using System.Text;
using AccountsBLL.ETDS;
using FastEndpoints;
using GB5Shared.DTO.Framework.Criteria;
using GB5Shared.DTO.Framework.Login;
using GB5Shared.DTO.Framework.ResponseStandard;
using Newtonsoft.Json;

namespace AccountsSL.EndPoints.TDSCategory
{
    // Faithful port of GB4 TDSCategory.svc's Form24Q123 (EtdsDAL.GetTDSReturnForm) — builds the
    // NSDL/TIN e-TDS quarterly-return flat file for a single TDSReturnId. GB4 wrote the file to
    // local disk; per explicit direction, GB5 streams the generated content back as an HTTP
    // download instead, so this is a plain Endpoint<T> (not BaseEndpoint) following the same
    // file-download convention as DMS/DMSSL/EndPoints/ESSDocument/DownloadDocument.cs.
    public class Form24Q123 : Endpoint<Form24Q123.Form24Q123Parameters>
    {
        private readonly IEtdsBLL _etdsBLL;

        public Form24Q123(IEtdsBLL etdsBLL)
        {
            _etdsBLL = etdsBLL;
        }

        public record Form24Q123Parameters(
            [property: FromHeader] string Login,
            [property: FromBody] CriteriaDTO CriteriaDTO
        );

        public override void Configure()
        {
            Post("/TDSCategory/ETDS/Form24Q123");
            AllowAnonymous();
        }

        public override async Task HandleAsync(Form24Q123Parameters req, CancellationToken ct)
        {
            LoginDTO? loginDTO;
            try
            {
                loginDTO = JsonConvert.DeserializeObject<LoginDTO>(req.Login);
                if (loginDTO is null) throw new Exception("Null LoginDTO");
            }
            catch
            {
                await WriteErrorAsync(401, "Login token is missing or invalid. Please sign in again.", ct);
                return;
            }

            try
            {
                var (fileName, content) = await _etdsBLL.GetTDSReturnForm(req.CriteriaDTO, loginDTO).ConfigureAwait(false);

                var bytes = Encoding.UTF8.GetBytes(content);
                using var ms = new MemoryStream(bytes);

                HttpContext.Response.StatusCode = 200;
                HttpContext.Response.ContentType = "text/plain";
                HttpContext.Response.Headers.Append(
                    "Content-Disposition",
                    $"attachment; filename=\"{Uri.EscapeDataString(fileName)}\"");

                await ms.CopyToAsync(HttpContext.Response.Body, ct).ConfigureAwait(false);
            }
            catch (Exception ex)
            {
                await WriteErrorAsync(500, ex.Message, ct);
            }
        }

        private Task WriteErrorAsync(int httpStatus, string message, CancellationToken ct)
        {
            var body = new ResponseStandardDTO<object>
            {
                Status = GB5Shared.DTO.Framework.Enum.FrameworkEnumDTO.ResponseStatus.Failed,
                Body = message,
                ErrorBody = message
            };

            HttpContext.Response.StatusCode = httpStatus;
            HttpContext.Response.ContentType = "application/json";
            return HttpContext.Response.WriteAsync(JsonConvert.SerializeObject(body), ct);
        }
    }
}