feat: Drop to import onto collection scene (#2005)

* Refactor to functional component

* feat: Basic drag and drop into collection

app/hooks/useImportDocument.js

@@ -0,0 +1,69 @@
+// @flow
+import invariant from "invariant";
+import * as React from "react";
+import { useTranslation } from "react-i18next";
+import { useHistory } from "react-router-dom";
+import useStores from "hooks/useStores";
+
+let importingLock = false;
+
+export default function useImportDocument(
+  collectionId: string,
+  documentId?: string
+): {| handleFiles: (files: File[]) => Promise<void>, isImporting: boolean |} {
+  const { documents, ui } = useStores();
+  const [isImporting, setImporting] = React.useState(false);
+  const { t } = useTranslation();
+  const history = useHistory();
+
+  const handleFiles = React.useCallback(
+    async (files = []) => {
+      if (importingLock) {
+        return;
+      }
+
+      // Because this is the onChange handler it's possible for the change to be
+      // from previously selecting a file to not selecting a file – aka empty
+      if (!files.length) {
+        return;
+      }
+
+      setImporting(true);
+      importingLock = true;
+
+      try {
+        let cId = collectionId;
+        const redirect = files.length === 1;
+
+        if (documentId && !collectionId) {
+          const document = await documents.fetch(documentId);
+          invariant(document, "Document not available");
+          cId = document.collectionId;
+        }
+
+        for (const file of files) {
+          const doc = await documents.import(file, documentId, cId, {
+            publish: true,
+          });
+
+          if (redirect) {
+            history.push(doc.url);
+          }
+        }
+      } catch (err) {
+        ui.showToast(`${t("Could not import file")}. ${err.message}`, {
+          type: "error",
+        });
+      } finally {
+        setImporting(false);
+        importingLock = false;
+      }
+    },
+    [t, ui, documents, history, collectionId, documentId]
+  );
+
+  return {
+    handleFiles,
+    isImporting,
+  };
+}