// -----------------------------------------------------------------------------
// RateLimitingExtensions.cs
// Sprint: SPRINT_3500_0002_0003_proof_replay_api
// Task: T4 - Rate Limiting
// Description: Rate limiting configuration for proof replay endpoints
// -----------------------------------------------------------------------------


using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.RateLimiting;
using Microsoft.Extensions.DependencyInjection;
using StellaOps.Scanner.WebService.Security;
using System.Threading.RateLimiting;

namespace StellaOps.Scanner.WebService.Extensions;

/// <summary>
/// Extensions for configuring rate limiting on proof replay endpoints.
/// </summary>
public static class RateLimitingExtensions
{
    /// <summary>
    /// Policy name for proof replay rate limiting (100 req/hr per tenant).
    /// </summary>
    public const string ProofReplayPolicy = "ProofReplay";

    /// <summary>
    /// Policy name for scan manifest rate limiting (100 req/hr per tenant).
    /// </summary>
    public const string ManifestPolicy = "Manifest";

    /// <summary>
    /// Add rate limiting services for scanner endpoints (proof replay, manifest, etc.).
    /// </summary>
    public static IServiceCollection AddScannerRateLimiting(this IServiceCollection services)
    {
        services.AddRateLimiter(options =>
        {
            options.RejectionStatusCode = StatusCodes.Status429TooManyRequests;

            // Proof replay: 100 requests per hour per tenant
            options.AddPolicy(ProofReplayPolicy, context =>
            {
                var tenantId = GetTenantId(context);
                return RateLimitPartition.GetFixedWindowLimiter(
                    partitionKey: $"proof-replay:{tenantId}",
                    factory: _ => new FixedWindowRateLimiterOptions
                    {
                        PermitLimit = 100,
                        Window = TimeSpan.FromHours(1),
                        QueueProcessingOrder = QueueProcessingOrder.OldestFirst,
                        QueueLimit = 0 // No queuing; immediate rejection
                    });
            });

            // Manifest: 100 requests per hour per tenant
            options.AddPolicy(ManifestPolicy, context =>
            {
                var tenantId = GetTenantId(context);
                return RateLimitPartition.GetFixedWindowLimiter(
                    partitionKey: $"manifest:{tenantId}",
                    factory: _ => new FixedWindowRateLimiterOptions
                    {
                        PermitLimit = 100,
                        Window = TimeSpan.FromHours(1),
                        QueueProcessingOrder = QueueProcessingOrder.OldestFirst,
                        QueueLimit = 0
                    });
            });

            // Configure rejection response
            options.OnRejected = async (context, cancellationToken) =>
            {
                context.HttpContext.Response.StatusCode = StatusCodes.Status429TooManyRequests;
                context.HttpContext.Response.Headers.RetryAfter = "3600"; // 1 hour

                if (context.Lease.TryGetMetadata(MetadataName.RetryAfter, out var retryAfter))
                {
                    context.HttpContext.Response.Headers.RetryAfter =
                        ((int)retryAfter.TotalSeconds).ToString();
                }

                await context.HttpContext.Response.WriteAsJsonAsync(new
                {
                    type = "https://stellaops.org/problems/rate-limit",
                    title = "Too Many Requests",
                    status = 429,
                    detail = "Rate limit exceeded. Please wait before making more requests.",
                    retryAfterSeconds = context.HttpContext.Response.Headers.RetryAfter.ToString()
                }, cancellationToken);
            };
        });

        return services;
    }

    /// <summary>
    /// Extract tenant ID from the HTTP context for rate limiting partitioning.
    /// </summary>
    private static string GetTenantId(HttpContext context)
    {
        // Try to get tenant from claims
        var tenantClaim = context.User?.FindFirst(ScannerClaims.TenantId);
        if (tenantClaim is not null && !string.IsNullOrWhiteSpace(tenantClaim.Value))
        {
            return tenantClaim.Value;
        }

        // Fallback to tenant header
        if (context.Request.Headers.TryGetValue("X-Tenant-Id", out var headerValue) &&
            !string.IsNullOrWhiteSpace(headerValue))
        {
            return headerValue.ToString();
        }

        // Fallback to IP address for unauthenticated requests
        return context.Connection.RemoteIpAddress?.ToString() ?? "unknown";
    }
}

/// <summary>
/// Scanner claims constants.
/// </summary>
public static class ScannerClaims
{
    public const string TenantId = "tenant_id";
}