using Org.BouncyCastle.Security;
using Org.BouncyCastle.X509;
using StellaOps.Cryptography.Plugin.Eidas.Timestamping;
using StellaOps.Plugin.Abstractions;
using StellaOps.Plugin.Abstractions.Capabilities;
using StellaOps.Plugin.Abstractions.Context;
using StellaOps.Plugin.Abstractions.Health;
using StellaOps.Plugin.Abstractions.Lifecycle;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using X509Certificate = Org.BouncyCastle.X509.X509Certificate;

namespace StellaOps.Cryptography.Plugin.Eidas;


/// <summary>
/// eIDAS cryptography plugin for EU qualified electronic signatures.
/// Implements ETSI TS 119 312 compliant signature operations.
/// </summary>
public sealed class EidasPlugin : CryptoPluginBase
{
    private EidasOptions? _options;
    private X509Certificate2? _signingCertificate;
    private X509Certificate? _bcCertificate;
    private RSA? _privateKey;
    private ICadesSignatureBuilder? _cadesBuilder;
    private ITimestampModeSelector? _timestampModeSelector;
    private IQualifiedTimestampVerifier? _timestampVerifier;
    private QualifiedTimestampingConfiguration? _timestampingConfiguration;

    /// <inheritdoc />
    public override PluginInfo Info => new(
        Id: "com.stellaops.crypto.eidas",
        Name: "eIDAS Cryptography Provider",
        Version: "1.0.0",
        Vendor: "Stella Ops",
        Description: "EU eIDAS qualified electronic signatures (ETSI TS 119 312)",
        LicenseId: "BUSL-1.1");

    /// <inheritdoc />
    public override IReadOnlyList<string> SupportedAlgorithms => new[]
    {
        "eIDAS-RSA-SHA256",
        "eIDAS-RSA-SHA384",
        "eIDAS-RSA-SHA512",
        "eIDAS-ECDSA-SHA256",
        "eIDAS-ECDSA-SHA384",
        "eIDAS-CAdES-BES",
        "eIDAS-CAdES-T",
        "eIDAS-CAdES-LT",
        "eIDAS-CAdES-LTA",
        "eIDAS-XAdES-BES"
    };

    /// <inheritdoc />
    protected override Task InitializeCryptoServiceAsync(IPluginContext context, CancellationToken ct)
    {
        _options = context.Configuration.Bind<EidasOptions>() ?? new EidasOptions();

        if (!string.IsNullOrEmpty(_options.CertificatePath))
        {
            LoadCertificate(_options.CertificatePath, _options.CertificatePassword);
            Context?.Logger.Info("eIDAS provider initialized with certificate from {Path}", _options.CertificatePath);
        }
        else if (!string.IsNullOrEmpty(_options.CertificateThumbprint))
        {
            LoadCertificateFromStore(_options.CertificateThumbprint, _options.CertificateStoreLocation);
            Context?.Logger.Info("eIDAS provider initialized with certificate from store");
        }
        else
        {
            Context?.Logger.Warning("eIDAS provider initialized without certificate - signing operations will fail");
        }

        _timestampingConfiguration = context.Configuration.Bind<QualifiedTimestampingConfiguration>("timestamping")
            ?? new QualifiedTimestampingConfiguration();
        _cadesBuilder = context.Services.GetService<ICadesSignatureBuilder>();
        _timestampModeSelector = context.Services.GetService<ITimestampModeSelector>();
        _timestampVerifier = context.Services.GetService<IQualifiedTimestampVerifier>();

        return Task.CompletedTask;
    }

    /// <inheritdoc />
    public override bool CanHandle(CryptoOperation operation, string algorithm)
    {
        return algorithm.StartsWith("eIDAS", StringComparison.OrdinalIgnoreCase) &&
               SupportedAlgorithms.Contains(algorithm, StringComparer.OrdinalIgnoreCase);
    }

