scadalink-design/tests/ScadaLink.AuditLog.Tests/Payload/InboundChannelCapTests.cs

using System.Text;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using ScadaLink.AuditLog.Configuration;
using ScadaLink.AuditLog.Payload;
using ScadaLink.Commons.Entities.Audit;
using ScadaLink.Commons.Types.Enums;

namespace ScadaLink.AuditLog.Tests.Payload;

/// <summary>
/// Pins the docs/plans/2026-05-23-inbound-api-full-response-audit-design.md
/// inbound carve-out: ApiInbound rows use InboundMaxBytes (default 1 MiB) for
/// RequestSummary / ResponseSummary truncation, NOT DefaultCapBytes /
/// ErrorCapBytes. Other channels keep the existing caps.
/// </summary>
/// <remarks>
/// Uses a file-local <see cref="StaticMonitor"/> helper mirroring the
/// convention in the sibling Payload tests (TruncationTests,
/// FilterIntegrationTests, BodyRegexRedactionTests, etc.) — the
/// <c>TestOptionsMonitor&lt;T&gt;</c> helper referenced by the plan is a
/// private nested class inside <c>AuditLogOptionsBindingTests</c> and thus
/// not reachable from this file.
/// </remarks>
public class InboundChannelCapTests
{
    private static AuditEvent MakeInbound(
        AuditStatus status,
        string? request = null,
        string? response = null) =>
        new()
        {
            EventId = Guid.NewGuid(),
            OccurredAtUtc = DateTime.UtcNow,
            Channel = AuditChannel.ApiInbound,
            Kind = AuditKind.InboundRequest,
            Status = status,
            RequestSummary = request,
            ResponseSummary = response,
        };

    [Fact]
    public void ApiInbound_Delivered_RequestBody_BelowInboundMaxBytes_NotTruncated()
    {
        // Body well above the legacy 8 KiB default cap but under the 1 MiB
        // inbound ceiling — must NOT truncate.
        var body = new string('a', 100_000);
        var opts = new AuditLogOptions();          // defaults
        var filter = new DefaultAuditPayloadFilter(
            new StaticMonitor(opts),
            NullLogger<DefaultAuditPayloadFilter>.Instance);

        var result = filter.Apply(MakeInbound(AuditStatus.Delivered, request: body));

        Assert.False(result.PayloadTruncated);
        Assert.Equal(100_000, Encoding.UTF8.GetByteCount(result.RequestSummary!));
    }

    [Fact]
    public void ApiInbound_Delivered_ResponseBody_BelowInboundMaxBytes_NotTruncated()
    {
        var body = new string('a', 100_000);
        var opts = new AuditLogOptions();
        var filter = new DefaultAuditPayloadFilter(
            new StaticMonitor(opts),
            NullLogger<DefaultAuditPayloadFilter>.Instance);

        var result = filter.Apply(MakeInbound(AuditStatus.Delivered, response: body));

        Assert.False(result.PayloadTruncated);
        Assert.Equal(100_000, Encoding.UTF8.GetByteCount(result.ResponseSummary!));
    }

    [Fact]
    public void ApiInbound_Failed_BodyAboveInboundMaxBytes_TruncatedToInboundMaxBytes()
    {
        // Even on error rows, the inbound cap is InboundMaxBytes (NOT ErrorCapBytes).
        var opts = new AuditLogOptions { InboundMaxBytes = 16_384 };
        var oversized = new string('z', 50_000);
        var filter = new DefaultAuditPayloadFilter(
            new StaticMonitor(opts),
            NullLogger<DefaultAuditPayloadFilter>.Instance);

        var result = filter.Apply(MakeInbound(AuditStatus.Failed, response: oversized));

        Assert.True(result.PayloadTruncated);
        Assert.True(Encoding.UTF8.GetByteCount(result.ResponseSummary!) <= 16_384);
    }

    [Fact]
    public void ApiOutbound_StillUsesDefaultCap_NotInboundMaxBytes()
    {
        // Regression guard: lifting the inbound cap MUST NOT change other
        // channels. An ApiOutbound 100 KB body still hits the 8 KiB cap.
        var opts = new AuditLogOptions();
        var body = new string('a', 100_000);
        var filter = new DefaultAuditPayloadFilter(
            new StaticMonitor(opts),
            NullLogger<DefaultAuditPayloadFilter>.Instance);

        var evt = new AuditEvent
        {
            EventId = Guid.NewGuid(),
            OccurredAtUtc = DateTime.UtcNow,
            Channel = AuditChannel.ApiOutbound,
            Kind = AuditKind.ApiCall,
            Status = AuditStatus.Delivered,
            RequestSummary = body,
        };
        var result = filter.Apply(evt);

        Assert.True(result.PayloadTruncated);
        Assert.True(Encoding.UTF8.GetByteCount(result.RequestSummary!) <= opts.DefaultCapBytes);
    }

    /// <summary>
    /// IOptionsMonitor test double — returns the same snapshot on every read,
    /// no change-token plumbing required for these tests. Mirrors the helper
    /// used in <c>TruncationTests</c>, <c>FilterIntegrationTests</c>, etc.
    /// </summary>
    private sealed class StaticMonitor : IOptionsMonitor<AuditLogOptions>
    {
        private readonly AuditLogOptions _value;

        public StaticMonitor(AuditLogOptions value) => _value = value;

        public AuditLogOptions CurrentValue => _value;

        public AuditLogOptions Get(string? name) => _value;

        public IDisposable? OnChange(Action<AuditLogOptions, string?> listener) => null;
    }
}