/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.beam.runners.core;

import com.google.common.collect.FluentIterable;
import com.google.common.collect.ImmutableList;
import com.google.protobuf.BytesValue;
import com.google.protobuf.InvalidProtocolBufferException;
import java.io.IOException;
import java.util.Collection;
import java.util.Map;
import org.apache.beam.fn.harness.fn.ThrowingConsumer;
import org.apache.beam.fn.v1.BeamFnApi;
import org.apache.beam.sdk.io.BoundedSource;
import org.apache.beam.sdk.io.Source.Reader;
import org.apache.beam.sdk.options.PipelineOptions;
import org.apache.beam.sdk.util.SerializableUtils;
import org.apache.beam.sdk.util.WindowedValue;

/**
 * A runner which creates {@link Reader}s for each {@link BoundedSource} and executes
 * the {@link Reader}s read loop.
 */
public class BoundedSourceRunner<InputT extends BoundedSource<OutputT>, OutputT> {
  private final PipelineOptions pipelineOptions;
  private final BeamFnApi.FunctionSpec definition;
  private final Collection<ThrowingConsumer<WindowedValue<OutputT>>> consumers;

  public BoundedSourceRunner(
      PipelineOptions pipelineOptions,
      BeamFnApi.FunctionSpec definition,
      Map<String, Collection<ThrowingConsumer<WindowedValue<OutputT>>>> outputMap) {
    this.pipelineOptions = pipelineOptions;
    this.definition = definition;
    this.consumers = ImmutableList.copyOf(FluentIterable.concat(outputMap.values()));
  }

  /**
   * The runner harness is meant to send the source over the Beam Fn Data API which would be
   * consumed by the {@link #runReadLoop}. Drop this method once the runner harness sends the
   * source instead of unpacking it from the data block of the function specification.
   */
  @Deprecated
  public void start() throws Exception {
    try {
      // The representation here is defined as the java serialized representation of the
      // bounded source object packed into a protobuf Any using a protobuf BytesValue wrapper.
      byte[] bytes = definition.getData().unpack(BytesValue.class).getValue().toByteArray();
      @SuppressWarnings("unchecked")
      InputT boundedSource =
          (InputT) SerializableUtils.deserializeFromByteArray(bytes, definition.toString());
      runReadLoop(WindowedValue.valueInGlobalWindow(boundedSource));
    } catch (InvalidProtocolBufferException e) {
      throw new IOException(
          String.format("Failed to decode %s, expected %s",
              definition.getData().getTypeUrl(), BytesValue.getDescriptor().getFullName()),
          e);
    }
  }

  /**
   * Creates a {@link Reader} for each {@link BoundedSource} and executes the {@link Reader}s
   * read loop. See {@link Reader} for further details of the read loop.
   *
   * <p>Propagates any exceptions caused during reading or processing via a consumer to the
   * caller.
   */
  public void runReadLoop(WindowedValue<InputT> value) throws Exception {
    try (Reader<OutputT> reader = value.getValue().createReader(pipelineOptions)) {
      if (!reader.start()) {
        // Reader has no data, immediately return
        return;
      }
      do {
        // TODO: Should this use the input window as the window for all the outputs?
        WindowedValue<OutputT> nextValue = WindowedValue.timestampedValueInGlobalWindow(
            reader.getCurrent(), reader.getCurrentTimestamp());
        for (ThrowingConsumer<WindowedValue<OutputT>> consumer : consumers) {
          consumer.accept(nextValue);
        }
      } while (reader.advance());
    }
  }

  @Override
  public String toString() {
    return definition.toString();
  }
}