package cn.home1.oss.lib.common.crypto;
   
   import static com.google.common.base.Preconditions.checkArgument;
   
   import lombok.Getter;
   
   /**
    * Created by zhanghaolun on 16/11/17.
    */
  public class AesKeyGenerator implements KeyGenerator {
  
    @Getter
    private final String spec;
    private KeyExpression key;
  
    public AesKeyGenerator(final String spec) {
      this.spec = spec;
    }
  
    @Override
    public KeyExpression generateKey() {
      this.key = AesKeyGenerator.generateAesKey(this.spec);
      return this.key;
    }
  
    @Override
    public KeyExpression getKey(final String spec) {
      checkArgument(this.spec.equals(spec), "spec " + spec + " not supported.");
      if (this.key == null) {
        this.generateKey();
      }
      return this.key;
    }
  
    public static KeyExpression generateAesKey(final String spec) {
      final int keySize = AesCbcKey.keySize(spec);
      final String value;
      if (keySize == 256) {
        value = RandomString.RandomStrings.RANDOM_BASE62.generate(43) + "="; // 32bytes after decoded
      } else {
        throw new IllegalArgumentException("unsupported spec " + spec);
      }
      return new KeyExpression(spec, value);
    }
  }