[New Exercise] Lens person

config.json

@@ -2621,6 +2621,22 @@
           "errors"
         ],
         "difficulty": 5
+      },
+      {
+        "slug": "lens-person",
+        "name": "Lens Person",
+        "uuid": "a1e71425-0e7e-442a-9c8e-cc252f440760",
+        "practices": [],
+        "prerequisites": [
+          "prototypes-and-classes",
+          "callbacks"
+        ],
+        "difficulty": 7,
+        "topics": [
+          "lens",
+          "classes",
+          "callbacks"
+        ]
       }
     ]
   },

exercises/practice/lens-person/.docs/instructions.md

@@ -0,0 +1,15 @@
+# Instructions
+
+Use lenses to update nested records (specific to languages with immutable data).
+
+Updating fields of nested, immutable records is kind of annoying.
+The code for such cases is as cumbersome as the structure is deep.
+If you have, say, a Person, that contains an Address, which has a Street, that has a Number, updating the Number requires creating a new Street with the new Number, then a new Address with the new Street and, finally, a new Person with the new Address.
+Confused already?
+
+One solution to this problem is to use [lenses][lenses].
+
+Implement several record accessing functions using lenses.
+The test suite also allows you to avoid lenses altogether so you can experiment with different approaches.
+
+[lenses]: https://en.wikibooks.org/wiki/Haskell/Lenses_and_functional_references

exercises/practice/lens-person/.docs/introduction.md

@@ -0,0 +1,7 @@
+In JavaScript, lenses are a functional programming concept that allows you to access and modify data in a modular and immutable way. They are essentially composable pairs of pure getter and setter functions that focus on a particular field inside an object.
+
+Lenses can be used to simplify code, make it more reusable, and avoid common programming errors. For example, lenses can be used to:
+
+- Access and modify nested data structures without having to worry about the specific structure of the data.
+- Update data in a pure way, without mutating the original object.
+- Compose multiple lenses together to create more complex lenses that can access and modify data in a variety of ways.

exercises/practice/lens-person/.eslintrc

@@ -0,0 +1,14 @@
+{
+  "root": true,
+  "extends": "@exercism/eslint-config-javascript",
+  "env": {
+    "jest": true
+  },
+  "overrides": [
+    {
+      "files": [".meta/proof.ci.js", ".meta/exemplar.js", "*.spec.js"],
+      "excludedFiles": ["custom.spec.js"],
+      "extends": "@exercism/eslint-config-javascript/maintainers"
+    }
+  ]
+}

exercises/practice/lens-person/.gitignore

@@ -0,0 +1,5 @@
+/node_modules
+/bin/configlet
+/bin/configlet.exe
+/pnpm-lock.yaml
+/yarn.lock

exercises/practice/lens-person/.meta/config.json

@@ -0,0 +1,25 @@
+{
+  "authors": [
+    "sarava338",
+    "Cool-Katt"
+  ],
+  "files": {
+    "solution": [
+      "lens-person.js"
+    ],
+    "test": [
+      "lens-person.spec.js"
+    ],
+    "example": [
+      ".meta/proof.ci.js"
+    ],
+    "editor": [
+      "address.js",
+      "born.js",
+      "lens.js",
+      "name.js",
+      "person.js"
+    ]
+  },
+  "blurb": "Use lenses to update nested records (specific to languages with immutable data)."
+}

exercises/practice/lens-person/.meta/proof.ci.js

@@ -0,0 +1,39 @@
+/* eslint-disable no-unused-vars */
+import { Address } from '../address';
+import { Born } from '../born';
+import { Lens } from '../lens';
+import { Name } from '../name';
+import { Person } from '../person';
+
+// Implement the nameLens with the getter and setter
+export const nameLens = new Lens(
+  (person) => person.name,
+  (person, name) => new Person(name, person.born, person.address),
+);
+
+// Implement the bornAtLens with the getter and setter
+export const bornAtLens = new Lens(
+  (person) => person.born.bornAt,
+  (person, bornAt) =>
+    new Person(
+      person.name,
+      new Born(bornAt, person.born.bornOn),
+      person.address,
+    ),
+);
+
+// Implement the streetLens with the getter and setter
+export const streetLens = new Lens(
+  (person) => person.address.street,
+  (person, street) =>
+    new Person(
+      person.name,
+      person.born,
+      new Address(
+        person.address.houseNumber,
+        street,
+        person.address.place,
+        person.address.country,
+      ),
+    ),
+);

exercises/practice/lens-person/.npmrc

@@ -0,0 +1 @@
+audit=false

exercises/practice/lens-person/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2021 Exercism
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

exercises/practice/lens-person/address.js

@@ -0,0 +1,15 @@
+export class Address {
+  /**
+   *
+   * @param {number} houseNumber
+   * @param {string} street
+   * @param {string} place
+   * @param {string} country
+   */
+  constructor(houseNumber, street, place, country) {
+    this.houseNumber = houseNumber;
+    this.street = street;
+    this.place = place;
+    this.country = country;
+  }
+}

exercises/practice/lens-person/babel.config.js

@@ -0,0 +1,4 @@
+module.exports = {
+  presets: ['@exercism/babel-preset-javascript'],
+  plugins: [],
+};

exercises/practice/lens-person/born.js

@@ -0,0 +1,11 @@
+export class Born {
+  /**
+   *
+   * @param {Address} bornAt
+   * @param {Date} bornOn
+   */
+  constructor(bornAt, bornOn) {
+    this.bornAt = bornAt;
+    this.bornOn = bornOn;
+  }
+}

