Add a StatementRank class

src/Statement/Statement.php

@@ -25,13 +25,19 @@
 class Statement implements Hashable, Comparable, PropertyIdProvider {
 
 	/**
-	 * Rank enum. Higher values are more preferred.
-	 *
-	 * @since 2.0
+	 * @deprecated since 4.4, use StatementRank::PREFERRED instead.
+	 */
+	const RANK_PREFERRED = StatementRank::PREFERRED;
+
+	/**
+	 * @deprecated since 4.4, use StatementRank::NORMAL instead.
 	 */
-	const RANK_PREFERRED = 2;
-	const RANK_NORMAL = 1;
-	const RANK_DEPRECATED = 0;
+	const RANK_NORMAL = StatementRank::NORMAL;
+
+	/**
+	 * @deprecated since 4.4, use StatementRank::DEPRECATED instead.
+	 */
+	const RANK_DEPRECATED = StatementRank::DEPRECATED;
 
 	/**
 	 * @var string|null
@@ -56,9 +62,9 @@ class Statement implements Hashable, Comparable, PropertyIdProvider {
 	private $references;
 
 	/**
-	 * @var integer, element of the Statement::RANK_ enum
+	 * @var int One of the StatementRank::... constants.
 	 */
-	private $rank = self::RANK_NORMAL;
+	private $rank = StatementRank::NORMAL;
 
 	/**
 	 * @since 2.0
@@ -192,19 +198,15 @@ public function addNewReference( $snaks = array() /*...*/ ) {
 
 	/**
 	 * Sets the rank of the statement.
-	 * The rank is an element of the Statement::RANK_ enum.
 	 *
 	 * @since 0.1
 	 *
-	 * @param integer $rank
+	 * @param int $rank One of the StatementRank::... constants.
+	 *
 	 * @throws InvalidArgumentException
 	 */
 	public function setRank( $rank ) {
-		$ranks = array( self::RANK_DEPRECATED, self::RANK_NORMAL, self::RANK_PREFERRED );
-
-		if ( !in_array( $rank, $ranks, true ) ) {
-			throw new InvalidArgumentException( 'Invalid rank specified for statement: ' . var_export( $rank, true ) );
-		}
+		StatementRank::assertIsValid( $rank );
 
 		$this->rank = $rank;
 	}

src/Statement/StatementRank.php

@@ -0,0 +1,165 @@
+<?php
+
+namespace Wikibase\DataModel\Statement;
+
+use InvalidArgumentException;
+
+/**
+ * Everything we know about statement's ranks and what they are supposed to mean.
+ *
+ * @see https://www.mediawiki.org/wiki/Wikibase/DataModel#Ranks_of_Statements
+ * @see https://meta.wikimedia.org/wiki/Wikidata/Data_model_update#Ranks_and_order
+ *
+ * @since 4.4
+ *
+ * @licence GNU GPL v2+
+ * @author Thiemo Mättig
+ */
+class StatementRank {
+
+	/**
+	 * Higher values are more preferred.
+	 * TODO: Link to discussion/documentation that guarantees increasing order.
+	 */
+	const DEPRECATED = 0;
+	const NORMAL = 1;
+	const PREFERRED = 2;
+
+	private static $names = array(
+		self::DEPRECATED => 'deprecated',
+		self::NORMAL => 'normal',
+		self::PREFERRED => 'preferred',
+	);
+
+	/**
+	 * @return string[] Array mapping all known self::... constants (integers) to string names.
+	 */
+	public static function getNames() {
+		return self::$names;
+	}
+
+	/**
+	 * @return int[] Array mapping string names to all known self::... constants (integers).
+	 */
+	public static function getAllRanks() {
+		return array_flip( self::$names );
+	}
+
+	/**
+	 * @param int $rank
+	 *
+	 * @throws InvalidArgumentException
+	 */
+	public static function assertIsValid( $rank ) {
+		if ( !self::isValid( $rank ) ) {
+			throw new InvalidArgumentException( 'Invalid rank' );
+		}
+	}
+
+	/**
+	 * @param int $rank
+	 *
+	 * @return bool
+	 */
+	public static function isValid( $rank ) {
+		return is_int( $rank ) && array_key_exists( $rank, self::$names );
+	}
+
+	/**
+	 * @param int $rank
+	 *
+	 * @throws InvalidArgumentException
+	 * @return bool Statements with a deprecated (or lower) rank are known to be false. But don't be
+	 *  fooled, this does not mean higher ranks are known to be true!
+	 */
+	public static function isFalse( $rank ) {
+		self::assertIsValid( $rank );
+
+		return $rank === self::DEPRECATED;
+	}
+
+	/**
+	 * @param int|null $rank1
+	 * @param int|null $rank2
+	 *
+	 * @throws InvalidArgumentException
+	 * @return bool True if the given ranks are equal.
+	 */
+	public static function isEqual( $rank1, $rank2 ) {
+		return self::compare( $rank1, $rank2 ) === 0;
+	}
+
+	/**
+	 * @param int|null $rank1
+	 * @param int|null $rank2
+	 *
+	 * @throws InvalidArgumentException
+	 * @return bool True if the first rank is less preferred than the second.
+	 */
+	public static function isLower( $rank1, $rank2 ) {
+		return self::compare( $rank1, $rank2 ) === -1;
+	}
+
+	/**
+	 * @param int|null $rank1
+	 * @param int|null $rank2
+	 *
+	 * @throws InvalidArgumentException
+	 * @return bool True if the first rank is more preferred than the second.
+	 */
+	public static function isHigher( $rank1, $rank2 ) {
+		return self::compare( $rank1, $rank2 ) === 1;
+	}
+
+	/**
+	 * @param int|null $rank1
+	 * @param int|null $rank2
+	 *
+	 * @throws InvalidArgumentException
+	 * @return int 0 if the ranks are equal, -1 if the first rank is less preferred than the second,
+	 *  or +1 if the first rank is more preferred than the second.
+	 */
+	public static function compare( $rank1, $rank2 ) {
+		if ( $rank1 !== null ) {
+			self::assertIsValid( $rank1 );
+		}
+		if ( $rank2 !== null ) {
+			self::assertIsValid( $rank2 );
+		}
+
+		if ( $rank1 === $rank2 ) {
+			return 0;
+		} elseif ( $rank1 === null || $rank1 < $rank2 ) {
+			return -1;
+		} else {
+			return 1;
+		}
+	}
+
+	/**
+	 * @param int[]|int $ranks
+	 * @param int [$rank2,...]
+	 *
+	 * @return int|null Best rank in the array or list of arguments, or null if none given.
+	 */
+	public static function findBestRank( $ranks = array() /*...*/ ) {
+		if ( !is_array( $ranks ) ) {
+			$ranks = func_get_args();
+		}
+
+		$best = null;
+
+		foreach ( $ranks as $rank ) {
+			if ( self::isHigher( $rank, $best ) ) {
+				$best = $rank;
+
+				if ( $best === self::PREFERRED ) {
+					break;
+				}
+			}
+		}
+
+		return $best;
+	}
+
+}