// -----------------------------------------------------------------------------
// SurfaceAwareReachabilityIntegrationTests.cs
// Sprint: SPRINT_3700_0004_0001_reachability_integration (REACH-013)
// Description: End-to-end integration tests for surface-aware reachability analysis.
// -----------------------------------------------------------------------------

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using FluentAssertions;
using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;
using StellaOps.Scanner.Reachability.Surfaces;
using Xunit;

namespace StellaOps.Scanner.Reachability.Tests;

/// <summary>
/// Integration tests for the surface-aware reachability analyzer.
/// Tests the complete flow from vulnerability input through surface query to reachability result.
/// </summary>
public sealed class SurfaceAwareReachabilityIntegrationTests : IDisposable
{
    private readonly InMemorySurfaceRepository _surfaceRepo;
    private readonly InMemoryCallGraphAccessor _callGraphAccessor;
    private readonly InMemoryReachabilityGraphService _graphService;
    private readonly SurfaceQueryService _surfaceQueryService;
    private readonly SurfaceAwareReachabilityAnalyzer _analyzer;
    private readonly IMemoryCache _cache;

    public SurfaceAwareReachabilityIntegrationTests()
    {
        _surfaceRepo = new InMemorySurfaceRepository();
        _callGraphAccessor = new InMemoryCallGraphAccessor();
        _graphService = new InMemoryReachabilityGraphService();
        _cache = new MemoryCache(new MemoryCacheOptions());

        _surfaceQueryService = new SurfaceQueryService(
            _surfaceRepo,
            _cache,
            NullLogger<SurfaceQueryService>.Instance,
            new SurfaceQueryOptions { EnableCaching = true });

        _analyzer = new SurfaceAwareReachabilityAnalyzer(
            _surfaceQueryService,
            _graphService,
            NullLogger<SurfaceAwareReachabilityAnalyzer>.Instance);
    }

    public void Dispose()
    {
        _cache.Dispose();
    }

    #region Confirmed Reachable Tests

    [Fact]
    public async Task AnalyzeAsync_WhenTriggerMethodIsReachable_ReturnsConfirmedTier()
    {
        // Arrange: Create a call graph with path to vulnerable method
        // Entrypoint → Controller → Service → VulnerableLib.Deserialize()
        _callGraphAccessor.AddEntrypoint("API.UsersController::GetUser");
        _callGraphAccessor.AddEdge("API.UsersController::GetUser", "API.UserService::FetchUser");
        _callGraphAccessor.AddEdge("API.UserService::FetchUser", "Newtonsoft.Json.JsonConvert::DeserializeObject");

        // Add surface with trigger method
        var surfaceId = Guid.NewGuid();
        _surfaceRepo.AddSurface(new SurfaceInfo
        {
            Id = surfaceId,
            CveId = "CVE-2023-1234",
            Ecosystem = "nuget",
            PackageName = "Newtonsoft.Json",
            VulnVersion = "12.0.1",
            FixedVersion = "12.0.3",
            ComputedAt = DateTimeOffset.UtcNow,
            TriggerCount = 1
        });
        _surfaceRepo.AddTriggers(surfaceId, new List<TriggerMethodInfo>
        {
            new() { MethodKey = "Newtonsoft.Json.JsonConvert::DeserializeObject", MethodName = "DeserializeObject", DeclaringType = "JsonConvert" }
        });

        // Configure graph service to find path
        _graphService.AddReachablePath(
            entrypoint: "API.UsersController::GetUser",
            sink: "Newtonsoft.Json.JsonConvert::DeserializeObject",
            pathMethods: new[] { "API.UsersController::GetUser", "API.UserService::FetchUser", "Newtonsoft.Json.JsonConvert::DeserializeObject" });

        var request = new SurfaceAwareReachabilityRequest
        {
            Vulnerabilities = new List<VulnerabilityInfo>
            {
                new()
                {
                    CveId = "CVE-2023-1234",
                    Ecosystem = "nuget",
                    PackageName = "Newtonsoft.Json",
                    Version = "12.0.1"
                }
            },
            CallGraph = _callGraphAccessor
        };

        // Act
        var result = await _analyzer.AnalyzeAsync(request);