exercises/practice/lens-person/lens-person.js

@@ -0,0 +1,41 @@
+//
+// This is only a SKELETON file for the 'Lense Person' exercise. It's been provided as a
+// convenience to get you started writing code faster.
+//
+
+/* eslint-disable no-unused-vars */
+import { Person } from './person';
+import { Name } from './name';
+import { Born } from './born';
+import { Address } from './address';
+import { Lens } from './lens';
+
+// Implement the nameLens with the getter and setter
+export const nameLens = new Lens(
+  () => {
+    throw new Error('Remove this statement and implement this function');
+  },
+  () => {
+    throw new Error('Remove this statement and implement this function');
+  },
+);
+
+// Implement the bornAtLens with the getter and setter
+export const bornAtLens = new Lens(
+  () => {
+    throw new Error('Remove this statement and implement this function');
+  },
+  () => {
+    throw new Error('Remove this statement and implement this function');
+  },
+);
+
+// Implement the streetLens with the getter and setter
+export const streetLens = new Lens(
+  () => {
+    throw new Error('Remove this statement and implement this function');
+  },
+  () => {
+    throw new Error('Remove this statement and implement this function');
+  },
+);

exercises/practice/lens-person/lens-person.spec.js

@@ -0,0 +1,94 @@
+import { Address } from './address';
+import { Born } from './born';
+import { Name } from './name';
+import { Person } from './person';
+
+import { bornAtLens, nameLens, streetLens } from './lens-person';
+
+// test data
+const person = new Person(
+  new Name('Saravanan', 'Lakshamanan'),
+  new Born(
+    new Address(100, 'Hospital street', 'Tamil Nadu', 'India'),
+    new Date(),
+  ),
+  new Address(1, 'Coder street', 'Tamil Nadu', 'India'),
+);
+
+// test suite for nameLens
+describe('nameLens', () => {
+  test('should get the name of the person', () => {
+    expect(nameLens.get(person)).toEqual(person.name);
+  });
+
+  xtest('should set a new forename for the person', () => {
+    const updatedPerson = nameLens.set(person, new Name('Sara', 'Lakshmanan'));
+    expect(nameLens.get(updatedPerson)).toEqual(updatedPerson.name);
+  });
+
+  xtest('should set a new surname for the person', () => {
+    const updatedPerson = nameLens.set(person, new Name('Saravanan', 'Laksh'));
+    expect(nameLens.get(updatedPerson)).toEqual(updatedPerson.name);
+  });
+
+  xtest('should ensure immutability by checking the original person object', () => {
+    expect(person).not.toStrictEqual(
+      new Person(new Name('Sara', 'Lakshamanan'), person.born, person.address),
+    );
+  });
+});
+
+// Test suite for bornAtLens
+describe('bornAtLens', () => {
+  xtest('should get the address where the person was born', () => {
+    expect(bornAtLens.get(person)).toEqual(person.born.bornAt);
+  });
+
+  xtest('should set a new street for the place where the person was born', () => {
+    const updatedPerson = bornAtLens.set(
+      person,
+      new Address(2, 'Exercism street', 'Tamil Nadu', 'India'),
+    );
+    expect(bornAtLens.get(updatedPerson)).toEqual(updatedPerson.born.bornAt);
+  });
+
+  xtest('should ensure immutability by checking the original person object', () => {
+    expect(person).not.toEqual(
+      new Person(
+        person.name,
+        new Born(
+          new Address(2, 'Exercism street', 'Tamil Nadu', 'India'),
+          person.born.bornOn,
+        ),
+        person.address,
+      ),
+    );
+  });
+});
+
+// Test suite for streetLens
+describe('streetLens', () => {
+  xtest('should get the current street of the person', () => {
+    expect(streetLens.get(person)).toEqual(person.address.street);
+  });
+
+  xtest('should set a new street for the current address of the person', () => {
+    const updatedPerson = streetLens.set(person, 'Exercism street');
+    expect(streetLens.get(updatedPerson)).toEqual(updatedPerson.address.street);
+  });
+
+  xtest('should ensure immutability by checking the original person object', () => {
+    expect(person).not.toEqual(
+      new Person(
+        person.name,
+        person.born,
+        new Address(
+          person.address.houseNumber,
+          'Exercism Street',
+          person.address.place,
+          person.address.country,
+        ),
+      ),
+    );
+  });
+});

exercises/practice/lens-person/lens.js

@@ -0,0 +1,30 @@
+export class Lens {
+  /**
+   *
+   * @param {Function} getter
+   * @param {Function} setter
+   */
+  constructor(getter, setter) {
+    this.get = getter;
+    this.set = setter;
+  }
+
+  /**
+   * Function to get the value from a lens
+   * @param {Person} person
+   * @returns {Person}
+   */
+  get(person) {
+    return this.get(person);
+  }
+
+  /**
+   * Function to set the value using a lens
+   * @param {Person} person
+   * @param {any} value
+   * @returns {Person}
+   */
+  set(person, value) {
+    return this.set(value, person);
+  }
+}

exercises/practice/lens-person/name.js

@@ -0,0 +1,11 @@
+export class Name {
+  /**
+   *
+   * @param {string} forename
+   * @param {string} surname
+   */
+  constructor(forename, surname) {
+    this.forename = forename;
+    this.surname = surname;
+  }
+}