w4c-workflows-api/Controllers/WorkflowQuotaController.cs

using Microsoft.AspNetCore.Mvc;
using w4c_workflows.Filters;
using w4c_workflows.Services.Quota;

namespace w4c_workflows.Controllers;

/// <summary>
/// Per-tenant workflow execution quota. <c>GET</c> returns the current period's
/// usage (drives the counter on the Workflows page). <c>POST reset</c> is a
/// platform-admin action: a tenant must not be able to zero its own counter, so
/// it additionally requires the shared <c>X-Admin-Key</c> matching
/// <c>Workflows:AdminApiKey</c> (fail-closed when unset).
/// </summary>
[ApiController]
[Route("api/workflows/quota")]
public class WorkflowQuotaController : ControllerBase
{
    private readonly WorkflowQuotaService _quota;
    private readonly string? _adminKey;

    public WorkflowQuotaController(WorkflowQuotaService quota, IConfiguration config)
    {
        _quota = quota;
        _adminKey = string.IsNullOrWhiteSpace(config["Workflows:AdminApiKey"])
            ? null
            : config["Workflows:AdminApiKey"];
    }

    private string TenantId => (string?)HttpContext.Items["TenantId"]
        ?? throw new InvalidOperationException("TenantId not resolved by auth middleware");

    /// <summary>Current execution usage against this tenant's monthly limit.</summary>
    [HttpGet]
    [RequireScope("read")]
    public async Task<IActionResult> Get(CancellationToken ct)
    {
        return Ok(await _quota.GetAsync(TenantId, ct));
    }

    /// <summary>
    /// Resets the current period's execution counter to zero. Platform admin only:
    /// requires the shared admin key in addition to the operator key.
    /// </summary>
    [HttpPost("reset")]
    [RequireScope("manage")]
    public async Task<IActionResult> Reset(CancellationToken ct)
    {
        if (!IsPlatformAdmin())
        {
            return StatusCode(StatusCodes.Status403Forbidden, new
            {
                error = "Resetting a tenant quota requires the platform admin key " +
                        "(header X-Admin-Key, configured as Workflows:AdminApiKey).",
            });
        }

        return Ok(await _quota.ResetAsync(TenantId, ct));
    }

    private bool IsPlatformAdmin()
    {
        if (_adminKey == null)
            return false;

        var provided = Request.Headers["X-Admin-Key"].FirstOrDefault();
        return provided != null && FixedTimeEquals(provided, _adminKey);
    }

    private static bool FixedTimeEquals(string a, string b)
    {
        var aBytes = System.Text.Encoding.UTF8.GetBytes(a);
        var bBytes = System.Text.Encoding.UTF8.GetBytes(b);
        if (aBytes.Length != bBytes.Length)
            return false;

        var result = 0;
        for (var i = 0; i < aBytes.Length; i++)
            result |= aBytes[i] ^ bBytes[i];
        return result == 0;
    }
}