Add StatementListChanger

Author: thiemowmde

composer.json

@@ -27,6 +27,7 @@
 		"wikimedia/assert": "~0.2.2"
 	},
 	"require-dev": {
+		"phpunit/phpunit": "~4.8",
 		"mediawiki/mediawiki-codesniffer": "~0.7",
 		"phpmd/phpmd": "~2.3"
 	},
@@ -57,7 +58,7 @@
 			"vendor/bin/phpcs src/* tests/* --standard=phpcs.xml --extensions=php -sp"
 		],
 		"phpmd": [
-			"vendor/bin/phpmd src/,tests/unit/ text phpmd.xml"
+			"vendor/bin/phpmd src/ text phpmd.xml"
 		]
 	}
 }

src/Statement/StatementListChanger.php

@@ -0,0 +1,174 @@
+<?php
+
+namespace Wikibase\DataModel\Services\Statement;
+
+use Wikibase\DataModel\Entity\PropertyId;
+use Wikibase\DataModel\Statement\Statement;
+use Wikibase\DataModel\Statement\StatementList;
+
+/**
+ * A collection of higher level utility functions to manipulate StatementList objects.
+ *
+ * @since 3.7
+ *
+ * @license GPL-2.0+
+ * @author Thiemo Mättig
+ */
+class StatementListChanger {
+
+	/**
+	 * @var StatementList
+	 */
+	private $statementList;
+
+	public function __construct( StatementList $statementList ) {
+		$this->statementList = $statementList;
+	}
+
+	/**
+	 * Makes sure all statements with the same property are next to each other (forming a group),
+	 * and reorders them if necessary. The position of the group in the list is determined by the
+	 * first statement with the same property.
+	 */
+	public function groupByProperty() {
+		$byId = [];
+
+		foreach ( $this->statementList->toArray() as $statement ) {
+			$id = $statement->getPropertyId()->getSerialization();
+			$byId[$id][] = $statement;
+		}
+
+		// FIXME: Use StatementList::clear, see https://github.com/wmde/WikibaseDataModel/pull/649
+		$this->clear();
+
+		foreach ( $byId as $statements ) {
+			foreach ( $statements as $statement ) {
+				$this->statementList->addStatement( $statement );
+			}
+		}
+	}
+
+	private function clear() {
+		foreach ( $this->statementList->toArray() as $statement ) {
+			$this->statementList->removeStatementsWithGuid( $statement->getGuid() );
+		}
+	}
+
+	/**
+	 * Adds a new statement to the list while respecting existing PropertyId groups.
+	 *
+	 * In contrast to the previously used ByPropertyIdArray implementation this method never moves
+	 * existing statements around. The provided index is only a hint. The new statement is either
+	 * added to an existing group of statements with the same PropertyId, or at a group border close
+	 * to the provided index.
+	 *
+	 * @param Statement $newStatement
+	 * @param int|null $index An absolute index in the list. If the index is not next to a statement
+	 *  with the same property, the closest possible position is used instead. Default is null,
+	 *  which adds the new statement after the last statement with the same property, or to the end.
+	 */
+	public function addToGroup( Statement $newStatement, $index = null ) {
+		$statements = $this->statementList->toArray();
+		$id = $newStatement->getPropertyId();
+
+		if ( $index === null ) {
+			$index = $this->getLastIndexWithinGroup( $statements, $id );
+		} else {
+			// Limit search range to avoid looping non-existing positions
+			$validIndex = min( max( 0, $index ), count( $statements ) );
+			$index = $this->getClosestIndexWithinGroup( $statements, $id, $validIndex );
+			if ( $index === null ) {
+				$index = $this->getClosestIndexAtGroupBorder( $statements, $validIndex );
+			}
+		}
+
+		$this->statementList->addStatement( $newStatement, $index );
+	}
+
+	/**
+	 * @param Statement[] $statements
+	 * @param PropertyId $id
+	 *
+	 * @return int|null
+	 */
+	private function getLastIndexWithinGroup( array $statements, PropertyId $id ) {
+		// Start searching from the end and stop at the first match
+		for ( $i = count( $statements ); $i > 0; $i-- ) {
+			if ( $statements[$i - 1]->getPropertyId()->equals( $id ) ) {
+				return $i;
+			}
+		}
+
+		return null;
+	}
+
+	/**
+	 * @param Statement[] $statements
+	 * @param PropertyId $id
+	 * @param int $index
+	 *
+	 * @return int|null
+	 */
+	private function getClosestIndexWithinGroup( array $statements, PropertyId $id, $index ) {
+		$longestDistance = max( $index, count( $statements ) - $index );
+
+		for ( $i = 0; $i <= $longestDistance; $i++ ) {
+			if ( $this->isWithinGroup( $statements, $id, $index - $i ) ) {
+				return $index - $i;
+			} elseif ( $i && $this->isWithinGroup( $statements, $id, $index + $i ) ) {
+				return $index + $i;
+			}
+		}
+
+		return null;
+	}
+
+	/**
+	 * @param Statement[] $statements
+	 * @param int $index
+	 *
+	 * @return int|null
+	 */
+	private function getClosestIndexAtGroupBorder( array $statements, $index ) {
+		$longestDistance = max( $index, count( $statements ) - $index );
+
+		for ( $i = 0; $i <= $longestDistance; $i++ ) {
+			if ( $this->isGroupBorder( $statements, $index - $i ) ) {
+				return $index - $i;
+			} elseif ( $i && $this->isGroupBorder( $statements, $index + $i ) ) {
+				return $index + $i;
+			}
+		}
+
+		return null;
+	}
+
+	/**
+	 * @param Statement[] $statements
+	 * @param PropertyId $id
+	 * @param int $index
+	 *
+	 * @return bool
+	 */
+	private function isWithinGroup( array $statements, PropertyId $id, $index ) {
+		$count = count( $statements );
+
+		// Valid if the index either precedes or succeeds a statement with the same property
+		return $index > 0 && $index <= $count && $statements[$index - 1]->getPropertyId()->equals( $id )
+			|| $index >= 0 && $index < $count && $statements[$index]->getPropertyId()->equals( $id );
+	}
+
+	/**
+	 * @param Statement[] $statements
+	 * @param int $index
+	 *
+	 * @return bool
+	 */
+	private function isGroupBorder( array $statements, $index ) {
+		// First and last possible position is always a border
+		return $index <= 0
+			|| $index >= count( $statements )
+			|| !$statements[$index - 1]->getPropertyId()->equals( $statements[$index]->getPropertyId() );
+	}
+
+}