using System;
using System.Collections.Generic;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using FastEndpoints;
using FrameworkBLL.Promotion;
using GB5Shared.Deployment;
using GB5Shared.DTO.Framework.Login;
using GB5Shared.DTO.Framework.ResponseStandard;
using GB5Shared.DTO.Promotion;
using GB5Shared.FastEndPoint;
using Microsoft.Extensions.Configuration;
using static FrameworkDAL.Constant.Constant;

namespace FrameworkSL.Endpoints.Promotion
{
    // ============================================================
    // ExportPromotionPackage — Tier 1 (manual carry) package dispatch.
    //
    // Synchronous, direct BLL call — NOT routed through GOP. A file-download
    // response needs its bytes immediately; GOP execution is deliberately
    // async/queued (GopQueueBLL.SubmitExecution enqueues and returns, a
    // background worker runs it later), which is the wrong fit for "stream me
    // a file right now." See PromotionExportNodeExecutor's own header comment
    // and the plan's Transport section for why Export and Ingest differ here.
    //
    // A package may batch several promotion candidates (req.Items) into one
    // encrypted file, per the user's explicit ask.
    // ============================================================
    public class ExportPromotionPackage : BaseEndpoint<
        ExportPromotionPackage.ExportPromotionPackageParameters, ResponseStandardDTO<object>>
    {
        private readonly IPromotionBLL _PromotionBLL;
        private readonly IConfiguration _Configuration;
        private readonly IGB5Environment _GB5Environment;

        public ExportPromotionPackage(IPromotionBLL promotionBLL, IConfiguration configuration, IGB5Environment gb5Environment)
        {
            _PromotionBLL   = promotionBLL;
            _Configuration  = configuration;
            _GB5Environment = gb5Environment;
        }

        public override void Configure()
        {
            Post("/Promotion/ExportPromotionPackage");
            AllowAnonymous();
        }

        public record ExportPromotionPackageParameters(
            [property: FromHeader] string Login,
            [property: FromBody] PromotionExportRequestDTO Request
        );

        protected override async Task<ResponseStandardDTO<object>> ExecuteAsync(
            ExportPromotionPackageParameters req, LoginDTO LoginDTO, CancellationToken ct)
        {
            try
            {
                if (req.Request.Items.Count == 0)
                    throw new ArgumentException("At least one item is required to export a package.");
                if (string.IsNullOrWhiteSpace(req.Request.DestinationEnvironmentCode))
                    throw new ArgumentException("DestinationEnvironmentCode is required.");

                // Defaults to this deployment's own tier code (Part A, GB5Shared.Deployment) —
                // the appsettings key is now an optional override only, for the rare case of
                // re-running a historical promotion under a different origin code. No longer
                // throws if unset (previously shipped as the literal "CHANGE_ME_PER_ENVIRONMENT"
                // placeholder, a "ships broken until hand-edited" footgun).
                var configuredOverride = _Configuration["Promotion:OriginEnvironmentCode"];
                var originEnvironmentCode = string.IsNullOrWhiteSpace(configuredOverride)
                    ? _GB5Environment.GopEnvironmentCode
                    : configuredOverride;

                var bundles = new List<PromotionBundleDTO>(req.Request.Items.Count);
                foreach (var item in req.Request.Items)
                {
                    var bundle = await _PromotionBLL.BuildExportBundleAsync(
                        item.EntityTypeCode, item.OriginEntityId, LoginDTO, ct).ConfigureAwait(false);
                    bundle.OriginEnvironmentCode = originEnvironmentCode;
                    bundles.Add(bundle);
                }

                var packageBytes = await _PromotionBLL.BuildPackageAsync(
                    bundles, req.Request.DestinationEnvironmentCode, LoginDTO, ct).ConfigureAwait(false);

                var fileName = $"promotion-package-{DateTime.UtcNow:yyyyMMddHHmmss}.gbpromo";
                using var ms = new MemoryStream(packageBytes);
                await HttpContext.Response.SendStreamAsync(
                    ms, fileName, ms.Length, "application/octet-stream", cancellation: ct);

                // Return value unused once SendStreamAsync has written the response.
                return null!;
            }
            catch (Exception ex)
            {
                return await GB5Shared.ResponseStandard.Response.CreateExceptionError<string>(
                    ex, CacheKeyLevel.NOT_REQUIRED, LoginDTO, ex.Message, 500);
            }
        }
    }
}