using System.Collections.Immutable;
using System.Formats.Tar;
using System.IO.Compression;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using StellaOps.Attestor.StandardPredicates.BinaryDiff;
using StellaOps.Cli.Commands.Scan;
using StellaOps.Cli.Services;
using StellaOps.Cli.Services.Models;
using StellaOps.Scanner.Analyzers.Native;
using StellaOps.Scanner.Contracts;
using StellaOps.TestKit;
using Xunit;

namespace StellaOps.Cli.Tests.Commands;

[Trait("Category", TestCategories.Unit)]
public sealed class BinaryDiffServiceTests
{
    [Fact]
    public async Task ComputeDiffAsync_InvalidReference_ThrowsBinaryDiffException()
    {
        var service = CreateService(new TestOciRegistryClient(), new TestElfSectionHashExtractor(), TimeProvider.System);

        var request = new BinaryDiffRequest
        {
            BaseImageRef = "",
            TargetImageRef = "registry.example.com/app:2",
            Mode = BinaryDiffMode.Elf
        };

        var exception = await Assert.ThrowsAsync<BinaryDiffException>(() =>
            service.ComputeDiffAsync(request, null, CancellationToken.None));

        Assert.Equal(BinaryDiffErrorCode.InvalidReference, exception.Code);
    }

    [Fact]
    public async Task ComputeDiffAsync_ExcludesUnchanged_WhenIncludeUnchangedFalse()
    {
        var baseRef = "registry.example.com/app:1";
        var targetRef = "registry.example.com/app:2";
        var baseLayer = CreateLayer(
            ("usr/bin/alpha", CreateElfBytes('a')),
            ("usr/bin/beta", CreateElfBytes('a')));
        var targetLayer = CreateLayer(
            ("usr/bin/alpha", CreateElfBytes('a')),
            ("usr/bin/beta", CreateElfBytes('b')),
            ("usr/bin/gamma", CreateElfBytes('b')));

        var registry = new TestOciRegistryClient();
        registry.AddImage(baseRef, "sha256:base", CreateManifest("sha256:layer-base", baseLayer.Length));
        registry.AddImage(targetRef, "sha256:target", CreateManifest("sha256:layer-target", targetLayer.Length));
        registry.AddBlob("sha256:layer-base", baseLayer);
        registry.AddBlob("sha256:layer-target", targetLayer);

        var service = CreateService(registry, new TestElfSectionHashExtractor(), TimeProvider.System);

        var result = await service.ComputeDiffAsync(
            new BinaryDiffRequest
            {
                BaseImageRef = baseRef,
                TargetImageRef = targetRef,
                Mode = BinaryDiffMode.Elf,
                IncludeUnchanged = false,
                Platform = new BinaryDiffPlatform { Os = "linux", Architecture = "amd64" }
            },
            null,
            CancellationToken.None);

        Assert.Equal(2, result.Findings.Length);
        Assert.All(result.Findings, finding => Assert.NotEqual(ChangeType.Unchanged, finding.ChangeType));

        var paths = result.Findings.Select(finding => finding.Path).ToArray();
        var sortedPaths = paths.OrderBy(path => path, StringComparer.Ordinal).ToArray();
        Assert.Equal(sortedPaths, paths);

        Assert.Equal(3, result.Summary.TotalBinaries);
        Assert.Equal(2, result.Summary.Modified);
        Assert.Equal(1, result.Summary.Unchanged);
        Assert.Equal(1, result.Summary.Added);
        Assert.Equal(0, result.Summary.Removed);
    }

    [Fact]
    public async Task ComputeDiffAsync_UsesTimeProviderForMetadata()
    {
        var baseRef = "registry.example.com/app:1";
        var targetRef = "registry.example.com/app:2";
        var baseLayer = CreateLayer(("usr/bin/app", CreateElfBytes('a')));
        var targetLayer = CreateLayer(("usr/bin/app", CreateElfBytes('b')));

        var registry = new TestOciRegistryClient();
        registry.AddImage(baseRef, "sha256:base", CreateManifest("sha256:layer-base", baseLayer.Length));
        registry.AddImage(targetRef, "sha256:target", CreateManifest("sha256:layer-target", targetLayer.Length));
        registry.AddBlob("sha256:layer-base", baseLayer);
        registry.AddBlob("sha256:layer-target", targetLayer);

        var fixedTime = new DateTimeOffset(2026, 1, 13, 1, 0, 0, TimeSpan.Zero);
        var service = CreateService(registry, new TestElfSectionHashExtractor(), new FixedTimeProvider(fixedTime));

        var result = await service.ComputeDiffAsync(
            new BinaryDiffRequest
            {
                BaseImageRef = baseRef,
                TargetImageRef = targetRef,
                Mode = BinaryDiffMode.Elf
            },
            null,
            CancellationToken.None);

