refactor: Changes pagination and sorting constants to improve readability. (#8)

BREAKING CHANGE: In pagination `forward` was renamed to `direction`.
BREAKING CHANGE: To paginate forward use `'forward'` in `pagination.direction` instead of `true` in `pagination.forward`. Use `import { forward } from '@js-entity-repos/core/dist/types/PaginationDirection'`.
BREAKING CHANGE: To paginate backward use `'backward'` in `pagination.direction` instead of `false` in `pagination.forward`. Use `import { backward } from '@js-entity-repos/core/dist/types/PaginationDirection'`.
BREAKING CHANGE: To sort in ascending order use `'asc'` in `sort` instead of `true`. Use `import { asc } from '@js-entity-repos/core/dist/types/SortOrder'`.
BREAKING CHANGE: To sort in descending order use `'desc'` in `sort` instead of `false`. Use `import { desc } from '@js-entity-repos/core/dist/types/SortOrder'`.

Author: ryasmi

Diff for: docs/options.md

@@ -101,13 +101,13 @@ The filter below is comprehensive example using all of the operators.
 
 
 ### Sort
-This is an object where a key represents the entity property to be sorted and the value represents the direction to sort. The value should be `true` to sort in ascending order and `false` to sort in descending order. The properties are sorted in order of their definition in the sort option, for example, the following sort option `{ createdAt: false, id: true }` will sort by the `createdAt` property first and then the the `id` property.
+This is an object where a key represents the entity property to be sorted and the value represents the direction to sort. The value should be `'asc'` to sort in ascending order and `'desc'` to sort in descending order. The properties are sorted in order of their definition in the sort option, for example, the following sort option `{ createdAt: false, id: true }` will sort by the `createdAt` property first and then the the `id` property.
 
-This package contains the [TypeScript Sort type definition](../src/types/Sort.ts).
+This package contains the [TypeScript Sort type definition](../src/types/Sort.ts). It also contains [constants for `'asc'` and `'desc'`](../src/types/SortOrder.ts) that should always be used to avoid breaking changes in the future.
 
 ### Pagination
-This is an object with three properties, `limit`, `forward`, and `cursor`. The `limit` property defines how many entities to return (maximum). The `forward` property defines whether the entities should be iterated through forwards (when `true`) or backwards (when `false`) from the `cursor`. The `cursor` property defines where to start iterating through the entities. Cursors have been used instead of `skip` and `limit` to avoid the [pagination issues discussed by Rakhitha Nimesh](https://www.sitepoint.com/paginating-real-time-data-cursor-based-pagination/).
+This is an object with three properties, `limit`, `direction`, and `cursor`. The `limit` property defines how many entities to return (maximum). The `direction` property defines whether the entities should be iterated through forwards (when `'forward'`) or backwards (when `'backward'`) from the `cursor`. The `cursor` property defines where to start iterating through the entities. Cursors have been used instead of `skip` and `limit` to avoid the [pagination issues discussed by Rakhitha Nimesh](https://www.sitepoint.com/paginating-real-time-data-cursor-based-pagination/).
 
 Concrete implementations of the facade can use the [`createCursorFromEntity`](../src/utils/createCursorFromEntity) and [`createPaginationFilter`](../src/utils/createPaginationFilter) utility functions to generate cursors.
 
-This package also contains the [TypeScript Pagination interface](../src/types/Pagination.ts) and the [TypeScript Cursor type definition](../src/types/Cursor.ts).
+This package contains the [TypeScript Pagination interface](../src/types/Pagination.ts) and the [TypeScript Cursor type definition](../src/types/Cursor.ts). It also contains [constants for `'forward'` and `'backward'`](../src/types/PaginationDirection.ts) that should always be used to avoid breaking changes in the future.

