// <copyright file="EbpfSignalMergerTests.cs" company="StellaOps">
// SPDX-License-Identifier: BUSL-1.1
// </copyright>

namespace StellaOps.Signals.Ebpf.Tests;

using Microsoft.Extensions.Logging.Abstractions;
using StellaOps.Scanner.Reachability;
using StellaOps.Scanner.Reachability.Runtime;
using StellaOps.Scanner.Reachability.Slices;
using StellaOps.Signals.Ebpf.Schema;
using Xunit;

/// <summary>
/// Tests for <see cref="EbpfSignalMerger"/>.
/// </summary>
public sealed class EbpfSignalMergerTests
{
    private readonly EbpfSignalMerger _merger;
    private readonly RuntimeStaticMerger _baseMerger;

    public EbpfSignalMergerTests()
    {
        _baseMerger = new RuntimeStaticMerger();
        _merger = new EbpfSignalMerger(
            _baseMerger,
            NullLogger<EbpfSignalMerger>.Instance);
    }

    [Fact]
    public void Merge_WithNoSignals_ReturnsSameGraph()
    {
        var graph = CreateTestGraph();

        var result = _merger.Merge(graph, null);

        Assert.Same(graph, result.MergedGraph);
        Assert.Empty(result.Evidence);
        Assert.Equal(2, result.Statistics.StaticEdgeCount);
        Assert.Equal(0, result.Statistics.RuntimeEventCount);
    }

    [Fact]
    public void Merge_WithEmptySignals_ReturnsSameGraph()
    {
        var graph = CreateTestGraph();
        var signals = new RuntimeSignalSummary
        {
            ContainerId = "container-123",
            StartedAt = DateTimeOffset.UtcNow.AddMinutes(-5),
            StoppedAt = DateTimeOffset.UtcNow,
            TotalEvents = 0,
            CallPaths = [],
            ObservedSymbols = [],
        };

        var result = _merger.Merge(graph, signals);

        Assert.Same(graph, result.MergedGraph);
        Assert.Empty(result.Evidence);
    }

    [Fact]
    public void Merge_WithMatchingSignals_CreatesConfirmedEvidence()
    {
        var graph = CreateTestGraph();
        var signals = new RuntimeSignalSummary
        {
            ContainerId = "container-123",
            StartedAt = DateTimeOffset.UtcNow.AddMinutes(-5),
            StoppedAt = DateTimeOffset.UtcNow,
            TotalEvents = 100,
            CallPaths = new List<ObservedCallPath>
            {
                new()
                {
                    Symbols = ["main", "processRequest"],
                    ObservationCount = 50,
                    FirstObservedAt = DateTimeOffset.UtcNow.AddMinutes(-5),
                    LastObservedAt = DateTimeOffset.UtcNow,
                },
            },
            ObservedSymbols = ["main", "processRequest"],
        };

        var result = _merger.Merge(graph, signals);

        Assert.NotEmpty(result.Evidence);
        Assert.Contains(result.Evidence, e =>
            e.Type == RuntimeEvidenceType.RuntimeConfirmed);
    }

    [Fact]
    public void Merge_WithRuntimeOnlyPath_CreatesRuntimeOnlyEvidence()
    {
        var graph = CreateTestGraph();
        var signals = new RuntimeSignalSummary
        {
            ContainerId = "container-123",
            StartedAt = DateTimeOffset.UtcNow.AddMinutes(-5),
            StoppedAt = DateTimeOffset.UtcNow,
            TotalEvents = 100,
            CallPaths = new List<ObservedCallPath>
            {
                new()
                {
                    // Path not in static graph
                    Symbols = ["dynamic_dispatch", "hidden_method"],
                    ObservationCount = 20,
                    FirstObservedAt = DateTimeOffset.UtcNow.AddMinutes(-5),
                    LastObservedAt = DateTimeOffset.UtcNow,
                },
            },
            ObservedSymbols = ["dynamic_dispatch", "hidden_method"],
        };

        var result = _merger.Merge(graph, signals);

        Assert.Contains(result.Evidence, e =>
            e.Type == RuntimeEvidenceType.RuntimeOnly);
        Assert.True(result.Statistics.RuntimeOnlyPathCount > 0);
    }

    [Fact]
    public void Merge_WithDetectedRuntimes_CreatesRuntimeDetectedEvidence()
    {
        var graph = CreateTestGraph();
        var signals = new RuntimeSignalSummary
        {
            ContainerId = "container-123",
            StartedAt = DateTimeOffset.UtcNow.AddMinutes(-5),
            StoppedAt = DateTimeOffset.UtcNow,
            TotalEvents = 100,
            CallPaths = [],
            ObservedSymbols = [],
            DetectedRuntimes = [RuntimeType.Node, RuntimeType.Python],
        };

        var result = _merger.Merge(graph, signals);

        Assert.Contains(result.Evidence, e =>
            e.Type == RuntimeEvidenceType.RuntimeDetected &&
            e.RuntimeType == "Node");
        Assert.Contains(result.Evidence, e =>
            e.Type == RuntimeEvidenceType.RuntimeDetected &&
            e.RuntimeType == "Python");
    }

