platform/packages/seeder/lib/angel_seeder.dart

import 'dart:math';
import 'package:angel_framework/angel_framework.dart';
import 'package:faker/faker.dart';
export 'package:faker/faker.dart';

/// Generates data using a [Faker].
typedef FakerCallback(Faker faker);

/// Used to seed nested objects.
typedef SeederCallback<T>(T created,
    seed(Pattern path, SeederConfiguration configuration, {bool verbose}));

/// Seeds the given service in development.
AngelConfigurer seed<T>(
  Pattern servicePath,
  SeederConfiguration<T> configuration, {
  bool verbose: false,
}) {
  return (Angel app) async {
    if (configuration.runInProduction != true) return;

    if (!app.services.containsKey(servicePath))
      throw new ArgumentError(
          "App does not contain a service at path '$servicePath'.");

    if (configuration.disabled == true) {
      print("Service '$servicePath' will not be seeded.");
      return;
    }

    var service = app.findService(servicePath);
    var faker = new Faker();

    Map _buildTemplate(Map data) {
      return data.keys.fold({}, (map, key) {
        var value = data[key];

        if (value is FakerCallback) {
          return map..[key] = value(faker);
        } else if (value is Function) {
          return map..[key] = value();
        } else if (value is Map)
          return map..[key] = _buildTemplate(value);
        else
          return map..[key] = value;
      });
    }

    _buildSeeder(Service service, {bool verbose}) {
      return (SeederConfiguration configuration) async {
        if (configuration.delete == true) await service.remove(null);

        int count = configuration.count ?? 1;
        var rnd = new Random();
        if (count < 1) count = 1;

        for (int i = 0; i < count; i++) {
          _gen(template) async {
            var data = template;

            if (data is Map) {
              data = _buildTemplate(data);
            } else if (data is Faker) {
              data = template(faker);
            }

            var params = {}..addAll(configuration.params ?? {});
            var result = await service.create(data, params);

            if (configuration.callback != null) {
              await configuration.callback(result,
                  (Pattern path, SeederConfiguration configuration,
                      {bool verbose}) {
                return _buildSeeder(app.findService(path),
                    verbose: verbose == true)(configuration);
              });
            }
          }

          if (configuration.template != null) {
            await _gen(configuration.template);
          } else if (configuration.templates?.isNotEmpty == true) {
            var template = configuration.templates
                .elementAt(rnd.nextInt(configuration.templates.length));
            await _gen(template);
          } else
            throw new ArgumentError(
                'Configuration for service \'$servicePath\' must define at least one template.');
        }

        if (verbose == true)
          print('Created $count object(s) in service \'$servicePath\'.');
      };
    }

    await _buildSeeder(service, verbose: verbose == true)(configuration);
  };
}

/// Configures the seeder.
class SeederConfiguration<T> {
  /// Optional callback on creation.
  final SeederCallback<T> callback;

  /// Number of objects to seed.
  final int count;

  /// If `true`, all records in the service are deleted before seeding.
  final bool delete;

  /// If `true`, seeding will not occur.
  final bool disabled;

  /// Optional service parameters to be passed.
  final Map params;

  /// Unless this is `true`, the seeder will not run in production.
  final bool runInProduction;

  /// A data template to build from.
  final template;

  /// A set of templates to choose from.
  final Iterable templates;

  SeederConfiguration(
      {this.callback,
      this.count: 1,
      this.delete: true,
      this.disabled: false,
      this.params: const {},
      this.runInProduction: false,
      this.template,
      this.templates: const []});
}