Handler.scala.txt

@*
 * Copyright (C) 2018-2020 Lightbend Inc. <https://www.lightbend.com>
 *@

@(service: akka.grpc.gen.javadsl.Service, powerApis: Boolean)

@akka.grpc.gen.Constants.DoNotEditComment
package @service.packageName;

import java.util.Iterator;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionStage;

import akka.japi.Function;
import akka.http.javadsl.model.*;
import akka.actor.ActorSystem;
import akka.stream.Materializer;

import akka.grpc.Trailers;
import akka.grpc.javadsl.GrpcMarshalling;
import akka.grpc.javadsl.GrpcExceptionHandler;
import akka.grpc.javadsl.package$;

@{if (powerApis) "import akka.grpc.javadsl.Metadata;\nimport akka.grpc.javadsl.MetadataBuilder;" else ""}

import static @{service.packageName}.@{service.name}.Serializers.*;

@defining(if (powerApis) service.name + "PowerApi" else service.name) { serviceName =>
  public class @{serviceName}HandlerFactory {

    private static final CompletionStage<HttpResponse> notFound = CompletableFuture.completedFuture(
      HttpResponse.create().withStatus(StatusCodes.NOT_FOUND));

    private static final CompletionStage<HttpResponse> unsupportedMediaType = CompletableFuture.completedFuture(
      HttpResponse.create().withStatus(StatusCodes.UNSUPPORTED_MEDIA_TYPE));

    /**
     * Creates a `HttpRequest` to `HttpResponse` handler that can be used in for example `Http().bindAndHandleAsync`
     * for the generated partial function handler and ends with `StatusCodes.NotFound` if the request is not matching.
     *
     * Use `akka.grpc.scaladsl.ServiceHandler.concatOrNotFound` with `@{service.name}Handler.partial` when combining
     * several services.
     */
    public static Function<HttpRequest, CompletionStage<HttpResponse>> create(@serviceName implementation, Materializer mat, ActorSystem system) {
      return create(implementation, @{service.name}.name, mat, system);
    }

    /**
     * Creates a `HttpRequest` to `HttpResponse` handler that can be used in for example `Http().bindAndHandleAsync`
     * for the generated partial function handler and ends with `StatusCodes.NotFound` if the request is not matching.
     *
     * Use `akka.grpc.scaladsl.ServiceHandler.concatOrNotFound` with `@{service.name}Handler.partial` when combining
     * several services.
     */
    public static Function<HttpRequest, CompletionStage<HttpResponse>> create(@serviceName implementation, Materializer mat, Function<ActorSystem, Function<Throwable, Trailers>> eHandler, ActorSystem system) {
      return create(implementation, @{service.name}.name, mat, eHandler, system);
    }

    /**
     * Creates a `HttpRequest` to `HttpResponse` handler that can be used in for example `Http().bindAndHandleAsync`
     * for the generated partial function handler and ends with `StatusCodes.NotFound` if the request is not matching.
     *
     * Use `akka.grpc.scaladsl.ServiceHandler.concatOrNotFound` with `@{service.name}Handler.partial` when combining
     * several services.
     *
     * Registering a gRPC service under a custom prefix is not widely supported and strongly discouraged by the specification.
     */
    public static Function<HttpRequest, CompletionStage<HttpResponse>> create(@serviceName implementation, String prefix, Materializer mat, ActorSystem system) {
      return partial(implementation, prefix, mat, GrpcExceptionHandler.defaultMapper(), system);
    }

    /**
     * Creates a `HttpRequest` to `HttpResponse` handler that can be used in for example `Http().bindAndHandleAsync`
     * for the generated partial function handler and ends with `StatusCodes.NotFound` if the request is not matching.
     *
     * Use `akka.grpc.scaladsl.ServiceHandler.concatOrNotFound` with `@{service.name}Handler.partial` when combining
     * several services.
     *
     * Registering a gRPC service under a custom prefix is not widely supported and strongly discouraged by the specification.
     */
    public static Function<HttpRequest, CompletionStage<HttpResponse>> create(@serviceName implementation, String prefix, Materializer mat, Function<ActorSystem, Function<Throwable, Trailers>> eHandler, ActorSystem system) {
      return partial(implementation, prefix, mat, eHandler, system);
    }

    /**
     * Creates a `HttpRequest` to `HttpResponse` handler that can be used in for example
     * `Http.get(system).bindAndHandleAsync`. It ends with `StatusCodes.NotFound` if the request is not matching.
     *
     * Use `akka.grpc.javadsl.ServiceHandler.concatOrNotFound` when combining several services.
     */
    public static Function<HttpRequest, CompletionStage<HttpResponse>> partial(@serviceName implementation, String prefix, Materializer mat, ActorSystem system) {
      return partial(implementation, prefix, mat, GrpcExceptionHandler.defaultMapper(), system);
    }

    /**
     * Creates a `HttpRequest` to `HttpResponse` handler that can be used in for example
     * `Http.get(system).bindAndHandleAsync`. It ends with `StatusCodes.NotFound` if the request is not matching.
     *
     * Use `akka.grpc.javadsl.ServiceHandler.concatOrNotFound` when combining several services.
     */
    public static Function<HttpRequest, CompletionStage<HttpResponse>> partial(@serviceName implementation, String prefix, Materializer mat, Function<ActorSystem, Function<Throwable, Trailers>> eHandler, ActorSystem system) {
      return (req -> {
        Iterator<String> segments = req.getUri().pathSegments().iterator();
        if (segments.hasNext() && segments.next().equals(prefix) && segments.hasNext()) {
          String method = segments.next();
          if (segments.hasNext()) return notFound; // we don't allow any random `/prefix/Method/anything/here
          else return handle(req, method, implementation, mat, eHandler, system);
        } else {
          return notFound;
        }
      });
    }

    public String getServiceName() {
      return @{service.name}.name;
    }

    private static CompletionStage<HttpResponse> handle(HttpRequest request, String method, @serviceName implementation, Materializer mat, Function<ActorSystem, Function<Throwable, Trailers>> eHandler, ActorSystem system) {
      return GrpcMarshalling.negotiated(request, (reader, writer) -> {
        final CompletionStage<HttpResponse> response;
        @{if(powerApis) { "Metadata metadata = MetadataBuilder.fromHeaders(request.getHeaders());" } else { "" }}
        switch(method) {
          @for(method <- service.methods) {
          case "@method.grpcName":
            response = @{method.unmarshal}(request.entity().getDataBytes(), @method.deserializer.name, mat, reader)
              .@{if(method.outputStreaming) { "thenApply" } else { "thenCompose" }}(e -> implementation.@{method.name}(e@{if(powerApis) { ", metadata" } else { "" }}))
              .thenApply(e -> @{method.marshal}(e, @method.serializer.name, writer, system, eHandler));
            break;
          }
          default:
            CompletableFuture<HttpResponse> result = new CompletableFuture<>();
            result.completeExceptionally(new UnsupportedOperationException("Not implemented: " + method));
            response = result;
        }
        return response.exceptionally(e -> GrpcExceptionHandler.standard(e, eHandler, writer, system));
      })
      .orElseGet(() -> unsupportedMediaType);
    }
  }
}