work-club-manager/backend/WorkClub.Infrastructure/Data/Interceptors/TenantDbConnectionInterceptor.cs

using System.Data.Common;
using Microsoft.AspNetCore.Http;
using Microsoft.EntityFrameworkCore.Diagnostics;
using Microsoft.Extensions.Logging;
using Npgsql;

namespace WorkClub.Infrastructure.Data.Interceptors;

public class TenantDbConnectionInterceptor : DbCommandInterceptor
{
    private readonly IHttpContextAccessor _httpContextAccessor;
    private readonly ILogger<TenantDbConnectionInterceptor> _logger;

    public TenantDbConnectionInterceptor(
        IHttpContextAccessor httpContextAccessor,
        ILogger<TenantDbConnectionInterceptor> logger)
    {
        _httpContextAccessor = httpContextAccessor;
        _logger = logger;
    }

    public override ValueTask<InterceptionResult<DbDataReader>> ReaderExecutingAsync(
        DbCommand command,
        CommandEventData eventData,
        InterceptionResult<DbDataReader> result,
        CancellationToken cancellationToken = default)
    {
        SetTenantContext(command);
        return base.ReaderExecutingAsync(command, eventData, result, cancellationToken);
    }

    public override InterceptionResult<DbDataReader> ReaderExecuting(
        DbCommand command,
        CommandEventData eventData,
        InterceptionResult<DbDataReader> result)
    {
        SetTenantContext(command);
        return base.ReaderExecuting(command, eventData, result);
    }

    public override ValueTask<InterceptionResult<int>> NonQueryExecutingAsync(
        DbCommand command,
        CommandEventData eventData,
        InterceptionResult<int> result,
        CancellationToken cancellationToken = default)
    {
        SetTenantContext(command);
        return base.NonQueryExecutingAsync(command, eventData, result, cancellationToken);
    }

    public override InterceptionResult<int> NonQueryExecuting(
        DbCommand command,
        CommandEventData eventData,
        InterceptionResult<int> result)
    {
        SetTenantContext(command);
        return base.NonQueryExecuting(command, eventData, result);
    }

    private void SetTenantContext(DbCommand command)
    {
        var tenantId = _httpContextAccessor.HttpContext?.Items["TenantId"] as string;
        
        if (!string.IsNullOrWhiteSpace(tenantId) && command.Connection is NpgsqlConnection conn)
        {
            // Prepend SET LOCAL to set tenant context
            // Note: EF Core creates implicit transactions for queries, so SET LOCAL will work
            command.CommandText = $"SET LOCAL app.current_tenant_id = '{tenantId}'; " + command.CommandText;
            _logger.LogInformation("SetTenantContext: Prepended SET LOCAL for tenant {TenantId}", tenantId);
        }
        else
        {
            _logger.LogWarning("ReaderExecuting: No tenant context available (tenantId={TenantId})", tenantId ?? "null");
        }
    }
}