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/*
 * Copyright (c) 2019 - Manifold Systems LLC
 *
 * 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 manifold.collections.api.range;

import java.math.BigInteger;
import java.util.Iterator;
import java.util.NoSuchElementException;

public final class BigIntegerRange extends NumberRange
{
  @SuppressWarnings({"UnusedDeclaration"})
  public BigIntegerRange( BigInteger left, BigInteger right )
  {
    this( left, right, BigInteger.ONE, true, true, false );
  }

  public BigIntegerRange( BigInteger left, BigInteger right, BigInteger step, boolean leftClosed, boolean rightClosed, boolean reverse )
  {
    super( left, right, step, leftClosed, rightClosed, reverse );

    if( step.compareTo( BigInteger.ZERO ) <= 0 )
    {
      throw new IllegalArgumentException( "The step must be greater than 0: " + step );
    }
  }

  @Override
  public Iterator iterateFromLeft()
  {
    return new ForwardIterator();
  }

  @Override
  public Iterator iterateFromRight()
  {
    return new ReverseIterator();
  }

  @Override
  public BigInteger getFromLeft( int iStepIndex )
  {
    if( iStepIndex < 0 )
    {
      throw new IllegalArgumentException( "Step index must be >= 0: " + iStepIndex );
    }

    if( !isLeftClosed() )
    {
      iStepIndex++;
    }
    BigInteger value = getLeftEndpoint().add( getStep().multiply( BigInteger.valueOf( iStepIndex ) ) );
    int iComp = value.compareTo( getRightEndpoint() );
    if( isRightClosed() ? iComp <= 0 : iComp < 0 )
    {
      return value;
    }

    return null;
  }

  @Override
  public BigInteger getFromRight( int iStepIndex )
  {
    if( iStepIndex < 0 )
    {
      throw new IllegalArgumentException( "Step index must be >= 0: " + iStepIndex );
    }

    if( !isRightClosed() )
    {
      iStepIndex++;
    }
    BigInteger value = getRightEndpoint().subtract( getStep().multiply( BigInteger.valueOf( iStepIndex ) ) );
    int iComp = value.compareTo( getLeftEndpoint() );
    if( isLeftClosed() ? iComp >= 0 : iComp > 0 )
    {
      return value;
    }

    return null;
  }

  private class ForwardIterator implements Iterator
  {
    private BigInteger _csr;

    public ForwardIterator()
    {
      _csr = getLeftEndpoint();
      if( !isLeftClosed() && hasNext() )
      {
        next();
      }
    }

    @Override
    public boolean hasNext()
    {
      int iComp = _csr.compareTo( getRightEndpoint() );
      return iComp < 0 || (isRightClosed() && iComp == 0);
    }

    @Override
    public BigInteger next()
    {
      int iComp = _csr.compareTo( getRightEndpoint() );
      if( iComp > 0 ||
          (!isRightClosed() && iComp == 0) )
      {
        throw new NoSuchElementException();
      }
      BigInteger ret = _csr;
      _csr = _csr.add( getStep() );
      return ret;
    }

    @Override
    public void remove()
    {
      throw new UnsupportedOperationException();
    }
  }

  private class ReverseIterator implements Iterator
  {
    private BigInteger _csr;

    public ReverseIterator()
    {
      _csr = getRightEndpoint();
      if( !isRightClosed() && hasNext() )
      {
        next();
      }
    }

    @Override
    public boolean hasNext()
    {
      int iComp = _csr.compareTo( getLeftEndpoint() );
      return iComp > 0 || (isLeftClosed() && iComp == 0);
    }

    @Override
    public BigInteger next()
    {
      int iComp = _csr.compareTo( getLeftEndpoint() );
      if( iComp < 0 ||
          (!isLeftClosed() && iComp == 0) )
      {
        throw new NoSuchElementException();
      }
      BigInteger ret = _csr;
      _csr = _csr.subtract( getStep() );
      return ret;
    }

    @Override
    public void remove()
    {
      throw new UnsupportedOperationException();
    }
  }
}