using System.Security.Claims;
using Microsoft.Extensions.Options;
using System.Text.RegularExpressions;
using YarpGateway.Services;

namespace YarpGateway.Middleware;

/// <summary>
/// 租户路由中间件
/// 
/// 安全说明：
/// 1. 验证 X-Tenant-Id Header 与 JWT 中的 tenant claim 一致
/// 2. 防止租户隔离绕过攻击
/// 3. 只有验证通过后才进行路由查找
/// </summary>
public class TenantRoutingMiddleware
{
    private readonly RequestDelegate _next;
    private readonly IRouteCache _routeCache;
    private readonly ILogger<TenantRoutingMiddleware> _logger;

    public TenantRoutingMiddleware(
        RequestDelegate next,
        IRouteCache routeCache,
        ILogger<TenantRoutingMiddleware> logger)
    {
        _next = next;
        _routeCache = routeCache;
        _logger = logger;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        var headerTenantId = context.Request.Headers["X-Tenant-Id"].FirstOrDefault();
        
        if (string.IsNullOrEmpty(headerTenantId))
        {
            await _next(context);
            return;
        }

        // 安全验证：检查 Header 中的租户 ID 是否与 JWT 一致
        if (context.User?.Identity?.IsAuthenticated == true)
        {
            var jwtTenantId = context.User.Claims
                .FirstOrDefault(c => c.Type == "tenant" || c.Type == "tenant_id")?.Value;

            if (!string.IsNullOrEmpty(jwtTenantId) && jwtTenantId != headerTenantId)
            {
                // 记录安全事件
                _logger.LogWarning(
                    "Tenant ID mismatch detected! JWT tenant: {JwtTenant}, Header tenant: {HeaderTenant}, User: {User}",
                    jwtTenantId,
                    headerTenantId,
                    context.User.FindFirst(ClaimTypes.NameIdentifier)?.Value ?? "unknown"
                );
                
                // 拒绝请求
                context.Response.StatusCode = StatusCodes.Status403Forbidden;
                await context.Response.WriteAsync("Tenant ID verification failed");
                return;
            }
        }

        var path = context.Request.Path.Value ?? string.Empty;
        var serviceName = ExtractServiceName(path);

        if (string.IsNullOrEmpty(serviceName))
        {
            await _next(context);
            return;
        }

        var route = _routeCache.GetRoute(headerTenantId, serviceName);
        if (route == null)
        {
            _logger.LogDebug("Route not found - Tenant: {Tenant}, Service: {Service}", headerTenantId, serviceName);
            await _next(context);
            return;
        }

        context.Items["DynamicClusterId"] = route.ClusterId;

        var routeType = route.IsGlobal ? "global" : "tenant-specific";
        _logger.LogDebug("Tenant routing - Tenant: {Tenant}, Service: {Service}, Cluster: {Cluster}, Type: {Type}",
            headerTenantId, serviceName, route.ClusterId, routeType);

        await _next(context);
    }

    private string ExtractServiceName(string path)
    {
        var match = Regex.Match(path, @"/api/(\w+)/?");
        return match.Success ? match.Groups[1].Value : string.Empty;
    }
}