package com.atlassian.asap.core.keys;
   
   import com.atlassian.asap.api.exception.CannotRetrieveKeyException;
   import com.atlassian.asap.core.SecurityProvider;
   import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo;
   import org.bouncycastle.openssl.PEMKeyPair;
   import org.bouncycastle.openssl.PEMParser;
   import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
   import org.bouncycastle.util.encoders.DecoderException;
  
  import java.io.IOException;
  import java.io.Reader;
  import java.security.PrivateKey;
  import java.security.Provider;
  import java.security.PublicKey;
  
  /**
   * Functions for reading PEM keys.
   */
  public class PemReader implements KeyReader {
  
      private final Provider provider;
  
      public PemReader() {
          this(SecurityProvider.getProvider());
      }
  
      public PemReader(Provider provider) {
          this.provider = provider;
      }
  
      /**
       * Reads a private key from a PEM file.
       *
       * @param reader source of the PEM data
       * @return the key
       * @throws CannotRetrieveKeyException if the key cannot be read, parsed, or the algorithm is unknown
       */
      public PrivateKey readPrivateKey(Reader reader) throws CannotRetrieveKeyException {
          try {
              PEMParser pemParser = new PEMParser(reader);
              Object keyPairObject = pemParser.readObject();
              if (keyPairObject instanceof PEMKeyPair) {
                  PEMKeyPair pemKeyPair = (PEMKeyPair) keyPairObject;
                  JcaPEMKeyConverter converter = new JcaPEMKeyConverter().setProvider(provider);
                  return converter.getPrivateKey(pemKeyPair.getPrivateKeyInfo());
              } else {
                  throw new CannotRetrieveKeyException("Error reading PEM private key, unknown key pair object type");
              }
          } catch (IOException | DecoderException e) {
              throw new CannotRetrieveKeyException("Error reading PEM private key", e);
          }
      }
  
      /**
       * Reads a public key from a PEM file.
       *
       * @param reader source of the PEM data
       * @return the key
       * @throws CannotRetrieveKeyException if the key cannot be read or parsed
       */
      public PublicKey readPublicKey(Reader reader) throws CannotRetrieveKeyException {
          try {
              PEMParser pemParser = new PEMParser(reader);
              Object object = pemParser.readObject();
  
              SubjectPublicKeyInfo pub = SubjectPublicKeyInfo.getInstance(object);
              JcaPEMKeyConverter converter = new JcaPEMKeyConverter().setProvider(provider);
  
              return converter.getPublicKey(pub);
          } catch (IOException | DecoderException e) {
              throw new CannotRetrieveKeyException("Error reading PEM public key", e);
          }
      }
  }