<?php

/**
 * Note that it uses the ProcessCacheLRUTestable class which extends some
 * properties and methods visibility. That class is defined at the end of the
 * file containing this class.
 *
 * @group Cache
 */
class ProcessCacheLRUTest extends PHPUnit\Framework\TestCase {

	use MediaWikiCoversValidator;

	/**
	 * Helper to verify emptiness of a cache object.
	 * Compare against an array so we get the cache content difference.
	 */
	protected function assertCacheEmpty( $cache, $msg = 'Cache should be empty' ) {
		$this->assertSame( 0, $cache->getEntriesCount(), $msg );
	}

	/**
	 * Helper to fill a cache object passed by reference
	 */
	protected function fillCache( &$cache, $numEntries ) {
		// Fill cache with three values
		for ( $i = 1; $i <= $numEntries; $i++ ) {
			$cache->set( "cache-key-$i", "prop-$i", "value-$i" );
		}
	}

	/**
	 * Generates an array of what would be expected in cache for a given cache
	 * size and a number of entries filled in sequentially
	 */
	protected function getExpectedCache( $cacheMaxEntries, $entryToFill ) {
		$expected = [];

		if ( $entryToFill === 0 ) {
			// The cache is empty!
			return [];
		} elseif ( $entryToFill <= $cacheMaxEntries ) {
			// Cache is not fully filled
			$firstKey = 1;
		} else {
			// Cache overflowed
			$firstKey = 1 + $entryToFill - $cacheMaxEntries;
		}

		$lastKey = $entryToFill;

		for ( $i = $firstKey; $i <= $lastKey; $i++ ) {
			$expected["cache-key-$i"] = [ "prop-$i" => "value-$i" ];
		}

		return $expected;
	}

	/**
	 * Highlight diff between assertEquals and assertNotSame
	 * @coversNothing
	 */
	public function testPhpUnitArrayEquality() {
		$one = [ 'A' => 1, 'B' => 2 ];
		$two = [ 'B' => 2, 'A' => 1 ];
		// ==
		$this->assertEquals( $one, $two );
		// ===
		$this->assertNotSame( $one, $two );
	}

	/**
	 * @dataProvider provideInvalidConstructorArg
	 * @covers ProcessCacheLRU::__construct
	 */
	public function testConstructorGivenInvalidValue( $maxSize ) {
		$this->expectException( Wikimedia\Assert\ParameterAssertionException::class );
		new ProcessCacheLRUTestable( $maxSize );
	}

	/**
	 * Value which are forbidden by the constructor
	 */
	public static function provideInvalidConstructorArg() {
		return [
			[ null ],
			[ [] ],
			[ (object)[] ],
			[ 0 ],
			[ '5' ],
			[ -1 ],
		];
	}

	/**
	 * @covers ProcessCacheLRU::get
	 * @covers ProcessCacheLRU::set
	 * @covers ProcessCacheLRU::has
	 */
	public function testAddAndGetAKey() {
		$oneCache = new ProcessCacheLRUTestable( 1 );
		$this->assertCacheEmpty( $oneCache );

		// First set just one value
		$oneCache->set( 'cache-key', 'prop1', 'value1' );
		$this->assertSame( 1, $oneCache->getEntriesCount() );
		$this->assertTrue( $oneCache->has( 'cache-key', 'prop1' ) );
		$this->assertEquals( 'value1', $oneCache->get( 'cache-key', 'prop1' ) );
	}

	/**
	 * @covers ProcessCacheLRU::set
	 * @covers ProcessCacheLRU::get
	 */
	public function testDeleteOldKey() {
		$oneCache = new ProcessCacheLRUTestable( 1 );
		$this->assertCacheEmpty( $oneCache );

		$oneCache->set( 'cache-key', 'prop1', 'value1' );
		$oneCache->set( 'cache-key', 'prop1', 'value2' );
		$this->assertEquals( 'value2', $oneCache->get( 'cache-key', 'prop1' ) );
	}

	/**
	 * This test that we properly overflow when filling a cache with
	 * a sequence of always different cache-keys. Meant to verify we correclty
	 * delete the older key.
	 *
	 * @covers ProcessCacheLRU::set
	 * @dataProvider provideCacheFilling
	 * @param int $cacheMaxEntries Maximum entry the created cache will hold
	 * @param int $entryToFill Number of entries to insert in the created cache.
	 */
	public function testFillingCache( $cacheMaxEntries, $entryToFill, $msg = '' ) {
		$cache = new ProcessCacheLRUTestable( $cacheMaxEntries );
		$this->fillCache( $cache, $entryToFill );

