualifierCode = string.Empty
                    }
                ];
            }

            return await service.ExecuteAsync(ctx, ct);
        }
    }

    // ============================================================
    // IQualifierService — contract for feature-module services
    //
    // Feature modules implement this interface and register with:
    //   services.AddKeyedScoped<IQualifierService, MyService>("MY_SERVICE_CODE");
    // ============================================================
    public interface IQualifierService
    {
        Task<IReadOnlyList<QualifierFinding>> ExecuteAsync(
            QualifierExecutionContext ctx,
            CancellationToken         ct);
    }
}