using Microsoft.Extensions.Logging.Abstractions;

namespace ScadaLink.Host.Tests;

/// <summary>
/// Host-010: startup preconditions (database migration) must tolerate a database
/// that is briefly unavailable at boot — common when an app container and its DB
/// container start together — via a bounded retry with backoff.
/// </summary>
public class StartupRetryTests
{
    [Fact]
    public async Task ExecuteWithRetry_SucceedsFirstTry_RunsOnce()
    {
        var attempts = 0;
        await StartupRetry.ExecuteWithRetryAsync(
            "test-op",
            () => { attempts++; return Task.CompletedTask; },
            maxAttempts: 5,
            initialDelay: TimeSpan.FromMilliseconds(1),
            NullLogger.Instance);

        Assert.Equal(1, attempts);
    }

    [Fact]
    public async Task ExecuteWithRetry_TransientFailures_RetriesUntilSuccess()
    {
        var attempts = 0;
        await StartupRetry.ExecuteWithRetryAsync(
            "test-op",
            () =>
            {
                attempts++;
                if (attempts < 3)
                    throw new InvalidOperationException("db not ready");
                return Task.CompletedTask;
            },
            maxAttempts: 5,
            initialDelay: TimeSpan.FromMilliseconds(1),
            NullLogger.Instance);

        Assert.Equal(3, attempts);
    }

    [Fact]
    public async Task ExecuteWithRetry_ExhaustsAttempts_RethrowsLastException()
    {
        var attempts = 0;
        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() =>
            StartupRetry.ExecuteWithRetryAsync(
                "test-op",
                () =>
                {
                    attempts++;
                    throw new InvalidOperationException($"failure {attempts}");
                },
                maxAttempts: 3,
                initialDelay: TimeSpan.FromMilliseconds(1),
                NullLogger.Instance));

        Assert.Equal(3, attempts);
        Assert.Equal("failure 3", ex.Message);
    }
}