using StellaOps.Cryptography;
using StellaOps.Scanner.Reachability.Gates;
using StellaOps.Scanner.Reachability.Witnesses;
using Xunit;

namespace StellaOps.Scanner.Reachability.Tests;

public class PathWitnessBuilderTests
{
    private readonly ICryptoHash _cryptoHash;
    private readonly TimeProvider _timeProvider;

    public PathWitnessBuilderTests()
    {
        _cryptoHash = DefaultCryptoHash.CreateForTests();
        _timeProvider = TimeProvider.System;
    }

    [Fact]
    public async Task BuildAsync_ReturnsNull_WhenNoPathExists()
    {
        // Arrange
        var graph = CreateSimpleGraph();
        var builder = new PathWitnessBuilder(_cryptoHash, _timeProvider);

        var request = new PathWitnessRequest
        {
            SbomDigest = "sha256:abc123",
            ComponentPurl = "pkg:nuget/Newtonsoft.Json@12.0.3",
            VulnId = "CVE-2024-12345",
            VulnSource = "NVD",
            AffectedRange = "<=12.0.3",
            EntrypointSymbolId = "sym:entry1",
            EntrypointKind = "http",
            EntrypointName = "GET /api/test",
            SinkSymbolId = "sym:unreachable", // Not in graph
            SinkType = "deserialization",
            CallGraph = graph,
            CallgraphDigest = "blake3:abc123"
        };

        // Act
        var result = await builder.BuildAsync(request);

        // Assert
        Assert.Null(result);
    }

    [Fact]
    public async Task BuildAsync_ReturnsWitness_WhenPathExists()
    {
        // Arrange
        var graph = CreateSimpleGraph();
        var builder = new PathWitnessBuilder(_cryptoHash, _timeProvider);

        var request = new PathWitnessRequest
        {
            SbomDigest = "sha256:abc123",
            ComponentPurl = "pkg:nuget/Newtonsoft.Json@12.0.3",
            VulnId = "CVE-2024-12345",
            VulnSource = "NVD",
            AffectedRange = "<=12.0.3",
            EntrypointSymbolId = "sym:entry1",
            EntrypointKind = "http",
            EntrypointName = "GET /api/test",
            SinkSymbolId = "sym:sink1",
            SinkType = "deserialization",
            CallGraph = graph,
            CallgraphDigest = "blake3:abc123"
        };

        // Act
        var result = await builder.BuildAsync(request);

        // Assert
        Assert.NotNull(result);
        Assert.Equal(WitnessSchema.Version, result.WitnessSchema);
        Assert.StartsWith(WitnessSchema.WitnessIdPrefix, result.WitnessId);
        Assert.Equal("CVE-2024-12345", result.Vuln.Id);
        Assert.Equal("sym:entry1", result.Entrypoint.SymbolId);
        Assert.Equal("sym:sink1", result.Sink.SymbolId);
        Assert.NotEmpty(result.Path);
    }

    [Fact]
    public async Task BuildAsync_GeneratesContentAddressedWitnessId()
    {
        // Arrange
        var graph = CreateSimpleGraph();
        var builder = new PathWitnessBuilder(_cryptoHash, _timeProvider);

        var request = new PathWitnessRequest
        {
            SbomDigest = "sha256:abc123",
            ComponentPurl = "pkg:nuget/Newtonsoft.Json@12.0.3",
            VulnId = "CVE-2024-12345",
            VulnSource = "NVD",
            AffectedRange = "<=12.0.3",
            EntrypointSymbolId = "sym:entry1",
            EntrypointKind = "http",
            EntrypointName = "GET /api/test",
            SinkSymbolId = "sym:sink1",
            SinkType = "deserialization",
            CallGraph = graph,
            CallgraphDigest = "blake3:abc123"
        };

        // Act
        var result1 = await builder.BuildAsync(request);
        var result2 = await builder.BuildAsync(request);

        // Assert
        Assert.NotNull(result1);
        Assert.NotNull(result2);
        // The witness ID should be deterministic (same input = same hash)
        // Note: ObservedAt differs, but witness ID is computed without it
        Assert.Equal(result1.WitnessId, result2.WitnessId);
    }

    [Fact]
    public async Task BuildAsync_PopulatesArtifactInfo()
    {
        // Arrange
        var graph = CreateSimpleGraph();
        var builder = new PathWitnessBuilder(_cryptoHash, _timeProvider);

        var request = new PathWitnessRequest
        {
            SbomDigest = "sha256:sbom123",
            ComponentPurl = "pkg:npm/lodash@4.17.21",
            VulnId = "CVE-2024-99999",
            VulnSource = "GHSA",
            AffectedRange = "<4.17.21",
            EntrypointSymbolId = "sym:entry1",
            EntrypointKind = "grpc",
            EntrypointName = "UserService.GetUser",
            SinkSymbolId = "sym:sink1",
            SinkType = "prototype_pollution",
            CallGraph = graph,
            CallgraphDigest = "blake3:graph456"
        };

