/*
 * Copyright (c) MuleSoft, Inc.  All rights reserved.  http://www.mulesoft.com
 * The software in this package is published under the terms of the CPAL v1.0
 * license, a copy of which has been included with this distribution in the
 * LICENSE.txt file.
 */
package org.mule.runtime.core.processor.strategy;

import static org.mule.runtime.core.api.rx.Exceptions.wrapFatal;
import static reactor.core.Exceptions.unwrap;
import static reactor.core.publisher.Flux.from;
import static reactor.core.publisher.Mono.just;

import org.mule.runtime.core.api.Event;
import org.mule.runtime.core.api.MuleContext;
import org.mule.runtime.core.api.construct.FlowConstruct;
import org.mule.runtime.core.api.construct.Pipeline;
import org.mule.runtime.core.api.processor.Processor;
import org.mule.runtime.core.api.processor.ReactiveProcessor;
import org.mule.runtime.core.api.processor.ReactiveProcessor.ProcessingType;
import org.mule.runtime.core.api.processor.Sink;
import org.mule.runtime.core.api.processor.strategy.ProcessingStrategy;
import org.mule.runtime.core.api.processor.strategy.ProcessingStrategyFactory;

/**
 * Processing strategy that processes the {@link Pipeline} in the caller thread and does not schedule the processing of any
 * {@link Processor} in a different thread pool regardless of their {@link ProcessingType}.
 * <p/>
 * When individual {@link Processor}'s execute non-blocking operations using additional threads internally (e.g. an outbound HTTP
 * request) the {@link Pipeline} will block until the operation response is available before continuing processing in the same
 * thread.
 */
public class BlockingProcessingStrategyFactory implements ProcessingStrategyFactory {

  public static final ProcessingStrategy BLOCKING_PROCESSING_STRATEGY_INSTANCE =
      new AbstractProcessingStrategy() {

        @Override
        public boolean isSynchronous() {
          return true;
        }

        @Override
        public Sink createSink(FlowConstruct flowConstruct, ReactiveProcessor pipeline) {
          return new StreamPerEventSink(pipeline, event -> {
          });
        }

        @Override
        public ReactiveProcessor onProcessor(ReactiveProcessor processor) {
          return publisher -> from(publisher).handle((event, sink) -> {
            try {
              Event result = just(event).transform(processor).block();
              if (result != null) {
                sink.next(result);
              }
            } catch (Throwable throwable) {
              sink.error(wrapFatal(unwrap(throwable)));
            }
          });
        }

      };

  @Override
  public ProcessingStrategy create(MuleContext muleContext, String schedulersNamePrefix) {
    return BLOCKING_PROCESSING_STRATEGY_INSTANCE;
  }

}