using System.Runtime.InteropServices;
using ProtonVPN.OperatingSystems.WebAuthn.Enums;
using ProtonVPN.OperatingSystems.WebAuthn.Interop.Marshalers;
using ProtonVPN.OperatingSystems.WebAuthn.Interop.StructVersions;

namespace ProtonVPN.OperatingSystems.WebAuthn.Interop.Structs.GetAssertion;

/// <summary>
/// Assertion
/// </summary>
/// <remarks>Corresponds to WEBAUTHN_ASSERTION.</remarks>
[StructLayout(LayoutKind.Sequential)]
public sealed class Assertion
{
    /// <summary>
    /// // Version of this structure, to allow for modifications in the future.
    /// </summary>
    public AssertionVersion Version { get; private set; }

    /// <summary>
    /// The size of the authenticator data.
    /// </summary>
    private int _authenticatorDataLength;

    /// <summary>
    /// A pointer to the authenticator data.
    /// </summary>
    private ByteArrayOut _authenticatorData;

    /// <summary>
    /// The size of the signature that was generated for this assertion.
    /// </summary>
    private int _signatureLength;

    /// <summary>
    /// A pointer to the signature that was generated for this assertion.
    /// </summary>
    private ByteArrayOut _signature;

    /// <summary>
    /// The credential that was used for this assertion.
    /// </summary>
    public CredentialOut Credential { get; private set; }

    /// <summary>
    /// The size of the user Id.
    /// </summary>
    private int _userIdLength;

    /// <summary>
    /// A pointer to the user Id.
    /// </summary>
    private ByteArrayOut _userId;

    /// <summary>
    /// A CBOR map from extension identifiers to their authenticator extension inputs,
    /// created by the client based on the extensions requested by the Relying Party, if any.
    /// </summary>
    /// <remarks>This field has been added in WEBAUTHN_ASSERTION_VERSION_2.</remarks>
    public ExtensionsOut Extensions { get; private set; }

    /// <summary>
    /// Size of the Large Blob
    /// </summary>
    /// <remarks>This field has been added in WEBAUTHN_ASSERTION_VERSION_2.</remarks>
    private int _largeBlobLength;

    /// <summary>
    /// A pointer to the credential blob.
    /// </summary>
    /// <remarks>This field has been added in WEBAUTHN_ASSERTION_VERSION_2.</remarks>
    private ByteArrayOut _largeBlob;

    /// <summary>
    /// Status of the credential blob.
    /// </summary>
    /// <remarks>This field has been added in WEBAUTHN_ASSERTION_VERSION_2.</remarks>
    public CredentialLargeBlobStatus LargeBlobStatus { get; private set; }

    /// <summary>
    /// A salt used to generate the HMAC secret.
    /// </summary>
    /// <remarks>This field has been added in WEBAUTHN_ASSERTION_VERSION_3.</remarks>
    private nint _hmacSecret;

    /// <summary>
    /// The transport that was used.
    /// </summary>
    /// <remarks>This field has been added in WEBAUTHN_ASSERTION_VERSION_4.</remarks>
    public AuthenticatorTransport UsedTransport { get; private set; }

    /// <remarks>This field has been added in WEBAUTHN_ASSERTION_VERSION_5.</remarks>
    private int _unsignedExtensionOutputsLength;

    /// <remarks>This field has been added in WEBAUTHN_ASSERTION_VERSION_5.</remarks>
    private ByteArrayOut _unsignedExtensionOutputs;

    /// <summary>
    /// Authenticator data that was created for this assertion.
    /// </summary>
    public byte[] AuthenticatorData => _authenticatorData?.Read(_authenticatorDataLength);

    /// <summary>
    /// Signature that was generated for this assertion.
    /// </summary>
    public byte[] Signature => _signature?.Read(_signatureLength);

    /// <summary>
    /// User Identifier
    /// </summary>
    public byte[] UserId => _userId?.Read(_userIdLength);

    /// <summary>
    /// Credential Large Blob
    /// </summary>
    public byte[] LargeBlob => _largeBlob?.Read(_largeBlobLength);

    /// <summary>
    /// Unsigned extension outputs.
    /// </summary>
    /// <remarks>This field has been added in WEBAUTHN_ASSERTION_VERSION_5.</remarks>
    public byte[] UnsignedExtensionOutputs => _unsignedExtensionOutputs?.Read(_unsignedExtensionOutputsLength);

    /// <summary>
    /// A salt used to generate the HMAC secret.
    /// </summary>
    /// <remarks>This field has been added in WEBAUTHN_ASSERTION_VERSION_3.</remarks>
    public HmacSecretSaltOut HmacSecret
    {
        get
        {
            if (_hmacSecret == nint.Zero)
            {
                return null;
            }

            return Marshal.PtrToStructure<HmacSecretSaltOut>(_hmacSecret);
        }
    }
}