// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// http://code.google.com/p/protobuf/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
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// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
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package akka.protobuf;

import java.util.Collections;
import java.util.List;

/**
 * Thrown when attempting to build a protocol message that is missing required
 * fields.  This is a {@code RuntimeException} because it normally represents
 * a programming error:  it happens when some code which constructs a message
 * fails to set all the fields.  {@code parseFrom()} methods <b>do not</b>
 * throw this; they throw an {@link InvalidProtocolBufferException} if
 * required fields are missing, because it is not a programming error to
 * receive an incomplete message.  In other words,
 * {@code UninitializedMessageException} should never be thrown by correct
 * code, but {@code InvalidProtocolBufferException} might be.
 *
 * @author kenton@google.com Kenton Varda
 */
public class UninitializedMessageException extends RuntimeException {
  private static final long serialVersionUID = -7466929953374883507L;

  public UninitializedMessageException(final MessageLite message) {
    super("Message was missing required fields.  (Lite runtime could not " +
          "determine which fields were missing).");
    missingFields = null;
  }

  public UninitializedMessageException(final List<String> missingFields) {
    super(buildDescription(missingFields));
    this.missingFields = missingFields;
  }

  private final List<String> missingFields;

  /**
   * Get a list of human-readable names of required fields missing from this
   * message.  Each name is a full path to a field, e.g. "foo.bar[5].baz".
   * Returns null if the lite runtime was used, since it lacks the ability to
   * find missing fields.
   */
  public List<String> getMissingFields() {
    return Collections.unmodifiableList(missingFields);
  }

  /**
   * Converts this exception to an {@link InvalidProtocolBufferException}.
   * When a parsed message is missing required fields, this should be thrown
   * instead of {@code UninitializedMessageException}.
   */
  public InvalidProtocolBufferException asInvalidProtocolBufferException() {
    return new InvalidProtocolBufferException(getMessage());
  }

  /** Construct the description string for this exception. */
  private static String buildDescription(final List<String> missingFields) {
    final StringBuilder description =
      new StringBuilder("Message missing required fields: ");
    boolean first = true;
    for (final String field : missingFields) {
      if (first) {
        first = false;
      } else {
        description.append(", ");
      }
      description.append(field);
    }
    return description.toString();
  }
}
