Add filter method to StatementList

This fixes #505

Author: JeroenDeDauw

src/Statement/ReferencedStatementFilter.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace Wikibase\DataModel\Statement;
+
+/**
+ * @since 4.1
+ *
+ * @licence GNU GPL v2+
+ * @author Jeroen De Dauw < jeroendedauw@gmail.com >
+ */
+class ReferencedStatementFilter implements StatementFilter {
+
+	/**
+	 * @param Statement $statement
+	 *
+	 * @return boolean
+	 */
+	public function statementMatches( Statement $statement ) {
+		return count( $statement->getReferences() ) !== 0;
+	}
+
+}

src/Statement/StatementFilter.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Wikibase\DataModel\Statement;
+
+/**
+ * @since 4.1
+ *
+ * @licence GNU GPL v2+
+ * @author Jeroen De Dauw < jeroendedauw@gmail.com >
+ */
+interface StatementFilter {
+
+	/**
+	 * @param Statement $statement
+	 *
+	 * @return boolean
+	 */
+	public function statementMatches( Statement $statement );
+
+}

src/Statement/StatementList.php

@@ -306,4 +306,23 @@ public function getFirstStatementWithGuid( $statementGuid ) {
 		return null;
 	}
 
+	/**
+	 * @since 4.1
+	 *
+	 * @param StatementFilter $filter
+	 *
+	 * @return self
+	 */
+	public function filter( StatementFilter $filter ) {
+		$statementList = new self();
+
+		foreach ( $this->statements as $statement ) {
+			if ( $filter->statementMatches( $statement ) ) {
+				$statementList->addStatement( $statement );
+			}
+		}
+
+		return $statementList;
+	}
+
 }

tests/unit/Statement/ReferencedStatementFilterTest.php

@@ -0,0 +1,61 @@
+<?php
+
+namespace Wikibase\DataModel\Tests\Statement;
+
+use DataValues\StringValue;
+use Wikibase\DataModel\Claim\Claims;
+use Wikibase\DataModel\Entity\PropertyId;
+use Wikibase\DataModel\Reference;
+use Wikibase\DataModel\ReferenceList;
+use Wikibase\DataModel\Snak\PropertyNoValueSnak;
+use Wikibase\DataModel\Snak\PropertySomeValueSnak;
+use Wikibase\DataModel\Snak\PropertyValueSnak;
+use Wikibase\DataModel\Snak\SnakList;
+use Wikibase\DataModel\Statement\ReferencedStatementFilter;
+use Wikibase\DataModel\Statement\Statement;
+use Wikibase\DataModel\Statement\StatementList;
+
+/**
+ * @covers Wikibase\DataModel\Statement\ReferencedStatementFilter
+ *
+ * @licence GNU GPL v2+
+ * @author Jeroen De Dauw < jeroendedauw@gmail.com >
+ */
+class ReferencedStatementFilterTest extends \PHPUnit_Framework_TestCase {
+
+	public function testReturnsFalseForMinimalStatement() {
+		$filter = new ReferencedStatementFilter();
+		$this->assertFalse( $filter->statementMatches( new Statement( new PropertyNoValueSnak( 42 ) ) ) );
+	}
+
+	public function testReturnsFalseForVerboseStatementWithoutReferences() {
+		$statement = new Statement( new PropertyValueSnak( 42, new StringValue( '\o/' ) ) );
+		$statement->setGuid( 'kittens of doom' );
+		$statement->setRank( Statement::RANK_PREFERRED );
+		$statement->setQualifiers( new SnakList( array(
+			new PropertyValueSnak( 1, new StringValue( 'wee' ) ),
+			new PropertyValueSnak( 2, new StringValue( 'woo' ) ),
+			new PropertyValueSnak( 3, new StringValue( 'waa' ) )
+		) ) );
+
+		$filter = new ReferencedStatementFilter();
+		$this->assertFalse( $filter->statementMatches( $statement ) );
+	}
+
+	public function testReturnsTrueForMinimalStatementWithReferences() {
+		$statement = new Statement( new PropertyValueSnak( 42, new StringValue( '\o/' ) ) );
+		$statement->setReferences( new ReferenceList( array(
+			new Reference( array(
+				new PropertyValueSnak( 1, new StringValue( 'wee' ) )
+			) ),
+			new Reference( array(
+				new PropertyValueSnak( 2, new StringValue( 'woo' ) ),
+				new PropertyValueSnak( 3, new StringValue( 'waa' ) )
+			) )
+		) ) );
+
+		$filter = new ReferencedStatementFilter();
+		$this->assertTrue( $filter->statementMatches( $statement ) );
+	}
+
+}

tests/unit/Statement/StatementListTest.php

@@ -5,10 +5,13 @@
 use DataValues\StringValue;
 use Wikibase\DataModel\Claim\Claims;
 use Wikibase\DataModel\Entity\PropertyId;
+use Wikibase\DataModel\Reference;
+use Wikibase\DataModel\ReferenceList;
 use Wikibase\DataModel\Snak\PropertyNoValueSnak;
 use Wikibase\DataModel\Snak\PropertySomeValueSnak;
 use Wikibase\DataModel\Snak\PropertyValueSnak;
 use Wikibase\DataModel\Snak\SnakList;
+use Wikibase\DataModel\Statement\ReferencedStatementFilter;
 use Wikibase\DataModel\Statement\Statement;
 use Wikibase\DataModel\Statement\StatementList;
 
@@ -626,4 +629,26 @@ public function testGivenInvalidGuid_getFirstStatementWithGuidReturnsNull() {
 		$this->assertNull( $statements->getFirstStatementWithGuid( false ) );
 	}
 
+	public function testFilter() {
+		$statement1 = new Statement( new PropertyNoValueSnak( 1 ) );
+		$statement2 = new Statement( new PropertyNoValueSnak( 2 ) );
+		$statement3 = new Statement( new PropertyNoValueSnak( 3 ) );
+		$statement4 = new Statement( new PropertyNoValueSnak( 4 ) );
+
+		$statement2->setReferences( new ReferenceList( array(
+			new Reference( array( new PropertyNoValueSnak( 20 ) ) )
+		) ) );
+
+		$statement3->setReferences( new ReferenceList( array(
+			new Reference( array( new PropertyNoValueSnak( 30 ) ) )
+		) ) );
+
+		$statements = new StatementList( $statement1, $statement2, $statement3, $statement4 );
+
+		$this->assertEquals(
+			new StatementList( $statement2, $statement3 ),
+			$statements->filter( new ReferencedStatementFilter() )
+		);
+	}
+
 }