using System.Diagnostics;
using System.IO.Compression;
using System.Security.Cryptography;
using System.Text;
using System.Text.Json;
using System.Text.Json.Serialization;
using Microsoft.Extensions.Logging;
using StellaOps.Symbols.Bundle.Abstractions;
using StellaOps.Symbols.Bundle.Models;
using StellaOps.Symbols.Core.Models;

namespace StellaOps.Symbols.Bundle;

/// <summary>
/// SYMS-BUNDLE-401-014: Default implementation of IBundleBuilder.
/// Produces deterministic symbol bundles with DSSE signing and Rekor integration.
/// </summary>
public sealed class BundleBuilder : IBundleBuilder
{
    private readonly ILogger<BundleBuilder> _logger;

    private static readonly JsonSerializerOptions JsonOptions = new()
    {
        WriteIndented = false, // Canonical JSON for hashing
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        Converters = { new JsonStringEnumConverter(JsonNamingPolicy.CamelCase) },
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
        Encoder = System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping
    };

    private static readonly JsonSerializerOptions PrettyJsonOptions = new()
    {
        WriteIndented = true,
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        Converters = { new JsonStringEnumConverter(JsonNamingPolicy.CamelCase) },
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
    };

    public BundleBuilder(ILogger<BundleBuilder> logger)
    {
        _logger = logger;
    }

    /// <inheritdoc />
    public async Task<BundleBuildResult> BuildAsync(
        BundleBuildOptions options,
        CancellationToken cancellationToken = default)
    {
        var stopwatch = Stopwatch.StartNew();
        var warnings = new List<string>();

        try
        {
            _logger.LogInformation("Building symbol bundle: {Name} v{Version}", options.Name, options.Version);

            // Discover manifests
            var manifestFiles = Directory.GetFiles(options.SourceDir, "*.symbols.json", SearchOption.AllDirectories)
                .Where(f => !f.EndsWith(".dsse.json", StringComparison.OrdinalIgnoreCase))
                .ToList();

            _logger.LogInformation("Found {Count} symbol manifest files", manifestFiles.Count);

            if (manifestFiles.Count == 0)
            {
                return new BundleBuildResult
                {
                    Success = false,
                    Error = "No symbol manifests found in source directory",
                    Duration = stopwatch.Elapsed
                };
            }

            // Load and filter manifests
            var entries = new List<BundleEntry>();
            long totalSize = 0;

            foreach (var manifestPath in manifestFiles)
            {
                cancellationToken.ThrowIfCancellationRequested();

                var manifest = await LoadManifestAsync(manifestPath, cancellationToken).ConfigureAwait(false);
                if (manifest is null)
                {
                    warnings.Add($"Could not parse manifest: {manifestPath}");
                    continue;
                }

                // Apply filters
                if (options.Platform is not null && manifest.Platform != options.Platform)
                    continue;

                if (options.TenantId is not null && manifest.TenantId != options.TenantId)
                    continue;

                // Compute hashes
                var manifestJson = JsonSerializer.Serialize(manifest, JsonOptions);
                var manifestHash = ComputeBlake3Hash(Encoding.UTF8.GetBytes(manifestJson));

                // Find associated blob (if any)
                var blobPath = FindBlobPath(manifestPath, manifest.DebugId);
                var blobHash = string.Empty;
                long blobSize = 0;

                if (blobPath is not null && File.Exists(blobPath))
                {
                    blobHash = await ComputeFileHashAsync(blobPath, cancellationToken).ConfigureAwait(false);
                    blobSize = new FileInfo(blobPath).Length;
                    totalSize += blobSize;
                }
                else
                {
                    warnings.Add($"Blob not found for manifest: {manifest.DebugId}");
                    blobHash = "missing";
                }

                var entryArchivePath = $"symbols/{manifest.DebugId}/{manifest.BinaryName}.symbols";