    /// <inheritdoc />
    public override async Task<byte[]> SignAsync(ReadOnlyMemory<byte> data, CryptoSignOptions options, CancellationToken ct)
    {
        EnsureActive();
        ct.ThrowIfCancellationRequested();

        if (_signingCertificate == null || _privateKey == null)
        {
            throw new InvalidOperationException("No signing certificate configured.");
        }

        var algorithm = options.Algorithm;
        byte[] signature;

        if (algorithm.Contains("CAdES", StringComparison.OrdinalIgnoreCase))
        {
            signature = await SignCadesAsync(data, options, ct).ConfigureAwait(false);
        }
        else if (algorithm.Contains("ECDSA", StringComparison.OrdinalIgnoreCase))
        {
            throw new NotSupportedException("ECDSA not yet implemented for eIDAS. Use RSA algorithms.");
        }
        else
        {
            // Standard RSA signature
            var hashAlgorithm = GetHashAlgorithmName(algorithm);
            signature = _privateKey.SignData(data.ToArray(), hashAlgorithm, RSASignaturePadding.Pkcs1);
        }

        Context?.Logger.Debug("Signed {DataLength} bytes with {Algorithm}", data.Length, algorithm);

        return signature;
    }

    /// <inheritdoc />
    public override async Task<bool> VerifyAsync(ReadOnlyMemory<byte> data, ReadOnlyMemory<byte> signature, CryptoVerifyOptions options, CancellationToken ct)
    {
        EnsureActive();
        ct.ThrowIfCancellationRequested();

        var algorithm = options.Algorithm;
        bool isValid;

        if (algorithm.Contains("CAdES", StringComparison.OrdinalIgnoreCase))
        {
            isValid = await VerifyCadesSignatureAsync(data, signature, options, ct).ConfigureAwait(false);
        }
        else
        {
            // Load verification certificate
            X509Certificate2 verificationCert;
            if (!string.IsNullOrEmpty(options.CertificateChain))
            {
                verificationCert = X509CertificateLoader.LoadCertificate(Convert.FromBase64String(options.CertificateChain));
            }
            else if (_signingCertificate != null)
            {
                verificationCert = _signingCertificate;
            }
            else
            {
                throw new InvalidOperationException("No verification certificate available.");
            }

            using var rsa = verificationCert.GetRSAPublicKey();
            if (rsa == null)
            {
                throw new InvalidOperationException("Certificate does not contain RSA public key.");
            }

            var hashAlgorithm = GetHashAlgorithmName(algorithm);
            isValid = rsa.VerifyData(data.ToArray(), signature.ToArray(), hashAlgorithm, RSASignaturePadding.Pkcs1);
        }

        Context?.Logger.Debug("Verified signature: {IsValid}", isValid);

        return isValid;
    }

    private async Task<byte[]> SignCadesAsync(ReadOnlyMemory<byte> data, CryptoSignOptions options, CancellationToken ct)
    {
        if (_signingCertificate == null)
        {
            throw new InvalidOperationException("Certificate not loaded for CAdES signing.");
        }

        var timestampContext = BuildTimestampContext(options.Metadata);
        var policy = ResolveTimestampPolicy(timestampContext);
        var requestedLevel = ResolveCadesLevel(options.Algorithm, policy);
        var provider = FindProvider(policy.TsaProvider);
        var signatureOptions = new CadesSignatureOptions
        {
            DigestAlgorithm = ResolveDigestAlgorithm(options.Algorithm),
            TsaProvider = provider?.Name ?? policy.TsaProvider,
            TsaUrl = provider?.Url ?? _options?.TimestampAuthorityUrl,
            RequireQualifiedTsa = policy.IsQualified,
            IncludeRevocationData = requestedLevel >= CadesLevel.CadesLT
        };

        if (_cadesBuilder is null)
        {
            Context?.Logger.Warning("CAdES builder not available; falling back to CAdES-BES.");
            return CreateCadesSignature(data.ToArray());
        }

