// Copyright 2012-2025 The NATS Authors
// Licensed under the Apache License, Version 2.0

namespace ZB.MOM.NatsNet.Server.IntegrationTests.Helpers;

/// <summary>
/// Helper for polling-style checks in integration tests.
/// Corresponds to Go's checkFor(t, timeout, interval, func) pattern.
/// </summary>
public static class CheckHelper
{
    /// <summary>
    /// Polls the provided check function until it returns null (success) or the timeout elapses.
    /// Throws an exception with the last error message if the timeout is reached.
    /// </summary>
    /// <param name="timeout">Maximum time to wait.</param>
    /// <param name="interval">Polling interval.</param>
    /// <param name="check">Function returning null on success, or an error message on failure.</param>
    public static async Task CheckFor(TimeSpan timeout, TimeSpan interval, Func<Task<string?>> check)
    {
        var deadline = DateTime.UtcNow + timeout;
        string? lastError = null;
        while (DateTime.UtcNow < deadline)
        {
            lastError = await check();
            if (lastError == null) return;
            await Task.Delay(interval);
        }
        throw new InvalidOperationException($"CheckFor timed out after {timeout}: {lastError}");
    }

    /// <summary>
    /// Polls the provided synchronous check function until it returns null (success) or the timeout elapses.
    /// </summary>
    public static async Task CheckFor(TimeSpan timeout, TimeSpan interval, Func<string?> check)
    {
        await CheckFor(timeout, interval, () => Task.FromResult(check()));
    }
}