Improve drive file operation

Resolve #3789
Resolve #3790

src/server/api/endpoints/admin/drive/show-file.ts

@@ -0,0 +1,28 @@
+import $ from 'cafy';
+import ID, { transform } from '../../../../../misc/cafy-id';
+import define from '../../../define';
+import DriveFile from '../../../../../models/drive-file';
+
+export const meta = {
+	requireCredential: true,
+	requireModerator: true,
+
+	params: {
+		fileId: {
+			validator: $.type(ID),
+			transform: transform,
+		},
+	}
+};
+
+export default define(meta, (ps, me) => new Promise(async (res, rej) => {
+	const file = await DriveFile.findOne({
+		_id: ps.fileId
+	});
+
+	if (file == null) {
+		return rej('file not found');
+	}
+
+	res(file);
+}));