        return requestedLevel switch
        {
            CadesLevel.CadesB => await _cadesBuilder.CreateCadesBAsync(data, _signingCertificate, signatureOptions, ct).ConfigureAwait(false),
            CadesLevel.CadesT => await _cadesBuilder.CreateCadesTAsync(data, _signingCertificate, signatureOptions, ct).ConfigureAwait(false),
            CadesLevel.CadesLT => await _cadesBuilder.CreateCadesLTAsync(data, _signingCertificate, signatureOptions, ct).ConfigureAwait(false),
            CadesLevel.CadesLTA => await _cadesBuilder.CreateCadesLTAAsync(data, _signingCertificate, signatureOptions, ct).ConfigureAwait(false),
            CadesLevel.CadesC => await _cadesBuilder.CreateCadesLTAsync(data, _signingCertificate, signatureOptions, ct).ConfigureAwait(false),
            _ => await _cadesBuilder.CreateCadesBAsync(data, _signingCertificate, signatureOptions, ct).ConfigureAwait(false)
        };
    }

    private async Task<bool> VerifyCadesSignatureAsync(
        ReadOnlyMemory<byte> data,
        ReadOnlyMemory<byte> signature,
        CryptoVerifyOptions options,
        CancellationToken ct)
    {
        if (_timestampVerifier is null)
        {
            return VerifyCadesSignature(data.ToArray(), signature.ToArray());
        }

        var requestedLevel = ResolveCadesLevel(options.Algorithm, ResolveTimestampPolicy(BuildTimestampContext(null)));
        var mode = _options?.TimestampMode ?? _timestampingConfiguration?.DefaultMode ?? TimestampMode.Rfc3161;
        var verifyOptions = new QualifiedTimestampVerificationOptions
        {
            RequireQualifiedTsa = mode == TimestampMode.Qualified || mode == TimestampMode.QualifiedLtv,
            VerifyLtvCompleteness = requestedLevel >= CadesLevel.CadesLT
        };

        var result = await _timestampVerifier.VerifyCadesAsync(signature, data, verifyOptions, ct).ConfigureAwait(false);
        return result.IsSignatureValid;
    }

    private TimestampPolicy ResolveTimestampPolicy(TimestampContext context)
    {
        if (_timestampModeSelector is not null)
        {
            return _timestampModeSelector.GetPolicy(context);
        }

        var mode = _options?.TimestampMode ?? _timestampingConfiguration?.DefaultMode ?? TimestampMode.Rfc3161;
        var provider = ResolveDefaultProvider(mode);

        return new TimestampPolicy
        {
            Mode = mode,
            TsaProvider = provider,
            SignatureFormat = _options?.SignatureFormat ?? CadesLevel.CadesT,
            MatchedPolicy = "options"
        };
    }

    private TimestampContext BuildTimestampContext(IReadOnlyDictionary<string, string>? metadata)
    {
        if (metadata is null)
        {
            return new TimestampContext();
        }

        metadata.TryGetValue("environment", out var environment);
        metadata.TryGetValue("repository", out var repository);
        metadata.TryGetValue("tags", out var tagsValue);
        metadata.TryGetValue("artifactType", out var artifactType);
        metadata.TryGetValue("artifactDigest", out var artifactDigest);

        return new TimestampContext
        {
            Environment = environment,
            Repository = repository,
            Tags = ParseTags(tagsValue),
            ArtifactType = artifactType,
            ArtifactDigest = artifactDigest,
            Properties = metadata
        };
    }

    private QualifiedTsaProvider? FindProvider(string providerName)
    {
        return _timestampingConfiguration?.Providers
            .FirstOrDefault(p => p.Name.Equals(providerName, StringComparison.OrdinalIgnoreCase));
    }

    private string ResolveDefaultProvider(TimestampMode mode)
    {
        var isQualified = mode == TimestampMode.Qualified || mode == TimestampMode.QualifiedLtv;
        var provider = _timestampingConfiguration?.Providers
            .FirstOrDefault(p => p.Qualified == isQualified);
        return provider?.Name ?? _timestampingConfiguration?.Providers.FirstOrDefault()?.Name ?? "default";
    }

