<?php
/**
 * Banker
 *
 * A Caching library implementing psr/cache
 *
 * PHP version 5.6
 *
 * @package     Banker
 * @author      Timothy J. Warren <tim@timshomepage.net>
 * @copyright   2016  Timothy J. Warren
 * @license     http://www.opensource.org/licenses/mit-license.html  MIT License
 * @version     1.0.0
 * @link        https://git.timshomepage.net/timw4mail/banker
 */

namespace Aviat\Banker;

use Psr\Cache\CacheItemInterface;
use Psr\Cache\CacheItemPoolInterface;

use Aviat\Banker\Driver;
use Aviat\Banker\Driver\DriverInterface;
use Aviat\Banker\Exception\InvalidArgumentException;
use Aviat\Banker\Item;

/**
 * The main cache manager
 */
class Pool implements CacheItemPoolInterface {

	/**
	 * Driver class for handling the chosen caching backend
	 *
	 * @var DriverInterface
	 */
	protected $driver;

	/**
	 * Cache Items to be saved
	 *
	 * @var array
	 */
	protected $deferred = [];

	/**
	 * Set up the cache backend
	 *
	 * @param array $config
	 */
	public function __construct(array $config)
	{
		$this->driver = $this->loadDriver($config);
	}

	/**
	 * Returns a Cache Item representing the specified key.
	 *
	 * This method must always return a CacheItemInterface object, even in case of
	 * a cache miss. It MUST NOT return null.
	 *
	 * @param string $key
	 *   The key for which to return the corresponding Cache Item.
	 *
	 * @throws InvalidArgumentException
	 *   If the $key string is not a legal value a \Psr\Cache\InvalidArgumentException
	 *   MUST be thrown.
	 *
	 * @return CacheItemInterface
	 *   The corresponding Cache Item.
	 */
	public function getItem($key)
	{
		if ( ! is_string($key))
		{
			throw new InvalidArgumentException("Cache key must be a string.");
		}

		$item = new Item($this->driver, $key);
		return $item;
	}

	/**
	 * Returns a traversable set of cache items.
	 *
	 * @param string[] $keys
	 *   An indexed array of keys of items to retrieve.
	 *
	 * @throws InvalidArgumentException
	 *   If any of the keys in $keys are not a legal value a \Psr\Cache\InvalidArgumentException
	 *   MUST be thrown.
	 *
	 * @return array|\Traversable
	 *   A traversable collection of Cache Items keyed by the cache keys of
	 *   each item. A Cache item will be returned for each key, even if that
	 *   key is not found. However, if no keys are specified then an empty
	 *   traversable MUST be returned instead.
	 */
	public function getItems(array $keys = [])
	{
		// Get the set of items selected
		$items = [];
		foreach($keys as $key)
		{
			$items[$key] = $this->getItem($key);
		}

		return new ItemCollection($items);
	}

	/**
	 * Confirms if the cache contains specified cache item.
	 *
	 * Note: This method MAY avoid retrieving the cached value for performance reasons.
	 * This could result in a race condition with CacheItemInterface::get(). To avoid
	 * such situation use CacheItemInterface::isHit() instead.
	 *
	 * @param string $key
	 *   The key for which to check existence.
	 *
	 * @throws InvalidArgumentException
	 *   If the $key string is not a legal value a \Psr\Cache\InvalidArgumentException
	 *   MUST be thrown.
	 *
	 * @return bool
	 *   True if item exists in the cache, false otherwise.
	 */
	public function hasItem($key)
	{
		if ( ! is_string($key))
		{
			throw new InvalidArgumentException("Cache item must be a string");
		}

		return $this->driver->exists($key);
	}

	/**
	 * Deletes all items in the pool.
	 *
	 * @return bool
	 *   True if the pool was successfully cleared. False if there was an error.
	 */
	public function clear()
	{
		return $this->driver->flush();
	}

	/**
	 * Removes the item from the pool.
	 *
	 * @param string $key
	 *   The key to delete.
	 *
	 * @throws InvalidArgumentException
	 *   If the $key string is not a legal value a \Psr\Cache\InvalidArgumentException
	 *   MUST be thrown.
	 *
	 * @return bool
	 *   True if the item was successfully removed. False if there was an error.
	 */
	public function deleteItem($key)
	{
		if ( ! is_string($key))
		{
			throw new InvalidArgumentException("Cache item must be a string");
		}

		if ( ! $this->hasItem($key))
		{
			return FALSE;
		}
		else
		{
			return $this->driver->delete($key);
		}
	}

	/**
	 * Removes multiple items from the pool.
	 *
	 * @param string[] $keys
	 *   An array of keys that should be removed from the pool.

	 * @throws InvalidArgumentException
	 *   If any of the keys in $keys are not a legal value a \Psr\Cache\InvalidArgumentException
	 *   MUST be thrown.
	 *
	 * @return bool
	 *   True if the items were successfully removed. False if there was an error.
	 */
	public function deleteItems(array $keys)
	{
		foreach ($keys as $key)
		{
			if ( ! is_string($key))
			{
				throw new InvalidArgumentException("Cache item must be a string");
			}
		}

		return $this->driver->deleteMultiple($keys);
	}

	/**
	 * Persists a cache item immediately.
	 *
	 * @param CacheItemInterface $item
	 *   The cache item to save.
	 *
	 * @return bool
	 *   True if the item was successfully persisted. False if there was an error.
	 */
	public function save(CacheItemInterface $item)
	{

	}

	/**
	 * Sets a cache item to be persisted later.
	 *
	 * @param CacheItemInterface $item
	 *   The cache item to save.
	 *
	 * @return bool
	 *   False if the item could not be queued or if a commit was attempted and failed. True otherwise.
	 */
	public function saveDeferred(CacheItemInterface $item)
	{
		$this->deferred[] = $item;
	}

	/**
	 * Persists any deferred cache items.
	 *
	 * @return bool
	 *   True if all not-yet-saved items were successfully saved or there were none. False otherwise.
	 */
	public function commit()
	{
		if (empty($this->deferred))
		{
			return TRUE;
		}

		$result = TRUE;

		foreach($this->deferred as $item)
		{
			$result = $result && $this->save($item);
		}

		return $result;
	}

	/**
	 * Instantiate the appropriate cache backend based on the config
	 *
	 * @param array $driverConfig
	 * @return DriverInterface
	 */
	protected function loadDriver(array $driverConfig)
	{
		$driver = ucfirst(strtolower($driverConfig['driver']));
		$class = "Driver\\${driver}Driver";

		return new $class($driverConfig['connection']);
	}
}