using IdentityShroud.Core.Contracts;
using IdentityShroud.Core.Security;

namespace IdentityShroud.Core.Services;

/// <summary>
/// 
/// </summary>
public class DekEncryptionService : IDekEncryptionService
{
    // Note this array is expected to have one item in it most of the during key rotation it will have two
    // until it is ensured the old key can safely be removed. More then two will work but is not really expected.
    private readonly KeyEncryptionKey[] _encryptionKeys;

    private KeyEncryptionKey ActiveKey => _encryptionKeys.Single(k => k.Active);
    private KeyEncryptionKey GetKey(KekId keyId) => _encryptionKeys.Single(k => k.Id == keyId);

    public DekEncryptionService(ISecretProvider secretProvider)
    {
        _encryptionKeys = secretProvider.GetKeys("master");
    }

    public EncryptedDek Encrypt(ReadOnlySpan<byte> plaintext)
    {
        var encryptionKey = ActiveKey;
        byte[] cipher = Encryption.Encrypt(plaintext, encryptionKey.Key);
        return new (encryptionKey.Id, cipher);
    }

    public void Decrypt(EncryptedDek input, Span<byte> output)
    {
        var encryptionKey = GetKey(input.KekId);
        Encryption.Decrypt(input.Value, encryptionKey.Key, output);
    }

    public int GetDecryptedSize(EncryptedDek input)
    {
        return Encryption.GetDecryptedLength(input.Value);
    }
}