        // Assert
        result.Findings.Should().HaveCount(1);
        var finding = result.Findings[0];
        finding.ConfidenceTier.Should().Be(ReachabilityConfidenceTier.Confirmed);
        finding.SinkSource.Should().Be(SinkSource.Surface);
        finding.Witnesses.Should().NotBeEmpty();
        result.ConfirmedReachable.Should().Be(1);
    }

    [Fact]
    public async Task AnalyzeAsync_WhenMultipleTriggerMethodsAreReachable_ReturnsMultipleWitnesses()
    {
        // Arrange: Create call graph with paths to multiple triggers
        _callGraphAccessor.AddEntrypoint("API.Controller::Action1");
        _callGraphAccessor.AddEntrypoint("API.Controller::Action2");
        _callGraphAccessor.AddEdge("API.Controller::Action1", "VulnLib::Method1");
        _callGraphAccessor.AddEdge("API.Controller::Action2", "VulnLib::Method2");

        var surfaceId = Guid.NewGuid();
        _surfaceRepo.AddSurface(new SurfaceInfo
        {
            Id = surfaceId,
            CveId = "CVE-2024-5678",
            Ecosystem = "npm",
            PackageName = "vulnerable-lib",
            VulnVersion = "1.0.0",
            FixedVersion = "1.0.1",
            ComputedAt = DateTimeOffset.UtcNow,
            TriggerCount = 2
        });
        _surfaceRepo.AddTriggers(surfaceId, new List<TriggerMethodInfo>
        {
            new() { MethodKey = "VulnLib::Method1", MethodName = "Method1", DeclaringType = "VulnLib" },
            new() { MethodKey = "VulnLib::Method2", MethodName = "Method2", DeclaringType = "VulnLib" }
        });

        _graphService.AddReachablePath("API.Controller::Action1", "VulnLib::Method1",
            new[] { "API.Controller::Action1", "VulnLib::Method1" });
        _graphService.AddReachablePath("API.Controller::Action2", "VulnLib::Method2",
            new[] { "API.Controller::Action2", "VulnLib::Method2" });

        var request = new SurfaceAwareReachabilityRequest
        {
            Vulnerabilities = new List<VulnerabilityInfo>
            {
                new() { CveId = "CVE-2024-5678", Ecosystem = "npm", PackageName = "vulnerable-lib", Version = "1.0.0" }
            },
            CallGraph = _callGraphAccessor
        };

        // Act
        var result = await _analyzer.AnalyzeAsync(request);

        // Assert
        result.Findings.Should().HaveCount(1);
        var finding = result.Findings[0];
        finding.ConfidenceTier.Should().Be(ReachabilityConfidenceTier.Confirmed);
        finding.Witnesses.Should().HaveCountGreaterOrEqualTo(2);
    }

    #endregion

    #region Unreachable Tests

    [Fact]
    public async Task AnalyzeAsync_WhenTriggerMethodNotReachable_ReturnsUnreachableTier()
    {
        // Arrange: Surface exists but no path to trigger
        _callGraphAccessor.AddEntrypoint("API.Controller::Action");
        _callGraphAccessor.AddEdge("API.Controller::Action", "SafeLib::SafeMethod");

        var surfaceId = Guid.NewGuid();
        _surfaceRepo.AddSurface(new SurfaceInfo
        {
            Id = surfaceId,
            CveId = "CVE-2023-9999",
            Ecosystem = "nuget",
            PackageName = "Vulnerable.Package",
            VulnVersion = "2.0.0",
            FixedVersion = "2.0.1",
            ComputedAt = DateTimeOffset.UtcNow,
            TriggerCount = 1
        });
        _surfaceRepo.AddTriggers(surfaceId, new List<TriggerMethodInfo>
        {
            new() { MethodKey = "Vulnerable.Package::DangerousMethod", MethodName = "DangerousMethod", DeclaringType = "Vulnerable.Package" }
        });

        // No paths configured in graph service = unreachable

        var request = new SurfaceAwareReachabilityRequest
        {
            Vulnerabilities = new List<VulnerabilityInfo>
            {
                new() { CveId = "CVE-2023-9999", Ecosystem = "nuget", PackageName = "Vulnerable.Package", Version = "2.0.0" }
            },
            CallGraph = _callGraphAccessor
        };

