// EN: Middleware to set PostgreSQL session variable for RLS policies.
// VI: Middleware để đặt biến session PostgreSQL cho RLS policies.

using System.Data;
using Npgsql;
using OrderService.API.Infrastructure.Tenant;

namespace OrderService.API.Middleware;

/// <summary>
/// EN: Sets PostgreSQL session variables (app.current_tenant_id) for row-level security.
///     This provides defense-in-depth: even if EF Core global query filters are bypassed
///     (e.g., via raw SQL/Dapper), PostgreSQL RLS policies will still enforce tenant isolation.
/// VI: Đặt biến session PostgreSQL (app.current_tenant_id) cho bảo mật row-level.
///     Điều này cung cấp phòng thủ theo chiều sâu: ngay cả khi global query filters của EF Core
///     bị bỏ qua (ví dụ: qua raw SQL/Dapper), RLS policies của PostgreSQL vẫn đảm bảo cách ly tenant.
/// </summary>
public class TenantMiddleware
{
    private readonly RequestDelegate _next;
    private readonly ILogger<TenantMiddleware> _logger;

    public TenantMiddleware(RequestDelegate next, ILogger<TenantMiddleware> logger)
    {
        _next = next;
        _logger = logger;
    }

    public async Task InvokeAsync(HttpContext context, ITenantProvider tenantProvider, IDbConnection dbConnection)
    {
        var shopId = tenantProvider.GetCurrentShopId();
        var merchantId = tenantProvider.GetCurrentMerchantId();
        var isServiceCall = tenantProvider.IsServiceCall();
        var isAdmin = tenantProvider.IsAdmin();

        // EN: Skip tenant SET for service-to-service calls and admin users
        // VI: Bỏ qua tenant SET cho cuộc gọi service-to-service và admin users
        if (!isServiceCall && !isAdmin)
        {
            if (shopId.HasValue)
            {
                await SetTenantContextAsync(dbConnection, shopId.Value, merchantId);
            }
            else
            {
                _logger.LogDebug(
                    "EN: No tenant context available for request {Path} / " +
                    "VI: Không có tenant context cho request {Path}",
                    context.Request.Path);
            }
        }

        await _next(context);
    }

    /// <summary>
    /// EN: Set PostgreSQL session variables for RLS enforcement.
    /// VI: Đặt biến session PostgreSQL cho RLS enforcement.
    /// </summary>
    private async Task SetTenantContextAsync(IDbConnection dbConnection, Guid shopId, Guid? merchantId)
    {
        try
        {
            if (dbConnection is NpgsqlConnection npgsqlConnection)
            {
                if (npgsqlConnection.State != ConnectionState.Open)
                {
                    await npgsqlConnection.OpenAsync();
                }

                // EN: Set shop_id as the primary tenant identifier
                // VI: Đặt shop_id làm tenant identifier chính
                await using var cmd = npgsqlConnection.CreateCommand();
                cmd.CommandText = $"SET LOCAL app.current_shop_id = '{shopId.ToString("D")}'";
                await cmd.ExecuteNonQueryAsync();

                if (merchantId.HasValue)
                {
                    cmd.CommandText = $"SET LOCAL app.current_merchant_id = '{merchantId.Value.ToString("D")}'";
                    await cmd.ExecuteNonQueryAsync();
                }

                _logger.LogDebug(
                    "EN: Tenant context set - ShopId: {ShopId}, MerchantId: {MerchantId} / " +
                    "VI: Tenant context đã đặt - ShopId: {ShopId}, MerchantId: {MerchantId}",
                    shopId, merchantId);
            }
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex,
                "EN: Failed to set PostgreSQL tenant context / " +
                "VI: Không thể đặt PostgreSQL tenant context");
        }
    }
}

/// <summary>
/// EN: Extension method for registering TenantMiddleware.
/// VI: Extension method để đăng ký TenantMiddleware.
/// </summary>
public static class TenantMiddlewareExtensions
{
    /// <summary>
    /// EN: Use tenant middleware for PostgreSQL RLS. Must be placed after UseAuthentication().
    /// VI: Sử dụng tenant middleware cho PostgreSQL RLS. Phải đặt sau UseAuthentication().
    /// </summary>
    public static IApplicationBuilder UseTenantMiddleware(this IApplicationBuilder builder)
    {
        return builder.UseMiddleware<TenantMiddleware>();
    }
}