using FastEndpoints;
using GB5Shared.DTO.Framework.Login;
using GoodBooks.PAY.PAYBLL.Webhook;
using Microsoft.Extensions.Logging;

namespace GoodBooks.PAY.PAYSL.Endpoints.Webhook
{
    // ─────────────────────────────────────────────────────────────────────────
    //  ReceiveWebhook
    //
    //  IMPORTANT: Inherits Endpoint<TReq, IResult> — NOT BaseEndpoint<>.
    //  BaseEndpoint<> reads a Login header to construct LoginDTO.
    //  External gateways (Razorpay, Stripe, Cashfree) never send that header.
    //  Using BaseEndpoint<> would cause a 500 error on every real webhook.
    //
    //  Route includes TenantId so the tenant is deterministically identified
    //  from the URL before parsing the untrusted payload body.
    //
    //  ALWAYS returns HTTP 200 — gateways retry on any other status,
    //  causing duplicate processing storms.
    // ─────────────────────────────────────────────────────────────────────────
    public class ReceiveWebhook : Endpoint<ReceiveWebhook.WebhookParameters, IResult>
    {
        private readonly IPayWebhookBLL          _bll;
        private readonly ILogger<ReceiveWebhook> _logger;

        public ReceiveWebhook(IPayWebhookBLL bll, ILogger<ReceiveWebhook> logger)
        {
            _bll    = bll;
            _logger = logger;
        }

        public record WebhookParameters(
            [property: RouteParam] string GatewayCode,
            [property: RouteParam] int    TenantId
        );

        public override void Configure()
        {
            Post("/Pay/Webhook/{GatewayCode}/{TenantId}");
            AllowAnonymous();
            // Raw endpoint — gateways do not send the Login header that BaseEndpoint<> expects
        }

        public override async Task HandleAsync(WebhookParameters req, CancellationToken ct)
        {
            // Step 1: Buffer request body so it can be read as a string
            HttpContext.Request.EnableBuffering();
            string rawPayload;
            using (var reader = new System.IO.StreamReader(
                HttpContext.Request.Body,
                leaveOpen: true))
            {
                rawPayload = await reader.ReadToEndAsync(ct).ConfigureAwait(false);
            }
            HttpContext.Request.Body.Position = 0;

            // Step 2: Extract gateway signature header (check all known header names)
            // Cashfree's real webhook headers are `x-webhook-signature` + a separate
            // `x-webhook-timestamp` (its HMAC is computed over timestamp+body, not the body
            // alone) — there is no single "X-Cashfree-Signature" header in Cashfree's real API.
            // Combined into the same "t=...,v1=..." compound-string convention Stripe's own
            // native header already uses, so CashfreeGateway can parse it the same way
            // StripeGateway parses Stripe-Signature — no interface change needed.
            string? cashfreeSig = HttpContext.Request.Headers["x-webhook-signature"].FirstOrDefault();
            string sigHeader =
                HttpContext.Request.Headers["X-Razorpay-Signature"].FirstOrDefault()  ??
                HttpContext.Request.Headers["Stripe-Signature"].FirstOrDefault()       ??
                (cashfreeSig is not null
                    ? $"t={HttpContext.Request.Headers["x-webhook-timestamp"].FirstOrDefault()},v1={cashfreeSig}"
                    : null) ??
                string.Empty;

            // Step 3: Build system-level LoginDTO (no user session for gateway callbacks)
            LoginDTO systemLogin;
            try
            {
                systemLogin = await _bll.BuildSystemLoginAsync(req.TenantId, req.GatewayCode, ct)
                    .ConfigureAwait(false);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "BuildSystemLogin failed {GatewayCode}/{TenantId}",
                    req.GatewayCode, req.TenantId);
                // Fall back to minimal login — BLL will handle gracefully
                systemLogin = new LoginDTO
                {
                    ClientId     = req.TenantId,
                    DatabaseName = "GoodBooks_Main",
                    UserId       = -1
                };
            }

            // Step 4: Process webhook — BLL never throws; catch here is belt-and-suspenders
            try
            {
                await _bll.ProcessWebhookAsync(
                    req.GatewayCode, req.TenantId, rawPayload, sigHeader, systemLogin, ct)
                    .ConfigureAwait(false);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Unexpected exception from PayWebhookBLL {GatewayCode}/{TenantId}",
                    req.GatewayCode, req.TenantId);
            }

            // Step 5: ALWAYS return 200 — any other status triggers gateway retry storms
            await Send.OkAsync(ct);
        }
    }
}