ScadaBridge/tests/ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests/Scripts/SiteScriptCompileCacheTests.cs

using Microsoft.CodeAnalysis.CSharp.Scripting;
using Microsoft.CodeAnalysis.Scripting;
using ZB.MOM.WW.ScadaBridge.SiteRuntime.Scripts;

namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests.Scripts;

/// <summary>
/// Tests for the process-wide <see cref="SiteScriptCompileCache"/>. The cache is
/// static/process-wide state, so this class shares the "SiteScriptCompileCache" xunit
/// collection with <c>ScriptCompilationServiceTests</c> (no cross-class parallelism) and
/// calls <see cref="SiteScriptCompileCache.Clear"/> at the top of each test.
/// </summary>
[Collection("SiteScriptCompileCache")]
public class SiteScriptCompileCacheTests
{
    private static ScriptCompilationResult Ok() =>
        ScriptCompilationResult.Succeeded(CSharpScript.Create<object?>("1", ScriptOptions.Default, typeof(ScriptGlobals)));

    [Fact]
    public void GetOrAdd_SameCodeAndGlobals_ComputesOnce()
    {
        SiteScriptCompileCache.Clear();
        var factoryCalls = 0;
        ScriptCompilationResult Factory() { factoryCalls++; return Ok(); }

        var r1 = SiteScriptCompileCache.GetOrAdd("return 1;", typeof(ScriptGlobals), Factory);
        var r2 = SiteScriptCompileCache.GetOrAdd("return 1;", typeof(ScriptGlobals), Factory);

        Assert.Equal(1, factoryCalls);
        Assert.Same(r1, r2);
        Assert.Equal(1, SiteScriptCompileCache.Hits);
    }

    [Fact]
    public void GetOrAdd_SameCode_DifferentGlobals_AreSeparateEntries()
    {
        SiteScriptCompileCache.Clear();
        SiteScriptCompileCache.GetOrAdd("1 > 0", typeof(ScriptGlobals), Ok);
        SiteScriptCompileCache.GetOrAdd("1 > 0", typeof(TriggerExpressionGlobals), Ok);

        Assert.Equal(2, SiteScriptCompileCache.Count);
        Assert.Equal(0, SiteScriptCompileCache.Hits); // no cross-globals hit
    }

    [Fact]
    public void Overflow_ClearsWholesale()
    {
        SiteScriptCompileCache.Clear();
        for (var i = 0; i <= SiteScriptCompileCache.MaxEntries; i++)
            SiteScriptCompileCache.GetOrAdd($"return {i};", typeof(ScriptGlobals), Ok);

        Assert.True(SiteScriptCompileCache.Count <= SiteScriptCompileCache.MaxEntries);
    }
}