Add API for getting facets.

extension.json

@@ -65,6 +65,10 @@
 		"WikibaseFacetedSearchConfig": "ProfessionalWiki\\WikibaseFacetedSearch\\EntryPoints\\SpecialWikibaseFacetedSearchConfig"
 	},
 
+	"APIModules": {
+		"wbfacetsearch": "ProfessionalWiki\\WikibaseFacetedSearch\\EntryPoints\\ApiWikibaseFacetedSearch"
+	},
+
 	"ResourceFileModulePaths": {
 		"localBasePath": "resources",
 		"remoteExtPath": "WikibaseFacetedSearch/resources"

src/EntryPoints/ApiWikibaseFacetedSearch.php

@@ -0,0 +1,141 @@
+<?php
+
+declare( strict_types=1 );
+
+namespace ProfessionalWiki\WikibaseFacetedSearch\EntryPoints;
+
+use ApiBase;
+use CirrusSearch\Search\CirrusSearchResultSet;
+use Elastica\Query\AbstractQuery;
+use MediaWiki\MediaWikiServices;
+use MediaWiki\Status\Status;
+use ProfessionalWiki\WikibaseFacetedSearch\Application\PropertyConstraints;
+use ProfessionalWiki\WikibaseFacetedSearch\WikibaseFacetedSearchExtension;
+
+class ApiWikibaseFacetedSearch extends ApiBase {
+
+	public function execute(): void {
+		try {
+			$params = $this->extractRequestParams();
+			$term = $params['search'];
+			$namespaces = $params['namespaces'];
+
+			$facets = $this->getFacets( $term, $namespaces );
+
+			$this->getResult()->addValue( null, $this->getModuleName(), $facets );
+		} catch ( \Throwable $e ) {
+			$this->getResult()->addValue( null, 'error', [
+				'message' => $e->getMessage(),
+				'trace' => $e->getTraceAsString(),
+				'file' => $e->getFile(),
+				'line' => $e->getLine()
+			] );
+		}
+	}
+
+	private function getFacets( string $term, ?array $namespaces ): array {
+		$results = $this->runSearch( $term, $namespaces );
+
+		if ( $results instanceof Status ) {
+			if ( !$results->isOK() ) {
+				return [];
+			}
+			$results = $results->getValue();
+		}
+
+		if ( !$results instanceof CirrusSearchResultSet ) {
+			return [];
+		}
+
+		$elasticaResultSet = $results->getElasticaResultSet();
+		if ( $elasticaResultSet === null ) {
+			return [];
+		}
+		$query = $elasticaResultSet->getQuery()->getQuery();
+
+		if ( is_array( $query ) ) {
+			$queryArr = $query;
+			$query = new class ( $queryArr ) extends AbstractQuery {
+				public function __construct( private array $arr ) {
+				}
+
+				public function toArray(): array {
+					return $this->arr;
+				}
+			};
+		}
+
+		$extension = WikibaseFacetedSearchExtension::getInstance();
+		$queryStringParser = $extension->getQueryStringParser();
+		$parsedQuery = $queryStringParser->parse( $term );
+
+		$itemType = $parsedQuery->getItemTypes()[0] ?? null;
+		if ( !$itemType ) {
+			return [];
+		}
+
+		$config = $extension->getConfig();
+		$facetConfigs = $config->getFacetConfigForItemType( $itemType );
+
+		$data = [];
+		$valueCounter = $extension->getValueCounter( $query );
+		$labelLookup = $extension->getLabelLookup( $this->getLanguage() );
+		$formatter = $extension->getFacetValueFormatter( $this->getLanguage() );
+
+		$data = [];
+		foreach ( $facetConfigs as $facetConfig ) {
+			$data[] = $this->buildFacetData(
+				$facetConfig,
+				$parsedQuery,
+				$valueCounter,
+				$labelLookup,
+				$formatter
+			);
+		}
+
+		return $data;
+	}
+
+	private function runSearch( string $term, ?array $namespaces ) {
+		$searchEngine = MediaWikiServices::getInstance()->newSearchEngine();
+		$searchEngine->setLimitOffset( 1 );
+
+		if ( $namespaces ) {
+			$searchEngine->setNamespaces( $namespaces );
+		}
+
+		return $searchEngine->searchText( $term );
+	}
+
+	private function buildFacetData(
+		$facetConfig,
+		$parsedQuery,
+		$valueCounter,
+		$labelLookup,
+		$formatter
+	): array {
+		$constraints = $parsedQuery->getConstraintsForProperty( $facetConfig->propertyId )
+			?? new PropertyConstraints( $facetConfig->propertyId );
+
+		$counts = $valueCounter->countValues( $constraints );
+
+		$propertyId = $facetConfig->propertyId;
+		$propertySerialization = $propertyId->getSerialization();
+
+		$facetData = [
+			'property' => $propertySerialization,
+			'label' => $labelLookup->getLabel( $propertyId )?->getText() ?? $propertySerialization,
+			'values' => [],
+		];
+
+		foreach ( $counts->asArray() as $valCount ) {
+			$facetData['values'][] = [
+				'value' => $valCount->value,
+				'count' => $valCount->count,
+				'label' => $formatter->getLabel( (string)$valCount->value, $propertyId ),
+			];
+		}
+
+		return $facetData;
+	}
+}