handle promise-returning handlers

Author: leonardodino

lib/serve.js

@@ -13,6 +13,36 @@ function handleErr(err, response) {
   return;
 }
 
+function createCallback(response) {
+  return function callback(err, lambdaResponse) {
+    if (err) {
+      return handleErr(err, response);
+    }
+
+    response.statusCode = lambdaResponse.statusCode;
+    for (const key in lambdaResponse.headers) {
+      response.setHeader(key, lambdaResponse.headers[key]);
+    }
+    response.write(
+      lambdaResponse.isBase64Encoded
+        ? base64.decode(lambdaResponse.body)
+        : lambdaResponse.body
+    );
+    response.end();
+  }
+}
+
+function promiseCallback(promise, callback) {
+  if (!promise) return;
+  if (typeof promise.then !== 'function') return;
+  if (typeof callback !== 'function') return;
+
+  promise.then(
+    function(data) {callback(null, data)},
+    function(err) {callback(err, null)}
+  );
+}
+
 function createHandler(dir) {
   return function(request, response) {
     var func = request.path.split("/").filter(function(e) {
@@ -39,22 +69,9 @@ function createHandler(dir) {
       isBase64Encoded: isBase64
     };
 
-    handler.handler(lambdaRequest, {}, function(err, lambdaResponse) {
-      if (err) {
-        return handleErr(err, response);
-      }
-
-      response.statusCode = lambdaResponse.statusCode;
-      for (const key in lambdaResponse.headers) {
-        response.setHeader(key, lambdaResponse.headers[key]);
-      }
-      response.write(
-        lambdaResponse.isBase64Encoded
-          ? base64.decode(lambdaResponse.body)
-          : lambdaResponse.body
-      );
-      response.end();
-    });
+    var callback = createCallback(response);
+    var promise = handler.handler(lambdaRequest, {}, callback);
+    promiseCallback(promise, callback);
   };
 }