package civitas.crypto;
   
   import java.security.NoSuchAlgorithmException;
   import java.security.NoSuchProviderException;
   import java.util.HashMap;
   import java.util.Map;
   
   import javax.crypto.KeyGenerator;
   
  import org.springframework.stereotype.Service;
  
  @Service
  public class GetSharedKeyGeneratorService {
  	private final Map<String, KeyGenerator> sharedKeyGenerators = new HashMap<>();
  
  	public KeyGenerator apply(final int keyLength) {
  		String genKey = String.valueOf(keyLength);
  		KeyGenerator g = sharedKeyGenerators.get(genKey);
  		if (g != null) {
  			return g;
  		}
  		try {
  			g = KeyGenerator.getInstance(Constants.SHARED_KEY_ALG, Constants.SHARED_KEY_PROVIDER);
  		} catch (NoSuchAlgorithmException | NoSuchProviderException impossible) {
  			throw new CryptoError(impossible);
  		}
  
  		g.init(keyLength);
  		sharedKeyGenerators.put(genKey, g);
  		return g;
  	}
  }