package com.atlassian.asap.core.keys.privatekey;
   
   import com.atlassian.asap.core.keys.DataUriKeyReader;
   import com.google.common.annotations.VisibleForTesting;
   import org.slf4j.Logger;
   import org.slf4j.LoggerFactory;
   
   import java.net.URI;
   import java.net.URISyntaxException;
  import java.util.Optional;
  
  import static com.google.common.base.Preconditions.checkArgument;
  
  /**
   * Reads private keys specified as data uri from environment variables.
   *
   * <p>Note that Environment variables are case-insensitive in some systems (Windows). However, ASAP key identifiers are case-sensitive.
   * That means that the same environment variable will provide the private key for "keyidentifier", "KEYIDENTIFIER", "keyIdentifier" and so on.
   *
   * @see System#getenv(String)
   */
  public final class EnvironmentVariableKeyProvider extends DataUriKeyProvider {
      static final String URL_SCHEME = "env";
      private static final Logger logger = LoggerFactory.getLogger(EnvironmentVariableKeyProvider.class);
  
      @VisibleForTesting
      EnvironmentVariableKeyProvider(String variableName, DataUriKeyReader keyReader, Environment environment) {
          super(getDataUriFromEnvironment(variableName, environment), keyReader);
      }
  
      private static URI getDataUriFromEnvironment(String variableName, Environment environment) {
          logger.debug("Reading private key from environment variable {}", variableName);
          String environmentVariableValue = environment.getVariable(variableName)
                  .orElseThrow(() -> new IllegalArgumentException("Undefined environment variable: " + variableName));
          try {
              return new URI(environmentVariableValue);
          } catch (URISyntaxException e) {
              throw new IllegalArgumentException("Value of environment variable " + variableName +
                      " cannot be parsed as a URI");
          }
      }
  
      /**
       * Instantiates the class by parsing a URL with the following syntax:
       * <code>env:///[BASE_ENV_VARIABLE_NAME]</code>.
       *
       * @param uri       URI with the syntax described above
       * @param keyReader reader of PEM documents
       * @return a new instance of the class
       */
      public static EnvironmentVariableKeyProvider fromUri(URI uri, DataUriKeyReader keyReader) {
          return fromUri(uri, keyReader, new Environment());
      }
  
      @VisibleForTesting
      static EnvironmentVariableKeyProvider fromUri(URI uri, DataUriKeyReader keyReader, Environment environment) {
          checkArgument(uri.isAbsolute(), "URL must be absolute"); // implies that scheme != null
          checkArgument(URL_SCHEME.equals(uri.getScheme()), "URL must have " + URL_SCHEME + " scheme");
          checkArgument(uri.getPath() != null && uri.getPath().startsWith("/"), "URL must have a path component");
          checkArgument(uri.getQuery() == null, "URL must not have a query component");
          checkArgument(uri.getAuthority() == null, "URL must not have an authority component");
  
          String basePropertyName = uri.getPath().substring(1); // remove the trailing slash
          return new EnvironmentVariableKeyProvider(basePropertyName, keyReader, environment);
      }
  
      static class Environment {
          public Optional<String> getVariable(String name) {
              return Optional.ofNullable(System.getenv(name));
          }
      }
  }