Diff for: src/tests/getEntities/paginationTest.ts

@@ -3,6 +3,7 @@ import * as assert from 'power-assert';
 import Facade from '../../Facade';
 import Cursor from '../../types/Cursor';
 import Pagination from '../../types/Pagination';
+import PaginationDirection, { backward, forward } from '../../types/PaginationDirection';
 import { TestEntity, testEntity } from '../utils/testEntity';
 
 export default (facade: Facade<TestEntity>) => {
@@ -16,8 +17,8 @@ export default (facade: Facade<TestEntity>) => {
     await facade.createEntity({ id: secondId, entity: secondEntity });
   };
 
-  const paginate = (cursor: Cursor, forward: boolean) => {
-    const pagination: Pagination = { cursor, forward, limit: 1 };
+  const paginate = (cursor: Cursor, direction: PaginationDirection) => {
+    const pagination: Pagination = { cursor, direction, limit: 1 };
     return facade.getEntities({ pagination });
   };
 
@@ -29,50 +30,50 @@ export default (facade: Facade<TestEntity>) => {
 
   it('should return first entity when there are two entities limitted to 1', async () => {
     await createTestEntities();
-    const pagination: Pagination = { cursor: undefined, forward: true, limit: 1 };
+    const pagination: Pagination = { cursor: undefined, direction: forward, limit: 1 };
     const result = await facade.getEntities({ pagination });
     assert.deepEqual(result.entities, [firstEntity]);
   });
 
   it('should return first entity when paginating forward without cursor', async () => {
     await createTestEntities();
-    const finalResult = await paginate(undefined, true);
+    const finalResult = await paginate(undefined, forward);
     assert.deepEqual(finalResult.entities, [firstEntity]);
   });
 
   it('should return second entity when paginating forward with first cursor', async () => {
     await createTestEntities();
-    const firstResult = await paginate(undefined, true);
-    const finalResult = await paginate(firstResult.nextCursor, true);
+    const firstResult = await paginate(undefined, forward);
+    const finalResult = await paginate(firstResult.nextCursor, forward);
     assert.deepEqual(finalResult.entities, [secondEntity]);
   });
 
   it('should return no entities when paginating forward with second cursor', async () => {
     await createTestEntities();
-    const firstResult = await paginate(undefined, true);
-    const secondResult = await paginate(firstResult.nextCursor, true);
-    const finalResult = await paginate(secondResult.nextCursor, true);
+    const firstResult = await paginate(undefined, forward);
+    const secondResult = await paginate(firstResult.nextCursor, forward);
+    const finalResult = await paginate(secondResult.nextCursor, forward);
     assert.deepEqual(finalResult.entities, []);
   });
 
   it('should return second entity when paginating backward without cursor', async () => {
     await createTestEntities();
-    const finalResult = await paginate(undefined, false);
+    const finalResult = await paginate(undefined, backward);
     assert.deepEqual(finalResult.entities, [secondEntity]);
   });
 
   it('should return first entity when paginating backward with first cursor', async () => {
     await createTestEntities();
-    const firstResult = await paginate(undefined, false);
-    const finalResult = await paginate(firstResult.previousCursor, false);
+    const firstResult = await paginate(undefined, backward);
+    const finalResult = await paginate(firstResult.previousCursor, backward);
     assert.deepEqual(finalResult.entities, [firstEntity]);
   });
 
   it('should return no entities when paginating backward with second cursor', async () => {
     await createTestEntities();
-    const firstResult = await paginate(undefined, false);
-    const secondResult = await paginate(firstResult.previousCursor, false);
-    const finalResult = await paginate(secondResult.previousCursor, false);
+    const firstResult = await paginate(undefined, backward);
+    const secondResult = await paginate(firstResult.previousCursor, backward);
+    const finalResult = await paginate(secondResult.previousCursor, backward);
     assert.deepEqual(finalResult.entities, []);
   });
 };