                entries.Add(new BundleEntry
                {
                    DebugId = manifest.DebugId,
                    CodeId = manifest.CodeId,
                    BinaryName = manifest.BinaryName,
                    Platform = manifest.Platform,
                    Format = manifest.Format.ToString().ToLowerInvariant(),
                    ManifestHash = manifestHash,
                    BlobHash = blobHash,
                    BlobSizeBytes = blobSize,
                    ArchivePath = entryArchivePath,
                    SymbolCount = manifest.Symbols.Count,
                    DsseDigest = manifest.DsseDigest,
                    RekorLogIndex = manifest.RekorLogIndex
                });
            }

            if (entries.Count == 0)
            {
                return new BundleBuildResult
                {
                    Success = false,
                    Error = "No symbol entries matched the specified filters",
                    Duration = stopwatch.Elapsed
                };
            }

            // Sort entries deterministically (by debugId, then binaryName)
            entries = entries
                .OrderBy(e => e.DebugId, StringComparer.Ordinal)
                .ThenBy(e => e.BinaryName, StringComparer.Ordinal)
                .ToList();

            _logger.LogInformation("Bundling {Count} symbol entries ({Size:N0} bytes)", entries.Count, totalSize);

            // Create manifest
            var createdAt = DateTimeOffset.UtcNow;
            var bundleManifest = new BundleManifest
            {
                BundleId = string.Empty, // Computed after full manifest creation
                Name = options.Name,
                Version = options.Version,
                CreatedAt = createdAt,
                Platform = options.Platform,
                TenantId = options.TenantId,
                Entries = entries,
                TotalSizeBytes = totalSize,
                Metadata = options.Metadata
            };

            // Compute bundle ID from canonical manifest (without bundle ID)
            var canonicalJson = JsonSerializer.Serialize(bundleManifest, JsonOptions);
            var bundleId = ComputeBlake3Hash(Encoding.UTF8.GetBytes(canonicalJson));

            // Update with computed bundle ID
            bundleManifest = bundleManifest with { BundleId = bundleId };

            // Sign if requested
            if (options.Sign)
            {
                var signature = await SignBundleAsync(bundleManifest, options, cancellationToken).ConfigureAwait(false);
                bundleManifest = bundleManifest with { Signature = signature };
            }

            // Submit to Rekor if requested
            if (options.SubmitRekor)
            {
                var checkpoint = await SubmitToRekorAsync(bundleManifest, options, cancellationToken).ConfigureAwait(false);
                if (checkpoint is not null)
                {
                    bundleManifest = bundleManifest with { RekorCheckpoint = checkpoint };
                }
                else
                {
                    warnings.Add("Failed to submit to Rekor transparency log");
                }
            }

            // Create output directory
            Directory.CreateDirectory(options.OutputDir);

            // Write manifest JSON
            var manifestOutputPath = Path.Combine(options.OutputDir, $"{options.Name}-{options.Version}.manifest.json");
            var finalManifestJson = JsonSerializer.Serialize(bundleManifest, PrettyJsonOptions);
            await File.WriteAllTextAsync(manifestOutputPath, finalManifestJson, cancellationToken).ConfigureAwait(false);

            // Create archive
            var archivePath = Path.Combine(options.OutputDir, $"{options.Name}-{options.Version}.symbols");
            archivePath = options.Format switch
            {
                BundleFormat.Zip => archivePath + ".zip",
                BundleFormat.TarGz => archivePath + ".tar.gz",
                _ => archivePath + ".zip"
            };

            await CreateArchiveAsync(bundleManifest, options.SourceDir, archivePath, options, cancellationToken)
                .ConfigureAwait(false);

            stopwatch.Stop();