    private static IReadOnlyList<string>? ParseTags(string? tagsValue)
    {
        if (string.IsNullOrWhiteSpace(tagsValue))
        {
            return null;
        }

        return tagsValue
            .Split([',', ';'], StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries)
            .Distinct(StringComparer.OrdinalIgnoreCase)
            .ToList();
    }

    private static string ResolveDigestAlgorithm(string algorithm)
    {
        if (algorithm.Contains("512", StringComparison.OrdinalIgnoreCase))
        {
            return "SHA512";
        }

        if (algorithm.Contains("384", StringComparison.OrdinalIgnoreCase))
        {
            return "SHA384";
        }

        return "SHA256";
    }

    private static CadesLevel ResolveCadesLevel(string algorithm, TimestampPolicy policy)
    {
        var level = algorithm switch
        {
            var a when a.Contains("CAdES-LTA", StringComparison.OrdinalIgnoreCase) => CadesLevel.CadesLTA,
            var a when a.Contains("CAdES-LT", StringComparison.OrdinalIgnoreCase) => CadesLevel.CadesLT,
            var a when a.Contains("CAdES-T", StringComparison.OrdinalIgnoreCase) => CadesLevel.CadesT,
            var a when a.Contains("CAdES-B", StringComparison.OrdinalIgnoreCase) => CadesLevel.CadesB,
            _ => policy.SignatureFormat
        };

        if (policy.Mode == TimestampMode.None)
        {
            return CadesLevel.CadesB;
        }

        return level;
    }

    /// <inheritdoc />
    public override Task<byte[]> EncryptAsync(ReadOnlyMemory<byte> data, CryptoEncryptOptions options, CancellationToken ct)
    {
        EnsureActive();
        ct.ThrowIfCancellationRequested();

        if (_signingCertificate == null)
        {
            throw new InvalidOperationException("No certificate configured for encryption.");
        }

        using var rsa = _signingCertificate.GetRSAPublicKey()
            ?? throw new InvalidOperationException("Certificate does not contain RSA public key.");

        var encrypted = rsa.Encrypt(data.ToArray(), RSAEncryptionPadding.OaepSHA256);

        Context?.Logger.Debug("Encrypted {DataLength} bytes", data.Length);

        return Task.FromResult(encrypted);
    }

    /// <inheritdoc />
    public override Task<byte[]> DecryptAsync(ReadOnlyMemory<byte> data, CryptoDecryptOptions options, CancellationToken ct)
    {
        EnsureActive();
        ct.ThrowIfCancellationRequested();

        if (_privateKey == null)
        {
            throw new InvalidOperationException("No private key configured for decryption.");
        }

        var decrypted = _privateKey.Decrypt(data.ToArray(), RSAEncryptionPadding.OaepSHA256);

        Context?.Logger.Debug("Decrypted {DataLength} bytes", data.Length);

        return Task.FromResult(decrypted);
    }

    /// <inheritdoc />
    public override Task<byte[]> HashAsync(ReadOnlyMemory<byte> data, string algorithm, CancellationToken ct)
    {
        EnsureActive();
        ct.ThrowIfCancellationRequested();

        byte[] hash = algorithm.ToUpperInvariant() switch
        {
            var a when a.Contains("512") => SHA512.HashData(data.Span),
            var a when a.Contains("384") => SHA384.HashData(data.Span),
            _ => SHA256.HashData(data.Span)
        };

