Feature/cache (#57)

* Corrects return type for array processor

* Replaces With_Object_Cache with the With_Cache trait. This makes it possible to set a cache strategy that determines how the cache is handled.

* Replaces With_Object_Cache with the With_Cache trait. This makes it possible to set a cache strategy that determines how the cache is handled.

lib/Traits/With_Cache.php

@@ -0,0 +1,88 @@
+<?php
+
+namespace Underpin\Traits;
+
+use Underpin\Exceptions\Cached_Item_Not_Found;
+use Underpin\Exceptions\Cache_Store_Failed;
+use Underpin\Interfaces\Cache_Strategy;
+use Underpin\Registries\Logger;
+
+trait With_Cache
+{
+	protected array $object_cache = [];
+
+	/**
+	 * @param string          $key      The cache key
+	 * @param callable        $setter   The setter that sets the cache value
+	 * @param ?Cache_Strategy $strategy The strategy to use when loading from the cache. If unset, this will default to
+	 *                                  Underpin's object cache strategy.
+	 *
+	 * @return mixed
+	 */
+	protected function load_from_cache(string $key, callable $setter, ?Cache_Strategy $strategy = null) : mixed
+	{
+		if (! $strategy) {
+			return $this->load_from_object($key, $setter);
+		}
+
+		return $this->load_from_strategy($key, $setter, $strategy);
+	}
+
+	/**
+	 * Loads the data using the provided strategy
+	 *
+	 * @param string         $key       The cache key
+	 * @param callable       $setter    The setter that sets the cache value
+	 * @param Cache_Strategy $strategy  The strategy to use when loading from the cache. If unset, this will default to
+	 *                                  Underpin's object cache strategy.
+	 *
+	 * @return mixed
+	 */
+	private function load_from_strategy(string $key, callable $setter, Cache_Strategy $strategy) : mixed
+	{
+		try {
+			$result = $strategy->get($key);
+		} catch (Cached_Item_Not_Found $e) {
+			$result = $setter();
+			$this->set_cache($key, $result, $strategy);
+		}
+
+		return $result;
+	}
+
+	/**
+	 * Stores the data in the provided cache strategy
+	 *
+	 * @param string         $key       The cache key
+	 * @param mixed          $value     The setter that sets the cache value
+	 * @param Cache_Strategy $strategy  The strategy to use when loading from the cache. If unset, this will default to
+	 *                                  Underpin's object cache strategy.
+	 *
+	 * @return void
+	 */
+	private function set_cache(string $key, mixed $value, Cache_Strategy $strategy) : void
+	{
+		try {
+			$strategy->set($key, $value);
+		} catch (Cache_Store_Failed $e) {
+			Logger::warning($e);
+		}
+	}
+
+	/**
+	 * Loads an item from the object cache.
+	 *
+	 * @param string   $key
+	 * @param callable $setter
+	 *
+	 * @return mixed
+	 */
+	private function load_from_object(string $key, callable $setter) : mixed
+	{
+		if (! isset($this->object_cache[$key])) {
+			$this->object_cache[$key] = $setter();
+		}
+
+		return $this->object_cache[$key];
+	}
+}