// -----------------------------------------------------------------------------
// PathExplanationServiceTests.cs
// Sprint: SPRINT_3620_0002_0001_path_explanation
// Description: Unit tests for PathExplanationService.
// -----------------------------------------------------------------------------

using Microsoft.Extensions.Logging.Abstractions;
using StellaOps.Scanner.Reachability.Explanation;
using StellaOps.Scanner.Reachability.Gates;
using Xunit;

namespace StellaOps.Scanner.Reachability.Tests;

public class PathExplanationServiceTests
{
    private readonly PathExplanationService _service;
    private readonly PathRenderer _renderer;

    public PathExplanationServiceTests()
    {
        _service = new PathExplanationService(
            NullLogger<PathExplanationService>.Instance);
        _renderer = new PathRenderer();
    }

    [Fact]
    public async Task ExplainAsync_WithSimplePath_ReturnsExplainedPath()
    {
        // Arrange
        var graph = CreateSimpleGraph();
        var query = new PathExplanationQuery();

        // Act
        var result = await _service.ExplainAsync(graph, query);

        // Assert
        Assert.NotNull(result);
        Assert.True(result.TotalCount >= 0);
    }

    [Fact]
    public async Task ExplainAsync_WithSinkFilter_FiltersResults()
    {
        // Arrange
        var graph = CreateGraphWithMultipleSinks();
        var query = new PathExplanationQuery { SinkId = "sink-1" };

        // Act
        var result = await _service.ExplainAsync(graph, query);

        // Assert
        Assert.NotNull(result);
        foreach (var path in result.Paths)
        {
            Assert.Equal("sink-1", path.SinkId);
        }
    }

    [Fact]
    public async Task ExplainAsync_WithGatesFilter_FiltersPathsWithGates()
    {
        // Arrange
        var graph = CreateGraphWithGates();
        var query = new PathExplanationQuery { HasGates = true };

        // Act
        var result = await _service.ExplainAsync(graph, query);

        // Assert
        Assert.NotNull(result);
        foreach (var path in result.Paths)
        {
            Assert.True(path.Gates.Count > 0);
        }
    }

    [Fact]
    public async Task ExplainAsync_WithMaxPathLength_LimitsPathLength()
    {
        // Arrange
        var graph = CreateDeepGraph(10);
        var query = new PathExplanationQuery { MaxPathLength = 5 };

        // Act
        var result = await _service.ExplainAsync(graph, query);

        // Assert
        Assert.NotNull(result);
        foreach (var path in result.Paths)
        {
            Assert.True(path.PathLength <= 5);
        }
    }

    [Fact]
    public async Task ExplainAsync_WithMaxPaths_LimitsResults()
    {
        // Arrange
        var graph = CreateGraphWithMultiplePaths(20);
        var query = new PathExplanationQuery { MaxPaths = 5 };

        // Act
        var result = await _service.ExplainAsync(graph, query);

        // Assert
        Assert.NotNull(result);
        Assert.True(result.Paths.Count <= 5);
        if (result.TotalCount > 5)
        {
            Assert.True(result.HasMore);
        }
    }

    [Fact]
    public void Renderer_Text_ProducesExpectedFormat()
    {
        // Arrange
        var path = CreateTestPath();

        // Act
        var text = _renderer.Render(path, PathOutputFormat.Text);

        // Assert
        Assert.Contains(path.EntrypointSymbol, text);
        Assert.Contains("SINK:", text);
    }

    [Fact]
    public void Renderer_Markdown_ProducesExpectedFormat()
    {
        // Arrange
        var path = CreateTestPath();

        // Act
        var markdown = _renderer.Render(path, PathOutputFormat.Markdown);

        // Assert
        Assert.Contains("###", markdown);
        Assert.Contains("```", markdown);
        Assert.Contains(path.EntrypointSymbol, markdown);
    }

    [Fact]
    public void Renderer_Json_ProducesValidJson()
    {
        // Arrange
        var path = CreateTestPath();

        // Act
        var json = _renderer.Render(path, PathOutputFormat.Json);

        // Assert
        Assert.StartsWith("{", json.Trim());
        Assert.EndsWith("}", json.Trim());
        Assert.Contains("sink_id", json);
        Assert.Contains("entrypoint_id", json);
    }

    [Fact]
    public void Renderer_WithGates_IncludesGateInfo()
    {
        // Arrange
        var path = CreateTestPathWithGates();

