remove( $item ) {
		if ( $this->key_valid( $item ) ) {
			unset( $this->items[ $item ] );
		}
		return $this;
	}

	/**
	 * Clear collection
	 * @return Current instance
	 */
	public function clear() {
		$this->items = array();
		return $this;
	}

	/**
	 * Checks if item exists in the collection
	 * @param mixed $item Item(s) to check for
	 * @return bool TRUE if item(s) in collection
	 */
	public function has( $items ) {
		// Attempt to locate item
		return false;
	}

	/**
	 * Retrieve item(s) from collection
	 * If no items specified, entire collection returned
	 * @param array $args (optional) Query arguments
	 * @return object|array Specified item(s)
	 */
	public function get( $args = null ) {
		$this->init();
		// Parse args
		$args_default = array(
			'orderby' => null,
			'order'   => 'DESC',
			'include' => array(),
			'exclude' => array(),
		);
		$r            = wp_parse_args( $args, $args_default );

		$items = $this->items;

		/* Sort */
		if ( ! is_null( $r['orderby'] ) ) {
			// Validate
			if ( ! is_array( $r['orderby'] ) ) {
				$r['orderby'] = array( 'item' => $r['orderby'] );
			}
			// Prep
			$metas = ( isset( $r['orderby']['meta'] ) ) ? $this->items_meta : array();
			// Sort
			foreach ( $r['orderby'] as $stype => $sval ) {
				/* Meta sorting */
				if ( 'meta' === $stype ) {
					// Build sorting buckets
					$buckets = array();
					foreach ( $metas as $item => $meta ) {
						if ( ! isset( $meta[ $sval ] ) ) {
							continue;
						}
						// Create bucket
						$idx = $meta[ $sval ];
						if ( ! isset( $buckets[ $idx ] ) ) {
							$buckets[ $idx ] = array();
						}
						// Add item to bucket
						$buckets[ $idx ][] = $item;
					}
					// Sort buckets
					ksort( $buckets, SORT_NUMERIC );
					// Merge buckets
					$pool = array();
					foreach ( $buckets as $bucket ) {
						$pool = array_merge( $pool, $bucket );
					}
					// Fill with items
					$items = array_merge( array_fill_keys( $pool, null ), $items );
				}
			}
			// Clear workers
			unset( $stype, $sval, $buckets, $pool, $item, $metas, $meta, $idx );
		}
		return $items;
	}

	/* Metadata */

	/**
	 * Add metadata for item
	 * @param string|int $item Item key
	 * @param string|array $meta_key Meta key to set (or array of metadata)
	 * @param mixed $meta_value (optional) Metadata value (if key set)
	 * @param bool $reset (optional) Whether to remove existing metadata first (Default: FALSE)
	 * @return object Current instance
	 */
	protected function add_meta( $item, $meta_key, $meta_value = null, $reset = false ) {
		// Validate
		if ( $this->key_valid( $item ) && ( is_array( $meta_key ) || is_string( $meta_key ) ) ) {
			// Prepare metadata
			$meta = ( is_string( $meta_key ) ) ? array( $meta_key => $meta_value ) : $meta_key;
			// Reset existing meta (if necessary)
			if ( is_array( $meta_key ) && func_num_args() > 2 ) {
				$reset = func_get_arg( 2 );
			}
			if ( ! ! $reset ) {
				unset( $this->items_meta[ $item ] );
			}
			// Add metadata
			if ( ! isset( $this->items_meta[ $item ] ) ) {
				$this->items_meta[ $item ] = array();
			}
			$this->items_meta[ $item ] = array_merge( $this->items_meta[ $item ], $meta );
		}
		return $this;
	}

	/**
	 * Remove item metadata
	 * @param string $item Item key
	 * @return object Current instance
	 */
	protected function remove_meta( $item, $meta_key = null ) {
		if ( $this->key_valid( $item ) && isset( $this->items_meta[ $item ] ) ) {
			if ( is_string( $meta_key ) ) {
				// Remove specific meta value
				unset( $this->items_meta[ $item ][ $meta_key ] );
			} else {
				// Remove all metadata
				unset( $this->items_meta[ $item ] );
			}
		}
		return $this;
	}

	/**
	 * Retrieve metadata
	 * @param string $item Item key
	 * @param string $meta_key (optional) Meta key (All metadata retrieved if no key specified)
	 * @return mixed|null Metadata value
	 */
	protected function get_meta( $item, $meta_key = null ) {
		$ret = null;
		if ( $this->key_valid( $item ) && isset( $this->items_meta[ $item ] ) ) {
			if ( is_null( $meta_key ) ) {
				$ret = $this->items_meta[ $item ];
			} elseif ( is_string( $meta_key ) && isset( $this->items_meta[ $item ][ $meta_key ] ) ) {
				$ret = $this->items_meta[ $item ][ $meta_key ];
			}
		}
		return $ret;
	}

	/* Collection */

	/**
	 * Build entire collection of items
	 * Prints output
	 */
	function build( $build_vars = array() ) {
		// Parse vars
		$this->parse_build_vars( $build_vars );
		$this->util->do_action_ref_array( 'build_init', array( $this ) );
		// Pre-build output
		$this->util->do_action_ref_array( 'build_pre', array( $this ) );
		// Build groups
		$this->build_groups();
		// Post-build output
		$this->util->do_action_ref_array( 'build_post', array( $this ) );
	}

	/**
	 * Parses build variables prior to use
	 * @uses this->reset_build_vars() to reset build variables for each request
	 * @param array $build_vars Variables to use for current request
	 */
	function parse_build_vars( $build_vars = array() ) {
		$this->reset_build_vars();
		$this->build_vars = $this->util->apply_filters( 'parse_build_vars', wp_parse_args( $build_vars, $this->build_vars ), $this );
	}

	/**
	 * Reset build variables to defaults
	 * Default Variables
	 * > groups     - array - Names of groups to build
	 * > context    - string - Context of current request
	 * > layout     - string - Name of default layout to use
	 */
	function reset_build_vars() {
		$this->build_vars = wp_parse_args( $this->build_vars, $this->build_vars_default );
	}
}