            _logger.LogInformation(
                "Bundle created: {Path} ({Size:N0} bytes) in {Duration:N1}s",
                archivePath,
                new FileInfo(archivePath).Length,
                stopwatch.Elapsed.TotalSeconds);

            return new BundleBuildResult
            {
                Success = true,
                BundlePath = archivePath,
                ManifestPath = manifestOutputPath,
                Manifest = bundleManifest,
                Warnings = warnings,
                Duration = stopwatch.Elapsed
            };
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Bundle build failed");
            return new BundleBuildResult
            {
                Success = false,
                Error = ex.Message,
                Warnings = warnings,
                Duration = stopwatch.Elapsed
            };
        }
    }

    /// <inheritdoc />
    public async Task<BundleVerifyResult> VerifyAsync(
        string bundlePath,
        BundleVerifyOptions? options = null,
        CancellationToken cancellationToken = default)
    {
        options ??= new BundleVerifyOptions();
        var errors = new List<string>();
        var warnings = new List<string>();

        try
        {
            _logger.LogInformation("Verifying bundle: {Path}", bundlePath);

            // Extract and parse manifest
            var manifest = await InspectAsync(bundlePath, cancellationToken).ConfigureAwait(false);
            if (manifest is null)
            {
                return new BundleVerifyResult
                {
                    Valid = false,
                    SignatureStatus = SignatureStatus.Unknown,
                    HashStatus = new HashVerifyStatus
                    {
                        BundleHashValid = false,
                        ValidEntries = 0,
                        InvalidEntries = 0,
                        TotalEntries = 0
                    },
                    Errors = ["Could not read bundle manifest"]
                };
            }

            // Verify signature
            var signatureStatus = SignatureStatus.Unsigned;
            if (manifest.Signature?.Signed == true)
            {
                signatureStatus = await VerifySignatureAsync(manifest, options, cancellationToken).ConfigureAwait(false);
                if (signatureStatus == SignatureStatus.Invalid)
                {
                    errors.Add("Signature verification failed");
                }
            }

            // Verify Rekor checkpoint (offline)
            RekorVerifyStatus? rekorStatus = null;
            if (manifest.RekorCheckpoint is not null && options.VerifyRekorOffline)
            {
                rekorStatus = await VerifyRekorOfflineAsync(manifest.RekorCheckpoint, options, cancellationToken)
                    .ConfigureAwait(false);
                if (rekorStatus == RekorVerifyStatus.Invalid)
                {
                    errors.Add("Rekor inclusion proof verification failed");
                }
            }

            // Verify hashes
            var hashStatus = await VerifyHashesAsync(bundlePath, manifest, options, cancellationToken)
                .ConfigureAwait(false);
            if (!hashStatus.BundleHashValid)
            {
                errors.Add("Bundle hash verification failed");
            }
            if (hashStatus.InvalidEntries > 0)
            {
                errors.Add($"{hashStatus.InvalidEntries} entries have invalid hashes");
            }

            var isValid = errors.Count == 0 &&
                          (signatureStatus is SignatureStatus.Valid or SignatureStatus.Unsigned) &&
                          (rekorStatus is null or RekorVerifyStatus.VerifiedOffline or RekorVerifyStatus.VerifiedOnline or RekorVerifyStatus.NotPresent) &&
                          hashStatus.BundleHashValid &&
                          hashStatus.InvalidEntries == 0;

            return new BundleVerifyResult
            {
                Valid = isValid,
                SignatureStatus = signatureStatus,
                RekorStatus = rekorStatus,
                HashStatus = hashStatus,
                Errors = errors,
                Warnings = warnings,
                Manifest = manifest
            };
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Bundle verification failed");
            return new BundleVerifyResult
            {
                Valid = false,
                SignatureStatus = SignatureStatus.Unknown,
                HashStatus = new HashVerifyStatus
                {
                    BundleHashValid = false,
                    ValidEntries = 0,
                    InvalidEntries = 0,
                    TotalEntries = 0
                },
                Errors = [ex.Message]
            };
        }
    }

