consumersFileMaker function

PartFile? consumersFileMaker(ServerServer server, String formatter(Spec))

Emits registerConsumers, which subscribes every @Consumes handler.

Mirrors routes(di): controllers are constructed the same way, so a singleton controller is shared with its routes rather than rebuilt for messages.

Returns null when nothing is annotated, so an app that uses no messaging gains no file and no generated wiring at all.

Implementation

PartFile? consumersFileMaker(
  ServerServer server,
  String Function(Spec) formatter,
) {
  final withConsumers = server.routes
      .where((route) => route.consumers.isNotEmpty)
      .toList();

  if (withConsumers.isEmpty) {
    return null;
  }

  final register = Method(
    (p) => p
      ..name = 'registerConsumers'
      ..modifier = MethodModifier.async
      ..returns = TypeReference(
        (b) => b
          ..symbol = 'Future'
          ..types.add(refer('void')),
      )
      ..requiredParameters.addAll([
        Parameter(
          (p) => p
            ..name = 'registry'
            ..type = refer((ConsumerRegistry).name),
        ),
        Parameter(
          (p) => p
            ..name = 'di'
            ..type = refer((DI).name),
        ),
      ])
      ..body = Block.of([
        for (final route in withConsumers)
          if (route.type == InstanceType.singleton)
            declareFinal(
              '_${route.variableName}',
            ).assign(createClass(route)).statement,
        const Code(''),
        for (final route in withConsumers)
          for (final consumer in route.consumers)
            refer('registry')
                .property('consume')
                .call(
                  [literalString(consumer.topic)],
                  {
                    'group': literalString(consumer.group),
                    'onMessage': Method(
                      (b) => b
                        ..lambda = true
                        ..requiredParameters.add(
                          Parameter((p) => p..name = 'message'),
                        )
                        ..body =
                            switch (route.type) {
                              InstanceType.singleton => refer(
                                '_${route.variableName}',
                              ),
                              InstanceType.factory => createClass(route),
                            }.property(consumer.name).call([
                              // A handler may take the message or nothing.
                              if (consumer.params.isNotEmpty) refer('message'),
                            ]).code,
                    ).closure,
                  },
                )
                .awaited
                .statement,
      ]),
  );

  final content = formatter(register);

  return PartFile(path: ['definitions', '__consumers'], content: content);
}