package com.atlassian.asap.core.keys.privatekey;
   
   import com.atlassian.asap.api.exception.CannotRetrieveKeyException;
   import com.atlassian.asap.core.keys.KeyProvider;
   import com.atlassian.asap.core.keys.KeyReader;
   import com.atlassian.asap.core.validator.ValidatedKeyId;
   import com.google.common.base.Preconditions;
   import org.slf4j.Logger;
   import org.slf4j.LoggerFactory;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.nio.charset.StandardCharsets;
  import java.security.PrivateKey;
  import java.util.Objects;
  
  import static com.atlassian.asap.core.keys.ClassPathUri.classPathUri;
  
  /**
   * Retrieves private keys from the classpath.
   */
  public class ClasspathPrivateKeyProvider implements KeyProvider<PrivateKey> {
      private static final Logger logger = LoggerFactory.getLogger(ClasspathPrivateKeyProvider.class);
  
      private final KeyReader keyReader;
      private final String classpathBase;
  
      /**
       * Create instance of ClasspathPrivateKeyProvider that reads private keys under the given classpath base.
       */
      public ClasspathPrivateKeyProvider(String classpathBase, KeyReader keyReader) {
          this.keyReader = Objects.requireNonNull(keyReader);
          this.classpathBase = Objects.requireNonNull(classpathBase);
          Preconditions.checkArgument(classpathBase.endsWith("/"), "Classpath prefix must end with a slash");
      }
  
      @Override
      public PrivateKey getKey(ValidatedKeyId validatedKeyId) throws CannotRetrieveKeyException {
          String pathToPrivateKey = classpathBase + validatedKeyId.getKeyId();
  
          logger.debug("Reading private key from classpath: {}", pathToPrivateKey);
  
          try (InputStream inputStream = ClasspathPrivateKeyProvider.class.getResourceAsStream(pathToPrivateKey)) {
              if (inputStream == null) {
                  throw new CannotRetrieveKeyException("Private key not found in the classpath", classPathUri(pathToPrivateKey));
              }
              try (InputStreamReader reader = new InputStreamReader(inputStream, StandardCharsets.US_ASCII)) {
                  return keyReader.readPrivateKey(reader);
              }
          } catch (IOException e) {
              throw new CannotRetrieveKeyException("Error retrieving private key from classpath", e, classPathUri(pathToPrivateKey));
          }
      }
  
      @Override
      public String toString() {
          return this.getClass().getSimpleName();
      }
  }