Diff for: src/tests/getEntities/sortTest.ts

@@ -2,6 +2,7 @@ import 'mocha'; // tslint:disable-line:no-import-side-effect
 import * as assert from 'power-assert';
 import Facade from '../../Facade';
 import Sort from '../../types/Sort';
+import { asc, desc } from '../../types/SortOrder';
 import { TestEntity, testEntity } from '../utils/testEntity';
 
 export default (facade: Facade<TestEntity>) => {
@@ -26,36 +27,36 @@ export default (facade: Facade<TestEntity>) => {
   it('should sort by one ascending property when entities are ordered', async () => {
     await facade.createEntity({ id: firstId, entity: firstEntity });
     await facade.createEntity({ id: secondId, entity: secondEntity });
-    await assertSort([firstEntity, secondEntity], { stringProp: true });
+    await assertSort([firstEntity, secondEntity], { stringProp: asc });
   });
 
   it('should sort by one ascending property when entities are unordered', async () => {
     await facade.createEntity({ id: secondId, entity: secondEntity });
     await facade.createEntity({ id: firstId, entity: firstEntity });
-    await assertSort([firstEntity, secondEntity], { stringProp: true });
+    await assertSort([firstEntity, secondEntity], { stringProp: asc });
   });
 
   it('should sort by one descending property when entities are ordered', async () => {
     await facade.createEntity({ id: secondId, entity: secondEntity });
     await facade.createEntity({ id: firstId, entity: firstEntity });
-    await assertSort([secondEntity, firstEntity], { stringProp: false });
+    await assertSort([secondEntity, firstEntity], { stringProp: desc });
   });
 
   it('should sort by one descending property when entities are unordered', async () => {
     await facade.createEntity({ id: firstId, entity: firstEntity });
     await facade.createEntity({ id: secondId, entity: secondEntity });
-    await assertSort([secondEntity, firstEntity], { stringProp: false });
+    await assertSort([secondEntity, firstEntity], { stringProp: desc });
   });
 
   it('should sort by two properties when ascending first and descending second', async () => {
     await facade.createEntity({ id: firstId, entity: firstEntity });
     await facade.createEntity({ id: secondId, entity: secondEntity });
-    await assertSort([firstEntity, secondEntity], { stringProp: true, numberProp: false });
+    await assertSort([firstEntity, secondEntity], { stringProp: asc, numberProp: desc });
   });
 
   it('should sort by two properties when descending first and ascending second', async () => {
     await facade.createEntity({ id: firstId, entity: firstEntity });
     await facade.createEntity({ id: secondId, entity: secondEntity });
-    await assertSort([secondEntity, firstEntity], { stringProp: false, numberProp: true });
+    await assertSort([secondEntity, firstEntity], { stringProp: desc, numberProp: asc });
   });
 };

Diff for: src/types/Pagination.ts

@@ -1,7 +1,8 @@
 import Cursor from './Cursor';
+import PaginationDirection from './PaginationDirection';
 
 export default interface Pagination {
   readonly cursor: Cursor;
-  readonly forward: boolean;
+  readonly direction: PaginationDirection;
   readonly limit: number;
 }

Diff for: src/types/PaginationDirection.ts

@@ -0,0 +1,6 @@
+export const forward = 'forward';
+export const backward = 'backward';
+
+type PaginationDirection = typeof forward | typeof backward;
+
+export default PaginationDirection;

Diff for: src/types/Sort.ts

@@ -1,7 +1,8 @@
 import Entity from './Entity';
+import SortOrder from './SortOrder';
 
 type Sort<E extends Entity> = {
-  readonly [P in keyof E]?: boolean;
+  readonly [P in keyof E]?: SortOrder;
 };
 
 export default Sort;

Diff for: src/types/SortOrder.ts

@@ -0,0 +1,6 @@
+export const asc = 'asc';
+export const desc = 'desc';
+
+type SortOrder = typeof asc | typeof desc;
+
+export default SortOrder;

Diff for: src/utils/createCursorFromEntity/index.test.ts

@@ -1,16 +1,17 @@
 import 'mocha'; // tslint:disable-line:no-import-side-effect
 import * as assert from 'power-assert';
 import { TestEntity, testEntity } from '../../tests/utils/testEntity';
+import { asc } from '../../types/SortOrder';
 import createCursorFromEntity from './index';
 
 describe('createCursorFromEntity', () => {
   it('should return undefined when the entity is undefined', () => {
-    const actualResult = createCursorFromEntity<TestEntity>(undefined, { id: true });
+    const actualResult = createCursorFromEntity<TestEntity>(undefined, { id: asc });
     assert.equal(actualResult, undefined);
   });
 
   it('should return the correct cursor when the entity is defined', () => {
-    const actualResult = createCursorFromEntity<TestEntity>(testEntity, { id: true });
+    const actualResult = createCursorFromEntity<TestEntity>(testEntity, { id: asc });
     assert.equal(actualResult, 'eyJpZCI6InRlc3RfaWQifQ==');
   });
 });

