<?php

// This doc comment block generated by idl/sysdoc.php
/**
 * ( excerpt from http://php.net/manual/en/class.limititerator.php )
 *
 * The LimitIterator class allows iteration over a limited subset of items
 * in an Iterator.
 *
 */
class LimitIterator extends IteratorIterator implements OuterIterator {

  private $offset;
  private $count;
  private $valid;

  // This doc comment block generated by idl/sysdoc.php
  /**
   * ( excerpt from http://php.net/manual/en/limititerator.construct.php )
   *
   * Constructs a new LimitIterator from an iterator with a given starting
   * offset and maximum count.
   *
   * @iterator   mixed   The Iterator to limit.
   * @offset     mixed   Optional offset of the limit.
   * @count      mixed   Optional count of the limit.
   *
   * @return     mixed   The new LimitIterator.
   */
  public function __construct($iterator, $offset = 0, $count = -1) {
    if ($offset < 0) {
      throw new OutOfRangeException(
        "Parameter offset must be >= 0");
    } else if ($count < -1) {
      throw new OutOfRangeException(
        "Parameter count must either be -1 or ".
        "a value greater than or equal 0");
    }
    parent::__construct($iterator);
    $this->offset = $offset;
    $this->count = $count;
  }

  // This doc comment block generated by idl/sysdoc.php
  /**
   * ( excerpt from http://php.net/manual/en/limititerator.getposition.php )
   *
   * Gets the current zero-based position of the inner Iterator.
   *
   * @return     mixed   The current position.
   */
  public function getPosition() {
    return $this->_getPosition();
  }

  // This doc comment block generated by idl/sysdoc.php
  /**
   * ( excerpt from http://php.net/manual/en/limititerator.rewind.php )
   *
   * Rewinds the iterator to the starting offset specified in
   * LimitIterator::__construct().
   *
   * @return     mixed   No value is returned.
   */
  public function rewind() {
    $this->getInnerIterator()->rewind();
    $this->_setPosition(0);
    $this->seek($this->offset);
  }

  // This doc comment block generated by idl/sysdoc.php
  /**
   * ( excerpt from http://php.net/manual/en/limititerator.next.php )
   *
   * Moves the iterator forward.
   *
   * @return     mixed   No value is returned.
   */
  public function next() {
    $this->getInnerIterator()->next();
    $this->_setPosition($this->_getPosition() + 1);
    if ($this->count == -1 ||
        $this->_getPosition() < $this->offset + $this->count) {
      $this->valid = $this->_fetch(true);
    }
  }

  // This doc comment block generated by idl/sysdoc.php
  /**
   * ( excerpt from http://php.net/manual/en/limititerator.seek.php )
   *
   * Moves the iterator to the offset specified by position.
   *
   * @position   mixed   The position to seek to.
   *
   * @return     mixed   Returns the offset position after seeking.
   */
  public function seek($position) {
    // Bounds checking
    if ($position < $this->offset) {
      throw new OutOfBoundsException(
        "Cannot seek to ".$position.
        " which is below the offset ".$this->offset);
    } else if ($this->count != -1 &&
               $position >= $this->offset + $this->count) {
      throw new OutOfBoundsException(
        "Cannot seek to ".$position.
        " which is behind offset ".$this->offset.
        " plus count ".$this->count);
    }

    $iter = $this->getInnerIterator();
    if ($this->_getPosition() != $position &&
        $iter instanceof SeekableIterator) {
      // We can use the underlying seek implementation.
      $iter->seek($position);
      $this->_setPosition($position);
      if (($this->count == -1 ||
           $this->_getPosition() < $this->offset + $this->count) &&
           $iter->valid()) {
        $this->valid = $this->_fetch(false);
      }
    } else {
      // We need to simulate the seek using rewind() and next().
      // Backwards seeking is done using rewind() first.
      if ($this->_getPosition() > $position) {
        $iter->rewind();
        $this->_setPosition(0);
      }
      // We can seek forwards using next().
      while ($this->_getPosition() < $position && $iter->valid()) {
        /*
         * Note that we're basically reimplementing next() here.
         * This is because the SPL implementation does not fetch
         * when it's walking the iterator - it only fetches when
         * it reaches the right position. This also accounts for
         * why we update _position manually (and similarly, why
         * we set it manually to 0 in the block above).
         */
        $iter->next();
        $this->_setPosition($this->_getPosition() + 1);
      }
      // Fetch.
      if ($iter->valid()) {
        $this->valid = $this->_fetch(true);
      }
    }
    return $this->_getPosition();
  }

  // This doc comment block generated by idl/sysdoc.php
  /**
   * ( excerpt from http://php.net/manual/en/limititerator.valid.php )
   *
   * Checks whether the current element is valid.
   *
   * @return     mixed   Returns TRUE on success or FALSE on failure.
   */
  public function valid() {
    return ($this->count == -1 ||
            $this->_getPosition() < $this->offset + $this->count) &&
            $this->valid;
  }
}