using Microsoft.Extensions.DependencyInjection;
using ZB.MOM.WW.ScadaBridge.SiteRuntime;
using ZB.MOM.WW.ScadaBridge.SiteRuntime.Scripts;

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

/// <summary>
/// Pins the DI lifetimes that carry a behavioural contract rather than a convention.
/// </summary>
public class SiteRuntimeServiceRegistrationTests
{
    /// <summary>
    /// Register row 100. <c>ScriptCompilationService</c> owns the
    /// <c>SiteScriptCompileCache</c>, so "one Roslyn compile per script body per process"
    /// (N4 / WP3.1's warm-then-gate deploy path) is precisely the statement that DI hands
    /// out ONE of these per host. The cache stopped being <c>static</c> when row 100 removed
    /// the process-global state tests were clobbering; this registration is what replaced
    /// the static as the guarantee, so it is pinned here.
    ///
    /// <para>Downgrading this to Scoped or Transient would give every consumer — the deploy
    /// gate, each Instance Actor's PreStart, SharedScriptLibrary — its own empty cache and
    /// silently reintroduce the recompile storms WP3.1 removed, with no functional test
    /// failing. This assertion is the only thing that would notice.</para>
    /// </summary>
    [Fact]
    public void AddSiteRuntime_RegistersScriptCompilationServiceAsSingleton_SoOneCompileCacheExistsPerProcess()
    {
        var services = new ServiceCollection();

        services.AddSiteRuntime();

        var descriptor = Assert.Single(
            services, d => d.ServiceType == typeof(ScriptCompilationService));
        Assert.Equal(ServiceLifetime.Singleton, descriptor.Lifetime);
    }
}