Diff for: src/utils/createPaginationFilter/index.test.ts

@@ -3,38 +3,40 @@ import * as assert from 'power-assert';
 import { TestEntity, testEntity } from '../../tests/utils/testEntity';
 import { Filter } from '../../types/Filter';
 import Pagination from '../../types/Pagination';
+import { backward, forward } from '../../types/PaginationDirection';
 import Sort from '../../types/Sort';
+import { asc, desc } from '../../types/SortOrder';
 import createCursorFromEntity from '../createCursorFromEntity';
 import createPaginationFilter from './index';
 
 describe('createCursorFromEntity', () => {
-  const sort: Sort<TestEntity> = { id: true, booleanProp: false };
+  const sort: Sort<TestEntity> = { id: asc, numberProp: desc };
 
   it('should return empty filter when the cursor is undefined', () => {
-    const pagination: Pagination = { cursor: undefined, forward: true, limit: 1 };
+    const pagination: Pagination = { cursor: undefined, direction: forward, limit: 1 };
     const actualResult = createPaginationFilter<TestEntity>(pagination, sort);
     const expectedResult = {};
     assert.deepEqual(actualResult, expectedResult);
   });
 
   it('should return the correct filter when the cursor is defined and going forward', () => {
     const cursor = createCursorFromEntity<TestEntity>(testEntity, sort);
-    const pagination: Pagination = { cursor, forward: true, limit: 1 };
+    const pagination: Pagination = { cursor, direction: forward, limit: 1 };
     const actualResult = createPaginationFilter<TestEntity>(pagination, sort);
     const expectedResult: Filter<TestEntity> = {
-      booleanProp: { $lte: testEntity.booleanProp },
       id: { $gt: testEntity.id },
+      numberProp: { $lte: testEntity.numberProp },
     };
     assert.deepEqual(actualResult, expectedResult);
   });
 
   it('should return the correct filter when the cursor is defined and going backward', () => {
     const cursor = createCursorFromEntity<TestEntity>(testEntity, sort);
-    const pagination: Pagination = { cursor, forward: false, limit: 1 };
+    const pagination: Pagination = { cursor, direction: backward, limit: 1 };
     const actualResult = createPaginationFilter<TestEntity>(pagination, sort);
     const expectedResult: Filter<TestEntity> = {
-      booleanProp: { $gte: testEntity.booleanProp },
       id: { $lt: testEntity.id },
+      numberProp: { $gte: testEntity.numberProp },
     };
     assert.deepEqual(actualResult, expectedResult);
   });

Diff for: src/utils/createPaginationFilter/index.ts

@@ -4,7 +4,9 @@ import Entity from '../../types/Entity';
 // tslint:disable-next-line:no-unused
 import Filter, { ConditionFilter, EntityFilter } from '../../types/Filter';
 import Pagination from '../../types/Pagination';
+import { forward } from '../../types/PaginationDirection';
 import Sort from '../../types/Sort';
+import { asc } from '../../types/SortOrder';
 
 const xor = (conditionA: boolean, conditionB: boolean) => {
   return (conditionA && !conditionB) || (!conditionA && conditionB);
@@ -16,8 +18,11 @@ export default <E extends Entity>(pagination: Pagination, sort: Sort<E>): Filter
   }
   const cursorObj = JSON.parse(atob(pagination.cursor));
   const filter = mapValues(cursorObj, (cursorValue, sortKey) => {
-    const forward = !xor(get(sort, sortKey), pagination.forward);
-    if (forward) {
+    const ascendingPagination = !xor(
+      get(sort, sortKey) === asc,
+      pagination.direction === forward,
+    );
+    if (ascendingPagination) {
       if (sortKey === 'id') {
         return { $gt: cursorValue };
       } else {