<?php
/**
 * List of Css Selector Sequences.
 *
 * @license http://www.opensource.org/licenses/mit-license.php The MIT License
 * @copyright Copyright 2010-2014 PhpCss Team
 */

namespace PhpCss\Ast\Selector {

  use ArrayAccess;
  use ArrayIterator;
  use Countable;
  use InvalidArgumentException;
  use IteratorAggregate;
  use PhpCss\Ast;

  /**
   * List of Css Selector Sequences.
   *
   * This is the root element of a standard selector string like:
   * "element, .class"
   *
   * Because it is a list the some standard interfaces are implemented for
   * easier usage.
   *
   * @package PhpCss
   * @subpackage Ast
   */
  class Group
    extends Ast\Selector
    implements ArrayAccess, Countable, IteratorAggregate {

    private $_sequences = [];

    /**
     * Create the object and assign sequences if provided. They
     * can be added later of course.
     *
     * @param array $sequences
     */
    public function __construct(array $sequences = []) {
      foreach ($sequences as $sequence) {
        $this->offsetSet(NULL, $sequence);
      }
    }

    /**
     * Check if a sequence at the given position is available in the list.
     *
     * @param integer $offset
     * @return boolean
     * @see ArrayAccess::offsetExists()
     */
    public function offsetExists($offset): bool {
      return isset($this->_sequences[$offset]);
    }

    /**
     * Return the sequence at the given position.
     *
     * @param integer $offset
     * @return Sequence
     * @see ArrayAccess::offsetGet()
     */
    public function offsetGet($offset): Sequence {
      return $this->_sequences[$offset];
    }

    /**
     * Set/Add and sequence at the given position or top the end
     *
     * @param integer|NULL $offset
     * @param Sequence $value
     * @throws InvalidArgumentException
     * @see \ArrayAccess::offsetSet()
     */
    public function offsetSet($offset, $value): void {
      if (!$value instanceof Sequence) {
        throw new InvalidArgumentException(
          sprintf(
            '$sequence is not an instance of %s but %s.',
            Sequence::CLASS,
            is_object($value) ? get_class($value) : gettype($value)
          )
        );
      }
      if (is_null($offset)) {
        $this->_sequences[] = $value;
      } else {
        $this->_sequences[(int)$offset] = $value;
        $this->_sequences = array_values($this->_sequences);
      }
    }

    /**
     * Remove the sequence at the given position
     *
     * @param integer $offset
     * @see ArrayAccess::offsetUnset()
     */
    public function offsetUnset($offset): void {
      unset($this->_sequences[$offset]);
      $this->_sequences = array_values($this->_sequences);
    }

    /**
     * Return the sequence list count.
     *
     * @return integer
     * @see Countable::count()
     */
    public function count(): int {
      return count($this->_sequences);
    }

    /**
     * Return an iterator for the sequences
     *
     * @return ArrayIterator
     * @see IteratorAggregate::getIterator()
     */
    public function getIterator(): ArrayIterator {
      return new ArrayIterator($this->_sequences);
    }

    /**
     * Accept visitors, because this element has children, enter and leave are called.
     *
     * @param Ast\Visitor $visitor
     * @return void
     */
    public function accept(Ast\Visitor $visitor): void {
      if ($visitor->visitEnter($this)) {
        /**
         * @var Sequence $sequence
         */
        foreach ($this as $sequence) {
          $sequence->accept($visitor);
        }
        $visitor->visitLeave($this);
      }
    }
  }
}