// Licensed to StellaOps under the BUSL-1.1 license.

using StellaOps.ReachGraph.Hashing;
using StellaOps.ReachGraph.Schema;
using StellaOps.ReachGraph.Serialization;
using Xunit;

namespace StellaOps.ReachGraph.Tests;

public class DigestComputerTests
{
    private readonly CanonicalReachGraphSerializer _serializer = new();
    private readonly ReachGraphDigestComputer _digestComputer;

    public DigestComputerTests()
    {
        _digestComputer = new ReachGraphDigestComputer(_serializer);
    }

    [Fact]
    public void ComputeDigest_WithSameInput_ProducesSameDigest()
    {
        // Arrange
        var graph = CreateSampleGraph();

        // Act
        var digest1 = _digestComputer.ComputeDigest(graph);
        var digest2 = _digestComputer.ComputeDigest(graph);

        // Assert
        Assert.Equal(digest1, digest2);
    }

    [Fact]
    public void ComputeDigest_ReturnsBlake3Format()
    {
        // Arrange
        var graph = CreateSampleGraph();

        // Act
        var digest = _digestComputer.ComputeDigest(graph);

        // Assert
        Assert.StartsWith("blake3:", digest);
        Assert.Equal(71, digest.Length); // "blake3:" (7) + 64 hex chars
    }

    [Fact]
    public void ComputeDigest_ExcludesSignatures()
    {
        // Arrange
        var unsigned = CreateSampleGraph();
        var signed = unsigned with
        {
            Signatures = [new ReachGraphSignature("key-1", "sig-base64")]
        };

        // Act
        var digestUnsigned = _digestComputer.ComputeDigest(unsigned);
        var digestSigned = _digestComputer.ComputeDigest(signed);

        // Assert - signatures should not affect digest
        Assert.Equal(digestUnsigned, digestSigned);
    }

    [Fact]
    public void ComputeDigest_DifferentInputs_ProduceDifferentDigests()
    {
        // Arrange
        var graph1 = CreateSampleGraph();
        var graph2 = graph1 with
        {
            Artifact = new ReachGraphArtifact("different-app", "sha256:different", ["linux/amd64"])
        };

        // Act
        var digest1 = _digestComputer.ComputeDigest(graph1);
        var digest2 = _digestComputer.ComputeDigest(graph2);

        // Assert
        Assert.NotEqual(digest1, digest2);
    }

    [Fact]
    public void VerifyDigest_ValidDigest_ReturnsTrue()
    {
        // Arrange
        var graph = CreateSampleGraph();
        var digest = _digestComputer.ComputeDigest(graph);

        // Act
        var result = _digestComputer.VerifyDigest(graph, digest);

        // Assert
        Assert.True(result);
    }

    [Fact]
    public void VerifyDigest_InvalidDigest_ReturnsFalse()
    {
        // Arrange
        var graph = CreateSampleGraph();
        var wrongDigest = "blake3:0000000000000000000000000000000000000000000000000000000000000000";

        // Act
        var result = _digestComputer.VerifyDigest(graph, wrongDigest);

        // Assert
        Assert.False(result);
    }

    [Fact]
    public void IsValidBlake3Digest_ValidFormat_ReturnsTrue()
    {
        // Arrange
        var validDigest = "blake3:abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789";

        // Act
        var result = ReachGraphDigestComputer.IsValidBlake3Digest(validDigest);

        // Assert
        Assert.True(result);
    }

    [Theory]
    [InlineData("sha256:abcdef")] // Wrong algorithm
    [InlineData("blake3:short")] // Too short
    [InlineData("blake3:ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ")] // Invalid hex
    [InlineData("")] // Empty
    [InlineData("blake3")] // No colon
    public void IsValidBlake3Digest_InvalidFormat_ReturnsFalse(string digest)
    {
        // Act
        var result = ReachGraphDigestComputer.IsValidBlake3Digest(digest);

        // Assert
        Assert.False(result);
    }

    [Fact]
    public void ParseDigest_ValidFormat_ReturnsComponents()
    {
        // Arrange
        var digest = "blake3:abc123def456";

        // Act
        var result = ReachGraphDigestComputer.ParseDigest(digest);

        // Assert
        Assert.NotNull(result);
        Assert.Equal("blake3", result.Value.Algorithm);
        Assert.Equal("abc123def456", result.Value.Hash);
    }

    [Theory]
    [InlineData("")]
    [InlineData("nocolon")]
    [InlineData(":noleft")]
    [InlineData("noright:")]
    public void ParseDigest_InvalidFormat_ReturnsNull(string digest)
    {
        // Act
        var result = ReachGraphDigestComputer.ParseDigest(digest);

        // Assert
        Assert.Null(result);
    }

    [Fact]
    public void ComputeDigest_IsDeterministic_AcrossNodeOrdering()
    {
        // Arrange - nodes in different order
        var graph1 = CreateSampleGraph() with
        {
            Nodes =
            [
                new ReachGraphNode { Id = "sha256:aaa", Kind = ReachGraphNodeKind.Function, Ref = "a()" },
                new ReachGraphNode { Id = "sha256:bbb", Kind = ReachGraphNodeKind.Function, Ref = "b()" }
            ]
        };
        var graph2 = CreateSampleGraph() with
        {
            Nodes =
            [
                new ReachGraphNode { Id = "sha256:bbb", Kind = ReachGraphNodeKind.Function, Ref = "b()" },
                new ReachGraphNode { Id = "sha256:aaa", Kind = ReachGraphNodeKind.Function, Ref = "a()" }
            ]
        };

        // Act
        var digest1 = _digestComputer.ComputeDigest(graph1);
        var digest2 = _digestComputer.ComputeDigest(graph2);

        // Assert - canonical serialization should produce same digest regardless of input order
        Assert.Equal(digest1, digest2);
    }

    private static ReachGraphMinimal CreateSampleGraph() => new()
    {
        Artifact = new ReachGraphArtifact("test-app", "sha256:abc123", ["linux/amd64"]),
        Scope = new ReachGraphScope(["/app/main"], ["prod"]),
        Nodes =
        [
            new ReachGraphNode { Id = "sha256:001", Kind = ReachGraphNodeKind.Function, Ref = "main()" }
        ],
        Edges = [],
        Provenance = new ReachGraphProvenance
        {
            Inputs = new ReachGraphInputs { Sbom = "sha256:sbom123" },
            ComputedAt = new DateTimeOffset(2025, 12, 27, 10, 0, 0, TimeSpan.Zero),
            Analyzer = new ReachGraphAnalyzer("test", "1.0.0", "sha256:toolchain")
        }
    };
}