fix(pagination): fix #668 edge case

Also code simplification

Author: Alexandre Stanislawski

dev/debug.css

@@ -1 +1 @@
-../css/debug.css
+../src/css/debug.css

src/components/Pagination/Paginator.js

@@ -8,22 +8,31 @@ class Paginator {
   }
 
   pages() {
-    let current = this.currentPage;
-    let padding = this.padding;
-    let paddingLeft = Math.min(this.calculatePaddingLeft(current, padding, this.total), this.total);
-    let paddingRight = Math.max(Math.min(2 * padding + 1, this.total) - paddingLeft, 1);
-    let first = Math.max(current - paddingLeft, 0);
-    let last = current + paddingRight;
+    const {total, currentPage, padding} = this;
+
+    const totalDisplayedPages = this.nbPagesDisplayed(padding, total);
+    if (totalDisplayedPages === total) return range(0, total);
+
+    const paddingLeft = this.calculatePaddingLeft(currentPage, padding, total, totalDisplayedPages);
+    const paddingRight = totalDisplayedPages - paddingLeft;
+
+    const first = currentPage - paddingLeft;
+    const last = currentPage + paddingRight;
+
     return range(first, last);
   }
 
-  calculatePaddingLeft(current, padding, total) {
+  nbPagesDisplayed(padding, total) {
+    return Math.min(2 * padding + 1, total);
+  }
+
+  calculatePaddingLeft(current, padding, total, totalDisplayedPages) {
     if (current <= padding) {
       return current;
     }
 
     if (current >= (total - padding)) {
-      return 2 * padding + 1 - (total - current);
+      return totalDisplayedPages - (total - current);
     }
 
     return padding;

src/components/Pagination/__tests__/Paginator-test.js

@@ -0,0 +1,161 @@
+/* eslint-env mocha */
+
+import expect from 'expect';
+
+import Paginator from '../Paginator';
+
+describe('paginator: simple cases', () => {
+  context('on the first page', () => {
+    const pager = new Paginator({
+      currentPage: 0,
+      total: 10,
+      padding: 2
+    });
+
+    it('should return the pages', () => {
+      const pages = pager.pages();
+      expect(pages.length).toBe(5);
+      expect(pages).toEqual([0, 1, 2, 3, 4]);
+    });
+
+    it('should be the first page', () => {
+      expect(pager.isFirstPage()).toBe(true);
+    });
+
+    it('should not be the last page', () => {
+      expect(pager.isLastPage()).toBe(false);
+    });
+  });
+
+  context('on 3rd page', () => {
+    const pager = new Paginator({
+      currentPage: 2,
+      total: 10,
+      padding: 2
+    });
+
+    it('should return the pages', () => {
+      const pages = pager.pages();
+      expect(pages.length).toBe(5);
+      expect(pages).toEqual([0, 1, 2, 3, 4]);
+    });
+
+    it('should not be the first page', () => {
+      expect(pager.isFirstPage()).toBe(false);
+    });
+
+    it('should not be the last page', () => {
+      expect(pager.isLastPage()).toBe(false);
+    });
+  });
+
+  context('on 5th page', () => {
+    const pager = new Paginator({
+      currentPage: 5,
+      total: 10,
+      padding: 2
+    });
+
+    it('should return the pages', () => {
+      const pages = pager.pages();
+      expect(pages.length).toBe(5);
+      expect(pages).toEqual([3, 4, 5, 6, 7]);
+    });
+
+    it('should not be the first page', () => {
+      expect(pager.isFirstPage()).toBe(false);
+    });
+
+    it('should not be the last page', () => {
+      expect(pager.isLastPage()).toBe(false);
+    });
+  });
+
+  context('on the page before the last', () => {
+    const pager = new Paginator({
+      currentPage: 8,
+      total: 10,
+      padding: 2
+    });
+
+    it('should return the pages', () => {
+      const pages = pager.pages();
+      expect(pages.length).toBe(5);
+      expect(pages).toEqual([5, 6, 7, 8, 9]);
+    });
+
+    it('should not be the first page', () => {
+      expect(pager.isFirstPage()).toBe(false);
+    });
+
+    it('should not be the last page', () => {
+      expect(pager.isLastPage()).toBe(false);
+    });
+  });
+
+  context('on last page', () => {
+    const pager = new Paginator({
+      currentPage: 9,
+      total: 10,
+      padding: 2
+    });
+
+    it('should return the pages', () => {
+      const pages = pager.pages();
+      expect(pages.length).toBe(5);
+      expect(pages).toEqual([5, 6, 7, 8, 9]);
+    });
+
+    it('should not be the first page', () => {
+      expect(pager.isFirstPage()).toBe(false);
+    });
+
+    it('should not be the last page', () => {
+      expect(pager.isLastPage()).toBe(true);
+    });
+  });
+});
+
+describe('paginator: number of pages is less than 2*padding+1', () => {
+  const pager = new Paginator({
+    currentPage: 0,
+    total: 1,
+    padding: 2
+  });
+
+  it('should return the pages', () => {
+    const pages = pager.pages();
+    expect(pages.length).toBe(1);
+    expect(pages).toEqual([0]);
+  });
+
+  it('should be the first page', () => {
+    expect(pager.isFirstPage()).toBe(true);
+  });
+
+  it('should not be the last page', () => {
+    expect(pager.isLastPage()).toBe(true);
+  });
+});
+
+describe('paginator: bug #668', () => {
+  const pager = new Paginator({
+    currentPage: 4,
+    total: 6,
+    padding: 3
+  });
+
+  it('should return the pages', () => {
+    const pages = pager.pages();
+    expect(pages.length).toBe(6);
+    expect(pages).toEqual([0, 1, 2, 3, 4, 5]);
+  });
+
+  it('should be the first page', () => {
+    expect(pager.isFirstPage()).toBe(false);
+  });
+
+  it('should not be the last page', () => {
+    expect(pager.isLastPage()).toBe(false);
+  });
+});