        Context?.Logger.Debug("Computed hash of {DataLength} bytes", data.Length);

        return Task.FromResult(hash);
    }

    /// <inheritdoc />
    public override ValueTask DisposeAsync()
    {
        _privateKey?.Dispose();
        _signingCertificate?.Dispose();
        _privateKey = null;
        _signingCertificate = null;
        _bcCertificate = null;
        State = PluginLifecycleState.Stopped;
        return ValueTask.CompletedTask;
    }

    private void LoadCertificate(string path, string? password)
    {
        _signingCertificate = X509CertificateLoader.LoadPkcs12FromFile(path, password, X509KeyStorageFlags.Exportable);
        _privateKey = _signingCertificate.GetRSAPrivateKey();
        _bcCertificate = DotNetUtilities.FromX509Certificate(_signingCertificate);
    }

    private void LoadCertificateFromStore(string thumbprint, StoreLocation storeLocation)
    {
        using var store = new X509Store(StoreName.My, storeLocation);
        store.Open(OpenFlags.ReadOnly);

        var certs = store.Certificates.Find(X509FindType.FindByThumbprint, thumbprint, validOnly: false);
        if (certs.Count == 0)
        {
            throw new InvalidOperationException($"Certificate with thumbprint {thumbprint} not found in store.");
        }

        _signingCertificate = certs[0];
        _privateKey = _signingCertificate.GetRSAPrivateKey();
        _bcCertificate = DotNetUtilities.FromX509Certificate(_signingCertificate);
    }

    private byte[] CreateCadesSignature(byte[] data)
    {
        if (_signingCertificate == null || _privateKey == null)
        {
            throw new InvalidOperationException("Certificate not loaded for CAdES signing.");
        }

        // Simplified CAdES-BES: Use .NET CMS for signing
        // For full CAdES compliance, a dedicated library like iText or DSS should be used
        var contentInfo = new System.Security.Cryptography.Pkcs.ContentInfo(data);
        var signedCms = new System.Security.Cryptography.Pkcs.SignedCms(contentInfo, detached: true);
        var signer = new System.Security.Cryptography.Pkcs.CmsSigner(_signingCertificate)
        {
            DigestAlgorithm = new Oid("2.16.840.1.101.3.4.2.1") // SHA-256
        };
        signedCms.ComputeSignature(signer);

        return signedCms.Encode();
    }

    private bool VerifyCadesSignature(byte[] data, byte[] signature)
    {
        try
        {
            // Use .NET CMS verification
            var contentInfo = new System.Security.Cryptography.Pkcs.ContentInfo(data);
            var signedCms = new System.Security.Cryptography.Pkcs.SignedCms(contentInfo, detached: true);
            signedCms.Decode(signature);
            signedCms.CheckSignature(verifySignatureOnly: true);
            return true;
        }
        catch
        {
            return false;
        }
    }

    private static HashAlgorithmName GetHashAlgorithmName(string algorithm)
    {
        return algorithm.ToUpperInvariant() switch
        {
            var a when a.Contains("SHA512") => HashAlgorithmName.SHA512,
            var a when a.Contains("SHA384") => HashAlgorithmName.SHA384,
            _ => HashAlgorithmName.SHA256
        };
    }
}

/// <summary>
/// Configuration options for eIDAS cryptography plugin.
/// </summary>
public sealed class EidasOptions
{
    /// <summary>
    /// Path to PKCS#12/PFX certificate file.
    /// </summary>
    public string? CertificatePath { get; init; }

    /// <summary>
    /// Password for the certificate file.
    /// </summary>
    public string? CertificatePassword { get; init; }

    /// <summary>
    /// Certificate thumbprint for loading from Windows certificate store.
    /// </summary>
    public string? CertificateThumbprint { get; init; }

    /// <summary>
    /// Certificate store location (CurrentUser or LocalMachine).
    /// </summary>
    public StoreLocation CertificateStoreLocation { get; init; } = StoreLocation.CurrentUser;

    /// <summary>
    /// Trusted timestamp authority URL for qualified signatures.
    /// </summary>
    public string? TimestampAuthorityUrl { get; init; }

    /// <summary>
    /// Timestamp mode to use (Rfc3161, Qualified, QualifiedLtv).
    /// </summary>
    public TimestampMode? TimestampMode { get; init; }

    /// <summary>
    /// CAdES signature format level.
    /// </summary>
    public CadesLevel? SignatureFormat { get; init; }

    /// <summary>
    /// Whether to validate certificate chain during operations.
    /// </summary>
    public bool ValidateCertificateChain { get; init; } = true;
}