        // Act
        var result = await builder.BuildAsync(request);

        // Assert
        Assert.NotNull(result);
        Assert.Equal("sha256:sbom123", result.Artifact.SbomDigest);
        Assert.Equal("pkg:npm/lodash@4.17.21", result.Artifact.ComponentPurl);
    }

    [Fact]
    public async Task BuildAsync_PopulatesEvidenceInfo()
    {
        // Arrange
        var graph = CreateSimpleGraph();
        var builder = new PathWitnessBuilder(_cryptoHash, _timeProvider);

        var request = new PathWitnessRequest
        {
            SbomDigest = "sha256:abc123",
            ComponentPurl = "pkg:nuget/Test@1.0.0",
            VulnId = "CVE-2024-12345",
            VulnSource = "NVD",
            AffectedRange = "<=1.0.0",
            EntrypointSymbolId = "sym:entry1",
            EntrypointKind = "http",
            EntrypointName = "TestController.Get",
            SinkSymbolId = "sym:sink1",
            SinkType = "sql_injection",
            CallGraph = graph,
            CallgraphDigest = "blake3:callgraph789",
            SurfaceDigest = "sha256:surface123",
            AnalysisConfigDigest = "sha256:config456",
            BuildId = "build:xyz789"
        };

        // Act
        var result = await builder.BuildAsync(request);

        // Assert
        Assert.NotNull(result);
        Assert.Equal("blake3:callgraph789", result.Evidence.CallgraphDigest);
        Assert.Equal("sha256:surface123", result.Evidence.SurfaceDigest);
        Assert.Equal("sha256:config456", result.Evidence.AnalysisConfigDigest);
        Assert.Equal("build:xyz789", result.Evidence.BuildId);
    }

    [Fact]
    public async Task BuildAsync_FindsShortestPath()
    {
        // Arrange - graph with multiple paths
        var graph = CreateGraphWithMultiplePaths();
        var builder = new PathWitnessBuilder(_cryptoHash, _timeProvider);

        var request = new PathWitnessRequest
        {
            SbomDigest = "sha256:abc123",
            ComponentPurl = "pkg:nuget/Test@1.0.0",
            VulnId = "CVE-2024-12345",
            VulnSource = "NVD",
            AffectedRange = "<=1.0.0",
            EntrypointSymbolId = "sym:start",
            EntrypointKind = "http",
            EntrypointName = "Start",
            SinkSymbolId = "sym:end",
            SinkType = "deserialization",
            CallGraph = graph,
            CallgraphDigest = "blake3:abc123"
        };

        // Act
        var result = await builder.BuildAsync(request);

        // Assert
        Assert.NotNull(result);
        // Short path: start -> direct -> end (3 steps)
        // Long path: start -> long1 -> long2 -> long3 -> end (5 steps)
        Assert.Equal(3, result.Path.Count);
        Assert.Equal("sym:start", result.Path[0].SymbolId);
        Assert.Equal("sym:direct", result.Path[1].SymbolId);
        Assert.Equal("sym:end", result.Path[2].SymbolId);
    }

    [Fact]
    public async Task BuildAllAsync_YieldsMultipleWitnesses_WhenMultipleRootsReachSink()
    {
        // Arrange
        var graph = CreateGraphWithMultipleRoots();
        var builder = new PathWitnessBuilder(_cryptoHash, _timeProvider);

        var request = new BatchWitnessRequest
        {
            SbomDigest = "sha256:abc123",
            ComponentPurl = "pkg:nuget/Test@1.0.0",
            VulnId = "CVE-2024-12345",
            VulnSource = "NVD",
            AffectedRange = "<=1.0.0",
            SinkSymbolId = "sym:sink",
            SinkType = "deserialization",
            CallGraph = graph,
            CallgraphDigest = "blake3:abc123",
            MaxWitnesses = 10
        };

        // Act
        var witnesses = new List<PathWitness>();
        await foreach (var witness in builder.BuildAllAsync(request))
        {
            witnesses.Add(witness);
        }

        // Assert
        Assert.Equal(2, witnesses.Count);
        Assert.Contains(witnesses, w => w.Entrypoint.SymbolId == "sym:root1");
        Assert.Contains(witnesses, w => w.Entrypoint.SymbolId == "sym:root2");
    }

