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<?php
namespace RebelCode\Wpra\Core\Data;
use ArrayAccess;
use RebelCode\Wpra\Core\Util\IteratorDelegateTrait;
use RebelCode\Wpra\Core\Util\MergedIterator;
use RuntimeException;
/**
* A data set implementation that delegates functionality to one of many children data sets, determined by a callback.
*
* @since 4.14
*/
class DelegatorDataSet implements DataSetInterface
{
/* @since 4.14 */
use IteratorDelegateTrait;
/**
* The children data set mapping.
*
* @since 4.14
*
* @var DataSetInterface[]|ArrayAccess
*/
protected $children;
/**
* The callable that maps a key to a data set.
*
* @since 4.14
*
* @var callable
*/
protected $mappingFn;
/**
* Constructor.
*
* @since 4.14
*
* @param ArrayAccess|DataSetInterface[] $children The mapping of data set keys to data set instances.
* @param callable $mappingFn The mapping function to use to determine which data set to
* use for which keys.
*/
public function __construct($children, callable $mappingFn)
{
$this->children = $children;
$this->mappingFn = $mappingFn;
}
/**
* Retrieves the child data set to use for the given key.
*
* @since 4.14
*
* @param int|string $key The data key.
*
* @return DataSetInterface The data set instance to use.
*
* @throws RuntimeException If the key returned by the callable does not correspond to a child data set.
*/
protected function getChildDataSetFor($key)
{
$dataSetKey = call_user_func_array($this->mappingFn, [$key]);
if (!isset($this->children[$dataSetKey])) {
throw new RuntimeException(sprintf('Child data set "%s" does not exist', $dataSetKey));
}
return $this->children[$dataSetKey];
}
/**
* @inheritdoc
*
* @since 4.14
*/
public function offsetGet($key)
{
return $this->getChildDataSetFor($key)->offsetGet($key);
}
/**
* @inheritdoc
*
* @since 4.14
*/
public function offsetExists($key)
{
return $this->getChildDataSetFor($key)->offsetExists($key);
}
/**
* @inheritdoc
*
* @since 4.14
*/
public function offsetSet($key, $value)
{
$this->getChildDataSetFor($key)->offsetSet($key, $value);
}
/**
* @inheritdoc
*
* @since 4.14
*/
public function offsetUnset($key)
{
$this->getChildDataSetFor($key)->offsetUnset($key);
}
/**
* @inheritdoc
*
* @since 4.14
*/
protected function getIterator()
{
return new MergedIterator($this->children);
}
/**
* Creates a mapping function that uses a fixed map of keys.
*
* @since 4.14
*
* @param string[]|ArrayAccess $keyMap The mapping of entry keys to child data set keys.
* @param string $default The default child data set key to use.
*
* @return callable
*/
public static function fixedMap($keyMap, $default)
{
return function ($key) use ($keyMap, $default) {
if (isset($keyMap[$key])) {
return $keyMap[$key];
}
return $default;
};
}
}