fix(createPaginationFilter): Fixes cursors for sorts with multiple keys. (#15)

Author: ryasmi

src/utils/createPaginationFilter/index.test.ts

@@ -11,7 +11,7 @@ import createCursorFromEntity from '../createCursorFromEntity';
 import createPaginationFilter from './index';
 
 describe('createCursorFromEntity', () => {
-  const sort: Sort<TestEntity> = { id: asc, numberProp: desc };
+  const sort: Sort<TestEntity> = { numberProp: desc, id: asc };
 
   it('should return empty filter when the cursor is start', () => {
     const pagination: Pagination = { cursor: start, direction: forward, limit: 1 };
@@ -25,8 +25,12 @@ describe('createCursorFromEntity', () => {
     const pagination: Pagination = { cursor, direction: forward, limit: 1 };
     const actualResult = createPaginationFilter<TestEntity>(pagination, sort);
     const expectedResult: Filter<TestEntity> = {
-      id: { $gt: testEntity.id },
-      numberProp: { $lte: testEntity.numberProp },
+      $or: [{
+        numberProp: { $lte: testEntity.numberProp },
+      }, {
+        id: { $gt: testEntity.id },
+        numberProp: testEntity.numberProp,
+      }],
     };
     assert.deepEqual(actualResult, expectedResult);
   });
@@ -36,8 +40,12 @@ describe('createCursorFromEntity', () => {
     const pagination: Pagination = { cursor, direction: backward, limit: 1 };
     const actualResult = createPaginationFilter<TestEntity>(pagination, sort);
     const expectedResult: Filter<TestEntity> = {
-      id: { $lt: testEntity.id },
-      numberProp: { $gte: testEntity.numberProp },
+      $or: [{
+        numberProp: { $gte: testEntity.numberProp },
+      }, {
+        id: { $lt: testEntity.id },
+        numberProp: testEntity.numberProp,
+      }],
     };
     assert.deepEqual(actualResult, expectedResult);
   });

src/utils/createPaginationFilter/index.ts

@@ -1,5 +1,5 @@
 import * as atob from 'atob';
-import { get, mapValues } from 'lodash';
+import { get } from 'lodash';
 import { start } from '../../types/Cursor';
 import Entity from '../../types/Entity';
 // tslint:disable-next-line:no-unused
@@ -13,30 +13,53 @@ const xor = (conditionA: boolean, conditionB: boolean) => {
   return (conditionA && !conditionB) || (!conditionA && conditionB);
 };
 
+const getCursorKeyFilter = <E extends Entity>(
+  sortKey: string,
+  sort: Sort<E>,
+  pagination: Pagination,
+  cursorObj: any,
+) => {
+  const sortOrder = get(sort, sortKey);
+  const ascendingPagination = !xor(
+    sortOrder === asc,
+    pagination.direction === forward,
+  );
+  const cursorValue = get(cursorObj, sortKey);
+  if (ascendingPagination) {
+    if (sortKey === 'id') {
+      return { $gt: cursorValue };
+    } else {
+      return { $gte: cursorValue };
+    }
+  } else {
+    if (sortKey === 'id') {
+      return { $lt: cursorValue };
+    } else {
+      return { $lte: cursorValue };
+    }
+  }
+};
+
 export default <E extends Entity>(pagination: Pagination, sort: Sort<E>): Filter<E> => {
-  if (pagination.cursor === start) {
+  const cursor = pagination.cursor;
+  if (cursor === start) {
     return {};
   }
-  const cursor = pagination.cursor;
+
   const cursorObj = JSON.parse(atob(cursor));
-  const filter = mapValues(cursorObj, (cursorValue, sortKey) => {
-    const ascendingPagination = !xor(
-      get(sort, sortKey) === asc,
-      pagination.direction === forward,
-    );
-    if (ascendingPagination) {
-      if (sortKey === 'id') {
-        return { $gt: cursorValue };
-      } else {
-        return { $gte: cursorValue };
-      }
-    } else {
-      if (sortKey === 'id') {
-        return { $lt: cursorValue };
-      } else {
-        return { $lte: cursorValue };
-      }
-    }
+  const sortKeys = Object.keys(sort);
+  const sortKeyFilters = sortKeys.map((sortKey, keyIndex) => {
+    const sortKeysToMatch = sortKeys.slice(0, keyIndex);
+    const matchFilter = sortKeysToMatch.reduce((result: any, sortKeyToMatch) => {
+      result[sortKeyToMatch] = cursorObj[sortKeyToMatch];
+      return result;
+    }, {});
+
+    const cursorKeyFilter = getCursorKeyFilter(sortKey, sort, pagination, cursorObj);
+    matchFilter[sortKey] = cursorKeyFilter;
+    return matchFilter;
   });
+
+  const filter = { $or: sortKeyFilters };
   return filter as any as Filter<E>;
 };