    [Fact]
    public async Task BuildAllAsync_RespectsMaxWitnesses()
    {
        // Arrange
        var graph = CreateGraphWithMultipleRoots();
        var builder = new PathWitnessBuilder(_cryptoHash, _timeProvider);

        var request = new BatchWitnessRequest
        {
            SbomDigest = "sha256:abc123",
            ComponentPurl = "pkg:nuget/Test@1.0.0",
            VulnId = "CVE-2024-12345",
            VulnSource = "NVD",
            AffectedRange = "<=1.0.0",
            SinkSymbolId = "sym:sink",
            SinkType = "deserialization",
            CallGraph = graph,
            CallgraphDigest = "blake3:abc123",
            MaxWitnesses = 1 // Limit to 1
        };

        // Act
        var witnesses = new List<PathWitness>();
        await foreach (var witness in builder.BuildAllAsync(request))
        {
            witnesses.Add(witness);
        }

        // Assert
        Assert.Single(witnesses);
    }

    #region Test Helpers

    private static RichGraph CreateSimpleGraph()
    {
        var nodes = new List<RichGraphNode>
        {
            new("n1", "sym:entry1", null, null, "dotnet", "method", "Entry1", null, null, null, null),
            new("n2", "sym:middle1", null, null, "dotnet", "method", "Middle1", null, null, null, null),
            new("n3", "sym:sink1", null, null, "dotnet", "method", "Sink1", null, null, null, null)
        };

        var edges = new List<RichGraphEdge>
        {
            new("n1", "n2", "call", null, null, null, 1.0, null),
            new("n2", "n3", "call", null, null, null, 1.0, null)
        };

        var roots = new List<RichGraphRoot>
        {
            new("n1", "http", "/api/test")
        };

        return new RichGraph(
            nodes,
            edges,
            roots,
            new RichGraphAnalyzer("test", "1.0.0", null));
    }

    private static RichGraph CreateGraphWithMultiplePaths()
    {
        var nodes = new List<RichGraphNode>
        {
            new("n0", "sym:start", null, null, "dotnet", "method", "Start", null, null, null, null),
            new("n1", "sym:direct", null, null, "dotnet", "method", "Direct", null, null, null, null),
            new("n2", "sym:long1", null, null, "dotnet", "method", "Long1", null, null, null, null),
            new("n3", "sym:long2", null, null, "dotnet", "method", "Long2", null, null, null, null),
            new("n4", "sym:long3", null, null, "dotnet", "method", "Long3", null, null, null, null),
            new("n5", "sym:end", null, null, "dotnet", "method", "End", null, null, null, null)
        };

        var edges = new List<RichGraphEdge>
        {
            // Short path: start -> direct -> end
            new("n0", "n1", "call", null, null, null, 1.0, null),
            new("n1", "n5", "call", null, null, null, 1.0, null),
            // Long path: start -> long1 -> long2 -> long3 -> end
            new("n0", "n2", "call", null, null, null, 1.0, null),
            new("n2", "n3", "call", null, null, null, 1.0, null),
            new("n3", "n4", "call", null, null, null, 1.0, null),
            new("n4", "n5", "call", null, null, null, 1.0, null)
        };

        var roots = new List<RichGraphRoot>
        {
            new("n0", "http", "/api/start")
        };

        return new RichGraph(
            nodes,
            edges,
            roots,
            new RichGraphAnalyzer("test", "1.0.0", null));
    }

    private static RichGraph CreateGraphWithMultipleRoots()
    {
        var nodes = new List<RichGraphNode>
        {
            new("n1", "sym:root1", null, null, "dotnet", "method", "Root1", null, null, null, null),
            new("n2", "sym:root2", null, null, "dotnet", "method", "Root2", null, null, null, null),
            new("n3", "sym:middle", null, null, "dotnet", "method", "Middle", null, null, null, null),
            new("n4", "sym:sink", null, null, "dotnet", "method", "Sink", null, null, null, null)
        };

        var edges = new List<RichGraphEdge>
        {
            new("n1", "n3", "call", null, null, null, 1.0, null),
            new("n2", "n3", "call", null, null, null, 1.0, null),
            new("n3", "n4", "call", null, null, null, 1.0, null)
        };

        var roots = new List<RichGraphRoot>
        {
            new("n1", "http", "/api/root1"),
            new("n2", "http", "/api/root2")
        };

        return new RichGraph(
            nodes,
            edges,
            roots,
            new RichGraphAnalyzer("test", "1.0.0", null));
    }

    #endregion
}