feat: add clearAll flag (Fixes #55)

README.md

@@ -161,6 +161,19 @@ import but only need the active ones you can trigger the task as follows:
 If you do not have access to a CLI (i.e Silverstripe Cloud) then you can also
 bulk reindex via a queued job `AlgoliaReindexAllJob`.
 
+### Optional
+
+`forceAll` forces every Silverstripe record to be re-synced.
+
+```
+./vendor/bin/sake dev/tasks/AlgoliaReindex "flush=1&forceAll=1"
+```
+
+`clearAll` truncates the search index before reindexing.
+
+```
+./vendor/bin/sake dev/tasks/AlgoliaReindex "flush=1&clearAll=1&forceAll=1"
+```
 
 ### Customising the indexed attributes (fields)
 

src/Tasks/AlgoliaReindex.php

@@ -64,6 +64,17 @@ public function run($request)
             $filter = 'AlgoliaIndexed IS NULL';
         }
 
+        /** @var AlgoliaService */
+        $algoliaService = Injector::inst()->create(AlgoliaService::class);
+
+        if ($request->getVar('clearAll')) {
+            $indexes = $algoliaService->initIndexes();
+
+            foreach ($indexes as $indexName => $index) {
+                $index->clearObjects();
+            }
+        }
+
         if ($targetClass) {
             $items = $this->getItems($targetClass, $filter);
 
@@ -78,7 +89,6 @@ public function run($request)
                 );
             }
         } else {
-            $algoliaService = Injector::inst()->create(AlgoliaService::class);
 
             // find all classes we have to index and do so
             foreach ($algoliaService->indexes as $index) {