class ChainedFastBackendTest

class ChainedFastBackendTest extends UnitTestCase {
  
  /**
   * The consistent cache backend.
   *
   * @var \Drupal\Core\Cache\CacheBackendInterface
   */
  protected $consistentCache;
  
  /**
   * The fast cache backend.
   *
   * @var \Drupal\Core\Cache\CacheBackendInterface
   */
  protected $fastCache;
  
  /**
   * The cache bin.
   *
   * @var string
   */
  protected $bin;
  
  /**
   * Tests a get() on the fast backend, with no hit on the consistent backend.
   */
  public function testGetDoesNotHitConsistentBackend() : void {
    $consistent_cache = $this->createMock('Drupal\\Core\\Cache\\CacheBackendInterface');
    $timestamp_cid = ChainedFastBackend::LAST_WRITE_TIMESTAMP_PREFIX . 'cache_foo';
    // Use the request time because that is what we will be comparing against.
    $timestamp_item = (object) [
      'cid' => $timestamp_cid,
      'data' => (int) $_SERVER['REQUEST_TIME'] - 60,
    ];
    $consistent_cache->expects($this->once())
      ->method('get')
      ->with($timestamp_cid)
      ->willReturn($timestamp_item);
    $consistent_cache->expects($this->never())
      ->method('getMultiple');
    $fast_cache = new MemoryBackend(new Time());
    $fast_cache->set('foo', 'baz');
    $chained_fast_backend = new ChainedFastBackend($consistent_cache, $fast_cache, 'foo');
    $this->assertEquals('baz', $chained_fast_backend->get('foo')->data);
  }
  
  /**
   * Tests a get() on consistent backend without saving on fast backend.
   */
  public function testSetInvalidDataFastBackend() : void {
    $cid = $this->randomString();
    $item = (object) [
      'cid' => $cid,
      'data' => serialize($this->randomObject()),
      'created' => ChainedFastBackend::LAST_WRITE_TIMESTAMP_PREFIX . 'cache_foo',
      'expire' => Cache::PERMANENT,
      'tags' => [],
      'valid' => FALSE,
    ];
    $consistent_cache = $this->createMock('Drupal\\Core\\Cache\\CacheBackendInterface');
    $consistent_cache->expects($this->once())
      ->method('get')
      ->withAnyParameters()
      ->willReturn(FALSE);
    $consistent_cache->expects($this->once())
      ->method('getMultiple')
      ->withAnyParameters()
      ->willReturn([
      $item,
    ]);
    $fast_cache = new MemoryBackend(new Time());
    $chained_fast_backend = new ChainedFastBackend($consistent_cache, $fast_cache, 'foo');
    // Perform a get using the allowing invalid data parameter.
    $this->assertEquals($item, $chained_fast_backend->get($cid, TRUE));
    // Perform a get directly on the fast cache to guarantee the invalid data
    // were not saved there.
    $this->assertEquals(NULL, $fast_cache->get($cid), 'Invalid data was not saved on the fast cache.');
  }
  
  /**
   * Tests that sets only get written to the consistent backend.
   */
  public function testSet() : void {
    $consistent_cache = $this->createMock(CacheBackendInterface::class);
    $fast_cache = $this->createMock(CacheBackendInterface::class);
    // The initial write to the fast backend should result in two writes to the
    // consistent backend, once to invalidate the last write timestamp and once
    // for the item itself. However subsequent writes during the same second
    // should only write to the cache item without further invalidations.
    $consistent_cache->expects($this->exactly(5))
      ->method('set');
    $fast_cache->expects($this->never())
      ->method('set');
    $fast_cache->expects($this->never())
      ->method('setMultiple');
    $chained_fast_backend = new ChainedFastBackend($consistent_cache, $fast_cache, 'foo');
    $chained_fast_backend->set('foo', TRUE);
    $chained_fast_backend->set('bar', TRUE);
    $chained_fast_backend->set('baz', TRUE);
    $chained_fast_backend->set('zoo', TRUE);
  }
  
  /**
   * Tests a fast cache miss gets data from the consistent cache backend.
   */
  public function testFastBackendGracePeriod() : void {
    $timestamp_item = (object) [
      'cid' => ChainedFastBackend::LAST_WRITE_TIMESTAMP_PREFIX . 'cache_foo',
      // This is set two seconds in the future so that the grace period before
      // writing through to the fast backend is observed.
'data' => time() + 2,
    ];
    $cache_item = (object) [
      'cid' => 'foo',
      'data' => 'baz',
      'created' => time(),
      'expire' => time() + 3600,
      'tags' => [
        'tag',
      ],
    ];
    $consistent_cache = $this->createMock(CacheBackendInterface::class);
    $fast_cache = $this->createMock(CacheBackendInterface::class);
    // We should get a call for the timestamp on the consistent backend.
    $consistent_cache->expects($this->once())
      ->method('get')
      ->with($timestamp_item->cid)
      ->willReturn($timestamp_item);
    // We should get a call for the cache item on the consistent backend.
    $consistent_cache->expects($this->once())
      ->method('getMultiple')
      ->with([
      $cache_item->cid,
    ])
      ->willReturn([
      $cache_item->cid => $cache_item,
    ]);
    // We should not get a call for the cache item on the fast backend.
    $fast_cache->expects($this->never())
      ->method('getMultiple');
    // We should not get a call to set the cache item on the fast backend.
    $fast_cache->expects($this->never())
      ->method('set');
    $chained_fast_backend = new ChainedFastBackend($consistent_cache, $fast_cache, 'foo');
    $this->assertEquals('baz', $chained_fast_backend->get('foo')->data);
  }
  
  /**
   * Tests a fast cache miss gets data from the consistent cache backend.
   */
  public function testFallThroughToConsistentCache() : void {
    // Make the last_write_timestamp two seconds in the past so that everything
    // is written back to the fast backend.
    $timestamp_item = (object) [
      'cid' => ChainedFastBackend::LAST_WRITE_TIMESTAMP_PREFIX . 'cache_foo',
      'data' => time() - 2,
    ];
    $cache_item = (object) [
      'cid' => 'foo',
      'data' => 'baz',
      // The created time is set one minute in the past, e.g. before the
      // consistent timestamp.
'created' => time() - 60,
      'expire' => time() + 3600,
      'tags' => [
        'tag',
      ],
    ];
    $consistent_cache = $this->createMock(CacheBackendInterface::class);
    $fast_cache = $this->createMock(CacheBackendInterface::class);
    // We should get a call for the timestamp on the consistent backend.
    $consistent_cache->expects($this->once())
      ->method('get')
      ->with($timestamp_item->cid)
      ->willReturn($timestamp_item);
    // We should get a call for the cache item on the consistent backend.
    $consistent_cache->expects($this->once())
      ->method('getMultiple')
      ->with([
      $cache_item->cid,
    ])
      ->willReturn([
      $cache_item->cid => $cache_item,
    ]);
    // We should get a call for the cache item on the fast backend.
    $fast_cache->expects($this->once())
      ->method('getMultiple')
      ->with([
      $cache_item->cid,
    ])
      ->willReturn([
      $cache_item->cid => $cache_item,
    ]);
    // We should get a call to set the cache item on the fast backend.
    $fast_cache->expects($this->once())
      ->method('set')
      ->with($cache_item->cid, $cache_item->data, $cache_item->expire);
    $chained_fast_backend = new ChainedFastBackend($consistent_cache, $fast_cache, 'foo');
    $this->assertEquals('baz', $chained_fast_backend->get('foo')->data);
  }

}