        // Act
        var result = await _analyzer.AnalyzeAsync(request);

        // Assert
        result.Findings.Should().HaveCount(1);
        var finding = result.Findings[0];
        finding.ConfidenceTier.Should().Be(ReachabilityConfidenceTier.Unreachable);
        finding.SinkSource.Should().Be(SinkSource.Surface);
        finding.Witnesses.Should().BeEmpty();
        result.Unreachable.Should().Be(1);
    }

    #endregion

    #region Likely Reachable (Fallback) Tests

    [Fact]
    public async Task AnalyzeAsync_WhenNoSurfaceButPackageApiCalled_ReturnsLikelyTier()
    {
        // Arrange: No surface exists, but package API is called
        _callGraphAccessor.AddEntrypoint("API.Controller::Action");
        _callGraphAccessor.AddEdge("API.Controller::Action", "UnknownLib.Client::DoSomething");

        // Configure graph service for fallback path detection
        _graphService.AddReachablePath("API.Controller::Action", "UnknownLib.Client::DoSomething",
            new[] { "API.Controller::Action", "UnknownLib.Client::DoSomething" });

        // No surface - will trigger fallback mode
        var request = new SurfaceAwareReachabilityRequest
        {
            Vulnerabilities = new List<VulnerabilityInfo>
            {
                new() { CveId = "CVE-2024-0001", Ecosystem = "nuget", PackageName = "UnknownLib", Version = "1.0.0" }
            },
            CallGraph = _callGraphAccessor
        };

        // Act
        var result = await _analyzer.AnalyzeAsync(request);

        // Assert
        result.Findings.Should().HaveCount(1);
        var finding = result.Findings[0];
        // Without surface, should be either Likely or Present depending on fallback analysis
        finding.SinkSource.Should().BeOneOf(SinkSource.PackageApi, SinkSource.FallbackAll);
        finding.ConfidenceTier.Should().BeOneOf(
            ReachabilityConfidenceTier.Likely,
            ReachabilityConfidenceTier.Present);
    }

    #endregion

    #region Present Only Tests

    [Fact]
    public async Task AnalyzeAsync_WhenNoCallGraphData_ReturnsPresentTier()
    {
        // Arrange: No surface, no call graph paths
        var request = new SurfaceAwareReachabilityRequest
        {
            Vulnerabilities = new List<VulnerabilityInfo>
            {
                new() { CveId = "CVE-2024-9999", Ecosystem = "npm", PackageName = "mystery-lib", Version = "0.0.1" }
            },
            CallGraph = null // No call graph available
        };

        // Act
        var result = await _analyzer.AnalyzeAsync(request);

        // Assert
        result.Findings.Should().HaveCount(1);
        var finding = result.Findings[0];
        finding.ConfidenceTier.Should().Be(ReachabilityConfidenceTier.Present);
        finding.SinkSource.Should().Be(SinkSource.FallbackAll);
    }

    #endregion

    #region Multiple Vulnerabilities Tests

    [Fact]
    public async Task AnalyzeAsync_WithMultipleVulnerabilities_ReturnsCorrectTiersForEach()
    {
        // Arrange: Set up mixed scenario
        _callGraphAccessor.AddEntrypoint("API.Controller::Action");
        _callGraphAccessor.AddEdge("API.Controller::Action", "Lib1::Method");

        // Vuln 1: Surface + path = Confirmed
        var surface1 = Guid.NewGuid();
        _surfaceRepo.AddSurface(new SurfaceInfo
        {
            Id = surface1,
            CveId = "CVE-2024-0001",
            Ecosystem = "nuget",
            PackageName = "Lib1",
            VulnVersion = "1.0.0",
            FixedVersion = "1.0.1",
            ComputedAt = DateTimeOffset.UtcNow,
            TriggerCount = 1
        });
        _surfaceRepo.AddTriggers(surface1, new List<TriggerMethodInfo>
        {
            new() { MethodKey = "Lib1::Method", MethodName = "Method", DeclaringType = "Lib1" }
        });
        _graphService.AddReachablePath("API.Controller::Action", "Lib1::Method",
            new[] { "API.Controller::Action", "Lib1::Method" });

