feat(pagination): Adds pagination utils.

Author: ryasmi

.circleci/config.yml

@@ -30,6 +30,9 @@ jobs:
       - run:
           name: Compiling Code
           command: npm run build
+      - run:
+          name: Testing Code
+          command: npm run cover
       - run:
           name: Linting Code
           command: npm run lint

.nyc_output/65ea4b5c367e61a6d125bed20586a974.json

@@ -0,0 +1 @@
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.nyc_output/75cfbd833d8f9238919b0e74815921a5.json

@@ -0,0 +1 @@
+{}

.nyc_output/fbad6bbe03e8a0186a1f4341fd28f801.json

@@ -0,0 +1 @@
+{}

@types/atob/index.d.ts

@@ -0,0 +1,4 @@
+declare module 'atob' {
+  const x: (stringToDecode: string) => string;
+  export = x;
+}

@types/btoa/index.d.ts

@@ -0,0 +1,4 @@
+declare module 'btoa' {
+  const x: (stringToEncode: string) => string;
+  export = x;
+}

package-lock.json

@@ -11,6 +11,8 @@
   "scripts": {
     "build": "tsc",
     "lint": "tslint --project ./tsconfig.json",
+    "test": "mocha $(find dist -name '*.test.js') --exit",
+    "cover": "nyc npm test",
     "duplication": "jscpd",
     "clean": "rimraf dist",
     "semantic-release": "ht2-release-private-circleci"
@@ -20,11 +22,14 @@
     "check-coverage": true
   },
   "dependencies": {
+    "btoa": "^1.1.2",
+    "lodash": "^4.17.4",
     "make-error": "^1.3.0"
   },
   "devDependencies": {
     "@ht2-labs/semantic-release": "1.0.9",
     "@ht2-labs/typescript-project": "1.0.0",
+    "@types/lodash": "^4.14.91",
     "@types/mocha": "2.2.44",
     "@types/power-assert": "1.4.29",
     "assert-rejects": "0.1.1",

package.json

@@ -0,0 +1,16 @@
+import 'mocha'; // tslint:disable-line:no-import-side-effect
+import * as assert from 'power-assert';
+import { TestEntity, testEntity } from '../../tests/utils/testEntity';
+import createCursorFromEntity from './createCursorFromEntity';
+
+describe('createCursorFromEntity', () => {
+  it('should return undefined when the entity is undefined', () => {
+    const actualResult = createCursorFromEntity<TestEntity>(undefined, { id: true });
+    assert.equal(actualResult, undefined);
+  });
+
+  it('should return the correct cursor when the entity is defined', () => {
+    const actualResult = createCursorFromEntity<TestEntity>(testEntity, { id: true });
+    assert.equal(actualResult, 'eyJpZCI6InRlc3RfaWQifQ==');
+  });
+});

src/utils/createCursorFromEntity/createCursorFromEntity.test.ts

@@ -0,0 +1,15 @@
+import * as btoa from 'btoa';
+import { get, set } from 'lodash';
+import Cursor from '../../types/Cursor';
+import Sort from '../../types/Sort';
+
+export default <Entity>(entity: Entity | undefined, sort: Sort<Entity>): Cursor => {
+  if (entity === undefined) {
+    return undefined;
+  }
+  const sortKeys = Object.keys(sort);
+  const cursorResult = sortKeys.reduce<Partial<Entity>>((result, sortKey) => {
+    return set(result, sortKey, get(entity, sortKey));
+  }, {});
+  return btoa(JSON.stringify(cursorResult));
+};

src/utils/createCursorFromEntity/createCursorFromEntity.ts

@@ -0,0 +1,37 @@
+import 'mocha'; // tslint:disable-line:no-import-side-effect
+import * as assert from 'power-assert';
+import { TestEntity, testEntity } from '../../tests/utils/testEntity';
+import Pagination from '../../types/Pagination';
+import createCursorFromEntity from '../createCursorFromEntity/createCursorFromEntity';
+import createPaginationFilter from './createPaginationFilter';
+
+describe('createCursorFromEntity', () => {
+  const sort = { id: true };
+
+  it('should return empty filter when the cursor is undefined', () => {
+    const pagination: Pagination = { cursor: undefined, forward: true, 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 actualResult = createPaginationFilter<TestEntity>(pagination, sort);
+    const expectedResult = {
+      id: { $gt: testEntity.id },
+    };
+    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 actualResult = createPaginationFilter<TestEntity>(pagination, sort);
+    const expectedResult = {
+      id: { $lt: testEntity.id },
+    };
+    assert.deepEqual(actualResult, expectedResult);
+  });
+});

src/utils/createPaginationFilter/createPaginationFilter.test.ts

@@ -0,0 +1,26 @@
+import * as atob from 'atob';
+import { get, mapValues } from 'lodash';
+// tslint:disable-next-line:no-unused
+import Filter, { AndFilter, NotFilter, OrFilter } from '../../types/Filter';
+import Pagination from '../../types/Pagination';
+import Sort from '../../types/Sort';
+
+const xor = (conditionA: boolean, conditionB: boolean) => {
+  return (conditionA && !conditionB) || (!conditionA && conditionB);
+};
+
+export default <Entity>(pagination: Pagination, sort: Sort<Entity>): Filter<Entity> => {
+  if (pagination.cursor === undefined) {
+    return {};
+  }
+  const cursorObj = JSON.parse(atob(pagination.cursor));
+  const filter = mapValues(cursorObj, (cursorValue, sortKey) => {
+    const forward = !xor(get(sort, sortKey), pagination.forward);
+    if (forward) {
+      return { $gt: cursorValue };
+    } else {
+      return { $lt: cursorValue };
+    }
+  });
+  return filter as any as Filter<Entity>;
+};