        Assert.Equal(fixedTime, result.Metadata.AnalysisTimestamp);
    }

    private static BinaryDiffService CreateService(
        IOciRegistryClient registryClient,
        IElfSectionHashExtractor extractor,
        TimeProvider timeProvider)
    {
        var options = Options.Create(new BinaryDiffOptions { ToolVersion = "test" });
        return new BinaryDiffService(
            registryClient,
            extractor,
            options,
            timeProvider,
            NullLogger<BinaryDiffService>.Instance);
    }

    private static OciManifest CreateManifest(string layerDigest, long size)
    {
        return new OciManifest
        {
            Layers = new List<OciDescriptor>
            {
                new OciDescriptor
                {
                    Digest = layerDigest,
                    Size = size,
                    MediaType = "application/vnd.oci.image.layer.v1.tar+gzip"
                }
            }
        };
    }

    private static byte[] CreateLayer(params (string Path, byte[] Content)[] entries)
    {
        using var output = new MemoryStream();
        using (var gzip = new GZipStream(output, CompressionLevel.Optimal, leaveOpen: true))
        using (var tarWriter = new TarWriter(gzip, TarEntryFormat.Pax))
        {
            foreach (var entry in entries)
            {
                var tarEntry = new PaxTarEntry(TarEntryType.RegularFile, entry.Path)
                {
                    Mode = UnixFileMode.UserRead | UnixFileMode.UserWrite | UnixFileMode.GroupRead | UnixFileMode.OtherRead,
                    ModificationTime = new DateTimeOffset(2026, 1, 13, 0, 0, 0, TimeSpan.Zero),
                    DataStream = new MemoryStream(entry.Content, writable: false)
                };
                tarWriter.WriteEntry(tarEntry);
            }
        }

        return output.ToArray();
    }

    private static byte[] CreateElfBytes(char marker)
    {
        return
        [
            0x7F,
            (byte)'E',
            (byte)'L',
            (byte)'F',
            (byte)marker
        ];
    }

    private static ElfSectionHashSet CreateHashSet(string path, char marker)
    {
        var hash = new string(marker, 64);
        var section = new ElfSectionHash
        {
            Name = ".text",
            Offset = 0,
            Size = 16,
            Sha256 = hash,
            Blake3 = null,
            SectionType = ElfSectionType.ProgBits,
            Flags = ElfSectionFlags.Alloc
        };

        return new ElfSectionHashSet
        {
            FilePath = path,
            FileHash = hash,
            BuildId = "build-" + marker,
            Sections = ImmutableArray.Create(section),
            ExtractedAt = new DateTimeOffset(2026, 1, 13, 0, 0, 0, TimeSpan.Zero),
            ExtractorVersion = "test"
        };
    }

    private sealed class TestOciRegistryClient : IOciRegistryClient
    {
        private readonly Dictionary<string, string> _digestsByReference = new(StringComparer.Ordinal);
        private readonly Dictionary<string, OciManifest> _manifestsByDigest = new(StringComparer.Ordinal);
        private readonly Dictionary<string, byte[]> _blobsByDigest = new(StringComparer.Ordinal);

        public void AddImage(string reference, string digest, OciManifest manifest)
        {
            _digestsByReference[reference] = digest;
            _manifestsByDigest[digest] = manifest;
        }

        public void AddBlob(string digest, byte[] blob)
        {
            _blobsByDigest[digest] = blob;
        }

        public Task<string> ResolveDigestAsync(OciImageReference reference, CancellationToken cancellationToken = default)
        {
            if (_digestsByReference.TryGetValue(reference.Original, out var digest))
            {
                return Task.FromResult(digest);
            }

            throw new InvalidOperationException($"Digest not configured for {reference.Original}");
        }

        public Task<string> ResolveTagAsync(string registry, string repository, string tag, CancellationToken cancellationToken = default)
        {
            throw new NotSupportedException("ResolveTagAsync is not used by these tests.");
        }

        public Task<OciReferrersResponse> ListReferrersAsync(
            OciImageReference reference,
            string digest,
            CancellationToken cancellationToken = default)
        {
            throw new NotSupportedException("ListReferrersAsync is not used by these tests.");
        }

        public Task<IReadOnlyList<OciReferrerDescriptor>> GetReferrersAsync(
            string registry,
            string repository,
            string digest,
            string? artifactType = null,
            CancellationToken cancellationToken = default)
        {
            throw new NotSupportedException("GetReferrersAsync is not used by these tests.");
        }

        public Task<OciManifest> GetManifestAsync(
            OciImageReference reference,
            string digest,
            CancellationToken cancellationToken = default)
        {
            if (_manifestsByDigest.TryGetValue(digest, out var manifest))
            {
                return Task.FromResult(manifest);
            }

            throw new InvalidOperationException($"Manifest not configured for {digest}");
        }

        public Task<byte[]> GetBlobAsync(
            OciImageReference reference,
            string digest,
            CancellationToken cancellationToken = default)
        {
            if (_blobsByDigest.TryGetValue(digest, out var blob))
            {
                return Task.FromResult(blob);
            }

            throw new InvalidOperationException($"Blob not configured for {digest}");
        }
    }

    private sealed class TestElfSectionHashExtractor : IElfSectionHashExtractor
    {
        public Task<ElfSectionHashSet?> ExtractAsync(string elfPath, CancellationToken cancellationToken = default)
        {
            var bytes = File.ReadAllBytes(elfPath);
            return ExtractFromBytesAsync(bytes, elfPath, cancellationToken);
        }

        public Task<ElfSectionHashSet?> ExtractFromBytesAsync(
            ReadOnlyMemory<byte> elfBytes,
            string virtualPath,
            CancellationToken cancellationToken = default)
        {
            if (elfBytes.Length < 5)
            {
                return Task.FromResult<ElfSectionHashSet?>(null);
            }

            var marker = (char)elfBytes.Span[4];
            var normalized = marker switch
            {
                'a' => 'a',
                'b' => 'b',
                _ => 'c'
            };

            return Task.FromResult<ElfSectionHashSet?>(CreateHashSet(virtualPath, normalized));
        }
    }

    private sealed class FixedTimeProvider : TimeProvider
    {
        private readonly DateTimeOffset _fixedTime;

        public FixedTimeProvider(DateTimeOffset fixedTime)
        {
            _fixedTime = fixedTime;
        }

        public override DateTimeOffset GetUtcNow() => _fixedTime;
    }
}