        // Vuln 2: Surface but no path = Unreachable
        var surface2 = Guid.NewGuid();
        _surfaceRepo.AddSurface(new SurfaceInfo
        {
            Id = surface2,
            CveId = "CVE-2024-0002",
            Ecosystem = "nuget",
            PackageName = "Lib2",
            VulnVersion = "2.0.0",
            FixedVersion = "2.0.1",
            ComputedAt = DateTimeOffset.UtcNow,
            TriggerCount = 1
        });
        _surfaceRepo.AddTriggers(surface2, new List<TriggerMethodInfo>
        {
            new() { MethodKey = "Lib2::DangerousMethod", MethodName = "DangerousMethod", DeclaringType = "Lib2" }
        });
        // No path to Lib2 = unreachable

        var request = new SurfaceAwareReachabilityRequest
        {
            Vulnerabilities = new List<VulnerabilityInfo>
            {
                new() { CveId = "CVE-2024-0001", Ecosystem = "nuget", PackageName = "Lib1", Version = "1.0.0" },
                new() { CveId = "CVE-2024-0002", Ecosystem = "nuget", PackageName = "Lib2", Version = "2.0.0" }
            },
            CallGraph = _callGraphAccessor
        };

        // Act
        var result = await _analyzer.AnalyzeAsync(request);

        // Assert
        result.Findings.Should().HaveCount(2);
        result.ConfirmedReachable.Should().Be(1);
        result.Unreachable.Should().Be(1);

        var confirmed = result.Findings.First(f => f.CveId == "CVE-2024-0001");
        confirmed.ConfidenceTier.Should().Be(ReachabilityConfidenceTier.Confirmed);

        var unreachable = result.Findings.First(f => f.CveId == "CVE-2024-0002");
        unreachable.ConfidenceTier.Should().Be(ReachabilityConfidenceTier.Unreachable);
    }

    #endregion

    #region Surface Caching Tests

    [Fact]
    public async Task AnalyzeAsync_CachesSurfaceQueries_DoesNotQueryTwice()
    {
        // Arrange
        var surfaceId = Guid.NewGuid();
        _surfaceRepo.AddSurface(new SurfaceInfo
        {
            Id = surfaceId,
            CveId = "CVE-2024-CACHED",
            Ecosystem = "nuget",
            PackageName = "CachedLib",
            VulnVersion = "1.0.0",
            FixedVersion = "1.0.1",
            ComputedAt = DateTimeOffset.UtcNow,
            TriggerCount = 1
        });
        _surfaceRepo.AddTriggers(surfaceId, new List<TriggerMethodInfo>
        {
            new() { MethodKey = "CachedLib::Method", MethodName = "Method", DeclaringType = "CachedLib" }
        });

        _callGraphAccessor.AddEntrypoint("App::Main");
        _callGraphAccessor.AddEdge("App::Main", "CachedLib::Method");
        _graphService.AddReachablePath("App::Main", "CachedLib::Method",
            new[] { "App::Main", "CachedLib::Method" });

        var request = new SurfaceAwareReachabilityRequest
        {
            Vulnerabilities = new List<VulnerabilityInfo>
            {
                new() { CveId = "CVE-2024-CACHED", Ecosystem = "nuget", PackageName = "CachedLib", Version = "1.0.0" }
            },
            CallGraph = _callGraphAccessor
        };

        // Act: Query twice
        await _analyzer.AnalyzeAsync(request);
        var initialQueryCount = _surfaceRepo.QueryCount;

        await _analyzer.AnalyzeAsync(request);
        var finalQueryCount = _surfaceRepo.QueryCount;

        // Assert: Should use cache, not query again
        finalQueryCount.Should().Be(initialQueryCount, "second analysis should use cached surface data");
    }

