Introduce filter for single id meta values #56

inc/Import/Filter/SingleIdMetaValueFilter.php

@@ -0,0 +1,67 @@
+<?php # -*- coding: utf-8 -*-
+
+namespace W2M\Import\Filter;
+
+use
+	W2M\Import\Data;
+
+/**
+ * Class SingleIdMetaValueFilter
+ *
+ * Filter scalar (meta) value (e.g. _thumbnail) and treat the value as object ID of a given type.
+ * Looks up the ID in a given MultiTypeIdMapperInterface.
+ *
+ * @package W2M\Import\Filter
+ */
+class SingleIdMetaValueFilter implements ValueFilterableInterface {
+
+	/**
+	 * @var Data\MultiTypeIdMapperInterface
+	 */
+	private $id_map;
+
+	/**
+	 * @var string
+	 */
+	private $type;
+
+	/**
+	 * @param $type
+	 * @param Data\MultiTypeIdMapperInterface $id_map
+	 */
+	public function __construct( $type, Data\MultiTypeIdMapperInterface $id_map ) {
+
+		$this->type   = (string) $type;
+		$this->id_map = $id_map;
+	}
+
+	/**
+	 * @param mixed $value
+	 * @param int $object_id
+	 *
+	 * @return mixed (Same type as $value)
+	 */
+	public function filter( $value, $object_id ) {
+
+		if ( ! $this->is_filterable( (int) $value, $object_id ) ) {
+			return $value;
+		}
+
+		return $this->id_map->local_id( $this->type, (int) $value );
+	}
+
+	/**
+	 * Return FALSE when the filter is not filterable due to missing data. E.g. a post
+	 * ID refers to a post which was not imported yet.
+	 *
+	 * @param mixed $value
+	 * @param int $object_id
+	 *
+	 * @return bool
+	 */
+	public function is_filterable( $value, $object_id ) {
+
+		return (bool) $this->id_map->local_id( $this->type, (int) $value );
+	}
+
+}

tests/phpunit/Unit/Import/Filter/SingleIdMetaValueFilterTest.php

@@ -0,0 +1,22 @@
+<?php # -*- coding: utf-8 -*-
+
+namespace W2M\Test\Unit\Import\Filter;
+
+use
+	W2M\Import\Filter,
+	W2M\Test\Helper;
+
+class SingleIdMetaValueFilterTest extends Helper\MonkeyTestCase {
+
+	public function test_filter() {
+
+		//Todo: Write tests
+		$this->markTestIncomplete( "Under construction" );
+	}
+
+	public function test_is_filterable() {
+
+		//Todo: Write tests
+		$this->markTestIncomplete( "Under construction" );
+	}
+}