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/*
 * Copyright 2011,2012 Metamarkets Group Inc.
 *
 * Licensed 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 com.metamx.common.guava;

import com.google.common.base.Throwables;
import com.google.common.io.Closeables;

import java.io.IOException;

/**
 */
public class ConcatSequence implements Sequence
{
  private final Sequence> baseSequences;

  public ConcatSequence(
      Sequence> baseSequences
  )
  {
    this.baseSequences = baseSequences;
  }

  @Override
  public  OutType accumulate(OutType initValue, final Accumulator accumulator)
  {
    return baseSequences.accumulate(
        initValue, new Accumulator>()
    {
      @Override
      public OutType accumulate(OutType accumulated, Sequence in)
      {
        return in.accumulate(accumulated, accumulator);
      }
    }
    );
  }

  @Override
  public  Yielder toYielder(
      final OutType initValue,
      final YieldingAccumulator accumulator
  )
  {
    Yielder> yielderYielder = baseSequences.toYielder(
        null,
        new YieldingAccumulator, Sequence>()
        {
          @Override
          public Sequence accumulate(Sequence accumulated, Sequence in)
          {
            yield();
            return in;
          }
        }
    );

    try {
      return makeYielder(yielderYielder, initValue, accumulator);
    }
    catch (RuntimeException e) {
      // We caught a RuntimeException instead of returning a really, real, live, real boy, errr, iterator
      // So we better try to close our stuff, 'cause the exception is what is making it out of here.
      CloseQuietly.close(yielderYielder);
      throw e;
    }
  }

  public  Yielder makeYielder(
      Yielder> yielderYielder,
      OutType initValue,
      YieldingAccumulator accumulator
  )
  {
    if (yielderYielder.isDone()) {
      return Yielders.done(initValue, yielderYielder);
    }

    while (!yielderYielder.isDone()) {
      Yielder yielder = yielderYielder.get().toYielder(initValue, accumulator);
      if (accumulator.yielded()) {
        return wrapYielder(yielder, yielderYielder, accumulator);
      }

      initValue = yielder.get();
      try {
        yielder.close();
      }
      catch (IOException e) {
        throw Throwables.propagate(e);
      }

      yielderYielder = yielderYielder.next(null);
    }

    return Yielders.done(initValue, yielderYielder);
  }

  private  Yielder wrapYielder(
      final Yielder yielder,
      final Yielder> yielderYielder,
      final YieldingAccumulator accumulator
  )
  {
    if (!accumulator.yielded()) {
      OutType nextInit = yielder.get();
      try {
        yielder.close();
      }
      catch (IOException e) {
        throw Throwables.propagate(e);
      }

      return makeYielder(yielderYielder.next(null), nextInit, accumulator);
    }

    return new Yielder()
    {
      @Override
      public OutType get()
      {
        return yielder.get();
      }

      @Override
      public Yielder next(OutType initValue)
      {
        return wrapYielder(yielder.next(initValue), yielderYielder, accumulator);
      }

      @Override
      public boolean isDone()
      {
        return false;
      }

      @Override
      public void close() throws IOException
      {
        yielder.close();
        yielderYielder.close();
      }
    };
  }
}