    #endregion

    #region Test Infrastructure

    /// <summary>
    /// In-memory implementation of ISurfaceRepository for testing.
    /// </summary>
    private sealed class InMemorySurfaceRepository : ISurfaceRepository
    {
        private readonly Dictionary<string, SurfaceInfo> _surfaces = new();
        private readonly Dictionary<Guid, List<TriggerMethodInfo>> _triggers = new();
        private readonly Dictionary<Guid, List<string>> _sinks = new();

        public int QueryCount { get; private set; }

        public void AddSurface(SurfaceInfo surface)
        {
            var key = $"{surface.CveId}|{surface.Ecosystem}|{surface.PackageName}|{surface.VulnVersion}";
            _surfaces[key] = surface;
        }

        public void AddTriggers(Guid surfaceId, List<TriggerMethodInfo> triggers)
        {
            _triggers[surfaceId] = triggers;
        }

        public void AddSinks(Guid surfaceId, List<string> sinks)
        {
            _sinks[surfaceId] = sinks;
        }

        public Task<SurfaceInfo?> GetSurfaceAsync(string cveId, string ecosystem, string packageName, string version, CancellationToken ct = default)
        {
            QueryCount++;
            var key = $"{cveId}|{ecosystem}|{packageName}|{version}";
            _surfaces.TryGetValue(key, out var surface);
            return Task.FromResult(surface);
        }

        public Task<IReadOnlyList<TriggerMethodInfo>> GetTriggersAsync(Guid surfaceId, int maxCount, CancellationToken ct = default)
        {
            return Task.FromResult<IReadOnlyList<TriggerMethodInfo>>(
                _triggers.TryGetValue(surfaceId, out var triggers) ? triggers : new List<TriggerMethodInfo>());
        }

        public Task<IReadOnlyList<string>> GetSinksAsync(Guid surfaceId, CancellationToken ct = default)
        {
            return Task.FromResult<IReadOnlyList<string>>(
                _sinks.TryGetValue(surfaceId, out var sinks) ? sinks : new List<string>());
        }

        public Task<bool> ExistsAsync(string cveId, string ecosystem, string packageName, string version, CancellationToken ct = default)
        {
            var key = $"{cveId}|{ecosystem}|{packageName}|{version}";
            return Task.FromResult(_surfaces.ContainsKey(key));
        }
    }

    /// <summary>
    /// In-memory implementation of ICallGraphAccessor for testing.
    /// </summary>
    private sealed class InMemoryCallGraphAccessor : ICallGraphAccessor
    {
        private readonly HashSet<string> _entrypoints = new();
        private readonly Dictionary<string, List<string>> _callees = new();
        private readonly HashSet<string> _methods = new();

        public void AddEntrypoint(string methodKey)
        {
            _entrypoints.Add(methodKey);
            _methods.Add(methodKey);
        }

        public void AddEdge(string caller, string callee)
        {
            if (!_callees.ContainsKey(caller))
                _callees[caller] = new List<string>();

            _callees[caller].Add(callee);
            _methods.Add(caller);
            _methods.Add(callee);
        }

        public IReadOnlyList<string> GetEntrypoints() => _entrypoints.ToList();

        public IReadOnlyList<string> GetCallees(string methodKey) =>
            _callees.TryGetValue(methodKey, out var callees) ? callees : new List<string>();

        public bool ContainsMethod(string methodKey) => _methods.Contains(methodKey);
    }

    /// <summary>
    /// In-memory implementation of IReachabilityGraphService for testing.
    /// </summary>
    private sealed class InMemoryReachabilityGraphService : IReachabilityGraphService
    {
        private readonly List<ReachablePath> _paths = new();

        public void AddReachablePath(string entrypoint, string sink, string[] pathMethods)
        {
            _paths.Add(new ReachablePath
            {
                EntrypointMethodKey = entrypoint,
                SinkMethodKey = sink,
                PathLength = pathMethods.Length,
                PathMethodKeys = pathMethods.ToList()
            });
        }

        public Task<IReadOnlyList<ReachablePath>> FindPathsToSinksAsync(
            ICallGraphAccessor callGraph,
            IReadOnlyList<string> sinkMethodKeys,
            CancellationToken cancellationToken = default)
        {
            // Return paths that match any of the requested sinks
            var matchingPaths = _paths
                .Where(p => sinkMethodKeys.Contains(p.SinkMethodKey))
                .ToList();

            return Task.FromResult<IReadOnlyList<ReachablePath>>(matchingPaths);
        }
    }

    #endregion
}