Fix lexicographic multi-key sorting (#356)

tests/MultisortTest.php

@@ -0,0 +1,84 @@
+<?php
+
+require_once dirname(__DIR__) . '/GameEngine/Multisort.php';
+
+function assertSameMultisort($expected, $actual, $message)
+{
+	if ($expected !== $actual) {
+		fwrite(
+			STDERR,
+			$message . PHP_EOL .
+			'Expected: ' . var_export($expected, true) . PHP_EOL .
+			'Actual:   ' . var_export($actual, true) . PHP_EOL
+		);
+		exit(1);
+	}
+}
+
+function sortedIds($rows)
+{
+	return array_column($rows, 'id');
+}
+
+$sorter = new multiSort();
+
+$rankings = array(
+	array('id' => 'a', 'x' => 0, 'y' => 0, 'pop' => 1),
+	array('id' => 'b', 'x' => 1, 'y' => 0, 'pop' => 9),
+	array('id' => 'c', 'x' => 0, 'y' => 1, 'pop' => 5),
+);
+
+assertSameMultisort(
+	array('a', 'c', 'b'),
+	sortedIds($sorter->sorte(
+		$rankings,
+		'x', true, 2,
+		'y', true, 2,
+		'pop', false, 2
+	)),
+	'Sort keys must be applied lexicographically in their declared order.'
+);
+
+$offers = array(
+	array('id' => 'slow', 'duration' => 30),
+	array('id' => 'fast', 'duration' => 5),
+	array('id' => 'medium', 'duration' => 15),
+);
+
+assertSameMultisort(
+	array('fast', 'medium', 'slow'),
+	sortedIds($sorter->sorte($offers, 'duration', true, 2)),
+	'Single-key numeric sorting must retain its existing behavior.'
+);
+
+$naturalNames = array(
+	array('id' => 'ten', 'name' => 'Item10'),
+	array('id' => 'two', 'name' => 'item2'),
+	array('id' => 'one', 'name' => 'ITEM1'),
+);
+
+assertSameMultisort(
+	array('one', 'two', 'ten'),
+	sortedIds($sorter->sorte($naturalNames, 'name', true, 1)),
+	'Case-insensitive natural sorting must retain its existing behavior.'
+);
+
+$ties = array(
+	array('id' => 'first', 'score' => 10),
+	array('id' => 'second', 'score' => 10),
+	array('id' => 'third', 'score' => 10),
+);
+
+assertSameMultisort(
+	array('first', 'second', 'third'),
+	sortedIds($sorter->sorte($ties, 'score', false, 2)),
+	'Rows equal across all criteria must retain their input order.'
+);
+
+assertSameMultisort(
+	$rankings,
+	$sorter->sorte($rankings),
+	'Calling sorte() without criteria must leave the input unchanged.'
+);
+
+echo "Multisort tests passed." . PHP_EOL;