[FEATURE] Support white/blacklist allowed FCE types

The same as the `allowedContentType` and `deniedContentTypes` feature in Flux:

```xml
<flux:grid.column variables="{Fluidcontent: {allowedContentTypes: 'fluidcontent_bootstrap:Alert.html'}}" />
```

And the same for `deniedContentTypes`. The setting is inherited from page column to container elements' columns, but not from container element to nested container element. Which means you can filter the allowed content types in both page template's Grid and FCE's content area.

Classes/Hooks/WizardItemsHookSubscriber.php

@@ -25,6 +25,7 @@
  ***************************************************************/
 
 use FluidTYPO3\Fluidcontent\Service\ConfigurationService;
+use FluidTYPO3\Flux\Form\FormInterface;
 use TYPO3\CMS\Backend\Wizard\NewContentElementWizardHookInterface;
 use TYPO3\CMS\Core\Utility\GeneralUtility;
 use TYPO3\CMS\Extbase\Object\ObjectManagerInterface;
@@ -79,6 +80,125 @@ public function __construct() {
 	 */
 	public function manipulateWizardItems(&$items, &$parentObject) {
 		$this->configurationService->writeCachedConfigurationIfMissing();
+		$items = $this->filterPermittedFluidContentTypesByInsertionPosition($items, $parentObject);
 	}
 
+	/**
+	 * @param array $items
+	 * @param \TYPO3\CMS\Backend\Controller\ContentElement\NewContentElementController $parentObject
+	 * @return array
+	 */
+	protected function filterPermittedFluidContentTypesByInsertionPosition(array $items, $parentObject) {
+		$whitelist = array();
+		$blacklist = array();
+		// if a Provider is registered for the "pages" table, try to get a Grid from it. If the Grid
+		// returned contains a Column which matches the desired colPos value, attempt to read a list
+		// of allowed/denied content element types from it.
+		$pageRecord = $GLOBALS['TYPO3_DB']->exec_SELECTgetSingleRow('*', 'pages', "uid = '" . $parentObject->id . "'");
+		$pageProviders = $this->configurationService->resolveConfigurationProviders('pages', NULL, $pageRecord);
+		foreach ($pageProviders as $pageProvider) {
+			$grid = $pageProvider->getGrid($pageRecord);
+			if (NULL === $grid) {
+				continue;
+			}
+			foreach ($grid->getRows() as $row) {
+				foreach ($row->getColumns() as $column) {
+					if ($column->getColumnPosition() === $parentObject->colPos) {
+						list ($whitelist, $blacklist) = $this->appendToWhiteAndBlacklistFromComponent($column, $whitelist, $blacklist);
+					}
+				}
+			}
+		}
+		// Detect what was clicked in order to create the new content element; decide restrictions
+		// based on this.
+		$defaultValues = GeneralUtility::_GET('defVals');
+		if (0 > $parentObject->uid_pid) {
+			// pasting after another element means we should try to resolve the Flux content relation
+			// from that element instead of GET parameters (clicked: "create new" icon after other element)
+			$relativeRecordUid = abs($parentObject->uid_pid);
+			$relativeRecord = $GLOBALS['TYPO3_DB']->exec_SELECTgetSingleRow('*', 'tt_content', "uid = '" . $relativeRecordUid . "'");
+			$fluxAreaName = $relativeRecord['tx_flux_column'];
+		} elseif (TRUE === isset($defaultValues['tt_content']['tx_flux_column'])) {
+			// attempt to read the target Flux content area from GET parameters (clicked: "create new" icon
+			// in top of nested Flux content area
+			$fluxAreaName = $defaultValues['tt_content']['tx_flux_column'];
+			$relativeRecordUid = $defaultValues['tt_content']['tx_flux_parent'];
+		}
+		// if these variables now indicate that we are inserting content elements into a Flux-enabled content
+		// area inside another content element, attempt to read allowed/denied content types from the
+		// Grid returned by the Provider that applies to the parent element's type and configuration
+		// (admitted, that's quite a mouthful - but it's not that different from reading the values from
+		// a page template like above; it's the same principle).
+		if (0 < $relativeRecordUid && FALSE === empty($fluxAreaName)) {
+			$relativeRecord = $GLOBALS['TYPO3_DB']->exec_SELECTgetSingleRow('*', 'tt_content', "uid = '" . $relativeRecordUid . "'");
+			$contentProviders = $this->configurationService->resolveConfigurationProviders('tt_content', NULL, $relativeRecord);
+			foreach ($contentProviders as $contentProvider) {
+				$grid = $contentProvider->getGrid($relativeRecord);
+				if (NULL === $grid) {
+					continue;
+				}
+				foreach ($grid->getRows() as $row) {
+					foreach ($row->getColumns() as $column) {
+						foreach ($column->getAreas() as $area) {
+							if ($area->getName() === $fluxAreaName) {
+								list ($whitelist, $blacklist) = $this->appendToWhiteAndBlacklistFromComponent($area, $whitelist, $blacklist);
+							}
+						}
+					}
+				}
+			}
+		}
+		// White/blacklist filtering. If whitelist contains elements, filter the list
+		// of possible types by whitelist first. Then apply the blacklist, removing
+		// any element types recorded herein.
+		$whitelist = array_unique($whitelist);
+		$blacklist = array_unique($blacklist);
+		if (0 < count($whitelist)) {
+			foreach ($items as $name => $item) {
+				if (FALSE !== strpos($name, '_') && 'fluidcontent_content' === $item['tt_content_defValues']['CType'] && FALSE === in_array($item['tt_content_defValues']['tx_fed_fcefile'], $whitelist)) {
+					unset($items[$name]);
+				}
+			}
+		}
+		if (0 < count($blacklist)) {
+			foreach ($blacklist as $contentElementType) {
+				foreach ($items as $name => $item) {
+					if ('fluidcontent_content' === $item['tt_content_defValues']['CType'] && $item['tt_content_defValues']['tx_fed_fcefile'] === $contentElementType) {
+						unset($items[$name]);
+					}
+				}
+			}
+		}
+		// Finally, loop through the items list and clean up any tabs with zero element types inside.
+		$preserveHeaders = array();
+		foreach ($items as $name => $item) {
+			if (FALSE !== strpos($name, '_')) {
+				array_push($preserveHeaders, reset(explode('_', $name)));
+			}
+		}
+		foreach ($items as $name => $item) {
+			if (FALSE === strpos($name, '_') && FALSE === in_array($name, $preserveHeaders)) {
+				unset($items[$name]);
+			}
+		}
+		return $items;
+	}
+
+	/**
+	 * @param FormInterface $component
+	 * @param array $whitelist
+	 * @param array $blacklist
+	 * @return array
+	 */
+	protected function appendToWhiteAndBlacklistFromComponent(FormInterface $component, array $whitelist, array $blacklist) {
+		$allowed = $component->getVariable('Fluidcontent.allowedContentTypes');
+		if (NULL !== $allowed) {
+			$whitelist = array_merge($whitelist, GeneralUtility::trimExplode(',', $allowed));
+		}
+		$denied = $component->getVariable('Fluidcontent.deniedContentTypes');
+		if (NULL !== $denied) {
+			$blacklist = array_merge($blacklist, GeneralUtility::trimExplode(',', $denied));
+		}
+		return array($whitelist, $blacklist);
+	}
 }