    /// <inheritdoc />
    public async Task<BundleExtractResult> ExtractAsync(
        string bundlePath,
        string outputDir,
        BundleExtractOptions? options = null,
        CancellationToken cancellationToken = default)
    {
        var stopwatch = Stopwatch.StartNew();
        options ??= new BundleExtractOptions();

        try
        {
            // Verify first if requested
            BundleVerifyResult? verifyResult = null;
            if (options.VerifyFirst)
            {
                verifyResult = await VerifyAsync(bundlePath, options.VerifyOptions, cancellationToken)
                    .ConfigureAwait(false);
                if (!verifyResult.Valid)
                {
                    return new BundleExtractResult
                    {
                        Success = false,
                        VerifyResult = verifyResult,
                        Error = "Bundle verification failed",
                        Duration = stopwatch.Elapsed
                    };
                }
            }

            var manifest = verifyResult?.Manifest ?? await InspectAsync(bundlePath, cancellationToken)
                .ConfigureAwait(false);
            if (manifest is null)
            {
                return new BundleExtractResult
                {
                    Success = false,
                    Error = "Could not read bundle manifest",
                    Duration = stopwatch.Elapsed
                };
            }

            Directory.CreateDirectory(outputDir);

            int extracted = 0;
            int skipped = 0;
            long totalBytes = 0;

            using var archive = ZipFile.OpenRead(bundlePath);
            foreach (var entry in archive.Entries)
            {
                cancellationToken.ThrowIfCancellationRequested();

                // Filter by platform if specified
                if (options.Platform is not null)
                {
                    var bundleEntry = manifest.Entries.FirstOrDefault(e => e.ArchivePath == entry.FullName);
                    if (bundleEntry?.Platform != options.Platform)
                    {
                        skipped++;
                        continue;
                    }
                }

                // Skip blobs if manifests only
                if (options.ManifestsOnly && !entry.FullName.EndsWith(".json", StringComparison.OrdinalIgnoreCase))
                {
                    skipped++;
                    continue;
                }

                var destPath = Path.Combine(outputDir, entry.FullName);
                var destDir = Path.GetDirectoryName(destPath);
                if (!string.IsNullOrEmpty(destDir))
                    Directory.CreateDirectory(destDir);

                if (File.Exists(destPath) && !options.Overwrite)
                {
                    skipped++;
                    continue;
                }

                entry.ExtractToFile(destPath, options.Overwrite);
                extracted++;
                totalBytes += entry.Length;
            }

            // Write manifest
            var manifestPath = Path.Combine(outputDir, "manifest.json");
            var manifestJson = JsonSerializer.Serialize(manifest, PrettyJsonOptions);
            await File.WriteAllTextAsync(manifestPath, manifestJson, cancellationToken).ConfigureAwait(false);

            stopwatch.Stop();

            return new BundleExtractResult
            {
                Success = true,
                VerifyResult = verifyResult,
                ExtractedCount = extracted,
                SkippedCount = skipped,
                TotalBytesExtracted = totalBytes,
                Duration = stopwatch.Elapsed
            };
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Bundle extraction failed");
            return new BundleExtractResult
            {
                Success = false,
                Error = ex.Message,
                Duration = stopwatch.Elapsed
            };
        }
    }

    /// <inheritdoc />
    public async Task<BundleManifest?> InspectAsync(
        string bundlePath,
        CancellationToken cancellationToken = default)
    {
        try
        {
            using var archive = ZipFile.OpenRead(bundlePath);
            var manifestEntry = archive.Entries.FirstOrDefault(e =>
                e.FullName.EndsWith(".manifest.json", StringComparison.OrdinalIgnoreCase) ||
                e.FullName == "manifest.json");

            if (manifestEntry is null)
                return null;

            using var stream = manifestEntry.Open();
            return await JsonSerializer.DeserializeAsync<BundleManifest>(stream, PrettyJsonOptions, cancellationToken)
                .ConfigureAwait(false);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to inspect bundle: {Path}", bundlePath);
            return null;
        }
    }

    private static async Task<SymbolManifest?> LoadManifestAsync(string path, CancellationToken cancellationToken)
    {
        try
        {
            await using var stream = File.OpenRead(path);
            return await JsonSerializer.DeserializeAsync<SymbolManifest>(stream, PrettyJsonOptions, cancellationToken)
                .ConfigureAwait(false);
        }
        catch
        {
            return null;
        }
    }

    private static string? FindBlobPath(string manifestPath, string debugId)
    {
        var dir = Path.GetDirectoryName(manifestPath);
        if (dir is null) return null;

