lib/options.dart

// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

part of protoc;

/// Helper function implementing a generic option parser that reads
/// `request.parameters` and treats each token as either a flag ("name") or a
/// key-value pair ("name=value"). For each option "name", it looks up whether a
/// [SingleOptionParser] exists in [parsers] and delegates the actual parsing of
/// the option to it. Returns `true` if no errors were reported.
bool genericOptionsParser(
    CodeGeneratorRequest request, CodeGeneratorResponse response,
    Map<String, SingleOptionParser> parsers) {
  var parameter = request.parameter != null ? request.parameter : '';
  var options = parameter.trim().split(',');
  var map = <String, String>{};
  var errors = [];

  for (var option in options) {
    option = option.trim();
    if (option.isEmpty) continue;
    var reportError = (details) {
      errors.add('Error found trying to parse the option: $option.\n$details');
    };

    var nameValue = option.split('=');
    if (nameValue.length != 1 && nameValue.length != 2) {
      reportError('Options should be a single token, or a name=value pair');
      continue;
    }
    var name = nameValue[0].trim();
    var parser = parsers[name];
    if (parser == null) {
      reportError('Unknown option ($name).');
      continue;
    }

    var value = nameValue.length > 1 ? nameValue[1].trim() : null;
    parser.parse(name, value, reportError);
  }

  if (errors.length == 0) return true;

  response.error = errors.join('\n');
  return false;
}

/// Options expected by the protoc code generation compiler.
class GenerationOptions {
  /// Maps a fully qualified field name, to the desired name we wish to
  /// generate. For example `MyMessage.has_field` to `HasFld`.
  final Map<String, String> fieldNameOverrides;

  GenerationOptions(this.fieldNameOverrides);
}

/// A parser for a name-value pair option. Options parsed in
/// [genericOptionsParser] delegate to instances of this class to
/// parse the value of a specific option.
abstract class SingleOptionParser {

  /// Parse the [name]=[value] value pair and report any errors to [onError]. If
  /// the option is a flag, [value] will be null. Note, [name] is commonly
  /// unused. It is provided because [SingleOptionParser] can be registered for
  /// multiple option names in [genericOptionsParser].
  void parse(String name, String value, onError(String details));
}

/// Parser used by the compiler, which supports the `field_name` option (see
/// [FieldNameOptionParser]) and any additional option added in [parsers]. If
/// [parsers] has a key for `field_name`, it will be ignored.
GenerationOptions parseGenerationOptions(
    CodeGeneratorRequest request, CodeGeneratorResponse response,
    [Map<String, SingleOptionParser> parsers]) {
  var fieldNameOptionParser = new FieldNameOptionParser();
  var map = {};
  if (parsers != null) parsers.forEach((k, v) { map[k] = v; });
  map['field_name'] = fieldNameOptionParser;
  if (genericOptionsParser(request, response, map)) {
    return new GenerationOptions(fieldNameOptionParser.mappings);
  }
  return null;
}

/// A [SingleOptionParser] to parse the `field_name` option. This option
/// overrides the default name given to some fields that would otherwise collide
/// with existing field names in Dart core objects or in [GeneratedMessage].
/// (see `README.md` for details).
class FieldNameOptionParser implements SingleOptionParser {
  /// Maps a fully qualified field name, to the desired name we wish to
  /// generate. For example `MyMessage.has_field` to `HasFld`.
  final Map<String, String> mappings = {};

  void parse(String name, String value, onError(String message)) {
    if (value == null) {
      onError('Invalid field_name option, expected a non-emtpy value.');
      return;
    }

    List<String> fromTo = value.split('|');
    if (fromTo.length != 2) {
      onError('Invalid field_name option, expected a single "|" separator.');
      return;
    }

    var fromName = fromTo[0].trim();
    var toName = fromTo[1].trim();
    if (fromName.isEmpty || toName.isEmpty) {
      onError('Invalid field_name option, '
          '"from" and "to" names should not be empty.');
      return;
    }

    mappings['.$fromName'] = toName;
  }
}