        // Act
        var text = _renderer.Render(path, PathOutputFormat.Text);

        // Assert
        Assert.Contains("Gates:", text);
        Assert.Contains("multiplier", text.ToLowerInvariant());
    }

    [Fact]
    public async Task ExplainPathAsync_WithValidId_ReturnsPath()
    {
        // Arrange
        var graph = CreateSimpleGraph();

        // This test verifies the API works, actual path lookup depends on graph structure
        // Act
        var result = await _service.ExplainPathAsync(graph, "entry-1:sink-1:0");

        // The result may be null if path doesn't exist, that's OK
        Assert.True(result is null || result.PathId is not null);
    }

    [Fact]
    public void GateMultiplier_Calculation_IsCorrect()
    {
        // Arrange - path with auth gate
        var pathWithAuth = CreateTestPathWithGates();

        // Assert - auth gate should reduce multiplier
        Assert.True(pathWithAuth.GateMultiplierBps < 10000);
    }

    [Fact]
    public void PathWithoutGates_HasFullMultiplier()
    {
        // Arrange
        var path = CreateTestPath();

        // Assert - no gates = 100% multiplier
        Assert.Equal(10000, path.GateMultiplierBps);
    }

    private static RichGraph CreateSimpleGraph()
    {
        return new RichGraph(
            Nodes: new[]
            {
                new RichGraphNode(
                    Id: "entry-1",
                    SymbolId: "Handler.handle",
                    CodeId: null,
                    Purl: null,
                    Lang: "java",
                    Kind: "http_handler",
                    Display: "GET /users",
                    BuildId: null,
                    Evidence: null,
                    Attributes: null,
                    SymbolDigest: null),
                new RichGraphNode(
                    Id: "sink-1",
                    SymbolId: "DB.query",
                    CodeId: null,
                    Purl: null,
                    Lang: "java",
                    Kind: "sql_sink",
                    Display: "executeQuery",
                    BuildId: null,
                    Evidence: null,
                    Attributes: new Dictionary<string, string> { ["is_sink"] = "true" },
                    SymbolDigest: null)
            },
            Edges: new[]
            {
                new RichGraphEdge("entry-1", "sink-1", "call", null, null, null, 1.0, null)
            },
            Roots: new[]
            {
                new RichGraphRoot("entry-1", "runtime", null)
            },
            Analyzer: new RichGraphAnalyzer("test", "1.0", null),
            Schema: "stellaops.richgraph.v1"
        );
    }

    private static RichGraph CreateGraphWithMultipleSinks()
    {
        return new RichGraph(
            Nodes: new[]
            {
                new RichGraphNode("entry-1", "Handler", null, null, "java", "handler", null, null, null, null, null),
                new RichGraphNode("sink-1", "Sink1", null, null, "java", "sink", null, null, null,
                    new Dictionary<string, string> { ["is_sink"] = "true" }, null),
                new RichGraphNode("sink-2", "Sink2", null, null, "java", "sink", null, null, null,
                    new Dictionary<string, string> { ["is_sink"] = "true" }, null)
            },
            Edges: new[]
            {
                new RichGraphEdge("entry-1", "sink-1", "call", null, null, null, 1.0, null),
                new RichGraphEdge("entry-1", "sink-2", "call", null, null, null, 1.0, null)
            },
            Roots: new[] { new RichGraphRoot("entry-1", "runtime", null) },
            Analyzer: new RichGraphAnalyzer("test", "1.0", null),
            Schema: "stellaops.richgraph.v1"
        );
    }

    private static RichGraph CreateGraphWithGates()
    {
        var gates = new[]
        {
            new DetectedGate
            {
                Type = GateType.AuthRequired,
                Detail = "@Authenticated",
                GuardSymbol = "AuthFilter",
                Confidence = 0.9,
                DetectionMethod = "annotation"
            }
        };

        return new RichGraph(
            Nodes: new[]
            {
                new RichGraphNode("entry-1", "Handler", null, null, "java", "handler", null, null, null, null, null),
                new RichGraphNode("sink-1", "Sink", null, null, "java", "sink", null, null, null,
                    new Dictionary<string, string> { ["is_sink"] = "true" }, null)
            },
            Edges: new[]
            {
                new RichGraphEdge("entry-1", "sink-1", "call", null, null, null, 1.0, null, gates)
            },
            Roots: new[] { new RichGraphRoot("entry-1", "runtime", null) },
            Analyzer: new RichGraphAnalyzer("test", "1.0", null),
            Schema: "stellaops.richgraph.v1"
        );
    }

