Merge pull request #305 from mixmaxhq/srinand/expose-encodePaginationTokens

feat: extract/expose a function to encode pagination tokens

Author: Srinand Balaji

src/index.js

@@ -4,6 +4,7 @@ const find = require('./find');
 const findWithReq = require('./findWithReq');
 const search = require('./search');
 const sanitizeQuery = require('./utils/sanitizeQuery');
+const { encodePaginationTokens } = require('./utils/query');
 const mongoosePlugin = require('./mongoose.plugin');
 
 module.exports = {
@@ -14,4 +15,5 @@ module.exports = {
   search,
   mongoosePlugin,
   sanitizeQuery,
+  encodePaginationTokens,
 };

src/utils/query.js

@@ -1,6 +1,40 @@
 const bsonUrlEncoding = require('./bsonUrlEncoding');
 const objectPath = require('object-path');
 
+/**
+ * Helper function to encode pagination tokens.
+ *
+ * NOTE: this function modifies the passed-in `response` argument directly.
+ *
+ * @param      {Object}  params
+ *   * @param      {String}  paginatedField
+ * @param      {Object}  response  The response
+ *   @param      {String?}  previous
+ *   @param      {String?}  next
+ *
+ * @returns void
+ */
+function encodePaginationTokens(params, response) {
+  const shouldSecondarySortOnId = params.paginatedField !== '_id';
+
+  if (response.previous) {
+    const previousPaginatedField = objectPath.get(response.previous, params.paginatedField);
+    if (shouldSecondarySortOnId) {
+      response.previous = bsonUrlEncoding.encode([previousPaginatedField, response.previous._id]);
+    } else {
+      response.previous = bsonUrlEncoding.encode(previousPaginatedField);
+    }
+  }
+  if (response.next) {
+    const nextPaginatedField = objectPath.get(response.next, params.paginatedField);
+    if (shouldSecondarySortOnId) {
+      response.next = bsonUrlEncoding.encode([nextPaginatedField, response.next._id]);
+    } else {
+      response.next = bsonUrlEncoding.encode(nextPaginatedField);
+    }
+  }
+}
+
 module.exports = {
   /**
    * Parses the raw results from a find or aggregate query and generates a response object that
@@ -13,7 +47,6 @@ module.exports = {
    */
   prepareResponse(results, params) {
     const hasMore = results.length > params.limit;
-    const shouldSecondarySortOnId = params.paginatedField !== '_id';
     // Remove the extra element that we added to 'peek' to see if there were more entries.
     if (hasMore) results.pop();
 
@@ -31,26 +64,13 @@ module.exports = {
       hasNext,
     };
 
-    if (response.previous) {
-      const previousPaginatedField = objectPath.get(response.previous, params.paginatedField);
-      if (shouldSecondarySortOnId) {
-        response.previous = bsonUrlEncoding.encode([previousPaginatedField, response.previous._id]);
-      } else {
-        response.previous = bsonUrlEncoding.encode(previousPaginatedField);
-      }
-    }
-    if (response.next) {
-      const nextPaginatedField = objectPath.get(response.next, params.paginatedField);
-      if (shouldSecondarySortOnId) {
-        response.next = bsonUrlEncoding.encode([nextPaginatedField, response.next._id]);
-      } else {
-        response.next = bsonUrlEncoding.encode(nextPaginatedField);
-      }
-    }
+    encodePaginationTokens(params, response);
 
     return response;
   },
 
+  encodePaginationTokens,
+
   /**
    * Generates a `$sort` object given the parameters
    *

test/utils/query.test.js

@@ -0,0 +1,34 @@
+const bsonUrlEncoding = require('../../src/utils/bsonUrlEncoding');
+const { encodePaginationTokens } = require('../../src/utils/query');
+
+describe('encodePaginationTokens', () => {
+  it('encodes the pagination tokens on the passed-in response object', () => {
+    const params = {
+      paginatedField: '_id',
+    };
+    const response = {
+      next: { _id: '789' },
+      previous: { _id: '456' },
+    };
+
+    encodePaginationTokens(params, response);
+
+    expect(response.next).toEqual(bsonUrlEncoding.encode('789'));
+    expect(response.previous).toEqual(bsonUrlEncoding.encode('456'));
+  });
+
+  it("constructs pagination tokens using both the _id and the paginatedField if the latter isn't the former", () => {
+    const params = {
+      paginatedField: 'name',
+    };
+    const response = {
+      next: { _id: '789', name: 'Test 2' },
+      previous: { _id: '456', name: 'Test' },
+    };
+
+    encodePaginationTokens(params, response);
+
+    expect(response.next).toEqual(bsonUrlEncoding.encode(['Test 2', '789']));
+    expect(response.previous).toEqual(bsonUrlEncoding.encode(['Test', '456']));
+  });
+});