using Omika.Core.Observability.Forwarding;

namespace Omika.Tests.Observability.Forwarding;

/// <summary>Tests du spool disque du forwarder (checkpoint, bornes, suppression, quota, rétention).</summary>
public class DiagnosticsForwarderSpoolTests : IDisposable
{
    private const string File001 = "omika-mobile-diagnostic-20261002-001.jsonl";
    private const string File002 = "omika-mobile-diagnostic-20261002-002.jsonl";
    private const string File003 = "omika-mobile-diagnostic-20261002-003.jsonl";

    private readonly string _dir = ForwardingTestHarness.CreateTempDirectory();

    private static DiagnosticsForwardingSpoolOptions DefaultSpool => new();

    public void Dispose() => ForwardingTestHarness.DeleteDirectory(_dir);

    private DiagnosticsForwarderSpool NewSpool(DiagnosticsForwardingSpoolOptions? options = null) =>
        new(_dir, "forwarder-checkpoint.json", options ?? DefaultSpool);

    [Fact]
    public void ReadNext_EmptyDirectory_ReturnsReachedEnd()
    {
        var spool = NewSpool();

        DiagnosticsForwarderBatch batch = spool.ReadNext(null, 10, 1024);

        Assert.Empty(batch.Records);
        Assert.True(batch.ReachedEnd);
    }

    [Fact]
    public void ReadNext_ReadsRecordsInOrder_AndResumesAcrossFiles()
    {
        ForwardingTestHarness.WriteSpoolFile(_dir, File001,
            [ForwardingTestHarness.NewRecord(component: "a"), ForwardingTestHarness.NewRecord(component: "b")]);
        ForwardingTestHarness.WriteSpoolFile(_dir, File002,
            [ForwardingTestHarness.NewRecord(component: "c")]);

        var spool = NewSpool();

        DiagnosticsForwarderBatch first = spool.ReadNext(null, 2, 1_000_000);
        Assert.Equal(2, first.Records.Count);
        Assert.Equal("a", first.Records[0].Event.Component);
        Assert.Equal("b", first.Records[1].Event.Component);
        Assert.NotNull(first.NextPosition);
        Assert.Equal(File001, first.NextPosition!.FileName);

        DiagnosticsForwarderBatch second = spool.ReadNext(first.NextPosition, 2, 1_000_000);
        Assert.Single(second.Records);
        Assert.Equal("c", second.Records[0].Event.Component);
        Assert.Equal(File002, second.NextPosition!.FileName);
    }

    [Fact]
    public void ReadNext_RespectsMaxBytes_StillReturnsAtLeastOneRecord()
    {
        ForwardingTestHarness.WriteSpoolFile(_dir, File001,
            [ForwardingTestHarness.NewRecord(), ForwardingTestHarness.NewRecord()]);

        var spool = NewSpool();

        DiagnosticsForwarderBatch batch = spool.ReadNext(null, 100, 10);

        Assert.Single(batch.Records); // premier seuil (octets) : 1 seul, jamais zéro.
    }

    [Fact]
    public void Commit_ThenLoadCheckpoint_ResumesFromNextLine()
    {
        ForwardingTestHarness.WriteSpoolFile(_dir, File001,
            [ForwardingTestHarness.NewRecord(component: "a"), ForwardingTestHarness.NewRecord(component: "b"), ForwardingTestHarness.NewRecord(component: "c")]);

        var spool = NewSpool();

        DiagnosticsForwarderBatch first = spool.ReadNext(null, 1, 1_000_000);
        Assert.Single(first.Records);
        Assert.Equal("a", first.Records[0].Event.Component);
        spool.Commit(first.NextPosition!);

        DiagnosticsForwarderPosition? checkpoint = spool.LoadCheckpoint();
        Assert.NotNull(checkpoint);
        Assert.Equal(File001, checkpoint!.FileName);
        Assert.Equal(0, checkpoint.LineIndex);

        DiagnosticsForwarderBatch second = spool.ReadNext(checkpoint, 10, 1_000_000);
        Assert.Equal(2, second.Records.Count);
        Assert.Equal("b", second.Records[0].Event.Component);
        Assert.Equal("c", second.Records[1].Event.Component);
    }

    [Fact]
    public void PruneConsumed_DeletesOlderFiles_NeverActiveFile()
    {
        ForwardingTestHarness.WriteSpoolFile(_dir, File001, [ForwardingTestHarness.NewRecord()]);
        ForwardingTestHarness.WriteSpoolFile(_dir, File002, [ForwardingTestHarness.NewRecord()]);
        ForwardingTestHarness.WriteSpoolFile(_dir, File003, [ForwardingTestHarness.NewRecord()]);

        var spool = NewSpool();

        int deleted = spool.PruneConsumed(new DiagnosticsForwarderPosition { FileName = File002, LineIndex = 0 });

        Assert.Equal(1, deleted); // seul 001 (antérieur) est supprimé.
        Assert.False(File.Exists(Path.Combine(_dir, File001)));
        Assert.True(File.Exists(Path.Combine(_dir, File002)));
        Assert.True(File.Exists(Path.Combine(_dir, File003))); // actif préservé.
    }

    [Fact]
    public void EnforceBounds_Quota_DeletesOldestFiles()
    {
        int chunk = 400 * 1024; // 3 × 400 Ko = 1.2 Mo > 1 Mo de quota.
        string padding = new string('a', chunk);
        ForwardingTestHarness.WriteRawSpoolFile(_dir, File001, padding);
        ForwardingTestHarness.WriteRawSpoolFile(_dir, File002, padding);
        ForwardingTestHarness.WriteRawSpoolFile(_dir, File003, padding);

        var spool = NewSpool(new DiagnosticsForwardingSpoolOptions { MaxTotalSizeMb = 1 });

        int deleted = spool.EnforceBounds(DateTimeOffset.UtcNow);

        Assert.Equal(1, deleted); // le plus ancien est évincé, total ≤ 1 Mo.
        Assert.False(File.Exists(Path.Combine(_dir, File001)));
        Assert.True(File.Exists(Path.Combine(_dir, File002)));
        Assert.True(File.Exists(Path.Combine(_dir, File003)));
    }

    [Fact]
    public void EnforceBounds_Retention_DeletesExpiredFiles_NotActive()
    {
        ForwardingTestHarness.WriteSpoolFile(_dir, File001, [ForwardingTestHarness.NewRecord()]);
        ForwardingTestHarness.WriteSpoolFile(_dir, File002, [ForwardingTestHarness.NewRecord()]);

        // 001 est ancien, 002 est l'actif (et récent).
        File.SetLastWriteTimeUtc(Path.Combine(_dir, File001), DateTime.UtcNow.AddDays(-2));
        File.SetLastWriteTimeUtc(Path.Combine(_dir, File002), DateTime.UtcNow);

        var spool = NewSpool(new DiagnosticsForwardingSpoolOptions { RetentionDays = 1, MaxTotalSizeMb = 1024 });

        int deleted = spool.EnforceBounds(DateTimeOffset.UtcNow);

        Assert.Equal(1, deleted);
        Assert.False(File.Exists(Path.Combine(_dir, File001)));
        Assert.True(File.Exists(Path.Combine(_dir, File002)));
    }
}