using Xunit;

namespace ZB.MOM.WW.OtOpcUa.Cluster.Tests;

/// <summary>Sets an environment variable for the scope's lifetime and restores its prior value on dispose.</summary>
public sealed class EnvVarScope : IDisposable
{
    private readonly string _name;
    private readonly string? _previous;

    /// <summary>Sets <paramref name="name"/> to <paramref name="value"/> until disposed.</summary>
    /// <param name="name">The environment variable name.</param>
    /// <param name="value">The value to set, or null to unset.</param>
    public EnvVarScope(string name, string? value)
    {
        _name = name;
        _previous = Environment.GetEnvironmentVariable(name);
        Environment.SetEnvironmentVariable(name, value);
    }

    /// <inheritdoc />
    public void Dispose() => Environment.SetEnvironmentVariable(_name, _previous);
}

/// <summary>
///     Serializes every test class that reads or writes the <c>OTOPCUA_ROLES</c> process environment.
/// </summary>
/// <remarks>
///     ⚠️ <b>Load-bearing since Gitea #532.</b> Environment variables are process-global while xUnit runs
///     test classes in an assembly <i>concurrently</i>, so a class that sets <c>OTOPCUA_ROLES</c> is
///     visible to every class running beside it. That was harmless while
///     <c>SplitTopologyTransportValidator</c> was the only code applying the fallback — its own tests both
///     set and read the variable. It stopped being harmless when <c>ConfigSourceOptionsValidator</c> and
///     <c>TelemetryOptionsValidator</c> started resolving effective roles the same way: their cases that
///     pass NO roles would intermittently observe another class's <c>driver,cluster-SITE-A</c> and change
///     verdict. Any test touching that variable, directly or through
///     <c>RoleParser.ResolveEffectiveRoles</c>, belongs in this collection.
/// </remarks>
[CollectionDefinition(Name, DisableParallelization = true)]
public sealed class RoleEnvironmentCollection
{
    /// <summary>The collection name to put on <c>[Collection]</c>.</summary>
    public const string Name = "role-environment";
}