using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using FluentAssertions;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using MongoDB.Bson;
using StellaOps.Scanner.Reachability;
using StellaOps.Signals.Models;
using StellaOps.Signals.Options;
using StellaOps.Signals.Parsing;
using StellaOps.Signals.Persistence;
using StellaOps.Signals.Services;
using StellaOps.Signals.Storage;
using StellaOps.Signals.Storage.Models;
using Xunit;

namespace StellaOps.ScannerSignals.IntegrationTests;

public sealed class ScannerToSignalsReachabilityTests
{
    private static readonly string RepoRoot = LocateRepoRoot();
    private static readonly string FixtureRoot = Path.Combine(RepoRoot, "tests", "reachability", "fixtures", "reachbench-2025-expanded", "cases");

    [Fact]
    public async Task ScannerBuilderFeedsSignalsScoringPipeline()
    {
        var caseId = "java-log4j-CVE-2021-44228-log4shell";
        var variant = "reachable";
        var variantPath = Path.Combine(FixtureRoot, caseId, "images", variant);
        Directory.Exists(variantPath).Should().BeTrue();

        var builder = ReachabilityGraphBuilder.FromFixture(variantPath);
        var artifactJson = builder.BuildJson(indented: false);
        var parser = new SimpleJsonCallgraphParser("java");
        var parserResolver = new StaticParserResolver(new Dictionary<string, ICallgraphParser>
        {
            ["java"] = parser
        });
        var artifactStore = new InMemoryCallgraphArtifactStore();
        var callgraphRepo = new InMemoryCallgraphRepository();
        var ingestionService = new CallgraphIngestionService(
            parserResolver,
            artifactStore,
            callgraphRepo,
            Options.Create(new SignalsOptions()),
            TimeProvider.System,
            NullLogger<CallgraphIngestionService>.Instance);

        var request = new CallgraphIngestRequest(
            Language: "java",
            Component: caseId,
            Version: variant,
            ArtifactContentType: "application/json",
            ArtifactFileName: "callgraph.static.json",
            ArtifactContentBase64: Convert.ToBase64String(Encoding.UTF8.GetBytes(artifactJson)),
            Metadata: null);

        var ingestResponse = await ingestionService.IngestAsync(request, CancellationToken.None);
        ingestResponse.CallgraphId.Should().NotBeNullOrWhiteSpace();

        var scoringService = new ReachabilityScoringService(
            callgraphRepo,
            new InMemoryReachabilityFactRepository(),
            TimeProvider.System,
            NullLogger<ReachabilityScoringService>.Instance);

        var truth = JsonDocument.Parse(File.ReadAllText(Path.Combine(variantPath, "reachgraph.truth.json"))).RootElement;
        var entryPoints = truth.GetProperty("paths").EnumerateArray()
            .Select(path => path[0].GetString()!)
            .Distinct(StringComparer.Ordinal)
            .ToList();
        var targets = truth.GetProperty("sinks").EnumerateArray().Select(s => s.GetProperty("sid").GetString()!).ToList();

        var recomputeRequest = new ReachabilityRecomputeRequest
        {
            CallgraphId = ingestResponse.CallgraphId,
            Subject = new ReachabilitySubject
            {
                ScanId = $"{caseId}:{variant}",
                Component = caseId,
                Version = variant
            },
            EntryPoints = entryPoints,
            Targets = targets,
            RuntimeHits = ReadRuntimeHits(Path.Combine(variantPath, "traces.runtime.jsonl"))
        };

        var fact = await scoringService.RecomputeAsync(recomputeRequest, CancellationToken.None);
        fact.States.Should().ContainSingle(state => state.Target == targets[0] && state.Reachable);
    }

    private static List<string> ReadRuntimeHits(string tracePath)
    {
        var hits = new List<string>();
        if (!File.Exists(tracePath))
        {
            return hits;
        }

        foreach (var line in File.ReadLines(tracePath))
        {
            if (string.IsNullOrWhiteSpace(line))
            {
                continue;
            }

            using var doc = JsonDocument.Parse(line);
            if (doc.RootElement.TryGetProperty("sid", out var sid))
            {
                hits.Add(sid.GetString()!);
            }
        }

        return hits;
    }

    private sealed class StaticParserResolver : ICallgraphParserResolver
    {
        private readonly IReadOnlyDictionary<string, ICallgraphParser> parsers;

        public StaticParserResolver(IReadOnlyDictionary<string, ICallgraphParser> parsers)
        {
            this.parsers = parsers;
        }

        public ICallgraphParser Resolve(string language)
        {
            if (parsers.TryGetValue(language, out var parser))
            {
                return parser;
            }

            throw new CallgraphParserNotFoundException(language);
        }
    }

    private sealed class InMemoryCallgraphRepository : ICallgraphRepository
    {
        private readonly Dictionary<string, CallgraphDocument> storage = new(StringComparer.Ordinal);

        public Task<CallgraphDocument?> GetByIdAsync(string id, CancellationToken cancellationToken)
        {
            storage.TryGetValue(id, out var document);
            return Task.FromResult(document);
        }

        public Task<CallgraphDocument> UpsertAsync(CallgraphDocument document, CancellationToken cancellationToken)
        {
            if (string.IsNullOrWhiteSpace(document.Id))
            {
                document.Id = ObjectId.GenerateNewId().ToString();
            }

            storage[document.Id] = document;
            return Task.FromResult(document);
        }
    }

    private sealed class InMemoryReachabilityFactRepository : IReachabilityFactRepository
    {
        private readonly Dictionary<string, ReachabilityFactDocument> storage = new(StringComparer.Ordinal);

        public Task<ReachabilityFactDocument?> GetBySubjectAsync(string subjectKey, CancellationToken cancellationToken)
        {
            storage.TryGetValue(subjectKey, out var document);
            return Task.FromResult(document);
        }

        public Task<ReachabilityFactDocument> UpsertAsync(ReachabilityFactDocument document, CancellationToken cancellationToken)
        {
            storage[document.SubjectKey] = document;
            return Task.FromResult(document);
        }
    }

    private sealed class InMemoryCallgraphArtifactStore : ICallgraphArtifactStore
    {
        public async Task<StoredCallgraphArtifact> SaveAsync(CallgraphArtifactSaveRequest request, Stream content, CancellationToken cancellationToken)
        {
            ArgumentNullException.ThrowIfNull(request);
            ArgumentNullException.ThrowIfNull(content);

            await using var buffer = new MemoryStream();
            await content.CopyToAsync(buffer, cancellationToken).ConfigureAwait(false);
            var bytes = buffer.ToArray();
            var computedHash = Convert.ToHexString(SHA256.HashData(bytes));

            if (content.CanSeek)
            {
                content.Position = 0;
            }

            if (!computedHash.Equals(request.Hash, StringComparison.OrdinalIgnoreCase))
            {
                throw new InvalidOperationException($"Hash mismatch for {request.FileName}: expected {request.Hash} but computed {computedHash}.");
            }

            return new StoredCallgraphArtifact(
                Path: $"cas://fixtures/{request.Component}/{request.Version}/{request.FileName}",
                Length: bytes.Length,
                Hash: computedHash,
                ContentType: request.ContentType);
        }
    }
    private static string LocateRepoRoot()
    {
        var current = new DirectoryInfo(AppContext.BaseDirectory);
        while (current != null)
        {
            if (File.Exists(Path.Combine(current.FullName, "Directory.Build.props")))
            {
                return current.FullName;
            }

            current = current.Parent;
        }

        throw new InvalidOperationException("Cannot locate repository root (missing Directory.Build.props).");
    }
}