    [Fact]
    public void ValidatePath_WithValidPath_ReturnsConfirmed()
    {
        var graph = CreateTestGraph();
        var path = new ObservedCallPath
        {
            Symbols = ["main", "processRequest"],
            ObservationCount = 10,
            FirstObservedAt = DateTimeOffset.UtcNow,
            LastObservedAt = DateTimeOffset.UtcNow,
        };

        var result = _merger.ValidatePath(graph, path);

        Assert.True(result.IsValid);
        Assert.Equal(PathType.Confirmed, result.PathType);
        Assert.Equal(1.0, result.MatchRatio);
    }

    [Fact]
    public void ValidatePath_WithUnknownPath_ReturnsRuntimeOnly()
    {
        var graph = CreateTestGraph();
        var path = new ObservedCallPath
        {
            Symbols = ["unknown", "method"],
            ObservationCount = 10,
            FirstObservedAt = DateTimeOffset.UtcNow,
            LastObservedAt = DateTimeOffset.UtcNow,
        };

        var result = _merger.ValidatePath(graph, path);

        Assert.True(result.IsValid);
        Assert.Equal(PathType.RuntimeOnly, result.PathType);
        Assert.Equal(0.0, result.MatchRatio);
    }

    [Fact]
    public void ValidatePath_WithShortPath_ReturnsInvalid()
    {
        var graph = CreateTestGraph();
        var path = new ObservedCallPath
        {
            Symbols = ["single"],
            ObservationCount = 10,
            FirstObservedAt = DateTimeOffset.UtcNow,
            LastObservedAt = DateTimeOffset.UtcNow,
        };

        var result = _merger.ValidatePath(graph, path);

        Assert.False(result.IsValid);
        Assert.Equal(PathType.Invalid, result.PathType);
    }

    [Fact]
    public void Merge_StatisticsAreAccurate()
    {
        var graph = CreateTestGraph();
        var signals = new RuntimeSignalSummary
        {
            ContainerId = "container-123",
            StartedAt = DateTimeOffset.UtcNow.AddMinutes(-5),
            StoppedAt = DateTimeOffset.UtcNow,
            TotalEvents = 500,
            CallPaths = new List<ObservedCallPath>
            {
                new()
                {
                    Symbols = ["main", "processRequest"],
                    ObservationCount = 100,
                    FirstObservedAt = DateTimeOffset.UtcNow.AddMinutes(-5),
                    LastObservedAt = DateTimeOffset.UtcNow,
                },
            },
            ObservedSymbols = ["main", "processRequest"],
            DroppedEvents = 10,
        };

        var result = _merger.Merge(graph, signals);

        Assert.Equal(2, result.Statistics.StaticEdgeCount);
        Assert.Equal(500, result.Statistics.RuntimeEventCount);
        Assert.Equal(1, result.Statistics.CallPathCount);
        Assert.Equal(10, result.Statistics.DroppedEventCount);
    }

    [Fact]
    public void RuntimeEvidence_ContainsContainerId()
    {
        var graph = CreateTestGraph();
        var signals = new RuntimeSignalSummary
        {
            ContainerId = "my-container-id",
            StartedAt = DateTimeOffset.UtcNow.AddMinutes(-5),
            StoppedAt = DateTimeOffset.UtcNow,
            TotalEvents = 100,
            CallPaths = new List<ObservedCallPath>
            {
                new()
                {
                    Symbols = ["main", "processRequest"],
                    ObservationCount = 10,
                    FirstObservedAt = DateTimeOffset.UtcNow.AddMinutes(-5),
                    LastObservedAt = DateTimeOffset.UtcNow,
                },
            },
            ObservedSymbols = [],
        };

        var result = _merger.Merge(graph, signals);

        Assert.All(result.Evidence, e =>
            Assert.Equal("my-container-id", e.ContainerId));
    }

    [Fact]
    public void EvidenceSource_IsEbpf()
    {
        var graph = CreateTestGraph();
        var signals = new RuntimeSignalSummary
        {
            ContainerId = "container-123",
            StartedAt = DateTimeOffset.UtcNow.AddMinutes(-5),
            StoppedAt = DateTimeOffset.UtcNow,
            TotalEvents = 100,
            CallPaths = new List<ObservedCallPath>
            {
                new()
                {
                    Symbols = ["main", "processRequest"],
                    ObservationCount = 10,
                    FirstObservedAt = DateTimeOffset.UtcNow.AddMinutes(-5),
                    LastObservedAt = DateTimeOffset.UtcNow,
                },
            },
            ObservedSymbols = [],
        };

        var result = _merger.Merge(graph, signals);

        Assert.All(result.Evidence, e =>
            Assert.Equal(EvidenceSource.Ebpf, e.Source));
    }

    private static RichGraph CreateTestGraph()
    {
        return new RichGraph(
            Nodes: new List<RichGraphNode>
            {
                new("main", "main", null, null, "native", "entrypoint", null, null, null, null, null),
                new("processRequest", "processRequest", null, null, "native", "function", null, null, null, null, null),
                new("handleError", "handleError", null, null, "native", "function", null, null, null, null, null),
            },
            Edges: new List<RichGraphEdge>
            {
                new("main", "processRequest", "call", null, null, null, 1.0, null),
                new("processRequest", "handleError", "call", null, null, null, 0.8, null),
            },
            Roots: new List<RichGraphRoot>
            {
                new("main", "main", "entrypoint")
            },
            Analyzer: new RichGraphAnalyzer("test-analyzer", "1.0.0", null)
        );
    }
}