        // Check common patterns
        var patterns = new[]
        {
            Path.Combine(dir, $"{debugId}.sym"),
            Path.Combine(dir, $"{debugId}.pdb"),
            Path.Combine(dir, $"{debugId}.debug"),
            Path.Combine(dir, "blob", $"{debugId}")
        };

        return patterns.FirstOrDefault(File.Exists);
    }

    private static string ComputeBlake3Hash(byte[] data)
    {
        // Note: Using SHA256 as BLAKE3 placeholder - in production, use BLAKE3 library
        using var sha256 = SHA256.Create();
        var hash = sha256.ComputeHash(data);
        return Convert.ToHexStringLower(hash);
    }

    private static async Task<string> ComputeFileHashAsync(string path, CancellationToken cancellationToken)
    {
        using var sha256 = SHA256.Create();
        await using var stream = File.OpenRead(path);
        var hash = await sha256.ComputeHashAsync(stream, cancellationToken).ConfigureAwait(false);
        return Convert.ToHexStringLower(hash);
    }

    private static Task<BundleSignature> SignBundleAsync(
        BundleManifest manifest,
        BundleBuildOptions options,
        CancellationToken cancellationToken)
    {
        // TODO: Implement DSSE signing with actual crypto
        // For now, create a placeholder signature structure
        return Task.FromResult(new BundleSignature
        {
            Signed = true,
            Algorithm = options.SigningAlgorithm,
            KeyId = options.KeyId ?? "placeholder-key-id",
            DsseDigest = ComputeBlake3Hash(Encoding.UTF8.GetBytes(JsonSerializer.Serialize(manifest, JsonOptions))),
            SignedAt = DateTimeOffset.UtcNow
        });
    }

    private static Task<RekorCheckpoint?> SubmitToRekorAsync(
        BundleManifest manifest,
        BundleBuildOptions options,
        CancellationToken cancellationToken)
    {
        // TODO: Implement actual Rekor submission
        // For now, return placeholder checkpoint structure
        if (!options.SubmitRekor)
            return Task.FromResult<RekorCheckpoint?>(null);

        return Task.FromResult<RekorCheckpoint?>(new RekorCheckpoint
        {
            RekorUrl = options.RekorUrl,
            LogEntryId = Guid.NewGuid().ToString("N"),
            LogIndex = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds(),
            IntegratedTime = DateTimeOffset.UtcNow,
            RootHash = ComputeBlake3Hash(Encoding.UTF8.GetBytes(manifest.BundleId)),
            TreeSize = 1
        });
    }

    private async Task CreateArchiveAsync(
        BundleManifest manifest,
        string sourceDir,
        string archivePath,
        BundleBuildOptions options,
        CancellationToken cancellationToken)
    {
        var compressionLevel = options.CompressionLevel switch
        {
            0 => CompressionLevel.NoCompression,
            < 4 => CompressionLevel.Fastest,
            < 7 => CompressionLevel.Optimal,
            _ => CompressionLevel.SmallestSize
        };

        using var archive = ZipFile.Open(archivePath, ZipArchiveMode.Create);

        // Add manifest
        var manifestEntry = archive.CreateEntry("manifest.json", compressionLevel);
        await using (var entryStream = manifestEntry.Open())
        {
            var manifestJson = JsonSerializer.Serialize(manifest, PrettyJsonOptions);
            await using var writer = new StreamWriter(entryStream, Encoding.UTF8, leaveOpen: true);
            await writer.WriteAsync(manifestJson).ConfigureAwait(false);
        }

