Bugfix - Pagination info edge cases

src/page-info.type.spec.ts

@@ -0,0 +1,87 @@
+import { PageInfo } from './page-info.type';
+
+const assert = require('assert');
+
+describe('PageInfo', function () {
+
+  it('should return correct pagination when all parameters are provided', function () {
+    let pageInfo = new PageInfo(100, 0, 10);
+    assert(pageInfo.hasNextPage === true);
+    assert(pageInfo.hasPreviousPage === false);
+  });
+
+  it('should return correct pagination when both limit and offset are not provided', function () {
+    let pageInfo = new PageInfo(100, undefined, undefined);
+    assert(pageInfo.hasNextPage === false);
+    assert(pageInfo.hasPreviousPage === false);
+  });
+
+  describe('limit', function () {
+
+    it('should return correct pagination when limit is bigger than count', function () {
+      let pageInfo = new PageInfo(100, 10, 200);
+      assert(pageInfo.hasNextPage === false);
+      assert(pageInfo.hasPreviousPage === true);
+    });
+
+    it('should return correct pagination when limit is smaller than count', function () {
+      let pageInfo = new PageInfo(100, 10, 10);
+      assert(pageInfo.hasNextPage === true);
+      assert(pageInfo.hasPreviousPage === true);
+    });
+
+    it('should return correct pagination when limit is a negative number', function () {
+      let pageInfo = new PageInfo(100, 10, -10);
+      assert(pageInfo.hasNextPage === false);
+      assert(pageInfo.hasPreviousPage === true);
+    });
+
+    it('should return correct pagination when limit is zero', function () {
+      let pageInfo = new PageInfo(100, 10, 0);
+      assert(pageInfo.hasNextPage === false);
+      assert(pageInfo.hasPreviousPage === true);
+    });
+
+    it('should return correct pagination when limit is not provided', function () {
+      let pageInfo = new PageInfo(100, 10, undefined);
+      assert(pageInfo.hasNextPage === false);
+      assert(pageInfo.hasPreviousPage === true);
+    });
+
+  });
+
+  describe('offset', function () {
+
+    it('should return correct pagination when offset is a bigger than count', function () {
+      let pageInfo = new PageInfo(100, 200, 10);
+      assert(pageInfo.hasNextPage === false);
+      assert(pageInfo.hasPreviousPage === true);
+    });
+
+    it('should return correct pagination when offset is smaller than count', function () {
+      let pageInfo = new PageInfo(100, 5, 10);
+      assert(pageInfo.hasNextPage === true);
+      assert(pageInfo.hasPreviousPage === true);
+    });
+
+    it('should return correct pagination when offset is a negative number', function () {
+      let pageInfo = new PageInfo(100, -5, 10);
+      assert(pageInfo.hasNextPage === true);
+      assert(pageInfo.hasPreviousPage === false);
+    });
+
+    it('should return correct pagination when offset is zero', function () {
+      let pageInfo = new PageInfo(100, 0, 10);
+      assert(pageInfo.hasNextPage === true);
+      assert(pageInfo.hasPreviousPage === false);
+    });
+
+    it('should return correct pagination when offset is not provided', function () {
+      let pageInfo = new PageInfo(100, undefined, 10);
+      assert(pageInfo.hasNextPage === true);
+      assert(pageInfo.hasPreviousPage === false);
+    });
+
+  });
+
+});

src/page-info.type.ts

@@ -1,13 +1,17 @@
 import * as graphql from 'graphql';
+
 import { GraphQLObjectType } from 'graphql';
 
 export class PageInfo {
 
-  private readonly hasNextPage: boolean;
-  private readonly hasPreviousPage: boolean;
+  public readonly hasNextPage: boolean;
+  public readonly hasPreviousPage: boolean;
 
   constructor(count: number, offset: number, limit: number) {
-    this.hasNextPage = offset !== null && limit !== null && count > (offset + limit);
+    count = count || 0;
+    offset = offset || 0;
+    limit = limit > 0 ? limit : count;
+    this.hasNextPage = count > (offset + limit);
     this.hasPreviousPage = offset > 0;
   }