/**
 * Graph Validation & NFC Tests
 * Sprint: SPRINT_9100_0003_0002 (Graph Validation & NFC Normalization)
 * Tasks: VALID-9100-021 through VALID-9100-028
 */

using Xunit;

namespace StellaOps.Resolver.Tests;

public class GraphValidationTests
{
    [Fact]
    public void NfcNormalization_ProducesConsistentNodeIds()
    {
        // VALID-9100-021: NFC normalization produces consistent NodeIds
        // Using different Unicode representations of the same character
        // é can be represented as:
        // - U+00E9 (precomposed: LATIN SMALL LETTER E WITH ACUTE)
        // - U+0065 U+0301 (decomposed: e + COMBINING ACUTE ACCENT)
        var precomposed = "caf\u00E9"; // café with precomposed é
        var decomposed = "cafe\u0301"; // café with decomposed é

        var nodeId1 = NodeId.From("package", precomposed);
        var nodeId2 = NodeId.From("package", decomposed);

        // After NFC normalization, both should produce the same NodeId
        Assert.Equal(nodeId1, nodeId2);
    }

    [Fact]
    public void EdgeReferencingNonExistentNode_Detected()
    {
        // VALID-9100-022
        var node1 = Node.Create("package", "a");
        var nonExistentNodeId = NodeId.From("package", "nonexistent");

        var edge = Edge.Create(node1.Id, "depends_on", nonExistentNodeId);

        var graph = EvidenceGraph.Create(new[] { node1 }, new[] { edge });

        var detector = new DefaultImplicitDataDetector();
        var violations = detector.Detect(graph);

        Assert.Contains(violations, v => v.ViolationType == "DanglingEdgeDestination");
    }

    [Fact]
    public void DuplicateNodeIds_Detected()
    {
        // VALID-9100-023
        var node1 = Node.Create("package", "a");
        var node2 = new Node(node1.Id, "package", "a-duplicate"); // Same ID, different key

        var graph = new EvidenceGraph
        {
            Nodes = [node1, node2],
            Edges = []
        };

        var detector = new DefaultImplicitDataDetector();
        var violations = detector.Detect(graph);

        Assert.Contains(violations, v => v.ViolationType == "DuplicateNodeId");
    }

    [Fact]
    public void DuplicateEdgeIds_Detected()
    {
        // VALID-9100-024
        var node1 = Node.Create("package", "a");
        var node2 = Node.Create("package", "b");

        var edge1 = Edge.Create(node1.Id, "depends_on", node2.Id);
        var edge2 = Edge.Create(node1.Id, "depends_on", node2.Id); // Same EdgeId

        var graph = new EvidenceGraph
        {
            Nodes = [node1, node2],
            Edges = [edge1, edge2]
        };

        var detector = new DefaultImplicitDataDetector();
        var violations = detector.Detect(graph);

        Assert.Contains(violations, v => v.ViolationType == "DuplicateEdgeId");
    }

    [Fact]
    public void ValidGraph_PassesAllChecks()
    {
        // VALID-9100-027
        var node1 = Node.Create("package", "a");
        var node2 = Node.Create("package", "b");
        var node3 = Node.Create("package", "c");

        var edge1 = Edge.Create(node1.Id, "depends_on", node2.Id);
        var edge2 = Edge.Create(node2.Id, "depends_on", node3.Id);

        var graph = EvidenceGraph.Create(new[] { node1, node2, node3 }, new[] { edge1, edge2 });

        var validator = new DefaultGraphValidator();
        var result = validator.Validate(graph);

        Assert.True(result.IsValid);
        Assert.Empty(result.Errors);
    }

    [Fact]
    public void NfcNormalization_IsIdempotent()
    {
        // VALID-9100-028: Property test - NFC is idempotent
        var normalizer = NfcStringNormalizer.Instance;
        var input = "café";

        var normalized1 = normalizer.Normalize(input);
        var normalized2 = normalizer.Normalize(normalized1);
        var normalized3 = normalizer.Normalize(normalized2);

        Assert.Equal(normalized1, normalized2);
        Assert.Equal(normalized2, normalized3);
    }

    [Fact]
    public void EmptyGraph_IsValid()
    {
        var graph = EvidenceGraph.Empty;

        var validator = new DefaultGraphValidator();
        var result = validator.Validate(graph);

        Assert.True(result.IsValid);
    }
}