    private static RichGraph CreateDeepGraph(int depth)
    {
        var nodes = new List<RichGraphNode>();
        var edges = new List<RichGraphEdge>();

        for (var i = 0; i < depth; i++)
        {
            var attrs = i == depth - 1
                ? new Dictionary<string, string> { ["is_sink"] = "true" }
                : null;
            nodes.Add(new RichGraphNode($"node-{i}", $"Method{i}", null, null, "java", i == depth - 1 ? "sink" : "method", null, null, null, attrs, null));

            if (i > 0)
            {
                edges.Add(new RichGraphEdge($"node-{i - 1}", $"node-{i}", "call", null, null, null, 1.0, null));
            }
        }

        return new RichGraph(
            Nodes: nodes,
            Edges: edges,
            Roots: new[] { new RichGraphRoot("node-0", "runtime", null) },
            Analyzer: new RichGraphAnalyzer("test", "1.0", null),
            Schema: "stellaops.richgraph.v1"
        );
    }

    private static RichGraph CreateGraphWithMultiplePaths(int pathCount)
    {
        var nodes = new List<RichGraphNode>
        {
            new("entry-1", "Handler", null, null, "java", "handler", null, null, null, null, null)
        };

        var edges = new List<RichGraphEdge>();

        for (var i = 0; i < pathCount; i++)
        {
            nodes.Add(new RichGraphNode($"sink-{i}", $"Sink{i}", null, null, "java", "sink", null, null, null,
                new Dictionary<string, string> { ["is_sink"] = "true" }, null));
            edges.Add(new RichGraphEdge("entry-1", $"sink-{i}", "call", null, null, null, 1.0, null));
        }

        return new RichGraph(
            Nodes: nodes,
            Edges: edges,
            Roots: new[] { new RichGraphRoot("entry-1", "runtime", null) },
            Analyzer: new RichGraphAnalyzer("test", "1.0", null),
            Schema: "stellaops.richgraph.v1"
        );
    }

    private static ExplainedPath CreateTestPath()
    {
        return new ExplainedPath
        {
            PathId = "entry:sink:0",
            SinkId = "sink-1",
            SinkSymbol = "DB.query",
            SinkCategory = Explanation.SinkCategory.SqlRaw,
            EntrypointId = "entry-1",
            EntrypointSymbol = "Handler.handle",
            EntrypointType = EntrypointType.HttpEndpoint,
            PathLength = 2,
            Hops = new[]
            {
                new ExplainedPathHop
                {
                    NodeId = "entry-1",
                    Symbol = "Handler.handle",
                    Package = "app",
                    Depth = 0,
                    IsEntrypoint = true,
                    IsSink = false
                },
                new ExplainedPathHop
                {
                    NodeId = "sink-1",
                    Symbol = "DB.query",
                    Package = "database",
                    Depth = 1,
                    IsEntrypoint = false,
                    IsSink = true
                }
            },
            Gates = Array.Empty<DetectedGate>(),
            GateMultiplierBps = 10000
        };
    }

    private static ExplainedPath CreateTestPathWithGates()
    {
        return new ExplainedPath
        {
            PathId = "entry:sink:0",
            SinkId = "sink-1",
            SinkSymbol = "DB.query",
            SinkCategory = Explanation.SinkCategory.SqlRaw,
            EntrypointId = "entry-1",
            EntrypointSymbol = "Handler.handle",
            EntrypointType = EntrypointType.HttpEndpoint,
            PathLength = 2,
            Hops = new[]
            {
                new ExplainedPathHop
                {
                    NodeId = "entry-1",
                    Symbol = "Handler.handle",
                    Package = "app",
                    Depth = 0,
                    IsEntrypoint = true,
                    IsSink = false
                },
                new ExplainedPathHop
                {
                    NodeId = "sink-1",
                    Symbol = "DB.query",
                    Package = "database",
                    Depth = 1,
                    IsEntrypoint = false,
                    IsSink = true
                }
            },
            Gates = new[]
            {
                new DetectedGate
                {
                    Type = GateType.AuthRequired,
                    Detail = "@Authenticated",
                    GuardSymbol = "AuthFilter",
                    Confidence = 0.9,
                    DetectionMethod = "annotation"
                }
            },
            GateMultiplierBps = 3000
        };
    }
}