using Omika.Core.Observability.Outbox;

namespace Omika.Tests.Observability.Outbox;

/// <summary>Tests du backoff borné avec jitter (§43).</summary>
public class DiagnosticBackoffPolicyTests
{
    [Fact]
    public void NextDelay_IsBoundedByMax()
    {
        var options = new DiagnosticUploadOptions
        {
            BackoffInitial = TimeSpan.FromSeconds(15),
            BackoffMax = TimeSpan.FromHours(1)
        };
        var policy = new DiagnosticBackoffPolicy(options);

        // Garantie absolue : 0 < délai <= MaxDelay, pour tout attempt, y compris les
        // valeurs extrêmes. Le jitter (aléatoire) ne peut JAMAIS faire dépasser MaxDelay
        // car la borne finale est appliquée après le jitter.
        int[] attempts = [0, 1, 5, 9, 20, 50, 100, int.MaxValue];
        foreach (int attempt in attempts)
        {
            TimeSpan delay = policy.NextDelay(attempt);
            Assert.True(delay > TimeSpan.Zero, $"attempt {attempt}: délai non strictement positif ({delay})");
            Assert.True(delay <= options.BackoffMax, $"attempt {attempt}: délai {delay} dépasse le maximum {options.BackoffMax}");
        }
    }

    [Fact]
    public void NextDelay_GrowsWithAttempts()
    {
        var policy = new DiagnosticBackoffPolicy(new DiagnosticUploadOptions
        {
            BackoffInitial = TimeSpan.FromSeconds(15),
            BackoffMax = TimeSpan.FromHours(1),
            BackoffJitter = 0.0
        });

        TimeSpan first = policy.NextDelay(1);
        TimeSpan second = policy.NextDelay(2);
        TimeSpan third = policy.NextDelay(3);

        Assert.True(second >= first);
        Assert.True(third >= second);
    }

    [Fact]
    public void NextDelay_WithJitter_StaysWithinJitterBounds()
    {
        var options = new DiagnosticUploadOptions
        {
            BackoffInitial = TimeSpan.FromSeconds(10),
            BackoffMax = TimeSpan.FromMinutes(1),
            BackoffJitter = 0.2
        };
        var policy = new DiagnosticBackoffPolicy(options);

        for (int i = 0; i < 100; i++)
        {
            TimeSpan delay = policy.NextDelay(1);
            Assert.InRange(delay.TotalMilliseconds, 8000, 12000);
        }
    }
}