		$this->assertSame(
			$this->getExpectedCache( $cacheMaxEntries, $entryToFill ),
			$cache->getCache(),
			"Filling a $cacheMaxEntries entries cache with $entryToFill entries"
		);
	}

	/**
	 * Provider for testFillingCache
	 */
	public static function provideCacheFilling() {
		// ($cacheMaxEntries, $entryToFill, $msg='')
		return [
			[ 1, 0 ],
			[ 1, 1 ],
			// overflow
			[ 1, 2 ],
			// overflow
			[ 5, 33 ],
		];
	}

	/**
	 * Create a cache with only one remaining entry then update
	 * the first inserted entry. Should bump it to the top.
	 *
	 * @covers ProcessCacheLRU::set
	 */
	public function testReplaceExistingKeyShouldBumpEntryToTop() {
		$maxEntries = 3;

		$cache = new ProcessCacheLRUTestable( $maxEntries );
		// Fill cache leaving just one remaining slot
		$this->fillCache( $cache, $maxEntries - 1 );

		// Set an existing cache key
		$cache->set( "cache-key-1", "prop-1", "new-value-for-1" );

		$this->assertSame(
			[
				'cache-key-2' => [ 'prop-2' => 'value-2' ],
				'cache-key-1' => [ 'prop-1' => 'new-value-for-1' ],
			],
			$cache->getCache()
		);
	}

	/**
	 * @covers ProcessCacheLRU::get
	 * @covers ProcessCacheLRU::set
	 * @covers ProcessCacheLRU::has
	 */
	public function testRecentlyAccessedKeyStickIn() {
		$cache = new ProcessCacheLRUTestable( 2 );
		$cache->set( 'first', 'prop1', 'value1' );
		$cache->set( 'second', 'prop2', 'value2' );

		// Get first
		$cache->get( 'first', 'prop1' );
		// Cache a third value, should invalidate the least used one
		$cache->set( 'third', 'prop3', 'value3' );

		$this->assertFalse( $cache->has( 'second', 'prop2' ) );
	}

	/**
	 * This first create a full cache then update the value for the 2nd
	 * filled entry.
	 * Given a cache having 1,2,3 as key, updating 2 should bump 2 to
	 * the top of the queue with the new value: 1,3,2* (* = updated).
	 *
	 * @covers ProcessCacheLRU::set
	 * @covers ProcessCacheLRU::get
	 */
	public function testReplaceExistingKeyInAFullCacheShouldBumpToTop() {
		$maxEntries = 3;

		$cache = new ProcessCacheLRUTestable( $maxEntries );
		$this->fillCache( $cache, $maxEntries );

		// Set an existing cache key
		$cache->set( "cache-key-2", "prop-2", "new-value-for-2" );
		$this->assertSame(
			[
				'cache-key-1' => [ 'prop-1' => 'value-1' ],
				'cache-key-3' => [ 'prop-3' => 'value-3' ],
				'cache-key-2' => [ 'prop-2' => 'new-value-for-2' ],
			],
			$cache->getCache()
		);
		$this->assertEquals( 'new-value-for-2',
			$cache->get( 'cache-key-2', 'prop-2' )
		);
	}

	/**
	 * @covers ProcessCacheLRU::set
	 */
	public function testBumpExistingKeyToTop() {
		$cache = new ProcessCacheLRUTestable( 3 );
		$this->fillCache( $cache, 3 );

		// Set the very first cache key to a new value
		$cache->set( "cache-key-1", "prop-1", "new value for 1" );
		$this->assertEquals(
			[
				'cache-key-2' => [ 'prop-2' => 'value-2' ],
				'cache-key-3' => [ 'prop-3' => 'value-3' ],
				'cache-key-1' => [ 'prop-1' => 'new value for 1' ],
			],
			$cache->getCache()
		);
	}
}

/**
 * Overrides some ProcessCacheLRU methods and properties accessibility.
 */
class ProcessCacheLRUTestable extends ProcessCacheLRU {
	public function getCache() {
		return $this->cache->toArray();
	}

	public function getEntriesCount() {
		return count( $this->cache->toArray() );
	}
}