implement/fix reverse iteration when iterating with ending_before (#1100

)
stripe · Jan 7, 2021 · 0149aa5 · 0149aa5
1 parent ec960ea
commit 0149aa5
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Showing 2 changed files with 644 additions and 417 deletions.
diff --git a/lib/autoPagination.js b/lib/autoPagination.js
@@ -5,6 +5,7 @@ const utils = require('./utils');
 
 function makeAutoPaginationMethods(self, requestArgs, spec, firstPagePromise) {
   const promiseCache = {currentPromise: null};
+  const reverseIteration = isReverseIteration(requestArgs);
   let listPromise = firstPagePromise;
   let i = 0;
 
@@ -22,15 +23,16 @@ function makeAutoPaginationMethods(self, requestArgs, spec, firstPagePromise) {
     }
 
     if (i < listResult.data.length) {
-      const value = listResult.data[i];
+      const idx = reverseIteration ? listResult.data.length - 1 - i : i;
+      const value = listResult.data[idx];
       i += 1;
       return {value, done: false};
     } else if (listResult.has_more) {
       // Reset counter, request next page, and recurse.
       i = 0;
-      const lastId = getLastId(listResult);
+      const lastId = getLastId(listResult, reverseIteration);
       listPromise = makeRequest(self, requestArgs, spec, {
-        starting_after: lastId,
+        [reverseIteration ? 'ending_before' : 'starting_after']: lastId,
       });
       return listPromise.then(iterate);
     }
@@ -138,8 +140,8 @@ function getItemCallback(args) {
   };
 }
 
-function getLastId(listResult) {
-  const lastIdx = listResult.data.length - 1;
+function getLastId(listResult, reverseIteration) {
+  const lastIdx = reverseIteration ? 0 : listResult.data.length - 1;
   const lastItem = listResult.data[lastIdx];
   const lastId = lastItem && lastItem.id;
   if (!lastId) {
@@ -241,3 +243,10 @@ function wrapAsyncIteratorWithCallback(asyncIteratorNext, onItem) {
       .catch(reject);
   });
 }
+
+function isReverseIteration(requestArgs) {
+  const args = [].slice.call(requestArgs);
+  const dataFromArgs = utils.getDataFromArgs(args);
+
+  return !!dataFromArgs.ending_before;
+}