        // Add symbol files
        foreach (var entry in manifest.Entries)
        {
            cancellationToken.ThrowIfCancellationRequested();

            // Find source manifest
            var manifestPath = Directory.GetFiles(sourceDir, $"{entry.DebugId}.symbols.json", SearchOption.AllDirectories)
                .FirstOrDefault();

            if (manifestPath is not null)
            {
                var manifestArchiveEntry = archive.CreateEntry($"{entry.ArchivePath}.json", compressionLevel);
                await using var manifestStream = manifestArchiveEntry.Open();
                await using var sourceStream = File.OpenRead(manifestPath);
                await sourceStream.CopyToAsync(manifestStream, cancellationToken).ConfigureAwait(false);
            }

            // Find source blob
            var blobPath = FindBlobPath(manifestPath ?? sourceDir, entry.DebugId);
            if (blobPath is not null && File.Exists(blobPath))
            {
                var blobArchiveEntry = archive.CreateEntry(entry.ArchivePath, compressionLevel);
                await using var blobStream = blobArchiveEntry.Open();
                await using var sourceStream = File.OpenRead(blobPath);
                await sourceStream.CopyToAsync(blobStream, cancellationToken).ConfigureAwait(false);
            }
        }
    }

    private static Task<SignatureStatus> VerifySignatureAsync(
        BundleManifest manifest,
        BundleVerifyOptions options,
        CancellationToken cancellationToken)
    {
        // TODO: Implement actual DSSE signature verification
        if (manifest.Signature is null || !manifest.Signature.Signed)
            return Task.FromResult(SignatureStatus.Unsigned);

        // For now, return valid if signature structure exists
        return Task.FromResult(SignatureStatus.Valid);
    }

    private static Task<RekorVerifyStatus> VerifyRekorOfflineAsync(
        RekorCheckpoint checkpoint,
        BundleVerifyOptions options,
        CancellationToken cancellationToken)
    {
        // TODO: Implement actual Merkle inclusion proof verification
        if (checkpoint.InclusionProof is null)
            return Task.FromResult(RekorVerifyStatus.NotPresent);

        // For now, return verified if proof structure exists
        return Task.FromResult(RekorVerifyStatus.VerifiedOffline);
    }

    private async Task<HashVerifyStatus> VerifyHashesAsync(
        string bundlePath,
        BundleManifest manifest,
        BundleVerifyOptions options,
        CancellationToken cancellationToken)
    {
        var validEntries = 0;
        var invalidEntries = new List<string>();

        using var archive = ZipFile.OpenRead(bundlePath);

        foreach (var entry in manifest.Entries)
        {
            cancellationToken.ThrowIfCancellationRequested();

            if (!options.VerifyBlobHashes)
            {
                validEntries++;
                continue;
            }

            var archiveEntry = archive.Entries.FirstOrDefault(e => e.FullName == entry.ArchivePath);
            if (archiveEntry is null)
            {
                invalidEntries.Add(entry.DebugId);
                continue;
            }

            await using var stream = archiveEntry.Open();
            using var sha256 = SHA256.Create();
            var computedHash = Convert.ToHexStringLower(await sha256.ComputeHashAsync(stream, cancellationToken)
                .ConfigureAwait(false));

            if (computedHash.Equals(entry.BlobHash, StringComparison.OrdinalIgnoreCase))
            {
                validEntries++;
            }
            else
            {
                invalidEntries.Add(entry.DebugId);
            }
        }

        return new HashVerifyStatus
        {
            BundleHashValid = invalidEntries.Count == 0,
            ValidEntries = validEntries,
            InvalidEntries = invalidEntries.Count,
            TotalEntries = manifest.Entries.Count,
            InvalidEntryIds = invalidEntries
        };
    }
}